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Success printing POM / Acetal

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Hi,

I just want to share my success printing Acetal/POM on a prusa i3 clone. I have had that roll for over one year and thought it was unprintable due to near to zero adhesion to anything and extreme shrinkage. I finally succeeded printing on clean borrosillicate glass.

The trick is to keep the base layer as close as possible to the melting temperature during the whole print (if the base layer is close to liquid, it'll stick to the borrosillicate glass). After some trials I succeeded with 160°C for the hotbed and 230°C for the hotend AND using cooling fans. The cooling fast are 2 12cm 12V fans (like the ones you find in a computer case) running at 6V and located around 40cm from each side of the printer. Acetal is totally transparent when above melting temperature, and becomes opaque below, the 2 first printing layers should be totally transparent, the following layers should be slightly opaque on the outside, around the 20th layer the whole layer should be opaque.

Here are some more infos:

  • Standard 20x20cm MK2 PCB heatbed
  • Hotbed is driven by a separate optocoupler/mosfet circuit, power hot hotbed cables have a 4mm^2 cross section.
  • Hotbed running at 20V (on the 12V input), beware it'll pump close to 20Amps -> 400W (I use 18V/30A switching supply which is asjustable from 14-21V)
  • Firmware has been modified to increase the max bed temperature (200°C).
  • At those temperatures, the difference between the center and sides is significant, I wouldn't recommend using more than a 10x10cm zone at the center of the hotbed.
  • Test print is an extruder gear which is ~2cm diameter and ~2cm high, the larger you go the harder it gets

Note: watch for ventillation or wear a full face respirator mask, printing acetal releases toxic fumes (acetaldehyde) which is highly irritant, however printing it at 230°C is quite ok (250°C is not)

David.

Comments deleted.

fuck off you show off

Tourette's syndrome?

This is very impressive. thanks for sharing, I have tried so many times without success, that i gave up.
Now i'll try again.
Thanks for sharing!

Wow 160. degree. THnaks for sharing!
Using FR4 on that temperature will be borderline (depending on the exact material type) Does anyone know if the aluminium heatbed versions can handle these temperatures better?

very extremely interesting! thanks for sharing!

wow. isnt it bad to run a hot bed that high? all the ones i have cant go above 110c

Ideally FR4 PCBs should be kept under 130°C, so I'm pushing it a little high indeed. But since the PCB hotbed is cheap, I don't mind taking the risk and I have 2 spares lying around. The biggest issue is heating uniformity... I'm thinking about using a copper plate between the PCB and the glass.

I've always wondered how this material performed but chose to use IGUS Tribo instead. It processes well and stick to kapton or glass but its strength works for bushings, not so much for small gears.

I guess its time to get a spool of POM and avoid that high cost Tribo... Thanks.
http://tinyurl.com/j2n33hk
http://tinyurl.com/hh34v78
http://tinyurl.com/zyy4xo7

Don't forget even though I got some success it's still a challenge printing POM, a few °C off and it'll be a disaster (melting or adhsion issue), the larger you go, the harder it gets (mostly because hotbed is not uniform). For small gears however it seems to be great, I have used mostly Nylon until now for that purpose.

Excellent, thank you for sharing

Good job ... where did you get the filament?

I got it from China : ShenZhen ChenYue Technology (www [dot] cycnsz [dot] com), I had (and still have) the plan to import and sell filament in Thailand this was one of the suppliers I sampled.

WOW this is impressive,
do u have any photo of the result?

Here are some pics (sorry for the low res, I saved them from my facebook):

http://www.ominix.com/pom1.jpg
http://www.ominix.com/pom2.jpg
http://www.ominix.com/pom3.jpg
http://www.ominix.com/pom4.jpg
http://www.ominix.com/pom5.jpg

The last picture with the 2 pieces: the one on left is Acetal/POM, the one on right is Polypropylene which is also a nightmare to print (printed at 215/135 with stronger cooling fans).

The hotbed temperature is crucial, a few °C can make the difference between success and failure and I realized how important temperature uniformity is, with this setup I have up to 30°C difference between the center and the sides.

On the first picture, you may notice the bottom layers are more translucid, in face they are slightly past the melting point of POM, which makes it pretty sticky, once below the melting point it will not stick anymore.

I'm using an industrial thermometer and a function that relises on integrals to control my temperature to be as uniform as possible. I have 0.2 degree oscillations and I'm very satisfied.
To keep the pad uniformly heated I suggest u to cover it with uniform resistor, u can search how to fix the heater of the posterior car glass to have a tutorial or simply buy a new pad (I prefer home made parts)
Let me know what way u chose.
Bye

Thanks!
Preetty awesome!