Best procedure to set the Z height

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Best procedure to set the Z height

Postby edk » 2013-Jan-Sun-16-Jan

Is there a good online guide or does anyone have any advice for setting the Z height of the extruder?

It is the one piece that seems to go out of alignment every other print or so, and I fumble around trying to dial it in with no real process to follow.
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Best procedure to set the Z height

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Re: Best procedure to set the Z height

Postby wd5gnr » 2013-Jan-Sun-17-Jan

I have found that once I have it set right it stays pretty well set unless I fiddle with something. How is your bed mounted?

Here's what I do. I do have a feeler gauge but you can use a piece of paper.

Heat everything up. Things expand when hot. Make sure the X axis is flat. If you can push on either side and feel give it is not flat. Move the Z nuts on the rods until it is flat.

Move the head about center. Drop the head. Keep in mind that the z home position will cause the head to stop even if it isn't in the right place. So once you are at the stops if the head is still too high, loosen the Z stop bolt and rehome it. Keep doing that until you are actually in contact (barely) with the bed and the paper. At this point you should not be able to pull the paper out.

Now turn the Z stop bolt to tighten until you just hear the stop switch click. Then reverse it until it clicks again. The paper should still be snug. Now move the head up .1mm at a time.. See if you can drag the paper out. It should feel like it is pulling at you a little but not require force. If you don't feel drag you went too far. If it is hard, you haven't gone far enough. When the paper can slip out, tighten the Z stop bolt until you just hear a click. Rehome. You may have to make tiny adjustments (without the click) to get it just right.

Now go check each corner of the bed. You may have to level the bed but try not to adjust the Z stop anymore. Then go check the center. You may have to do this more than once.

The other thing I have been thinking about is setting the Z stop to like 2mm above the glass (measured with the feelers) and then offsetting the Z axis in software which would be pretty easy to control. You still need level for that and so far I am ok with what I have.

Good luck. Stick with it. If you are like me, you will start out with pretty good prints. Then they will get terrible as you experiment. Then when you are ready to despair they will get really good ;-)
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Re: Best procedure to set the Z height

Postby Michele31415 » 2013-Jan-Mon-15-Jan

I'll second that. I use the "pull the paper" method and it works fine. It shouldn't be loose but it shouldn't require more than a light pull. You can verify if it's OK by looking at the perimeter trace when a print starts. If it's laying down a round strip of plastic, you're too high. If it's laying down a flat smear, too low. Anywhere between those two should work. I don't think it's super-critical.
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Re: Best procedure to set the Z height

Postby plexus » 2013-Jan-Mon-16-Jan

For more repeatability, i use a 0.02" steel feeler. i found this to be the best size for setting Z clearance. i use it like the paper and set it for a little bit of drag on the feeler when i remove it. unlike paper a steel feeler will deform quite a bit less and there is a known thickness, unlike with paper. i also have spring loaded my Z bolt stop so that there is less slop and backlash also i machined the end of the bolt down to point for better repeatability. my next mod is going to be to replace the 6-32 bolt with a machine bolt with a finer thread.
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Re: Best procedure to set the Z height

Postby wd5gnr » 2013-Jan-Mon-16-Jan

Yep I use a feeler also. I have thought about actually making the limit switch work different so that it detects electrical contact instead of making the leaf move because that's the "slop" in the measurement.
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Re: Best procedure to set the Z height

Postby plexus » 2013-Jan-Mon-16-Jan

That has been on my mind too. definitely the leaf switch is a source of error. i was thinking optical.
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Re: Best procedure to set the Z height

Postby wd5gnr » 2013-Jan-Mon-19-Jan

Yes optical is OK until it gets plastic gunk. Thought Hall effect but afraid that might have too much variability. Reed switch would be easy. A simple contact point would also work. Reed switch. Hmmm.
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Re: Best procedure to set the Z height

Postby plexus » 2013-Jan-Mon-21-Jan

wd5gnr wrote:Yes optical is OK until it gets plastic gunk. Thought Hall effect but afraid that might have too much variability. Reed switch would be easy. A simple contact point would also work. Reed switch. Hmmm.


A reed switch will rely on magnetic flux to trip. ideally the switch should be a mechanical actuation. thats why i think optical is the way to go. or mechanical like a better solution than the stock switch. tonight i was fighting with the Z stop switch so i think some kind of upgrade here is going to happen sooner than later with my printer.
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Re: Best procedure to set the Z height

Postby nepaholic » 2013-Jan-Tue-01-Jan

wow guys this is some very good information.
An admin might sticky that thread?!

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