A Guide to Creating Good STL Files

imageThe STL file is the linqua-franca of the prototyping world, the file format that all geometry creation tools write, and that all prototyping systems read. When you make a prototype it will be an exact copy of your STL file. If your file is not accurate, then your prototype will not be accurate. If there are errors in your file, you may not be able to get a prototype made. Therefore, a little bit of time understanding STL files and how to create a good one is a good investment that will pay off in the long run.

About STL Files

When additive manufacturing was just starting the manufacturers of machines faced a problem – they needed a way to get 3D solid models from a large number of CAD systems to their machines for processing. The common file format for geometry interchange, IGES, was not robust enough because of toleranceing issues. Writing a program to slice up each CAD format was also not practical. So they looked at the problem and realized they did not need exact mathematical models made up of NURB, Bezier, or analytical geometry. The algorithm that sliced up each layer just needed polygons on the surface. So the STL file just needed to have those polygons. And the STL file was born.

Lets talk about that slicing process. If you remember, almost all additive manufacturing processes work by creating stacked layers that are a cross section of the part you want. To build the part you must slice the geometry in software, calculating that cross section. Doing the intersection of a plane with a complex NURB surface is hard math, but the intersection with a triangle is very easy and results in a line segment. This makes creating the path for each layer much easier.

STL stands for STereoLithography, or Standard Tessellation Language, depending on which source you check. It was invented for 3D Systems by the Albert Consulting Group way back in 1987 to support the first Stereolithography machines. The format describes a collection of facets, or polygons. Each polygon is defined by a normal “outward” vector and the vertices that define it. Although the format supports more than three vertices per facet, in practice everyone uses three, defining a triangle. The file can be a text file (ASCII) or a binary file.

Users almost never have to worry about the file because the programs they use to create their geometry automatically generate STL files in the proper format. If you do need to write your own routine to output an STL file, it is fairly simple.

Faceting

clip_image001 The way an STL file is made is the program that creates the STL file goes through the topology of the model and meshes it:

1: First it puts points on all of the shared edges of all the surfaces
2: Then it creates triangles on each surface

The algorithm used to create the facets varies from program to program, but most of them use the same routines they use to make facets for the 3D graphics you see on your monitor.

There are two things to note about faceting. The first is that each corner must be coincident with at least one other corner. No corners can touch the edge of another triangle. The second is that a triangle is flat and your surface can be curved. To make your curved surface look curved you need enough triangles to make it appear like a continuous surface.

Leaky Geometry

The most common problem these days with STL files is leaky geometry. When your CAD tool creates the STL file your solid may not be a true solid in that you have holes in your topology. This can be caused by gaps, ill-defined curves and surface, or corners (vertices) not lining up. If you cut out the triangles and glued them together then filled the resulting object with water, the water would leak out.

You CAD package can make leaky STL files if it has loosened up the tolerances on the geometry modeling to the point where edges on its surface do not really line up. They trick themselves into accepting this through some hand waving inside their database, and it really is not a problem till you want to do something with the surfaces. Something like make an STL file.

One way to fix this problem is to clean up the original geometry. Run diagnostics on it and see where there are holes. You should do this anyway because in the end, a messy solid will cause problems when you make your drawings, calculate tool paths, or try and do simulation.

If that is not an option, you can use repair software. If you use an RP service provider, they should be able to repair most STL files. But if you constantly need them to do so, you should really look at changing your modeling practices or investing in some repair tools.

If you are doing your own prototyping, you have two good options. The first is free: Meshlab. It is an open source tool for working with faceted geometry and has repair and diagnostic capabilities. It does a lot so the interface can be a bit confusing, but it is free. If you want to save time and probably money in the long run, we recommend that you purchase a copy of SolidView. It is purpose built for repairing STL files and can really cut down on your repair time.

Faceted Geometry

Even if your prototyping tool can read your geometry and make a valid part, it may come out looking all clunky because your geometry is to faceted. As discussed above, the STL file is made up of triangles. If you have too few triangles on a curved surface then it comes out looking all flat and ugly. Here is a simple example:

The key to controlling this is to set the options in your CAD package to create more facets.

This is such an important topic, we actually have a whole posting dedicated to it:

STL File Tolerance: A Short Explanation of Faceting and Chord Height

In the old days we tried to minimize the number of triangles in an STL file because that file had to be uploaded, often via a modem.  But now we can email very large files, so you can make some pretty big STL files. Don’t go crazy, but don’t sacrifice surface quality either.

Degenerate Triangles and Inverted Faces

It is very rare for a CAD tool to create bad triangles, but it happens every once in a while. When trying to create a build from an STL file you might get a “Degenerate Triangle” or “Inverted Faces” error message.  There is not much you can do with this other than try one of the repair tools mentioned above or try and fix your underlying geometry.  If you get this type of error, there is something very wrong with your solid model.

Feature Sizes

Another problem that people often run across is that some of their small features do not show up on their prototype.  This can be because their STL file is not refined enough and that can be solved by tightening up the tolerance on their STL file creation.  If that does not work, the feature may just be too small for the technology.  Take a look at what the true machine resolution is. Make sure that is is smaller than your smallest features.

Make an Investment in Productivity

Having a bad STL file can really slow down the rapid part of Rapid Prototyping.  That is why PADT recommends that you take the time when you create your solid models to make good, robust, water tight solids that can be used down stream.  If you have nasty geometry or a less than precise CAD tool (can anyone say CATIA) you may have to invest in a repair program like Meshlab or SolidView.  Some up-front investment will pay in the long run, especially when you need that prototype first thing in the morning.

Printing from this Blog

A quick note before I head out for a Chris Isaac concert (my wife is a fan, and I’m supportive… but let me note that she did not support me by going to see Rush) I wanted to let our readers know about printing on this new blog.

Long time The Focus readers are used to having a “Print” link that will make a  nicely formatted printout of articles.  Some people like to do that and then share them with others or keep them in a book for reference. On the new WordPress based blog there is no need for that. Simply go to the article itself by clicking on the title, then print it out using your browsers print function. WordPress takes care of the formatting.

