1 Topic by heisenburgers (edited by heisenburgers 2015-03-05 05:39:33)

  • heisenburgers
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Topic: Problem with nozzle hitting print.

For whatever reason, my Press' print head often hits the print when transitioning between islands. I'm printing at 230c, extrusion mult of 1.0, 105 steps per mm on the extruder, extruder trimpot voltage set to 1.51v~. I don't think its a problem with over extruding.

I did notice on significant overhangs, the print starts curling up, if that happens and the head transitions through that area, it hits the print pretty hard. I am not sure if that is the same thing that is happening on areas without overhangs that the print head is hitting.

It is also possible that this only happens during the first few cm of the print.

Anyone have any experience with this?

2 Reply by trayracing

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Re: Problem with nozzle hitting print.

Yes, I've had curling too. reorienting or adding a web to the model helps. Also I found the ABS shipped with the printer curled a bit more than Microcenter's "Toner Plastics" ABS. At least it did until I dried the SD plastic in the oven.  They both still curl, but it was enough to keep from unhorsing my print from the bed.

Others have suggested putting a fan next to the open printer to cool the part, but for me this chills the bed enough to release the part. (My heater bed is seriously weak, but SD silently closed the request to fix that.)

3 Reply by Skyblue

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Re: Problem with nozzle hitting print.

trayracing wrote:

Yes, I've had curling too. reorienting or adding a web to the model helps. Also I found the ABS shipped with the printer curled a bit more than Microcenter's "Toner Plastics" ABS. At least it did until I dried the SD plastic in the oven.  They both still curl, but it was enough to keep from unhorsing my print from the bed.

Others have suggested putting a fan next to the open printer to cool the part, but for me this chills the bed enough to release the part. (My heater bed is seriously weak, but SD silently closed the request to fix that.)

If you are using Repeiter, in the Slic3r settings, enable z-lift.  Then set amount from 1.mm to .50mm.  There will probably be instances on some models where curling happens, slow down print, raise temp to 235, bed to 95.  Check box that says lift only crossing perimeters.

4 Reply by heisenburgers

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Re: Problem with nozzle hitting print.

I am noticing the nozzle seems to be pressing (no pun intended) the bed down after the print has started. This problem seems to go away after the nozzle gets far enough away from the bed. I can see the bed flex down a bit (damn cantilever design, never again) when the nozzle makes it way on top of previously printed layers vs in mid air. This is starting to make me think its an over extrusion problem, but the a lot of the prints are turning out in great quality, which makes me worried I'll lose that if I turn down the extrusion mult.

5 Reply by trayracing

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Re: Problem with nozzle hitting print.

heisenburgers wrote:

I can see the bed flex down a bit (damn cantilever design, never again) when the nozzle makes it way on top of previously printed layers vs in mid air.

Something in the system has to give if the nozzle is commanded into an obstacle. A little flex is better than destroying your print. Or printer. The Z axis has the least acceleration, so that's the best place to put a little compliance. Flex in X & Y it would cause ringing unless you cranked the acceleration way down, which would slow printing.

(That said, I think my bed has progressed from flex to flop, which is not good.)