TPE - bridging?

I finally got my extruder running with TPE so now I'm trying to dial in the settings to get good prints. I'm doing ok on perimeters, but infill tends to break up and I'm getting next to no bridging ability at all. If anyone could pass me some tips on what settings are working for them that would be great!

Flex stuff needs very low speeds to start with and are not really know for their good bridging capabilities.
I have seen recommendations as low as 15mm/s for good print results...
For the bridging I would suggest to get the temp as low as possible without loosing adhesion and to use a bit more extrusion with even lower speeds.
You can't really stretch that stuff during bridging like ABS for example.

Well, it's interesting stuff for sure. I'm happy that the new extruder setup has been running TPE pretty much non-stop today without any clogs or stalls, and I've managed to get my first useful print with it, a vibration damper that goes under the printer foot. I'm really liking the TPE, it has a warm rubbery feel that would be excellent for handles and grips for tools, is soft enough to use for gaskets and dampers, but tough enough to take a lot of abuse. It sticks easily to the bed with no sign of warping, and has great layer to layer adhesion at temperatures as low as 175C. I haven't found the lower limit yet, I couldn't quite believe what I was seeing. The downside is I still haven't found good settings for the infill, and I'm getting next to no bridging.

For posterity, my first complete print with TPE, failed top layers not withstanding. The white skirt is TPU from the previous print that I hadn't purged.



I did a few more test cylinders that gradually improved and increased my confidence, so I celebrated with something suitably stretchy with which to impress the family. I'm not sure they appreciated the full wonder of the moment.



This was the last print I did before I realised that I didn't need a brim. It's a shame I didn't catch on just a bit sooner, because getting that brim off those curly tentacles was a right pain in the derrière.

Finally, a demonstration of the remarkable bridging capabilities, or lack thereof. The direction of bridging was from bottom to top of the photo, and as far as I could see the filament broke immediately the head moved off the supported area.

Interesting.
Sounds like you need to increase the bridge flow ratio.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

I have only done a few sample pieces of flex material but here are the settings that worked on my oldie:
Print speed: 20mm/s
Perimeters 10mm/s
Infill 20mm/s
Bridging 8mm/s, flow to 120%
Layer height 0.35mm using a .7mm nozzle

Some samples could have been printed faster in the end but I found the best way is to start to slow and work your way up to the max the roll of filament supports properly.
Similar story for the temp.
I start really low, so that I can just extrude by hand.
Some samll test pieces to check the layer adhesion and the temp is increased until the layers won't split when pushing a cutting knife in them.
Of course, if you increase the print speed you need to check the temps again so you won't loose the layer adhesion.

For complicated prints and/or materials I actually prefer to use the volumetric extrusion settings in Slic3r as it keeps the pressur inside the nozzle almost constant.
So retraction only if really required for the part, although I noticed some people even use retraction when printing a cube...

Ah, that's interesting. I'm currently printing at 15mm/s - so using 8 for the bridging would be a big difference. I'll have to give that a go along with the extra flow. I've increased layer thickness to .32 (from .24) and infill width to 0.7 in the hope that a bigger filament might hold together better. It may have made a small improvement, but the infill is still basically a mess. The stuff just seems to be very sticky and tends to ball up at the slightest chance. I'm using a .4 nozzle and I've been wondering if this wouldn't be better suited to a larger bore. I originally tried with a .3, and that didn't go very well at all! I have some drills on order, at the moment I have nothing between 0.4mm and 1mm.

Thanks to you both for the suggestions.

Slicer outputs bridging at nozzle diameter, and uses layer height at the bridge location to accommodate that specific nozzle height, with the lines at or just over nozzle width apart. So changing the layer height should not matter.

If the lines are too thin they will snap, too fat and they sag. You could try a LOT bigger flow ratio to see if it will bridge without breaking.

The first bridge line may not have enough pressure and may fail - but that's another issue...

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

OK, that makes sense. I was confusing the two issues of bad infill and poor bridging.

For the samples that caused massive problems I found that using a very thin layer height improved the mess quite a bit.
Keep in mind that with flex you can't rely on normal layer bonding.
You always have to force the new filament onto the previous layer.
That is why lower temps often work so much better here as the stuff is not coming out like fairy floss.
Try just to print a single layer onto the bed at different layer heights.
When you start to loose bed adhesion divide the current layer height by two and round to the next 2 digits.
E.g.: At 0.43mm layer height it starts peeling off.
0.43 / 2 = 0.215, rouded up to 0.22mm.

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JamesK
OK, that makes sense. I was confusing the two issues of bad infill and poor bridging.

Actually, they are directly related in a couple of ways.
- Sparse infill with Slicer - like Rectilinear - has layers that only touch where they cross - and this is a form of bridging - but worse. If done too fast, or too narrow it will break, especially when crossing other strands. The same thing happens with support. The answer is to extrude wider, slower, or both. This of course can cause big pressure fluctuations.

- Slic3r uses the bridging extrusion rate for the first solid layer over sparse infill. If there is enough flow then the first layer over can be entirely closed. I often use bridge flow of 1.42.

Edit: Do you think a fan might be needed with this material?

Edited 1 time(s). Last edit at 02/09/2016 01:14AM by Paul Wanamaker.

Thanks again guys, you've given me more options to explore and think about. At some point I'll try and grab some time to take a methodical approach to testing this (so little time, so much interesting stuff to explore!).

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When you start to loose bed adhesion...

Funny you should say that - after having no problems with bed adhesion on Sunday, last night's prints were coming unstuck. And the difference? I had increased the layer heights. I shall try going the other way again.

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Do you think a fan might be needed with this material?

My first prints were done at the hot end of the temperature range and everything looked very melty, so at that point I added quite high fan settings and I've been running with that ever since. One of the things I should probably try is reducing it in case I'm using too much cooling now that I'm using much lower hotend temperatures.

Progress, with increased extrusion width for the infill (and corresponding reduced speed in autospeed mode) I was able to get well formed infill. This made a big difference to print quality and I was able to print the rest of the feet for the printer - the first one must have been a bit of a fluke.

It may be a while before I get to look more at the bridging as now the feet are done I need to swap print heads back so that I can print pla and abs again. Sure would be nice to have dual extruders hooked up.