Have a great weekend!

Wicked Games

Rush

Local Involvement: PADT Leading Efforts to Improve Business Climate in Littleton, CO

PADT’s very own Norman Stucker is leading efforts through the South Metro Denver Chamber of Commerce to grow the business community in Littleton. Norman is heading up a commitee charged with creating coordination and synergy between businesses, non-profits, and local government.

This morning was the first community meeting for the committee. Speakers included a small graphic arts company owner, the director of the local YMCA, and the Littleton city manager. The messaclearly the same from everyone, that Littleton is “open for business”

PADT is very proud to have one of our employees play such an important role in the community.

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PADT at the 9th Annual Colorado Space Roundup

PADT is pleased to be an exhibitor at this years Colorado Space Roundup. This is a great event where everyone involved in space gets together and talks about what needs to be done to improve and grow the aerospace ecosystem in the state. We are pleased to see many of our customers here, and have already met some new friends.

The location is at the Denver Museum of Nature and Science, a very cool facility with a nice view out front. It was also nice to see so many grcrust companies, many who are customers, listed with PADT on the sponsor page.

Veebow.com: Smart Phone Coupons

imagePADT Angel Investment Profiles
Giving back to the community you come from is something that PADT strongly believes in. We extend this belief not just to charities, but also to the technology business community that helped to create the company we are today.  One way in which we do that is through strategic Angel investments in local technology startup companies.
In this series, we will take a look at the companies that PADT has invested in, where they are in the startup process, and why PADT invested in them.  Hopefully we will cover two a month.  To learn more about PADT’s investment program, visit our Technology Investing page.

 

imageVeebow.com is not a typical technology investment for PADT.  The company “was founded by Tom Vitale and Edward Loew to connect buyers with savvy companies through local, regional and national special deals using a free application on smart phones and mobile devices.”  Why does PADT have an interest in a mobile phone coupon application? We will get to that below, but first a little bit about the company.

The Company

Based in the Phoenix area, with offices in Los Angeles, Veebow.com is a startup that was born out of a missing capability in the market place.  No one provides a method for consumers and merchants to easily and affordably  use coupons on a smart phone. There are plenty of discount applications out there, but non of them are free AND mobile oriented.  They usually cost money for the consumer, or are web based systems moved to mobile.  Veebow is mobile from the ground up, and costs the consumer nothing. In fact, you actually make some money when you use a coupon through the application, because users earn points that can be redeemed for gift cards.

Veebow Couponing app developed by Amadeus ConsultingThe merchant side is also different.  Instead of having to pay for deals to get published, or instead of using the deal company as a middleman to pre-sell things, Veebow only charges the merchant when a coupon is used.  The merchant only pays when they get a customer.  That is very attractive to merchants that are unhappy with most of the deal sites out there.

One other thing that makes Veebow different is where the idea for the company came from.  Tom Vitale, one of the founders, is married to the actress Valarie Bertinelli.  A life long coupon clipper, she was complaining about what a pain it is to use coupons, and that all of the online and mobile options are difficult to use or cost money.  From that complaint came the idea and the name for Veebow – Tom’s nickname for his wife.  Her involvement is a significant marketing advantage for the company.

veebow-managementThe Veebow Management Team

The Technology

The technology on for this startup is not bleeding edge. The mobile apps are written in native IOS and Android and use standard location services and communication to work.  There is a backend tool that sits in the cloud which houses the database and does all of the heavy lifting as far as finding what the user is looking for.  Nothing too special, but a lot of work to implement and something that needs to be done right.  So the technology focus is really on executing correctly

Because of this, the real technology challenge for this product was taking the desired user experience and making it a reality.  It is one thing to sit in a room and talk about how an application should work, and another to make it happen in the real world.  Veebow just released their first major revision of the user application and you can tell they have really thought things out and put a lot of effort into making the experience special.  As the product matures and they modify and improve the user experience, look for more sophistication and ease of use in the application.

PADT’s Interest

Eric_and_VB1We are interested in this company for three reasons. And no, one of them was not meeting Valarie Bertinelli. (although, that was pretty cool, and she is as nice and funny in person as you imagined. We did get a picture with yours truly during an event in Phoenix).  As PADT grows our services and works with a wider range of companies, we have to continually learn more about other spaces and other processes used to get products to market and sold.  Sometimes we make investments in companies because their products or services are directly related to what we do, and sometimes it is because they offer us the opportunity to learn about areas we want to understand better.  The latter is why we invested in Veebow.

The first area of interest for us is the mobile application aspect.  As products get smarter they are going to be moving towards monitoring and control through mobile applications. This is already showing itself to be true in medical devices, and we are seeing it with more customers in other industries every day.  Our involvement with Veebow has already taught us a lot about mobile app development, connections to cloud based backend database applications, and user experience issues.

A unique challenge that Veebow faces is that they need to market to consumers and vendors at the same time.  PADT has no direct experience with marketing to retail merchants or consumers, but many of our customers deal with this on a daily basis.  We feel that by being involved with Veebow we will get an up close look at this very important dynamic, and give us insight that we can use when working with our customers.

The most important reason for our investment in Veebow is that we think it is a great idea, with a good team, and a workable plan. In short, we think it is a good investment that will make a nice return on our investment while growing jobs and the technology ecosystem in Arizona.  This is the type of win-win situation we strive for.

Status

The team at Veebow is very busy with a local test launch in the Phoenix area, closing out this round of funding, and finishing up some very nice tools for their merchants.  They are starting to see some traction with consumers, as they get more merchants signed up.  This is an effort where they need growth on both sides at the same time to be successful.

They are also adding to their team, making some great hires for key positions that will allow them to grow and be successful. We have already seen a positive impact on the software side and are seeing some very serious momentum on the customer acquisition side of things.  Local restaurant company Fox Restaurant Concepts is an early participant as is the national hat chain Lids.  Many others are in negotiations.

Best of all, the users seem to like it.  The droid version has 4.5 stars out of 5 and the iPhone version has 4 out of 4.  We feel that is pretty good considering how picky consumers are.

You can help PADT help our local tech startup community by downloading the application for your iPhone or Android device and using it.  It works all around the country.  What is the worst thing that will happen? You might save some money.

I know, this is bordering on advertising, but at the same time we would really like people to use it and spread the word.  Growth of this company will provide PADT with experience and capital that we can use to provide you with better products and services..  Also, when this is the next big thing, you can tell your friends that you know someone who invested in the idea early.

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Startup Lesson Learned 1: If you Build it, They Will NOT Come

10_Tech_Startup_Lessons_Learned-1About the Series “10 Tech Startup Lessons Learned”

PADT is a company focused on helping companies bring their physical products to market. As “We Make Innovation Work” for our customers, we learn a lot about what does and does not work in technology startup companies. In addition, we were once a startup ourselves and we now participate in Angel investing.  All of this has taught us a lot of valuable lessons.
In this series we will share some of those lessons learned and explore the basic concepts and ideas that will help startups overcome the odds and become successful.

This posting is the first installment for our series.  We hope that you find it useful and we look forward to sharing the the other nine articles.

We see it over and over again. Someone has a great idea. They borrow money from their friends and family, they max out their credit card, they get angel funding.  They then build their product, putting every ounce of enthusiasm and drive they have into making the product perfect. All along they show it to people and get fantastic feedback like “I would buy that is a second” and “I wish I would have thought of that, it is a great idea.”  They are dripping with passion.  As soon as they can, they put their product out there…

And the product fails.

And they wonder why. They get frustrated and sometimes angry.  What the majority of startups fail to recognize is that no mater how good an idea is, no matter how real and tangible the market need is, products do not sell themselves.  This failure mode is different from failure caused by mistakes in execution, pricing, growth, or missing the market. What we are talking about here are perfectly good viable products that do not make it off the ground because the startup that created it felt that just building it was good enough.

product_in_desert

“Building it” is just one step of many in getting a startup to success.  You must also plan and implement everything that is required to build a business and launch a product. Those things do not come automatically. If you have a great idea with demand, then the implementation will be easier, but it is very rare for the idea or need alone to make a product a success.

There are many different areas that a startup must focus on beyond the product itself.  Many a book and even a few text books have been written to talk in detail about how to plan and implement a entrepreneurial business plan.  However, in our experience, there three critical parts of the business that every startup must carry out well to be successful.

Marketing

The first is marketing – because if no one knows you have a product and what it does, you do not have the opportunity to acquire them as customers.   You have to do it, and you have to do all of it: branding, messaging, social media, website, advertising, networking, trade shows, press, etc…. You do not have to do it big, and you can scale as you grow, but you must make sure that customers know your product exists and what it does.

We see many of our customers go to market with a name and maybe a basic website. When nothing happens they do not understand why the orders are not rolling in.  A consistent and properly scaled marketing strategy with a concise message that conveys the products value is what is missing. Coming up with this is not easy and time and thought needs to be put into it.  The good news is that this is one area where outside consultants can really help.

Sales

The critical partner to marketing is sales.  The ease of direct to customer transactions through the internet gives many startups the false impression that they can simply put their product on the web and they will get orders.  Even if no human interaction is involved, there is a sales cycle and you need to plan for it, manage it, and maximize the return on investment from the sales effort.

Sales is something that everyone in a company needs to be involved in to some extent. Success in this area usually comes when a sales process is developed that fits the product, and everyone sticks to it from the receptionist in the lobby to the CEO at the top.  It is also a skill that most people do not have, or can not do over the long term. It is important to hire real sales professionals and if needed, managers, to head up the effort.

Complete the Product

There is one more major step that needs to be taken for success, to get people to come and buy a product.  You need an actual product, and not just an idea.  This seems obvious, and not even worth noting. Many times we have been involved in projects or mentoring where, when you dig deep enough, you find out that the “product” is just an idea, or a half formed prototype, and all of the details have not been worked out.  To them they have built something great, so money and customers should be coming.  But money and customers need something real and finished before they will engage.

product_on_stage_cheering

Build It [finish it, market it, sell it], And they WILL Come

If you are thinking of doing a startup, or if you are in a startup now, take some time to look at your strategy and decide if you are counting too much on the power of your product’s appeal to make your successful. You probably are because most people make that mistake.  Be honest about what you need to do, plan and execute, and you can defy the odds and be that technology startup that makes it.

PADT’s New Website on Lynx

We were testing out the new Website on different browsers and some smarty-mc-smarty decided to try it on Lynx:

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It is not as bad as I thought it would be…  Who remembers using Lynx?

Welcome to the new PADTINC.com and Expanded Blog

padtinc_com_home_page_screen_shotIt has been a long road but we have finally arrived. You can see it at www.PADTINC.com. Not only is the site new, but we have a new and expanded blog that covers the whole company and not just ANSYS related topics. 

Jump right in and take a look, or hang here a bit as we share a little history of how we ended up with the site we have:

About three years ago we decided to redo our website.  Several of us tried, but we were just too busy with other things. Or we found we lacked one or two critical skills to get it done. Plus our old site was still doing well with the search engines, bringing in business, and providing information to the community. No one was pushing us to get it done (OK, our sales team was getting pretty frustrated) and it was not easy, so it languished. Still no new website.

So about a year ago, we started looking for a website design company that would work with us the way we wanted to work. This was a more difficult task then we envisioned.  We were not looking for someone to make us an online brochure. We were also not looking for someone to set up a content management system that we could upload short bits and pieces to.  We also did not want someone that would create a site that we could not get into and mess with.  We also ran into a problem with people really not understanding the kind of customer who comes to the PADT website and the type of content they expect. And we wanted it in Adobe Dreamweaver (I know, 2005 called and they want their web design tool back. At least we are not using ColdFusion.)

After looking for a while, we found Newhouse Studios, http://webstrategyaz.com/. They have worked with technical companies in the past, and actually still had people who could use Dreamweaver.  They took us through a real design process where different designers (artists really) shot us different look and feel concepts:

We opted for the second one, and the real hard work began.  After refining the colors and fonts, we started laying out the site.  What a chore!  PADT really can be represented on the web as 4 or 5 different companies, and the web needs of each area of the PADT is a bit different. But we did it, lots of multi-color post-it notes all over a big board with arrows going everywhere.

Then we slowed down because we had to write content.  And lots of content. Over 90 pages of content. Some were short, some very long, some cut and paste. And each one had to be proofed, optimized for search engines and then formatted properly.

Somewhere in the middle of it all we found we needed some nice images, so we called on DM Photo to put on their commercial photography hat and shoot a bunch of stuff in and around the office. The results were better than we could have hoped for and upped the professional look of the site.

So we just kept on crunching out pages, adding images, and reorganizing as we went.

padt_blog_pagesAnd in parallel, we launched a new blog hosting server using WordPress, and we expanded the topics for our blog from just ANSYS to all the area that PADT works in.  It will also be where we post news, like this posting. So our blog now has: News, The Focus, Product Development, PADT Medical, The RP Resource, and Fun. It is our hope that The RP Resource will become as popular as The Focus. We also hope that the “Fun” page will be fun. That is yet to be proven.

And we worked, and we let other things get in the way, and we dropped a few balls.  Nothing unusual for a new website. If you have tried to do this, you know what it is like. But we kept moving forward, and we eventually got there. We are done!

Thank you to everyone who helped out and all of our customers and vendors who put up with the old site.  We are pleased with the results and hope you find it useful and entertaining.

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12 Things Every Engineer Should Know about Rapid Prototyping

PADT has been providing various forms of rapid prototyping since 1994, focused on providing high quality prototypes to engineers involved in product development. Over that time, we have learned a lot about what our customers need to know in order to get the most out of their rapid prototyping investment. As we launch our new The RP Resource, we think now is a good time to share some of the things we have learned.

1: Know what you are going to use your prototype for

This is the most important thing for any engineer to know when they are using rapid prototyping. A good understanding of how the prototype will be used is critical to making decisions on the technology applied, the material used, the build options set, and the post processing that is carried out. When we look into why a customer who is unhappy with their prototype, nine times out of ten we find out that they did not convey to us what their end use was, so we did not make them the prototype they actually needed.

2: Rapid Prototyping, Direct Digital Manufacturing, 3D Printing: They are all additive manufacturing

The technology may vary from machine to machine, but in the end they all kind of work the same – they build a part one thin layer at a time. This is important because the part you end up getting will be made with layered manufacturing. The strength will be non-uniform, features that overhang may droop a bit if not properly supported, and the surface finish will not be smooth unless you chemically treat it or sand it after the build is done.

3: You will get an exact copy of your STL or CAD file, so make sure it is a good one.

The prototype that you are making is a direct digital copy of the file you ask it to print. None of the processes improve on the geometry you send to them, so it is important that you provide a high quality model. If you are starting with an STL file, you need to make sure that you have enough facets on your model so that they are not visible on the prototype. We like the maximum deviation of the facet from the actual shape (chord height) to be less than 0.001 inches. We recently did a post on this very topic.

The same goes true for “bad” STL files. You may get errors, or the prototyping system may not even be able to build your part. Making sure you have a quality STL or CAD will save everyone a lot of time.

4: Build orientation has a big impact on cost, surface quality, and strength

Remember that you are using a layered manufacturing process. The number of layers and their orientation relative to your part can make a bid difference on cost, the surface quality, and strength.

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In the exaggerated illustration above, you can see the same shape will have different stepping, and a different number of layers depending on how it is oriented. The taller the part, the longer it takes to build. The lower the slope, the more “stair-stepy” the surface.

Something else to take into account is that the parts will be weaker when the layers are put under load that causes them to delaminate. Imagine your prototype was made up of a deck of stacked playing cards with a glue between each card. You want to load it in a way that will not cause those cards to want to pull apart.

5: The amount of material in you part is a big cost driver

One of the biggest drivers of the cost on a prototype is the amount of material used to build the part. This is especially true when you are using some of the more expensive materials.  Take a look at using options in your machine software to more sparsely filled part.  You can also shell your part on your CAD system. If you are working with a service provider, ask them to take a look at this on your prototypes.

6: Part geometry can come from CAD, or a scan

Customers occasionally come to us with an existing part and ask us to make a CAD model of it so they can prototype it. In some cases, it may be easier to just make some soft tooling of the part, skip the prototyping process entirely. But if that does not work, you can use a variety of scanning technologies to get a faceted representation of the real part.

7: Warping and shrinking distortion is above and beyond published machine accuracy

When you look at the published accuracy of a given machine what they show you is the accuracy of the process that traces an outline or sets the thickness of a layer. The accuracy of the mechanisms in the machine itself. Your part may have much less accuracy because most parts warp and shrink slightly during the manufacturing process. Overhangs may also droop if they are not supported correctly.

The key to solving this problem is to really know the machine you are using, or work with a service provider who knows how to plan for and adapt to this reality. Some technologies may just not be suited for your geometry, and you may need to go with a different machine type.

8: Build the full cost or prototyping into your product developments budget

People who use prototyping effectively in their product development always budget for the proper amount to pay for prototyping. Too often this important tool is left out of the budget and when a prototype is needed, funding can not be found or shortcuts are taken that diminish the value of the prototypes. In order to do things right the first time, you should plan for the expense.

9: You are not stuck with the material color that the part is made with

It is fairly easy and affordable to paint or dye most rapid prototyping parts. It does add time to the project because painting or dyeing takes time. Users should be aware that they can get almost any color they need on their part.  A talented technician can also provide almost any surface finish that is needed.

10: Your prototype can be used as a pattern for casting multiple parts

If you need multiple copies of your part, it may be more affordable to only make one additive manufacturing part and then use soft tooling to make copies. This is also a way to get material properties that are not available with any of the additive manufacturing technologies.  In some cases, you can even cast injection molding tooling from a prototype part.

