Newbie TPU advice

Hi all,

I'm pretty new to 3D printing and so far have just been using PLA. I have an item that I'd like to print, but it needs to be in TPU. I searched online for some settings (which seemed contradictory), and tested them, but they seemed to leave holes in the finished prints.

I decided to start from scratch (my PLA settings), look at the filament suppliers recommendations, and changed the heats to match them. The resulting print is in the photo I've attached. Whats' confusing me is that the top half (above the locking tabs, about 15mm from the sides) is pretty much perfect (to me), but below has gaps and is not smooth. Up to that point, support is needed, so I'm wondering if this has anything to do with the issues? It will take time to print the support, so maybe the piece is cooling down too much before the next layer?

I'm using a Prusa i3 Mk1 and the following settings:

• Bed: 30 degrees (layer 1) then off
• Nozzle: 230 degrees (1st layer) then 220 degrees
• 40mm/s (2400 mm/min) speed

*EDIT: Remaining settings

• Extrusion Width: 0.45mm (0.4mm nozzle)
• Layer Height: 0.2mm
• Top Solid Layers: 6
• Bottom Solid Layers: 6
• Perimiters: 4
• First Layer Height: 100%
• First Layer Width: 100%
• First Layer Speed: 60%
• Infill: Grid at 20%
• Fan Speed: Layer 1 - 0 | All other layers 100%
• Support Infill: 30%
• Support Inflation Distance: 2mm
• Horizontal Separation: 0.4mm
• Support pillar resolution: 3mm
• Max overhang: 45 degrees
• Retraction Distance: 1.5mm
• Extra Restart Distance: 0.0mm
• Retraction Vertical Lift: 0.0mm
• Retraction Speed: 1800.0mm/min (30mm/s)
• Coast Distance:0.20mm
• Wipe Distance:2.00mm

I'm looking for any advice to get the bottom half of the print to be as good a quality as the top.

Thanks for your time,

Darren

Edited 1 time(s). Last edit at 03/10/2018 07:19AM by DarrenLines.

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My Thingiverse

You shouldn't 't use retraction with TPU or other flex filament. Printing with support means lots of retractions or blobs/strings.
You could modify the part and add your own support structure. That works better most of the times.

edit: maybe you can redesign the part, so it lays flat on the print bed? It is flex filament and will bend to the final shape, if done right.

Edited 1 time(s). Last edit at 03/10/2018 02:29AM by o_lampe.

Thanks, I'll have a go with retraction turned off, see what happens.

I've never tried designing my own support, so will look in to that. I don't think printing flat would be an option as there is a handle piece on the rear that you can't see in the photo. This is the Thingiverse link.

Thanks for the advice on the no retraction. I did a test print of the Kitten statue as 25mm high and it came out amazing compared to my previous attempt. The image is as it came off the bed (photo a bit blurry round the face, sorry). So thought I'd go for it with the goggle protector. It came out great, loads of stringing, but structurally sound. I used the same settings as before with generated supports (upped to 4mm), but turned off the retraction. The photo is post-cleanup.

Thanks again, very happy with the result.