I've read conflicting information on use of supports for TPU printed items. Mainly the fact that due to the flexible nature of TPU, the supports seemingly end up merging themselves into the actual printed part making them difficult, if not impossible to remove without ruining the printed item.

I have a challenging part I need to print for my Acrobrat frame which has a number of overhangs and voids that needs to have supporting material underneath and within them if I want to end up with a successful print.

The item in question is a bumper bar and is the 6th image for the Thingiverse item below (the bumper bar which fully encases the motor mounts). If you view that part in the Thingiview 3D viewer and have a look at it from different angles you will see what I mean. There are upper and lower platforms with a void between that go over the carbon parts of of the frame for the motor mounts, and there is a void in the bar between the two ends that fits over the carbon crossbar of the Acrobrat frame.

https://www.thingiverse.com/thing:3044444



The summary description and print settings say to use supports, but with no indication of how or where to place them, which doesn't really help a newbie like me.

Can anyone who has printed TPU with supporting material before please offer me some advice and/or upload a screenshot of a sliced image of this part in their slicing software which shows where they would ideally put supports, and how to do it in such a way so that they can be removed without too many problems (i.e. what print settings to use).

That particular part would be a nightmare to get the support material out of the arm end pockets. I had downloaded the wrong one first it did not have the "softmount" at the end of the file name. That one would not be too tough. The overhang along the front edge should be easy to clear the support material from. TPU is so soft it cuts really well with a scalpel or xacto knife. But getting it out of the version you want is going to be a problem whatever the material.

I clicked "automatic supports" in Simplify3D and it did this , the second shot is with the top half not done yet so you can see inside.





You may want to consider splitting it in half and printing a top and bottom and glue the 2 halves together with some E6000.

Scott

Thanks Scott. Some people suggest using a different material for the supports (i.e. PLA) but that would require an additional extruder and I'm not ready to spend another $300 (just yet) on an MMU2S head for my i3. I'm not sure I want to split the print into two halves and then glue it back together, but I guess it's a last resort option. Maybe I'll settle for trying one of the other two bumper bars without the integrated softmounts so there is no enclosed pockets to deal with.

If I select to use automatic supports "everywhere" in the PrusaSlicer software, below is what it gives me at each significant layer, so it seems to be a bit more liberal with the supports than Simplify3D, especially where it also seems to build support skirts around the item for no apparent good reason that I can see. I could potentially try to do away with the denser support material interface (dark green) and try to get away with just using the more sparse main support material (light green). Of course I can also play around with the support pattern and spacing or do away with the auto generated supports and just add manual supports in relevant places to reduce the amount of removal work afterwards. It's just knowing the best place to start because this is quite a large print so I could end up with quite a lot of wasted TPU if I keep getting it wrong. It's all a bit of minefield

  

Hey Snow

I cut the model so only a bit of one end is left. This way you could try several approaches to see if it works without wasting a lot of material.



I saved it as an stl , let me know if you want it. Or maybe you could do the same in Fusion.

Scott

(14-Aug-2019, 08:50 PM)Scott_M Wrote: I cut the model so only a bit of one end is left. This way you could try several approaches to see if it works without wasting a lot of material.

I saved it as an stl , let me know if you want it. Or maybe you could do the same in Fusion.

That's a great suggestion  I don't know why I didn't think of that myself

I think I can chop things up like that in PrusaSlicer. Let me check and see. If I can't then I'll get you to send me the STL file.

I would rotate the print so that the empty area where the carbon goes faces up.  Then all the supports would be on the outer face of the print and you can cut them off.  Not perfect, but way better than trying to get the tpu supports out from inside the middle of the print.

(14-Aug-2019, 09:44 PM)5zero7rc Wrote: I would rotate the print so that the empty area where the carbon goes faces up.  Then all the supports would be on the outer face of the print and you can cut them off.  Not perfect, but way better than trying to get the tpu supports out from inside the middle of the print.

That is a good idea and worth a try. But be sure and use a brim to give it more surface area to stick to the bed. The other issue is that it is pretty flimsy that way and may move around and give a sloppy print by the time you get to the top. But worth a try for sure. On the small segment test piece.

Scott

(14-Aug-2019, 10:08 PM)Scott_M Wrote: That is a good idea and worth a try. But be sure and use a brim to give it more surface area to stick to the bed. The other issue is that it is pretty flimsy that way and may move around and give a sloppy print by the time you get to the top. But worth a try for sure. On the small segment test piece.

Scott

Exactly what I was thinking and in fact, I'd try it without supports.  I might even try running it myself

Thanks for all the help guys. Much appreciated. It at least gives me a few options to try. I think I now just have to knuckle down with a trial & error exercise and start wasting some TPU

@RENO - I can't see how this could be printed without any supports because those sections are all 90 degree overhangs covering a considerable area, so surely the TPU will just sag and the whole print will end up ruined. Obviously I have no prior experience with TPU so I'm just going on what the laws of physics say. If you do manage to do it successfully then please let us know and show us the result because if it does work then I'm all game for giving it a go on my printer as well 

(14-Aug-2019, 08:50 PM)Scott_M Wrote: I cut the model so only a bit of one end is left. This way you could try several approaches to see if it works without wasting a lot of material.

I saved it as an stl , let me know if you want it. Or maybe you could do the same in Fusion.

(14-Aug-2019, 09:43 PM)SnowLeopardFPV Wrote: I think I can chop things up like that in PrusaSlicer. Let me check and see. If I can't then I'll get you to send me the STL file.

I just tried it and yes, I was able to cut off the bit I want to do some testing with in PrusaSlicer and export it as a new STL So I'll use this smaller piece for my trial & error exercises.

I would try flipping the oreintation. 90 degrees. So that the inside openning of the support bar is facing up. This would only require supports on the parts front edge which would be easily removed.

Like this



I'll try to get one sliced up for you tonight to share a pic

Printed vertically like this will save you big. Supports @ 75 deg. and only touching build plate.



Any internal overhangs will be a bridge and should print without issues on a decently tuned printer.

Due to real life getting in the way I had to put this on hold for a couple of months so I've only just got back to it. To recap, and as suggested, I've been printing a test section of the actual item in an upright orientation so that the void in the middle doesn't need any supports.

   

I've spent quite a number of hours of trial and error with various slicer settings but I still haven't yet managed to get it right. Probably not helped by the fact that this item is a fairly complex design with some thin walls. The walls just come out looking a mess, the holes are laughable, and the supports just end up becoming part of the print itself which are either difficult or near impossible to remove without ruining the item. I think I'm probably going to have to go back to the drawing board and start printing a few things in TPU which are a much simpler design and that require no supports until I at least have some experience with printing TPU.

Photos of the car crash are below. This was actually the best one of the bunch LOL. Total disaster.

I've just come across this guy's video on YouTube. He has some stunning looking TPU items that he's printed on a Monoprice Select Mini V2 using a bowden tube extruder, so I will be extremely disappointed if I can't get similar results on my direct drive Prusa i3.

I'll try and translate the Cura settings he's using to PrusaSlicer and see if it makes any different to my prints.



Rather than trying to print that complex Acrobrat bumper bar, I'm going to try to printing some of the front camera cage bumpers (HERE) which are a far simpler design and don't need any supports. I'll report back with my results once I've had a go.