11: The quoted price of the prototype is just part of the total cost of having a prototype made

When looking at cost it is important to calculate the total cost.  When doing rapid prototyping you need to look at the quoted price of having a prototype made, internally or externally, as only one of many costs. Other activities that impact total cost are:  cost of reworking prototypes; shipping/delivery costs; delay in schedule due to build, post processing, and shipping time; time and money spent modifying tests to fit the prototypes shortcomings, time and cost required to deal with prototype failures, etc… 

12: Take some time to learn the strengths and weaknesses of every available technology

Even if you have one particular technology any engineer who needs to do a significant amount of rapid prototyping should invest the time in understanding all of the available technologies. Each has advantages and disadvantages, and if you understand them and you understand what the usage of your prototype will be, you can save yourself and your company a lot of time and money by choosing the proper technology for each prototypes. 

We hope to have some time in the coming months to provide some in depth information on all of the major prototyping technologies, so check this blog for more information.

Rapid Prototyping FAQ

PADT has been providing Rapid Prototyping Services since 1994 to companies around the world, and over that time we have been asked a lot of questions. The lists below present the most Frequently Asked Questions, our FAQ. The list starts with general Rapid Prototyping questions and is followed by questions that are specific to working with the experts at PADT to do your Rapid Prototyping.

If you do not see your specific question, please feel free to contact PADT and we will be happy to answer it directly.

General Rapid Prototyping Questions

What is Rapid Prototyping?

Rapid Prototyping is a manufacturing technology that quickly builds a prototype part. Many different technologies are available that are considered Rapid Prototyping, and many can also be used for production manufacturing. Although most Rapid Prototyping systems use a form of layered additive manufacturing, they can also use a variety of other methods such as high-speed machining, molding, casting, and extruding.

Rapid Prototyping, often called RP, is rapid prototyping when the entire process of going from a computer design to a physical model is faster than more traditional manufacturing technologies. Wikipedia has a good article on the subject.[ http://en.wikipedia.org/wiki/Rapid_prototyping]

What is Rapid Tooling and how is it Different from Rapid Prototyping?

The only difference between Rapid Tooling and Rapid Manufacturing is the end use of the parts produced with the process. Both use rapid prototyping technologies to quickly make a part. But for Rapid Tooling, the part is used in another manufacturing process as a tool.

What is 3D Printing and how is it Different from Rapid Prototyping?

3D Printing refers to a subset of rapid prototyping that goes directly from a 3D computer model to a prototype with very little user interaction other than defining some preferences. The process is designed to be as easy as printing from a computer to paper.

In many ways the name is a marketing label to clearly emphasize the affordability and ease of making prototypes using systems that are labeled as 3D Printers. It is also meant to appeal to a larger, less engineering and manufacturing oriented audience. PADT uses 3D Printing systems as well as Rapid Prototyping and Manufacturing systems.

What are some of the other names for Rapid Prototyping?

3D Printing, layered manufacturing, additive manufacturing, direct digital manufacturing, digital prototyping, digital fabricator, desktop fabricator, desktop manufacturing, desktop prototyping.

People often use the names of various prototyping techniques to refer to rapid prototyping, and even more often the acronyms for those technologies. Examples are Stereolithography or SLA and Fused Deposition Modeling or FDM.

What is Layered Manufacturing and why do most Rapid Prototyping Technologies Use it?

Layered Manufacturing builds parts up, one thin layer at a time. Most traditional manufacturing methods start with a block and remove material, or shapes material using a tool of some kind. Layered manufacturing is often called Additive Manufacturing because it adds material rather than taking it away or molding it.

The best way to visualize layered manufacturing is to think of taking a real part and chopping it into very thin layers. Then stack those layers back up one on top of the other. Layered manufacturing does the chopping in a computer program, and tells a machine how to create each layer.

When and how is Rapid Prototyping used in Product Development?

Rapid prototyping can be used at almost every step in your product development process. At any point where you need a physical part you can benefit from Rapid Prototyping. Examples are:
Conceptualization: concept models, marketing mockups
Initial Design: form, fit, and function testing, visualization
Detail Design: testing, test fixtures, assembly testing, fit, form and function testing.
Production: tooling, mockups for process planning

What are the different types of Rapid Prototyping Technologies and their Advantages and Disadvantages?

Unfortunately there is no one technology that is perfect at everything. The following table is a basic listing of the main advantages and disadvantages.

TECHNOLOGY ADVANTAGE DISADVANTAGE BEST USE
SLA Smooth Accurate Detail Temperature Sensitive, Brittle, Brittles over Time Marketing Models Fit Checks
SLS Durable, Speed on Large Projects Rough Surface, Erratic Accuracy Functional Models
FDM Cost Effective Durable True Plastics Lower Resolution Weak Layer-to-layer Engineering Models Internal Reviews
POLYJET Adjustable Material Properties Speed Fine Layers Weak Material Properties Cost Elastomeric Models Overmold Models
CNC MACHINING Accurate True Materials Long Lead Time Cost Metal Models Precision Work

What is a STL File?

The STL file is a file format developed in the early days of Rapid Prototyping by 3D Systems as a simple and portable format that could be used across CAD systems to define the solid geometry to be made in a Rapid Prototyping machine. It is a triangular facet representation, the surfaces of the solid are modeled as a collection of triangles that share vertices and edges with neighboring triangles. Most CAD tools can output an STL file.

You should also know that there are two types, ASCII (text) and binary. Binary tends to be more compact.

Learn more on Wikipedia. [http://en.wikipedia.org/wiki/STL_file]

My part is about “this” big, how much will it cost to make a prototype of it?

It is very difficult to estimate the cost of a prototype without knowing many different factors. These include the volume of the part, the height in the “up” direction, the process being used, the material being used, and the finishing that is required. The best way to find out the cost is to send a part to PADT for a quote. If you do not have a computer model yet, then sending the basic dimensions and calling our engineers should result in a ball park estimate.

How long does it take to make a Rapid Prototyping Part?

IT can take as little as five minutes and as long as 3 or 4 days depending on the size, the process, and the amount of finishing required. However, most parts can be made within a 24 hour period.

Can I use Rapid Prototyping to make tooling for Injection Molding?

