Avoiding an obstacle on the print bed

I recently upgraded the heat bed on my RepRapPro Huxley with a cold glass bed. It is held in place with four binder clips, one in each corner. Every time a print is about to start, the nozzle strikes the clip closest to the home position. Even though this acts as a decent nozzle wipe, I'd like to know how I can avoid this obstacle in Slic3r before each print.

Adding "G1 Z3 F5000" in the Start G-code lifts the nozzle once, only to lower it again as the print begins, thus hitting the clip.

Unfortunately, moving this clip is not an option right now.

I avoid such problems by defining the origin in the middle of the bed instead of a corner.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> I avoid such problems by defining the origin in
> the middle of the bed instead of a corner.


That would make sense, but I would still have to dodge the clip after all the axes find their end-stops. This clip is only a few centimeters away from the homing position.

Edited 1 time(s). Last edit at 09/17/2013 01:46PM by Physics_Dude.

I just moved my clip to the right. The rear clips and the front right one are near the corners. The left front clip is a few centimeters to the right. I almost never print that close to the edge and when I do, I reposition the clips to where they will work best. Your host software should give you some indication of where the safe locations should be.

Physics_Dude Wrote:
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> Unfortunately, moving this clip is not an option
> right now.


Why is that?

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Waitaki 3D Printer

waitaki Wrote:
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>
> Why is that?

It used to be because of a 1mm spacer to go between the glass and PCB heat bed for protecting its thermister. This spacer was designed in an"X" shape with one end in each corner of the print bed. The binder clips would otherwise warp the PCB if not placed individually in each corner. You can kind of see the outline of it in the picture from before.

Right now however, I am printing a 135mm² by 1mm spacer to replace this. It is being printed with zero top and bottom horizontal shells and a 25% honeycomb infill. This will allow me to move the clips anywhere along the perimeter.

Edited 1 time(s). Last edit at 09/17/2013 09:38PM by Physics_Dude.

I put a dab of silicone in the 4 corners or the heat bed, topped with 4 small discs of greaseproof paper, then lowered the glass onto it (pressed down lightly) - left overnight then put the clips on.

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Waitaki 3D Printer

I see your problem which could be mine as well.
Problem is that Z axes is positioned first at first level layer and then x,y with z at low level.
It would be nice that Slic3r did make this different and moved x,y first or made it selectable.

Change the first move in your Gode to let z move in sync with x,y like this example with layerheight 0.2:

original:
G0 Z0.200 F1200.000 E-1.50000 ; set first layer level layer and retract
G0 X82.339 Y65.690; move to first skirt point

changed code
G0 F1200.000 E-1.50000 ; retract before first layer
G0 X82.339 Y65.690 F1200.000 z0.200; move to first skirt point

X,Y,Z are then moved at same time to first position and starts printing. It assumes z was positioned high parked after homing.
Works on my homebuild CNC/3D machine at least.
Good luck
justcurious.