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jeremy-gillick

Smushed Printed Pins

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I was printing pins for the iPhone gear case thing (http://www.thingiverse.com/thing:65810) and for the small pins the print head would extrude plastic and push it around as a glob. This caused those pins to finish as pretty much balls of PLA.

 

This is with the Normal quality print mode on my UM2. I also went into custom settings and set the time per layer to 10 seconds and with the same result.

 

What else can I change to get a better result?

 

photo 1

photo 2

photo 4

photo 3

 

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Did you print all the pins at the same time, or one at a time? Printing them all at the same time will give the plastic time to cool better - with very tiny parts, setting a long layer cooling time is counter-prodcutive, as it keeps the head over the print for a long time, transferring heat back into the print, instead of letting it cool. Printing multiple parts at once gives the head somewhere else to go while the print is cooling.

 

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You should definetly use Brim! Helps a lot with these small parts, so that they stick to the build platform better.

If you print them all at once, you may just have to place some more than you actually need, until they get enough time to cool.

I don't know if the "cool head lift" feature could be of use here?

 

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There is a sudden improvement in ability to stick to the glass around 40C and above that threshold there is no difference. Use 50C to be safe. Raw data from experiments are here:

http://umforum.ultimaker.com/index.php?/topic/3404-printing-on-glass/

For very large parts there is another threshold (glass temp) to avoid lifting/curling if you can't avoid it for any other method. This threshold is around 75C but it is better to improve stickiness than to keep the bottom layers above the glass temp as it will be very soft and easily damaged and printing overhangs will come out bad on the bottom 10mm of the part because they never fully cool.

 

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Thanks for all the input! Having it print all the pins at once definitely helped. There was still a bit of deformity and strings between the parts, but nothing preventing them from being used. That being the case, I'm going to print them a few more times trying the other suggestions (brim and fans) to see how much better I can get them. Thanks!

 

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deformity and strings between the parts,

 

Deformity might be caused by glass too hot.

Strings: Did you have retraction enabled? You can see if retraction is working in slice view because the blue "non extruding" moves/lines have a vertical line at the start if there is retraction (the vertical lines doesn't indicate Z movement - it is just a symbolic way of showing retraction).

If retraction is enabled and you still have stringing, try reducing print speed (reduces pressure in nozzle) and reduce nozzle temp (increases viscosity of plastic - more like toothpaste than honey).

Some stringing tests:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

 

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Deformity might be caused by glass too hot.

Strings: Did you have retraction enabled?

 

I'm pretty sure I had retraction on. I'll try adjusting the speed and nozzle temp.

I'll also try doing it on a cold bed with a layer of glue.

Thanks for all the advice and input!

 

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I'm pretty sure I had retraction on

Um - okay - you need to take better notes or something or have better work flow. I never overwrite a gcode file that was used to print something. In cura you can always choose "load profile from gcode..." (profile means settings) then look to see if retraction was enabled (although there are 6 settings for this).

Even better, load the gcode as the model and look at it in layer view and see EXACTLY where retraction occurred for every move. You can then pick a string in real life and look at that exact move in layer view and see if there is that vertical line that indicates retraction. You can also look at

 

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I'll also try doing it on a cold bed with a layer of glue.

Um - I think you want at least 40C - I forget - did you read my post #7 above? I did a lot of experiments and I have to always refer to that to remember what works.

 

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