Yes you can. A special process and special materials are required, as is a special mold base. But a low volume injection mold can be made using Rapid Prototyping. PADT can also help find a supplier that can use rapid machining to make molds almost as fast as rapid prototyping.

My buddy has a MakerBot/RepRap/Build-your-Own-3D-Printer. How is that different from these commercial Rapid Prototyping systems?

There has been an explosion of do it yourself RP systems at around 2010-2011. Most of these are based on the fact that the patent for Fused Deposition modeling ran out. The majority of homemade systems, or personal systems, are variations on the systems made for decades by Stratasys. They differ from commercial or industrial systems in two ways: lower cost, and fewer capabilities. In general, the parts made on these systems are not usable for engineering or even visualization models because the material is too soft, the material does not fully harden or bond, there is considerable shrinkage or warping, and the actual precision of the device is low.

What is the most commonly used Rapid Prototyping Technology?

For many years the most commonly used technology is Fused Deposition Modeling. Originally only available from Stratasys, many other providers have adopted the technology. The best way to see how the various technologies stack up is through the Wohlers Report, an annual summary of the industry. [http://wohlersassociates.com]

Is there free software out there that I can use to look at my model before I send it to you? Can I convert a file I made for animation or rendering to a file you can use?

Yes. Meshlab is a tool for dealing with all types of faced data and it works with STL files as well. It can be sued for translating, repair and visualization. [http://meshlab.sourceforge.net/]

MiniMagics is a free STL viewer from Materialise [http://software.materialise.com/minimagics].

PADT’s Rapid Prototyping Services

I need a Quote, How do I get one?

Basically you need to send us a file containing the geometry you want prototyped and let us know what you need your prototype for, or if you already know, what technology you would like us to use. Detailed information can be found on our Rapid Prototyping support page [/support/rapid-prototyping.html]

What Rapid Prototyping Technologies does PADT have in House?

PADT currently has the following Rapid Prototyping technologies in house:

In addition, PADT offers the following related technologies that are often used with Rapid Prototyping:

Which Technology Should I use for my Prototype?

That depends greatly upon the use you have in mind for your prototype and your budget. Each technology has a variety of strengths and weaknesses as well as cost. What sets PADT apart from most Rapid Prototyping service providers is that our engineers have the experience and the expertise to work with you to determine the proper technology for your needs.

What does PADT need to Quote my Rapid Prototyping Job?

At a minimum, an STL or CAD file and a way to contact you. To speed along the process you can provide us with information about any preferred processes or the intended uses for your prototype.

What File Types (formats) does PADT Accept?

The best format to send to PADT is an STL file.

PADT currently has the ability to use the following Native CAD file formats:

  • NX
  • Pro/E or Creo
  • SolidEdge
  • SolidWorks

PADT can also usually work with the following non-native formats:

  • IGES
  • Parasolid
  • SAT (ACIS)
  • STEP

What settings should I use when making an STL file for PADT?

The default settings are generally acceptable for us. We do recommend that you use a “finer” setting if your part is complicated. If we find that your file is not refined enough, our engineers will contact you and let you know how to increase the accuracy for the CAD system you are using.

How do I Send a File to PADT?

We provide multiple methods for sending files to PADT:

Email it to rp@padtinc.com with your contact information.

Put it into a dropbox or secure file sharing location and send us a link via email to rp@padtinc.com.

Upload it to www.padtinc.com/upload

see www.padtinc.com/support/rapid-prototyping.htmlfor details.

I don’t have a CAD file, can you make me one?

Depending on what you need, PADT can quote solid modeling and design services or we can also recommend one of the local companies or individuals that we work with on a regular basis to help people create CAD models of their parts. Please speak with one of our engineers so we can better understand your needs and we will recommend the best course of action.

I don’t know what a CAD file is, or how to get one, what should I do?

Simply contact us at PADT and we will walk you through the whole process. You may also want to visit PADT’s The RP Resource, it contains a wealth of useful information for experienced users and those who are new to the technology.

My design is Confidential, how do I make sure it will stay that way?

PADT has provided prototyping services to over a thousand companies and individuals without a single confidentiality issue. We treat every customer’s part as confidential. If needed, we have a standard 2-way confidentiality agreement that we can sign to provide additional assurance that we will keep your ideas secure.

How precise are the Rapid Prototyping Technologies that PADT offers?

Precision and accuracy are very geometry dependent as well as machine dependent. Below are basic baselines to consider.

TECHNOLOGY ACCURACY
SLA +/-0.005″ plus 0.001″ per inch
SLS +/-0.010″ plus 0.002″ per inch
FDM +/-0.008″ plus 0.001″ per inch
POLYJET +/-0.008″ plus 0.001″ per inch
CNC MACHINING +/-0.003″

Why does PADT have so many different Rapid Prototyping Technologies?

Because each technology has advantages and disadvantages. By having each of the leading technologies, and multiple materials options for each, PADT can meet almost any rapid prototyping need.

The only common technology that PADT does not have is a ZPrinter. Why?

Frankly the parts are too fragile. Although the technology does allow you to print in color, the resulting parts are not robust enough for our customers.

What is the largest part you can make?

The largest part we can make in one run can fit in a 14 x 10 x 10 in volume. But PADT has made parts that are several over six feet long by simply building individual pieces together. We also partner with other service providers that have specialty very large machines.

How small of a part can you make? What is the smallest feature you can replicate?

Small features and thin walls are very geometry dependent as well as machine dependent. Below are basic baselines to consider.

TECHNOLOGY TYPICAL ABSOLUTE BEST
SLA 0.010″ 0.004″
SLS 0.020″ 0.010″
FDM 0.030″ 0.020″
POLYJET 0.010″ 0.002″
CNC MACHINING Material dependent Material dependent

My part needs to look like the final production part, can you do that? Can you paint my part? Can you put a surface finish on it?

Yes, in fact that is a specialty of PADT. Our technicians are true artists that know how to prep, sand, and paint a part so that when they are done, it looks like a final product. We can apply your specified surface finish or paint color.

