0.0mm or 0.1mm

All of the calibration guides I've seen suggest using a piece of paper (0.1mm) as a feeler gauge.

This would mean that when you issue X0 Y0 Z0 it will actually be X0 Y0 Z0.1 should I be subtracting out that 0.1mm so that the hotend is actually at Z=0?

Seems to me that if I don't the Slicer will make a 0.2mm layer 1 at 0.3mm in height.

Maybe your right but it's going to fall to 0.0

Zeroing the printer is usually not exact. In most printers there is some vertical movement in the extruder nozzle position, and the bed surface is not perfectly flat, so there's no exact position for the zero point. One way you could zero the bed exactly, would be to form a circuit between the nozzle and the bed surface and watch for the point where the nozzle just contacts the bed. Then you'd have exactly zero at that specific point on the bed surface. Move across the bed and all bets are off. Unless you build your printer so it prints on a granite slab and the mechanism is so precisely made that it doesn't deviate in the Z axis as it moves, that's about as good as it can get.

Edited 1 time(s). Last edit at 03/23/2016 06:21PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
WZ9V
All of the calibration guides I've seen suggest using a piece of paper (0.1mm) as a feeler gauge.

This would mean that when you issue X0 Y0 Z0 it will actually be X0 Y0 Z0.1 should I be subtracting out that 0.1mm so that the hotend is actually at Z=0?

Seems to me that if I don't the Slicer will make a 0.2mm layer 1 at 0.3mm in height.

You are correct. I use a piece of stock that is 19mm to set my zero, it could just as easily be 12.3765mm or any arbitrary number. I have fine jog buttons setup so that I can move .01mm at a step. I move the head to where I think is Z19 (or a little below) and then jog up until I can slide the shim between the head and the bed. If you don't have other means (tool and work probe etc etc) this is the best way to set Z0 in a mill too, jog UP until a shim clears, avoids running into the work or part. Avoids chipped tools, or in our case dented nozzles or beds. I then issue G92 Z19.0, setting the Z at that point to be 19.0 When I measure the thickness of that first layer it's what I expect it to be from the program. If the shim piece is different thickness you use that number instead of 19.

Practically it does not matter. You can use 1mm thick feeler gauge to level the bed. Then you use experimentation to find a gap for an optimal adhesion. So if you are using 0.2mm layer height you might have your nozzle 0.1mm or 0.12mm or 0.18mm or 0.3mm away from the bed in order to achieve proper adhesion that allows removal of the part without it warping while printing. And this even depends on the part's geometry. Some warp prone parts might need that first layer gap really small whereas other parts would end up being very hard to remove using the same first layer gap.

Quote
Koko76
You are correct. I use a piece of stock that is 19mm to set my zero, it could just as easily be 12.3765mm or any arbitrary number. I have fine jog buttons setup so that I can move .01mm at a step. I move the head to where I think is Z19 (or a little below) and then jog up until I can slide the shim between the head and the bed. If you don't have other means (tool and work probe etc etc) this is the best way to set Z0 in a mill too, jog UP until a shim clears, avoids running into the work or part. Avoids chipped tools, or in our case dented nozzles or beds. I then issue G92 Z19.0, setting the Z at that point to be 19.0 When I measure the thickness of that first layer it's what I expect it to be from the program. If the shim piece is different thickness you use that number instead of 19.

That's a nice way of approaching the problem. It reminds me of the way I was taught to use a microscope - lower the lens close to the slide while looking from the side, then focus by moving away from the glass.