A circle should be a circle, shouldn't it?

Many thanks for the attached files. I learned "Autodesk Inventor" and I do not know how tu use the commands in Openscad especially if it is getting complicated like Helix and Sweep. The using of Freecad is more or less similar to Inventor. Freecad uses also the Opanscad engine as far as I know.

I cannot do the tests right now. I exchanged my extruder to a new one. Unfortunately I printed it in HIPS, because I thought it is similar to ABS and you have less warping. Indeed this is right but it is in some cases not as strong as ABS. So my Extruder gears (remix from DC42) broke - the screw was not turning with the gear so I did not have any extrusion.
I fixed this problem for the moment (Using a standard gear unfortunaelty also printed in HIPS) and the small hexagonal gear but I have to use another gear so that the gear does not come off the axis.
I am not able to print spare part at the moment because the ABS does not stick on the bed after 10-20 layers of 50. But I do not want to use the original extruder because of ABS.

So give me some time please and I can test these parts with Slic3r and Cura. Maybe also Kisslicer. Kisslicer looks good but it does not seem to be good enough for paying 40$. That is my personal opinion. Cura makes a better impression to me. I got very good prints using Slic3r instead of the seam, but I think I found a solution for this problem.

So do I understand an other thread correct that maybe there is some kind of problem in the dc42-fork that maybe can cause that circles are not circles and this problem is maybe less in RRP or ZPL firmware?

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Treito
So do I understand an other thread correct that maybe there is some kind of problem in the dc42-fork that maybe can cause that circles are not circles and this problem is maybe less in RRP or ZPL firmware?

No, it can cause a jerky movement - and only with arcs & circles, a perimeter of gear teeth would be fine. I still believe that your issue is most likely related to the belt, which is quite likely to have worse accuracy in the center of the bed than at the edges because the geometry of the belt changes.

This weekend it so happened that I had need to print some disks that had to be a stiff push-fit inside a length of plastic water pipe. I had to tweak the diameter a few times to get a perfect fit, but the final result was definitely a part that was pretty much a perfect circle - a gap of even 0.05mm on one side would have been noticeable when held up to the light. Therefore I know that the Ormerod design and firmware can achieve that accuracy (though it needed finishing by filing down the inevitable start/end seam).

Dave

I had this problem also with a cylindric object. It is betting getter know. My main issue probably was the angle of the hot end nozzle. I temporarly fixed this for the moment. In fact as I wrote above I printed roughly 10 cylindric object (I did not count them) with PLA because the dimensions did not fit. It has an outer diamter and two holes on the inside. one is roughly 19.1 mm und 12mm height (with a thread) and the other one is 32mm and 18mm height. So the total height was 30mm. The outer diameter was 45mm. That was an ideal test object in my opinion. You can test roundness, height, all angels like the ormerod axis.
But it seems like some other parts get weak for example the y clamps that connect the heated bed with the rods - they both loose the rods and so the bed gets instable. But my main problem is that I cannot adjust the rod on the x-carriage for the angle of the hotend. The y-belts are tight now thanks to imaburny y-belt clamps. Mayb they are even too tight but not loose,
The last printed gear nearly was good except for this damn warping of roughly 1mm.
How much infill do I need for the Ormerod parts when I print them in ABS?

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Treito
But my main problem is that I cannot adjust the rod on the x-carriage for the angle of the hotend.

Why not? The screw holding the X runner bearing moves in a slot, which is how you adjust the angle. If it's right up at the end of the slot nearest the X arm, then replace the 9mm runner bearing by a 10mm one (623ZZ) as I did, or stick a shim on the X arm.

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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].

It is hart to explain especially if you have to explain it in a language where you are not really familar with, let me try:

My original X-runner part got weak and lost easily the big rod. So I printed a new one and of course in ABS (if I have to do so, I did not want to exchange this later).
But I got a little bit warping and especially shrinking. So the M3 nut barely fits in the slot but there is not much m ovement, so I am not able to put the runner bearing close enough to the X arm. I now taped some blue painter tape on the X arm until I can print an new one. But my main problem is the Extruder. I do not know how long my printed spare parts last especially I printed them in HIPS.
Luckily I was able to print a new large Extruder Gear in ABS without warping. I decided also to exchange the Extruder to the spring loaded Extruder because the Herringbone gears are easier to fit. Last time I placed the nut into the large gear. It works but if the connection gets loose, the filament gear is not coupled to the Extruder Gear and you may have a problem.
So if i can reproduce the result I will tell you what I did. At the moment I can tell you that you need Slic3r 1.2.x. Cura and Kisslicer will not work. But I have to recreate the results first. Maybe a butterfly hits a tree somewhere and that was why I did not get warping.

Regards,

Sven

Unfortunatly I could not reproduce the result but that I did expect.