My product has hard and soft pieces, can you make a prototype with different stiffness? Can you make a flexible part? Can you make a rubber part?

Yes. PADT has multiple technologies available that allow us to make parts that mimic several different soft materials, including over molding on a more rigid part.

My part needs to operate at a high temperature | in water | outside | under pressure | with nasty chemicals | around clumsy people. Can you make me a prototype that will survive?

In most cases we can. Most of our machines have materials that work well with water and pressure. Please contact us with your specifications and we will go over your options with you. For higher temperatures and specific chemicals, we will have to do a little research.

Can I use a prototype as a production part?

Yes. Using parts made on “prototyping” equipment as production parts is becoming more and more common for low volume manufacturing and certain smaller parts that can only be made using an additive manufacturing process.

Can rapid prototyping parts be used for tooling and fixtures?

Yes. In fact, this is one of the fastest growing areas of rapid prototyping: rapid tooling. It is becoming mainstream for many different manufacturing processes because the parts can be made very quickly and, if the proper technology is used, they can be made very strong.

Can you make a part that is clear or a certain color?

Yes. Several of our technologies have a clear material. In addition, several solid material colors are available. And, if needed, PADT can always paint your part any color you need.

I need more than one part, can you make multiple parts? Is there a less expensive way to make copies of my part?

PADT uses soft tooling and prototype injection molding extensively to make multiple copies of a part. Our soft tooling technicians are very experienced and skilled and are able to compete effectively on speed and cost with many other options, including off-shore manufacturing.

Do you do machining, vacuum forming, traditional model making?

In addition to the Rapid Prototyping technologies that PADT has in house, our shop is also equipped with a CNC mill and lathe, a vacuum forming machine, and all of the tools needed to do traditional model making.

Can you make sheet metal prototypes?

This is one of the few prototyping options that PADT does not offer. But if you are looking for a sheet metal prototyping provider, we have several we can recommend.

Can you make metal parts?

We do not offer metal parts at this time unless we use our CNC machining center. But we do partner with several providers that can make metal parts using rapid prototyping technology.

Turkey Feed at PADT, 2012

As we gear up for the holidays we think it is very important to prepare our employees for the coming trials.  As part of that, we have an annual Turkey Feed the Friday before Thanksgiving.  This allows us to spend some time together as a company before the craziness starts, share some food, and be thankful in our own way.

It was a perfect day out there today as we got ready:

turkeyday_2012_2

The food was from Boston Market.  Not great cousin, but hot, on time, and tasty.

We all enjoyed taking some time out of our cubicles and in the sun:

turkeyday_2012_1

We wish all of you a very Happy Thanksgiving and a joyous and peace filled holiday season.

Some Stuff ANSYS Users Should Know about Excel

imageWhat is the software tool that us numerical simulation types use almost as much as ANSYS products, maybe even more?  Most of you will answer Microsoft Excel.  We all use it almost every day for a variety of things. Every time I see someone doing something sophisticated with Excel, I learn something new, a tool I can use to be more efficient. 

For this week’s The Focus posting I will be sharing some stuff in Excel, tips and tricks, that ANSYS users should find useful.  I am using Microsoft Excel 2010 and the assumption is that the reader is a good user of Excel, maybe not an expert, but good.  I have tried to pick things that have a direct impact on user efficiency.  You may already know some or even most of these things, but hopefully you will find some of it useful.  If you have something to share, please add it to the comments.

Take the Time to Setup Tables

I love tables.  I’m always getting made fun of because I always convert what I’m working on into tables.  Why are they so great? 

    • They auto-format
    • They have filtering built in
    • You can refer to the table, columns, rows, and cells in equations with names rather than ranges
    • When you add a formula in a column, it automatically copies it to the whole table (my favorite)
    • It does automatic totals, averages, etc…

Making a table is easy:

    1. Select the columns you want in your table
      1. It is a good idea to have the headers defined
    2. Go to the Insert Tab
    3. Click on Table

image

That give you:

image

Click on the downward facing triangle icons to filter.  Use the options in the Table Tools > Design tab to set the name, remove duplicates, turn on the total row, and change the basic formatting (color).  Once you have played with these for a while, you will find you can not live without them and people will ask you why you use tables so often.

Concatenation

One of the ways that we use Excel is to convert some sort of text data in row/column form into a command, mostly MAPDL commands.  A key to this is the ability to concatenate text strings and the values of cells.  I’ve even seen someone write a NASTRAN to ANSYS translator in Excel.

To do so you create a formula (start with =) and string together the text you want with ampersands: &

As an example, if we want to add a column to the table we used above to create N commands we simply click on any of the cells in the empty column next to our table and enter:

=”n, “&[@N]&”, “&[@X]&”, “&[@[Y ]]&”, “&[@Z]

Because we are using a table, the command uses the column reference [@name] from the tables rather than cells.  In a non table the command would look like:

=”n, “&$A6&”, “&$B6&”, “&$C6&”, “&$D6

Either way you are stringing the values in your cells together with text to make a command:

image

That column can be pasted into a text file, an ANSYS Mechanical code snippet window, or saved to a file.

Text to Columns

After tables, the next most useful feature in Excel for the analyst is the ability to convert the text in a column into multiple columns. This is a lot like the text import window that opens up when you open a text file, but it can be used at any time on any column in your spreadsheet.  To use it, simply select the column you want to convert:

image

Then go to the Data tab and click on “Text to Columns”

image

This will bring up the wizard that steps you through the process:

image

If you are working with a NASTRAN type input file, formatted with fixed columns, you can chose “Fixed Width” here. If not, choose delimited.  Click next.

For fixed, you get a ruler that you can drag the column lines back and forth on till you get what you want. Pretty simple.

For delimited, you get the delimiter screen.  Specify your delimiter here.  In the example, we will use a comma. But it can be spaces, tabs, or any other character. When you specify the delimiter, it shows you how Excel will break it up. 

image

I usually click finish here because the next screen is formatting and I usually play with that once I have the data in Excel.

That is it. Very simple.

image

One thing to note, it converts to columns by overwriting columns to the right. So if you have data in those columns, you should insert enough blank columns before you use this command, so you don’t overwrite anything.

