Installing a Metal 3D Printer: Part 5 (Housekeeping)

Download all 5 parts of this series as a single PDF here.

This is my final post in our 5 part series discussing things we learned installing a metal 3D printer (specifically, a laser powder bed fusion machine). If you haven’t already done so, please read the previous posts using the links below.

If you prefer, you can register for a webinar to be held on July 26, 2017 @ 2pm EDT (US) where I will be summarizing all 5 parts of this blog series. Register by clicking on the image below:

Housekeeping may seem too minor a thing to dedicate a post to, but when it comes to metal 3D printing, this is arguably the single most important thing to do on a regular basis once the equipment, facilities, safety and environmental considerations are addressed up front. In this post, I list some of the activities specific to our Concept Laser MLab Cusing R machine that we do on a routine basis as indicative of the kinds of things that one needs to set aside time to do, in order to maintain a safe working environment. In this post, I break down the housekeeping into the 3D printer, the wet separator and the filter change.

1. The 3D Printer

All 3D printers need to be routinely cleaned, but for powder based metal 3D printers, this needs to be done after every build. Three steps need to be performed during cleaning of the printer:

  • Powder Retrieval: After the build, the powder is either still in the dose/feed chamber or not. All powder that is not in the dose chamber needs to be brushed to the overflow chamber for recycling. While it is possible to vacuum this powder, that is not recommended since it results in greater loss of powder and also increases the burden on cleaning the vacuum and creating wet waste.
  • Process Chamber Cleaning: The process chamber after a build gets covered with fine combustion particles (soot) that need to be wiped away, as shown in Figure 1. The recommendation is to do this cleaning using lint-free or clean room wipes moistened with an ammonia based cleaner like Windex Original.
  • Lens Cleaning: Special lens cleaning wipes are to be used to clean the protective lens that separates the chamber from the laser. Standard lens cleaning wipes can be used for this, in a gentle single-pass movement.

It is important to wear appropriate PPE and also NOT contaminate the lens. Improper or irregular cleaning will result in soot particles interfering in subsequent builds. Soot particles can occasionally seen in subsequent builds especially when the inert gas and the ventilator (circulating fan) are turned on – this is more likely to happen if the chamber is not routinely and properly cleaned.

Figure 1. Post-build cleaning of the 3D printer and required materials

2. Wet Separator

The wet separator (vacuum) sucks up stray powder and suspends it in a water column. The metal particles will descend to the bottom of the water column (as shown in Figure 2) and need to be routinely cleaned out. This cleaning procedure is recommended daily for reactive metals – failing this, the metal particles will weld themselves to the metal container and prove to be very difficult to scrape out. For non-reactive metals, a daily flush may be excessive (since this will add to the cost in terms of labor and disposal) and a weekly routine may be preferable for a wet separator that serves 1-2 machines.

To reduce the water needed to flush out the powder sludge at the bottom, a standard pump sprayer is very effective. Further reduction in water usage and disposal can be achieved by a filtration device such as the one developed by the folks at Kinetic Filtration.

Figure 2. Cleaning a wet separator

 

3. Filter Change

Filters need to be changed periodically as shown in Figure 3. A video below (set to start at the 2:58 mark) shows how the filter change is performed for our MLab, for a non-reactive metal, so I shall not describe the procedure further. A reactive metal alloy filter needs to be stored in water to passivate it at all times, even through disposal. Other OEMs recommend sand and other materials, so it is important to follow the specific instructions provided by your supplier for passivation.

Figure 3. Removing, passivating and disposing the filter

 

Summary

Good housekeeping for metal 3D printing is vital and more than just aesthetic – there is a modest chance that failing to follow your supplier’s instructions on one or more of the items above will result in a safety incident. This is especially true for reactive alloys, where filter changes are recommended after each build and wet separator clean on a daily basis.

Disclaimers

  • This is intended to supplement the supplier training you must receive before using the equipment and not meant to replace it – in case of conflicting information, your supplier’s training and equipment requirements override any discussion here. PADT and the author assume no legal responsibilities for any decisions or actions taken by the readers of this document.
  • My personal experience derives specifically from the use of Laser-based metal 3D printing tools, specifically Concept Laser’s MLab Cusing R equipment. I expect majority of this information to be of use to users of other laser based powder bed fusion metal systems and to a lesser extent to Electron Beam systems, but have no personal experience to vouch for this.

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Final Thoughts

This concludes my 5-part post on what we learned installing a metal 3D printer. If you have any thoughts on the content or would like to discuss this subject further, please let me know by messaging me on LinkedIn or by sending an email to info@padtinc.com, citing this blog post. I will be happy to include any suggestions in my posts with due credit.

Thank you for reading – I hope this has added value to the discussion on safely and effectively advancing metal 3D printing technology.

Installing a Metal 3D Printer: Part 2 (Facilities)

Download all 5 parts of this series as a single PDF here.

This is part 2 of a 5-part series on the lessons we learned installing our first Metal 3D printer, a Concept Laser MLab Cusing R. Please read the first post if you haven’t already, where I listed all the different equipment (in addition to the 3D printer itself) one needs to run this process.

