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Setting Up 3 Point Leveling

Posted by 2DMatt 
Setting Up 3 Point Leveling
December 25, 2016 11:16AM
Hello Everyone!

I'm setting up three point leveling on my new heated bed. What arraignment should I use for the adjustment points in the bed; does it have to be an isosceles triangle? I was planning on putting the one point on the back of the bed, but if I put the adjustment in the middle the heater wires will be in the way. Can I offset that point to make an oblique triangle, or should I offset all three adjustment points to keep an isosceles triangle?

Any advice will be appreciated!

Thanks,
matt
Re: Setting Up 3 Point Leveling
December 25, 2016 12:49PM
Two of the screws should be along one axis, either X or Y. The third screw can be anywhere along the opposite edge of the plate, but putting it in the center is usually convenient and doesn't leave one corner further from support than the other. As you have discovered, placement is a practical issue that requires consideration of the construction of the printer, possible interferences, and ease of access.

All leveling and zeroing adjustments should be done at print temperatures- nozzle and bed!

You really only need to adjust two of the screws if you use one as a reference. The reference screw should be one of the two that are aligned parallel to one axis. Let's assume that's the X axis. You'll move the extruder nozzle close to the reference screw, adjust either the screw or the nozzle until it just catches a piece of paper, then move the nozzle close to the other screw along the X axis, and adjust the screw until the nozzle just catches a piece of paper. Now the pitch in the X axis is set. Any adjustment made to the third screw will not affect the pitch in the X axis. Move the nozzle to the opposite edge of the bed and adjust the third screw (the "roll" screw) until the nozzle just catches a piece of paper. In theory, the bed is now parallel to the XY plane (as defined by the guide rails) in the printer. You may have to go back and forth on the first adjustment a couple times depending on where the screws are located and where you placed the nozzle when making adjustments - if they are at the corners of the bed, one adjustment should do the trick. If they are closer to the center of the bed and you put the nozzle at the corner of the bed, you may have to go back and forth a couple times to ensure the pitch is adjusted correctly. Once the pitch is good, the roll adjustment is dead simple and has absolutely no effect on the pitch.

Since the slicers tend to place prints near the center of the bed, you might want to move the nozzle to the center and set the zero point there. That way if your bed isn't perfectly flat (few are), you'll at least have the center of the bed level enough that your print will probably stick.

You can place the pitch adjustment screws along the Y axis and the roll screw on the opposite side of the bed. It makes no difference.

By definition, leveling a surface requires that that surface be reasonably flat. If you don't have a pretty darned close to flat surface, good luck to you.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Setting Up 3 Point Leveling
December 25, 2016 01:26PM
You can place the screws anywhere. In theory, you could have all 3 in the center of the bed, but the edges of the bed would be harder to adjust. The larger the triangle the easier fine adjustment is.

Assuming your bed could not bow under its own weight the screws can be anywhere. 2 screws define a straight line between the 2 screws, and the 3rd defines a 2D plane (eg, it defines the slope of the plane). As DD says, 2 adjusting screws and a fixed point also works well but make sure you can adjust your Z endstop easily.
Re: Setting Up 3 Point Leveling
December 25, 2016 06:47PM
A little less complex answer. Back/ rear, right rear, front center. Make the hardest rear corner to get at the reference screw.
Re: Setting Up 3 Point Leveling
December 25, 2016 07:24PM
Thank you all for your responses!

My mistake was thinking that the back adjustment would be the reference point.

I bought a aluminum tooling plate, so I shouldn't have to worry about the plate being uneven or sagging under it's own weight. At least, I hope so. smiling smiley

Thanks again!
matt

Edited 1 time(s). Last edit at 12/25/2016 07:25PM by 2DMatt.
Re: Setting Up 3 Point Leveling
December 27, 2016 05:18PM
I had new Y-carriage and heated bed support lasered in acrylic for mine. I put tabs just outside the heater outline so the adjusters could be placed on the top/accessible side of the bed, and use locking nuts on all three. Two of the adjusters are along the Y axis, the third in the middle of the opposite side, largely as described above. It's proved very handy. Locknuts are especially good. I found M4 threaded knurled nuts about 16mm in diameter for these.
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