Questions about the printed orthogonal axis

Finally, after six months of building, testing, failing, and re-building, I finally managed to get my orthogonal axis printed! It's done in ABS with a Volcano nozzle, so I had to tweak the bed/hotend temps in the GCode to get it to stick.

I'm trying to follow RRP's calibration instructions, and I'm confused about how to construct the M556 command because the instructions are sort of ambiguous. I've assembled the thumbscrew and captured an M3 nut, but I'm getting lost with the numbers for XY, YZ, and XZ.

My initial measurement with the set square is 27 notches (clockwise) until the screw hits the square. According to the docs, clockwise indicates a negative value. From that:
XY = (27 + 3) = 30 notches. (-0.3 * 0.5) = -0.15
YZ = (27 - 21) = 6 notches. (2.1 * 0.5) = 1.05
XZ = (27 - 21) = 6 notches. (2.1 * 0.5) = 1.05
d = 56mm (from corner to centre of screw)

I believe that the command is therefore

M556 S56 X-0.15 Y1.05 Z1.05

When I tried my second print, the base of the outer bar (the wonky one with the screw hole) was even more askew than the first time around, so I've either measured my values incorrectly or I'm making the incorrect assumptions about how this thing is measured.

Also, my Z axis is nearly 10x10 mm square, but X and Y axis are "pancaked" in the Z direction. They're each 10mm wide, but only 6mm tall. Is that normal?

Any help would be appreciated!

~0

You only have to count the different turns after hitting the square. One full turn clockwise means -0.5mm. The turns needed to hit the square doesn't count.
Also you should print this in PLA as the warping risk is too big if printed in ABS.
There is a bigger model of the orthogonal axis meant for the Ormerod. Your piece was meant for smaller printers.

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Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.

-0

I agree, always use the biggest available test piece.

I haven't printed the smaller test piece so don't know whether it's 6mm or 10mm; you can check the file in WordPad, it's only a long text file, it'll be obvious when only the z arm is printing, read back & find the last value for z; I suspect it'll be 6.00. I.d also expect the 3 arms to be the same length. If the z arm is 60mm when the others are 100mm there's a problem.

I didn't like the test piece & designed a larger, more rigid calibration stand which can use a digital caliper. Get the printer as square as possible then print the larger stand.

It's amazing how accurately you can measure the test piece with just the set-square!

Good luck
CUA193

edit

Being a curious sort of chap I've just checked the gcode & stl for both calibration pieces, the x & y arms should indeed be 10mm square, all arms should be 60mm, 90mm for the bigger one. There is a problem which could well be mechanical.

Before recalibrating the z motor check the obvious - like wiring. Check for free movement of the x arm, make sure the bearings aren't binding. The whole x arm assembly should rise and drop with as little friction as possible. It might be an idea to increase the power of the z motor; make sure the gears aren't binding & that the threaded rod is running true.

I've had trouble with the arm binding, I've just made a one-piece bearing holder from a billet of aluminium which has cured the problem.

Edited 1 time(s). Last edit at 03/25/2016 07:33AM by cua193.

I don't like digital calipers even though I am a technic freak and normally I would prefer a digital version. I had a digital caliper. Besides that the batteries were fast empty, the zero offset didn't work correctly. Once opened and closed it showed me 0.02mm instead of 0.00mm so after each measuring I had to recalibrate it, so I use nowadays the good old analog one.

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Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.

Treito,

An analogue caliper will fit if you prefer, I habitually use both.

I this case a digital unit is much simpler, clamp it in the stand, zero it against the set-square then measure the test piece, it'll show plus or minus instantly - my poor old brain can't handle sums any more!

CUA193

I think I've had a bit of beginner's luck, and have not been able to re-print the orthogonal axis after setting the S556 command that I've worked out above. It's like it's not homing properly - my filament is not able to get initial contact with the bed and the print always fails on the first layer.

My print setup process goes something like this:

1. Home X
2. Home Y
3. Auto bed compensation
4. Use @dmould's paper trick. Move to 100,100,10
5. Move Z lower until it pins a sheet of paper to the bed
6. Add 0.1mm until it releases the paper
7. Subtract 0.1mm
8. Send G92 X100 Y100 Z0

I use the G92 command because I'm using an E3D Volcano hotend. It's slightly taller, so the Z sensor is not as accurate when Z hits the bed.

If I home Z using the paper trick (G92 X100 Y100 Z0), the filament either comes out of the nozzle just barely too high and doesn't stick to the bed, or it's stringy and gets dragged along the print head as it moves.
If I home Z with the sensor, the head drags on the painter's tape. This usually clogs the nozzle, and requires me to use some nasty solvent overnight to set it right.

It's like the printer needs to be homed within 0.1 mm, and the user is greeted with certain death if incorrect. Is this normal? I've tried some different hotend and bed temperatures but nothing seems to remedy it. Any ideas where I might be going wrong?

Yes you need to get the Z height setting accurate to within about 0.1mm (preferably 0.05mm) to get good prints.

If you are using the standard 1.09 firmware then I suggest you upgrade to either my 1.10+4-dc42 firmware or to chrishamm's latest. Also update the web interface to DWC 1.11 There are some bugs in orthogonal axis compensation in 1.09.

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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].