A reminder at the outset: these posts are meant to be informative only, to give you a sense of what questions you need to ask and get answers to. Specific requirements will vary by equipment and your site specific needs.

1. Electrical

Most metal 3D printers, including the Concept Laser machines, are manufactured in Europe and have electrical requirements that differ from what most American machine shops are setup for (which is the scope of this section). If you have installed 230 V European equipment before and know what L-N and PE stand for and how they differ between European and American systems, you can skip this section. If not, read on.

There are two key items here one needs to be aware of: first of course is the fact that these pieces of equipment typically run on single-phase 230 V (3-phase 400V for the very large machines like Concept Laser’s XLine 2000R) as opposed to the standard 110V. Secondly, and this is easier to miss, European electrical connections have one “hot” line (L) for a single-phase, one Neutral line (N) and one Protected Earth (PE) – this is different from the US standard where you have 2 “hot” lines and 1 ground. The reason for these differences and how to address them electrically is beyond the scope of this post (or my understanding), but the main point is to have an electrician familiar with European codes review this early on. A dedicated custom transformer for all your European 230V equipment is one solution, and the one we employed here at PADT, as shown in Figure 1. (I rarely give shout-outs, but our experience with Fargo Electric on procuring a custom, affordable transformer was one of the best transactions I have ever had.)

electrical-european
Fig 1. Dedicated transformer in use for PADT’s metal 3D printer. Also note the L-N-PE connections and the plugs used on the different equipment.

2. Inert Gas

nitrogen
Fig 2. Nitrogen line running to our MLab

Laser melting of powder metals needs to be conducted in an inert atmosphere. Most suppliers recommend using Argon for Aluminum and Titanium alloys, but that Nitrogen is fine for the non-reactive alloys such as steel, Inconel and Cobalt-Chrome alloys. At PADT, we leveraged our existing nitrogen generator and added an additional line running to our metal 3D printer (Figure 2). Before doing this, you need to add up all the consumption rates for the machines (at their peaks) to make sure you don’t exceed the generator’s capabilities. It is a good idea to demarcate space for Argon cylinders should you need them at a later stage.

3. ESD Mats or Floors (for Reactive Metals)

As we will see in the next blog post in this series, avoiding charge dissipation into metal powder is a key safety requirement for operating metal 3D printers – this is achieved through a range of strategies like ESD (Electro Static Discharge) armbands, grounding ElgiloyHastelloy C4 wires etc. If you plan on running reactive metals and especially if you expect to have many operators, an ESD coated floor with ESD shoes or boot straps, along with an ESD meter (like the one Honeywell installed at their facility) is a good strategy. From personal experience with ESD boot straps, I know these can be fickle in passing an ESD meter test. Connecting the ESD meter to the entryway door so entry is only provided after passing the test is one way to ensure only those with functioning straps enter the workspace. For those without this strategy, grounded ESD mats and ESD armbands connected to the machine are also alternative strategies which I will discuss in more detail in the next post. From a facilities standpoint, if you do want to enable ESD coated floors, boot straps and ESD meters, you need to plan this early, which is why I have included it here.

4. Water

Fig 3. Water column in a wet separator – this has to be cleaned out and replenished frequently

Access to running water is essential for cleaning the wet separator (vacuum) that is used for sucking up fugitive powder – ideally the water source is near your liquid waste storage so you can clean out the wet separator and pour the powder-contaminated water into storage. Alternatively, you can also use a garden sprayer for smaller machines, like we do at PADT. Fill up the sprayer with water and use it to rinse out the wet separator right on top of the waste storage bin.

Another reason you need access to water is to passivate the filter. While not all OEMs recommend water passivation, Concept Laser does and we find it to be very user friendly, as I demonstrate in the video below (video starts 2:58 in, which is when I discuss filter passivation with water).

 5. Access Control

It is important to restrict access to your metal AM laboratory through badge scanning or key pad entry to those who are trained on using the machine, and your building facilities team. It also helps to provide as much visibility through glass windows so that folks that are entering can study what activity is in progress before entering.

Fig 4. Door lock with combination to restrict access, window to provide visibility

6. Structure & Ventilation

Here I move into the subjective (gray area) domain – I request anyone who has more specific information on these matters to kindly share them with me for inclusion in this post (with due credit). I have heard anecdotally that in some places the city has required the supplier to install blast walls and other explosion resistant infrastructure – yet others have not required such infrastructure (including ours). I am not well informed in this space and can only emphasize the need to have these discussions out in the open in the early stage of planning your facility and ask your city’s building safety person if the walls you have planned (or already have installed) are adequate or not – this is likely to be a function of the amount and reactivity of the powder you are handling, proximity to vulnerable areas, human occupancy and other concerns. With regard to ventilation, the more open the space the better (these machines can heat up a small, closed room) – at the same time the space needs to be sealed off from the elements including wind. I know this too is a subjective matter, so discussions with city representatives are the best way to go.

Please send any of your comments, questions or suggestions for improvement to info@padtinc.com, citing this blog post, or connect with me on LinkedIn.

And now go on to PART 3a (SAFETY)

Acknowledgements

Special thanks to Gregg Rand at PADT, Martin Perez (City of Phoenix) and Dave Tallman (City of Tempe), and engineers at Concept Laser Inc.