Ultimaker TPU95A not printing overhangs

[Max_Rackstraw 0]

Hello, first post here on this forum and just to get it out of the way... I'm new to 3D printing! So I have recently started to use an ultimaker 2 extended+ for my personal use. It prints PLA to a very high standard however I'm struggling to get it to print my new TPU 95A filament. As I understand it, this filament is inherently difficult to print, especially on Bowden setups... however I believe that ultimaker's support webpage for TPU 95A (https://support.ultimaker.com/hc/en-us/articles/360011940440-How-to-print-with-Ultimaker-TPU-95A) does state that the ultimaker 2 extended+ can print TPU and is supported. I understand that you need low print speeds and highly optimised retraction settings. Due to the flexible properties of this material I would assume its also difficult to achieve what I'm after with prints involving overhangs since the material will just flop down rather than maintain a straight line following the nozzle's path. I also believe half of the trouble I am having is due to the model I am actually trying to print. It seems like it would benefit from support structures however when sliced with support structures enabled, they are generated in lots of places where they simply are not required, and would be almost impossible to remove without damaging the print itself. I will include the .stl file i am trying to print along with the curaproject, a PNG with the overhang area concerned highlighted and PNG's of my slicer settings. Also please note that the slicer settings I am using are the result of many test prints and I have been able to significantly improve my prints from the initial attempt..... any suggestions, explanations or pointers are much appreciated and further details can be provided if I have missed anything necessary to this post. 

 

p.s. I am not sure if this matters that much but I am using the gcode flavour "Marlin" instead of the default "Ultimaker 2" in order to gain access to lots of slicer settings such as retraction distance and speed that are not available in the flavour "Ultimaker 2".

OSIRIS-SESSION-30.stl UM2E_OSIRIS-SESSION-30.3mf

[gr5 2,224]

So what is the problem?  Is it stringing too much (you mentioned retraction a lot which helps prevent stringing).  Or is it underextruding?  (underextrusion is the most common problem with soft filaments) Or does printing fail completely? (also common with soft filaments - the filament can get crumpled up in the feeder).

 

Regarding "too much support", look into "support blocker" feature of cura.  There are great videos on youtube and other explanations if you google how to use the support blocker feature.  It makes it very easy to block support in any one spot of your model.

[gr5 2,224]

Regarding gcode flavor, if you use the ultimaker2 flavor then you can control retraction live while it's printing and experiment.  You can do this in the TUNE menu.  You can also create a custom filament type on the printer (e.g. TPU95) and it can have custom settings for a few things including retraction distance (and speed I think?), nozzle temp, bed temp, fan speed.

 

I actually have a few parts that I print a lot in 2 different materials (nGen and PLA) but I only have one gcode file for both as I select the material on the printer.

[Max_Rackstraw 0]

ah yeah... strangely I wrote my post and then forgot to outline the exact problem... never mind and my mistake. What's going on is when that overhanging part of the model gets printed, or when that part's first layer is printed, it doesn't actually form anything. The material flops down and tangles itself up into a ball rather than forming a line from the rest of the model. When the print has finished, some of the overhang is there however the lower part which was printed first with no layers below it is just a mess and completely unusable. As for stringing, its not really a problem with this model since the nozzle never leaves the walls of the print. Sometimes I get underextrusion however I think I've got that under control now after altering temps, speed, material flow and cleaning out the nozzle (it cant help that my nozzle I'm using is a good 3 or 4 years old and... very well used...). I've just now had a look at the "support blocker" feature of cura and I've got a new gcode file to try using this feature, I think using support and this feature is probably the best solution to my overhang problem. I think i will start using the "ultimaker 2" gcode flavour once again to be able to tune the print live, that was a useful feature. Thanks for your recommendation it has been very useful so far and ill get back to you in a couple days or so when I've got another print done using these new settings.

[gr5 2,224]

I'd still like to see a picture of the problem please.

[geert_2 558]

As I understand it, the overhangs are not formed well, but sag into spaghetti instead? Is that correct? You need a support structure to print overhangs and big roofs, they can not print in plain air without sagging.

 

So you need to enable support in the slicer. Or otherwise, design custom supports into your model in CAD. This is what I usually do, so I have more control over the support. This will prevent it from sagging. After printing, remove the supports, and clean up the model.

 

Or you could redesign the model, so there are no more steep overhangs. (If its functionality allows redesigning.)

 

 

A few of the custom support concepts I used during the years:

 

Table with custom supports:

 

After printing. Notice how the supports did sag, but that doesn't matter, but the table itself is nice and straight:

 

After removing the supports and a little bit of cleaning, it looks like this. For reference: all panels are 1mm thick in this model: