Delta printer misalignment

I'm currently using a deltaprinter, but I struggle with getting perfect calibration. I get perfect distance at each axis, but when I center the hotend it's slightly higher than at the edges. What should I do?

My first thought is that some lengths or offsets are specified wrong in the marlin software, but I'm not sure what to try.

You need to re-adjust the Smooth_Delta_Rod_Offset. It is an arbitrary value that doesn't properly apply to all types of delta so it has to be found another way.

A quick method I use:
- Make sure your end-stops are fairly accurate by measuring from the base of the printer.
- Place a piece of masking tape on one side of your bed along the X axis from center to edge.
- Lower nozzle to the bed and scribble around it with a pencil, raise and find center of circle left behind.
- Find an accurate ruler, square, fabric measuring tape ect. and mark out 20, 40, 60 and 80mm from center to edge.
- Move the nozzle along the bed on the X axis and see if it scales to 60-80mm properly, you should find it will be out by 1/2mm or so.

Change Smooth_Delta_Rod_Offset up and down to compensate. You eventually want to adjust it in .25mm intervals, until the nozzle ends up bang on at 80mm. The reason why you need multiple measurements is if one is 1/2mm wrong, it will stick out and you can re-mark it.

when i was pre-configuring my mini kossel i played around with delta radius to level it from being concaved or bowl

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@ohfurryone: Isnt that the deltaradius that make that pattern?

Quote
ohfurryone
You need to re-adjust the Smooth_Delta_Rod_Offset. It is an arbitrary value that doesn't properly apply to all types of delta so it has to be found another way.

A quick method I use:
- Make sure your end-stops are fairly accurate by measuring from the base of the printer.
- Place a piece of masking tape on one side of your bed along the X axis from center to edge.
- Lower nozzle to the bed and scribble around it with a pencil, raise and find center of circle left behind.
- Find an accurate ruler, square, fabric measuring tape ect. and mark out 20, 40, 60 and 80mm from center to edge.
- Move the nozzle along the bed on the X axis and see if it scales to 60-80mm properly, you should find it will be out by 1/2mm or so.

Change Smooth_Delta_Rod_Offset up and down to compensate. You eventually want to adjust it in .25mm intervals, until the nozzle ends up bang on at 80mm. The reason why you need multiple measurements is if one is 1/2mm wrong, it will stick out and you can re-mark it.

I will try that.

What I've one so far is measure the distance from between the vertical rods the carrier rides on and to the center and defined this in the config, but it didn't change much, even though the previous distance was off by 4mm.

What I did was marking a point about center of plate and then measure the distance for each carrier and then averaging the distances. In theory this should give the correct distance as far as I understand.

From my understanding, the delta radius calculation should be left alone unless the actual bed is bowed. Marlin was initially designed with only a few printers in mind so the method of finding the smooth rod offset varies for others. The 'drawing-on-masking-tape' method I've found is a fairly decent universal way of finding that value, once found the nozzle should travel flat.

Quote
LarsT81
What I did was marking a point about center of plate and then measure the distance for each carrier and then averaging the distances. In theory this should give the correct distance as far as I understand.

That is the correct way for many printers but not all, it would have worked well if yours was similar to those designs. Sadly most delta instructions are written for specific printers.

Try my Delta calibration calculator at [www.escher3d.com]. Use 4 factor calibration initially and make sure you enter the height errors with the correct sign.

Questions specific to delta printers are best asked on the section of these forums that is dedicated to them.

Edited 1 time(s). Last edit at 11/02/2016 04:00PM by dc42.

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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].