TPU clumping in Fuse 1

We have experienced clumping of the TPU powder in the Fuse 1 printer. The debris catcher has been removed. Would love tips on how to agitate the material automatically inside the hopper, as we are planning to run prints overnight, where we won’t be able to manually stir the powder.

Can you show us some photos of what the lumping of the material looks like?

Unfortunately, I’m not able to get pictures of the clumping because it happens at the bottom of the hopper, underneath the bulk powder. I’ve attached a picture that may be representative of what’s happening (but more on what’s happening in the picture in a moment). The clumping results in a cavity in the powder and prevents the material from dropping down into the doser (not across the entire doser, but one side of it) and results in a shortfeed. When I agitate the powder manually, I can feel it drop down as the clumping tension breaks, and then the recoater gets powder again. The clumping happens very frequently, I would say every 20 minutes and sometimes as little as 5 minutes, if I don’t manually stir the powder in the hopper.

Today, we’re trying a stirring device we fashioned (a PTFE stirring rod attached to a motor). So far there hasn’t been a short-feed in the first 60 minutes of the print, but I can see the material forming a channel around the stirring rod, which may be happening underneath as well. That’s the piture I’ve attached.

Hi @Impressio ,
We’re sorry to hear about your clumping issues. If you haven’t yet read this article, check out our TPU Fuse 1 Guide this excerpt gives a good method to avoid clumping:

Due to the Fuse 1’s sensitivity to powder jams, only fill the Fuse 1 hopper with slightly more powder than the amount required for an upcoming print job as indicated by Preform. The weight of additional powder can lead to powder clumping and subsequent underdosing. Print smaller jobs with fewer parts whenever possible to help prevent jams.

TPU 90A Powder requires stirring to ensure that it flows properly. Use the recommended stirring rod or other wooden rod to agitate the powder in the hopper before printing.

As you can see in the article, ultimately a yard stick and short prints are the best solution to prevent clumping. Note that a Fuse 1+ does have a built in agitator to remove this possibility all together.

If you’re still struggling after integrating these steps, we definitely encourage you to reach out to our services team here, so they can get more detailed info about your specific workflow.

Good luck and please keep us posted!
Diana

Thank you for reaching out, Diana. Unfortunately, I’ve already reached out to the service team, and they directed me here to the forums.

I have already reviewed the guide for printing TPU on a Fuse 1 and have taken the steps listed. I removed the debris catcher from the bottom of the hopper, which did help a little bit, but we still get frequent clumping in the hopper, such that I am unable to leave the printer alone for even 30 minutes before we get a shortfeed. I rarely have more than 3 kg of material in the hopper for a print (we’re currently doing builds which PreForm has told me uses about 2.5 kg of material). We are located in Denver, which is very dry, so we are definitely below the suggested level as being below 50% humidity for TPU.

We are a small company, so we are unable to afford the Fuse 1+, which is much more expensive. I’m assuming that the Fuse 1+ dosing assembly is not compatible with the Fuse 1, is that correct?

Shorter prints, unfortunately, won’t be sustainable for the project we’re working on, especially if the printer needs to be tended to constantly. Ultimately, we’re trying to find a way to agitate the powder automatically while it’s in the hopper. Has anyone else tried this in the past?

If I were you I would keep working on some sort of agitator. Maybe rather than an vertical auger type device you could try a paddle wheel of sorts that rotates slowly above where the grate would be. Something like that.

I don’t print TPU material but I had similar problems with lumping with PA12 material because I have higher humidity here. I solved the problem by making a vibrating shaker - I made a similar device for my sandblasters. I’m not at the machine right now to send you photos, but if I remember, I’ll take a photo and send it to you how I solved it.