# Bed Plane Compensation

Posted by stevelup
 Bed Plane Compensation March 02, 2014 04:08AM Registered: 10 years ago Posts: 65
Hi Folks,

Got my machine finished yesterday and have to say my first two prints (snowman and coat hook of course) look great.

Took quite a bit of tinkering and hair pulling at first, but got there in the end.

Couple of questions.

1) What's the optimum height of the nozzle above the bed?
2) Bed Plane Compensation - doesn't seem to do anything!

I've done this three times now:-

M561
M556 S100 X0 Y0 Z0
G1 X60 Y20
G92 Z0
G30 P0
G1 X60 Y180
G30 P1
G1 X180 Y180
G30 P2
G1 X180 Y20
G30 P3

My Z values were 0.00, 0.70, 2.29, 1.10

I then run 'circle.g' and the ormerod scribes a perfect circle, except the back half of it is nowhere near the bed, and I don't see the Z motor move once!

What am I doing wrong?

Edited 1 time(s). Last edit at 03/02/2014 04:10AM by stevelup.
 Re: Bed Plane Compensation March 02, 2014 04:18AM Registered: 10 years ago Posts: 36
Hi Steve,

You need the 'S' after your G30 P3, ie 'G30 P3 S'. I believe the 'S' makes the Ormerod do the calculations.

Hth

Mike
 Re: Bed Plane Compensation March 02, 2014 04:28AM Registered: 10 years ago Posts: 65
D'oh... Many thanks!
 Re: Bed Plane Compensation March 02, 2014 04:36AM Registered: 10 years ago Posts: 1,230
Quote
stevelup
1) What's the optimum height of the nozzle above the bed?

The optimum height is zero, to let the nozzle touch the glass surface - when you start e.g. a 0.24 layer print the nozzle is raised 0.24 from your G92 Z0 set point
..or to put it another way, the distance from glass surface to your nozzle zero point will be added to the first layer

Erik
 Re: Bed Plane Compensation March 02, 2014 04:48AM Registered: 10 years ago Posts: 65
Perfect - thanks!
 Re: Bed Plane Compensation March 02, 2014 11:23AM Registered: 10 years ago Posts: 65
Can someone advise if the following homing strategy is sound?

1) Home X and Y

2) Manually home Z using the same target position I used for the first bed compensation setting.

3) Run job ensuring any G28 commands are commented out

I'm getting inconsistent results. Sometimes the nozzle goes so low that it rips the Kapton tape, other times it's too high and doesn't adhere.

Every now and then, 100% perfect. I don't really understand where the variance is coming from...
 Re: Bed Plane Compensation March 02, 2014 11:27AM Registered: 10 years ago Posts: 14,681
After everything else, it's a good ideas to put the nozzle at X=100 Y=100 and then manually z-home it by lowering the nozzle to the bed and doing G92 Z0. Then print.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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