For simple shapes like containers, it’s relatively easy to clean them and to be fairly certain that no cross contamination occurred. For more complex equipment such as atomizers, screeners, and printers it can consume over a week to thoroughly clean them. You need to worry about each and every nook and cranny; including things that the equipment manufacturer probably never thought you would see – vacuum lines, flanges, and gas supply lines to name a few. Oftentimes what looks clean (such as the inside of this atomization tower), will miserably fail the ‘white glove’ test as seen here.
Printers pose an ever larger challenge. We have yet to see one that was designed with switching material systems in mind (imagine having to take a tire off to get at the oil filter). They contain horizontal surfaces, ribbed cables, blind holes. So now there is not only a contamination concern, but also a safety hazard, but that’s a topic for another newsletter.
We are in the process of developing more defined cleaning recommendations for printers, but the first recommendation is to dedicate a printer to a particular alloy system if possible. If that can’t be followed we can recommend some strategies based on our experience.
A customer was having trouble getting their powder to spread (yet another topic!). We took some used powder out of their system, analyzed it, and found long fibers in the powder. We found that they were using a paint brush to perform intermediate cleaning and those fibers found their way into the powder. This was one of the reasons that we developed our hopper shipping container system for our larger customers – you simply hook it up to your printer and never have to touch the powder.
The solution to contamination issues comes down to a rigorous set of Standard Operating Procedures (SOPs). These SOP’s need to cover everything from what type of rags you use to where and when the cleaning needs to be done. If you’re talking with a powder supplier, they should be proud to share their cleanliness practices and contamination mitigation efforts with you – if not, you might want to think about looking elsewhere!
In addition to robust SOP’s, we also dedicate equipment to certain alloys, so there is very minimal risk. Again, for printing shops, we realize that this is oftentimes not a practical solution – give us a call to discuss your situation and we’ll be happy to relate some of our experiences and recommendations.