Bed levelling...

Ok. So after an hour or so fiddling about, using the 3mm nuts as jack-screws, I have my bed as level as I can get it, the four points read 0, 0, 0, 0.9 on the z axis,, seems one corner - the bottom right hand one just will not go lower without upsetting the others.

I've set those figures in my setbed.g file.

Does that sound reasonable?


I'm running the Ormaxis.g gile now.

That sounds not too bad, but it also suggests that you have a slight twist between the Y-axis rods.

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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].

That's possible, I'll check that out thanks,

Quote
Davek0974
That's possible, I'll check that out thanks,

You could IMHO save yourself a lot of time, trouble and hair on your head doing this and that in this order:

This:
Sagging MDF, the Q & D fix that anyone can do
[forums.reprap.org]

That:
While we wait on a functional auto-probing...
[forums.reprap.org]

Erik

I'd do as Erik says - the mdf is pretty poor for constraining anything. As dc42 says, one reason for the slope could be that the two Y bars are twisted vertically relative to each other - another might be clamping (if you have the bottom left corner clamped, but not the lower right, then the glass may be not sitting straight on the bed, or may be bowed down on the three clamped corners with a crown in the centre, and the lower right at a similar height to the crown -you can test this by probing 100,100)

Ray

Edited 1 time(s). Last edit at 03/02/2014 05:20PM by rayhicks.

Quote
rayhicks
I'd do as Erik says - the mdf is pretty poor for constraining anything. As dc42 says, one reason for the slope could be that the two Y bars are twisted vertically relative to each other - another might be clamping (if you have the bottom left corner clamped, but not the lower right, then the glass may be not sitting straight on the bed, or may be bowed down on the three clamped corners with a crown in the centre, and the lower right at a similar height to the crown -you can test this by probing 100,100)

Ray

The odd thing is that the readings are perfect on the bar nearest the Y axis frame, its the front right corner that is out and as both bars are supported by the same acrylic I cant see how they could be twisted, this corner has the machine support foot on it so if i twisted the acrylic surely it would put the readings on rear bar out??

I am going hunting tonight to find the error of my ways, I'll likely also mod the bed so it has a true three-point mount, maybe swap the heat spreader down to create a stable base and trim the two outer corners off the mdf as they do not serve a purpose and could possibly be pulling my bed out of alignment.

I'm also going to try resetting the Z-probe and try the auto bed compensation again.

If i have run setbed.g does running an auto-level override the setbed figures??

My guess is that it does.

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Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

I think a 3-point mount is best. You can then adjust the back two levelling screws to get no difference in height between the two Z probe levelling targets at the back of the bed, and the front screw to get the same height at the front centre. If you have a slight twist in the alignment of the y-rods, then the left front and right front corners will be below and above the front centre height, by the same amount. You should be able to correct the twist by slackening the two screws that hold one of the acrylic pieces to the printed part, repositioning it to get rid of the twist, and tightening the screws. But I haven't done this, it's just theory.

Your next problem will be that the back corners of the MDF bed support are not stable with temperature, for which a number of solutions have been published in this forum, such as replacing the bed support with aluminium or Tufnol, reinforcing the MDF with carbon fibre square tube, or moving the heat spreader down. I prefer to keep the heat spreader in its original place because it will give a more even temperature out to the edges of the bed, which may matter when doing large prints.

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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].

Surely as the heat spreader and hot bed are bolted together as one unit, it matters not where the the aluminium plate is in the sandwich from a strength POV??

physically it has the same stability when the order is glass-alu-heatbed or glass-heatbed-alu ???

Thermally, the story could be different


MDF is definitely poo when it comes to being stable, I may look into the alu space-frame style mounts soon.

---

Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

I've pulled the bed, fitted the modified belt tensioner set I found on the forum - these really are excellent and make belt fitting and tensioning a doddle. I also trimmed the mdf to a T shape as the front corners really were not bringing anything to the party, got her all back together ready to set up again tomorrow.

Also fitted a 12mm long brass tube nut to the Z lift screw, this should spread the load placed in this weak point a bit.

I even discovered what the bit of plastic I had left over was - the Z column foot

Edited 1 time(s). Last edit at 03/03/2014 02:54PM by Davek0974.

---

Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

Re calibrated the z probe tonight and also levelled the bed manually using the three point system, MUCH better, very easy.

Sad to say the mdf drooped after an hour or so but I was impressed, will look into the alumnium mods on the forum next.

Also tried auto bed compensation and it too worked reasonably well but even in my office with one ceiling light on, moving around and causing shadows gave vastly different results.

Printed out the test piece again and it's perfect in two planes and only 0.45mm out in the other.

---

Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.