Names

Usually you refer to a cell or a range of cells with the old LetterNumber syntax: A3, B7:NN2145, etc…  That can be a real pain to deal with and it really doesn’t tell you what the data in that range is.  A better way to deal with chunks of information, or critical cells, is to use names. 

Creating names is very easy.  The simplest is to click on the cell or cells you want to name and then type in the name you want in the input box in the upper left corner:

image

Now, if you want to know the max value of those numbers, you can use the formula =max(MyData)

image

If I have a lot of constants I want to define, I can use the “Create from Selection” tool in the Formulas tab:

image

This command brings up a dialog box and you can tell Excel where to grab your names from. Three or Four clicks and you have named parameters instead of cell locations.  This is very useful if you have a group of key parameters you want to use in your calculations.  Now when you look at your formulas, the descriptive name of the parameters are there rather than a reference.

image

Use the Name Manager in the same Formulas tab to view, edit, and delete your names.

Dynamic Range

A related trick for Excel is creating dynamic ranges. What do you do when you name a range and then the amount of data in that range changes? You have to redefine your range.  Nope, you don’t. You can define the range using a formula that changes as the length of the column, or row, changes. 

The name can be defined for a column as: =OFFSET(startCell,0,0,COUNTA(column)-1)

Or for a row: =OFFSET(startCell,0,0,0,COUNTA(row)-1)

This may be the most time saving trick I know in Excel.

You put the formula into the “Define Name” dialog box found on the Formulas tab:

image

Now, no matter how long the column of data is, MyVals will always contain it.  A big time saver.

Relative Reference on Record Macro

How many times have you gotten data in Excel, or imported data into Excel, where you want to make a small change to every line. But you have several thousand lines. If you do a “Record Macro” that doesn’t work because you have to click down to the next line, then run the macro and repeat that over and over again. Wouldn’t it be great if you could simply record a macro with some sort of relative reference. 

For years (maybe decades) I didn’t know you could do that. There is an option under the Developer Tab called “Relative Reference.”  Click that before you record your macro and you are good to go.

image

As an example, take a look at this data. Nodal coordinates on one line, rotations on the second. 

image

I want to grab the rotations, paste them on the same line as the coordinates, delete the rotation line, then move to the next node.

Here is a video that shows the process:

That is all fine and dandy if you have a few dozen lines, but your fingers will get tired CTRL-e’ing that many times.  I quick fix is to go into the macro and add a simple loop.  First we use CountA() to see how many nodes we have, then we loop on that with a for statement:

Sub Macro3()

'

' Macro3 Macro

'

' Keyboard Shortcut: Ctrl+e

'

    cnt = Application.CountA(Range("a:a"))

    For i = 1 To cnt

    ActiveCell.Offset(1, 1).Range("A1:C1").Select

    Selection.Cut

    ActiveCell.Offset(-1, 3).Range("A1").Select

    ActiveSheet.Paste

    ActiveCell.Offset(1, 0).Rows("1:1").EntireRow.Select

    Selection.Delete Shift:=xlUp

    ActiveCell.Select

    Next i

End Sub

Of course you could have done this with *VREAD’s in MAPDL, or python. But sometimes Excel is just faster.

Building CUBE Mini-Clusters in the Clean Room

It is a busy time in the world of CUBE computers. We are building our own new cluster, replacing a couple of older file servers we bought from “those other guys” and building a 128 core mini-cluster for a new CUBE customer.  We ran out of room in the IT cubicle so we looked around and found that PADT’s clean room was not being used.  A few tables and tools later and we had a mini-cluster assembly facility.

CUBE-HVPC-CleanRoom_Asembly

With the orders that customers have told us are on the way before the end of the year, this is going to be a busy area through December.

STL File Tolerance: A Short Explanation of Faceting and Chord Height

When you are making a prototype of a CAD file, you send an STL file to the software that the machine uses to calculate how to build the part.  An STL file is made up of triangles, called facets, that cover the surface of your part.  Imagine having a a real part and a box full of small triangle. You have to paste the triangles all over the surfaces of the part till you have covered every part of the surfaces.

To illustrate what we are talking about lets start with a simple geometry: a block with a hole:

image

When we make an STL file the CAD package breaks the surfaces of the part up into triangles.  The result is something like this:

facet_02

Notice how the surface is made up of triangles.  Triangles are flat so if you don’t have enough, if the triangles are too large, you end up with visibly flat surfaces.  This example shows the default for many CAD tools, and if we make a prototype of it we will see the flat triangle bits, and it will look bad.

To solve this you need to set your tolerance to a smaller number. Each CAD package has a different way of specifying this.  Most of them use some sort of Chord Height tolerance. 

image

image

The chord height is the maximum distance from the actual surface (orange) to the facet face (green).  The smaller the Chord Height, the smaller the facets and the more accurate the curvature of the surface is represented.

Here are some examples of our sample part with different tolerances (the hole has a 2” diameter):

facet_01

0.1” Chord Height

facet_02

0.01” Chord Height

facet_03

0.001” Chord Height

facet_00

0.0001” Chord Height

That last example may be a bit extreme. 

Why not just set your tolerance very small and be done with it?  The problem with that approach is that you force the program to make a ton of triangles, and your STL file gets huge.  So you need to find a nice compromise.  0.001” seems to work well for us and is a good place to start.

if you want to view your STL files, you can usually do so in the software you use to send your parts to your RP machine. If you are using a service provider, you may want to download a tool like Meshlab or MiniMagics.

The PADT Hat Visits ASU’s Formula SAE Team

PADT was honored to be invited to come out and see the Formula SAE car that Arizona State University has been working on as part of their Press Day at the Bondurant School of High Performance Driving.  The PADT Hat came along and got a picture:

ASU-Formula-SAE

We helped out the team last year by printing them an intake manifold and by offering some assistance to the Aero design team.  It was a very nice design and in their first year of competition, they came in 24th out of 80 teams.DSC09593

Congratulations to all the students involved and we are looking forward to working with them in the coming season.