Lulzbot Quality Control
Question
Jeff -
How do you do quality control for 3D printer production? When you produce a printer in house - do you actually test it for print quality at the end with some long and demanding prints, or are you done at the point of in-process checks and short sample print?
I am trying to figure out the quality control requirement for the built machine - in terms of what steps we should be taking - if any - once the machine is completed and ready for printing. It seems to me that the only thing we need to do with the finished machine is to do one test print, and one long and demanding print over the entire print bed. The former tests basic functionality - and the latter would test for any quality control issues not evident in a short test print.
Answer
Marcin,
Good question, there is a lot to it. There's two main areas to QC (and/or QA). The first is incoming products from suppliers. The second is what you are building yourself.
The supply chain is critical for operating and building goods. It is the part woefully underestimated by the kickstarters of the world and why so many of them flop in the end. It is a certainty that some suppliers will deliver late, out of spec, too few, damaged goods, the wrong part, etc. So there has to be good receiving in place that will count and make sure you really got what you ordered. We do this in our shipping/receiving section (where it gets entered into the ERP, with it's shelf location). It then goes over to incoming QC (here too, the shelf movement gets recorded in the ERP). In QC they actually will measure, test, etc. the various products depending upon what it is. If something incoming that has had an issue, we'll often inspect 100%. For instance, we test every single E3D thermistor (not to slight them, they're great, but like I said, it is a certainty they will screw up somehow). Every single rod gets measured for diameter and straightness. I mean *every one*, 100%. Every single metal enclosure gets inspected, and on and on. We try to put the exact specs of what we'll test for (e.g. thickness of spray coating) in the PDF/FreeCAD mechanical drawing. We also have a lot of docs for this, I presume they are on our devel server somewhere, but I'm not certain. I can hunt them down if you want.
Then there is QC of the parts that we're building internally. Here, there is QC done at every stage. Basically if something is moved from one part of the company to another part, it gets QC'd before it is moved. For instance, the cluster will QC 100% of the printed parts before sending them on to production/assembly (there's 3-4% scrap, btw). So there are different areas doing the electronics enclosure and wire harnesses, one doing toolheads, PEM inserts, frame assembly, etc. And they all QC before pushing it up to the next stage. This should basically all be in https://ohai.lulzbot.com to get an idea on the process there. Having written instructions and making sure everyone does everything the exact.same.way. is critical too.
Ok, so we've had QC on incoming, QC on sub assemblies, then the whole printer gets assembled for final calibration. We have four people doing this stage, typically. The docs for it are here: https://ohai.lulzbot.com/project/calibration-mini2/mini-2/
In sum, it does about a 20 minute burn in, where it just moves XYZ progressively faster. The toolhead has been tested before this stage once already, during toolhead asssembly, so the test here is a second test of it. It then prints the octopus, which ships with the printer. Every printer we've shipped since 2011 has included an octopus that was printed on the machine. :) We used to do a + cross print of 100mm x 100m to confirm that was accurate, but we stopped doing that long ago as it never failed. We have a department called MER (Manufacturing Engineering and Repair) that looks at any issues that come up during assembly.
We also send a packing list and QA doc with the printer. The QA doc is signed by the person that does final calibration and the packing list is signed by the person that packs the box.
https://download.lulzbot.com/Mini/2.0.4/production_docs/Packing_List_Print_Shop.pdf https://download.lulzbot.com/Mini/2.0.4/production_docs/Quality_Assurance_Record_Print_Shop.pdf https://ohai.lulzbot.com/project/packaging-mini2/mini-2/
Also, you have to make sure that what gets *delivered* will work well too. If it is perfectly built in your lab, then improperly packed and shipped, it will get destroyed. Shipping companies wreck and lose everything, it is quite amazing. So we send our final shipping box with printer to a shipping lab in Colorado and also to FedEx's lab in Memphis where they do drop tests, vibration tests, etc. and we get a report for that. For FedEx, this also helps us settle any insurance dispute (impossible, tbh) by showing the box we're using is good enough for the printer. So if it arrives damaged, they are responsible.
Our QC is far better than pretty much everyone else out there, by the way (not doing a sales job here, just sayin'). For instance, we get far fewer returns on Amazon than other 3d printer companies.
We have a lot of docs in general about this here (also rsync'able, if you do that):
https://devel.alephobjects.com/ao/manufacturing/
The QC of printed parts is in a tab here:
We do electronics testing at a lab along the Colorado Front Range, PDF report here ($15k ?): https://download.lulzbot.com/Mini/2.0.4/production_docs/compliance/FINAL_103436795LAX-003
The Mini also did UL testing, which takes forever and was probably $25k+ (just guessing, I didn't do it).
I tried to track down the main receiving QC docs, but didn't see them. I attached a couple NCMR (Non-Conforming Materials Report) docs that are from our internal wiki. If there's anything in particular you're looking for, let me know.
Happy hacking,
-Jeff
