What started as a fun little 3D Printing project for my daughter’s birthday party activities, turned into a test run for using 100% “old” powder without curling or other sintering issues. NICE!
I had been talking with 3D Chimera about how to manipulate the laser offset and hatch patterns to achieve stronger and more durable SLS prints for my company’s inventory, and things were going well. I did have a slight size issue, which led to a few of my prints fusing together and the interconnected parts where too tight to turn easily.
So I took this fun print job as an opportunity to test out variation on the laser hatch and perimeter offset values in the “Custom” section of Sintratec Central.
The good thing is, my modified values have the same perimeter value as the standard Sintratec Central presets, and they were able to sinter 100% old powder without any hint of curling. I ran this test with my usual 173.8 deg surface temp, with a 515 laser speed. But the hatch and outline values were altered, as stated in this video:
Just to reiterate, Sintratec HIGHLY recommends you use a 70%-30% ratio of “new” to “old” powder to ensure proper sintering and structural integrity. Whenever I use this ratio, I experience outstanding sintering success with the kit, and it’s truly great. But after a few dozen prints, you slowly fill a storage bottle with super old powder, that likely has seen the inside of the oven for a bunch of times. It doesn’t sinter well, and it builds up over time.
Don’t get me wrong, I don’t let this old powder go to waste. When I fill up my trays, I use this old powder for the left side tray, and the very bottom 8mm of the right tray. Then I use good powder on top of that low layer on the right side. The kit is designed to sinter plastic on a bed of powder, so that first pile of powder on the left side isn’t going to see the light of day. When the machine is “preparing powder,” that is just sliding over 26 layers of right-side powder on top of the already 5-9mm of powder that was there when I filled the left side tray. So why not use that old powder… it’s just there to support the first sintered layer, which could be as much as 15mm from the left tray.
The innovation of this “fun” print was, I used 100% “old” powder in conjunction with modified laser hatch and perimeter settings to make it sinter properly.
This is a huge advancement. Whenever I want to do quick and dirty prototyping, I’ll use these values in the future to save some money on the PA12 supply. Kewl!