Print dimensions off
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If I print a square that has a square hole in it the outside dimensions are perfect but the internal square is undersize by .4mm. If I then print a round disc with a hole in it the outside and inside dimensions are undersize by .4mm.
Maybe this can help you:
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I print everything with an extrusion multiplier of 90% which gives me the best dimensional accuracy and the best surface finish. No idea why it works but for me it does. My ageing Mendel prints everything slightly small compared to my newer CoreXY - same gcode files, same print settings, same filament and hot end end design. Again, no idea why. I recently discovered that with two parts which dovetail together for a sliding fit with negligible play, making them both in black worked well but making the male part in gold coloured PLA gave a loose sloppy fit. Changing the clearances so that printing the male part in gold PLA gave a nice smooth sliding fit, then printing the same male part in black PLA resulted in a too tight interference fit. Both filaments measured spot on at 1.75mm and of course, this was the same gcode file printed on the same machine with exactly the same settings, so yet again no idea why. I think that where dimensional accuracy is critical, it's just a matter of trial and error to get a perfect fit and what works on one machine, may not work on another.
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uvarovkv,
I can see your analogy but the path is surely controlled by the slicer which is not taking into account that this is a hole and the path needs to change.
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deckingman,
I totally agree with what your saying. But I am just trying to get my printer tuned in with one filament to start with and can then adapt from there.
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My twopence worth the issue with external and internal dimensions specially holes is that holes are often too small due to the fact that they are polygons not circles.
Ian that extrusion multiplier..I know we talked about it before regarding titan extruder steps/mm. But if you set your steps/mm 10% higher and used 100% extrusion multiplier you'd get the exact same result. All those numbers are all just a measure of how many revs of the drive gear are performed for x mm (or mm3) of filament requested.
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…...................Ian that extrusion multiplier..I know we talked about it before regarding titan extruder steps/mm. But if you set your steps/mm 10% higher and used 100% extrusion multiplier you'd get the exact same result. All those numbers are all just a measure of how many revs of the drive gear are performed for x mm (or mm3) of filament requested.
Yeh, I know. Two different ways to achieve the same result. I have the extrusion multiplier set in Slic3r under "Filament settings" so everything gets sliced using 0.9 extrusion multiplier and I don't have to think about it. It's just my personal preference to have config set to the "correct" value and then tweak it in the slicer. It's kind of like the Z offset that we've spoken about - I prefer to use a (negative) number in my G31 but you prefer to use an offset in your slicer. It's just personal preference and there is no right or wrong way to do it as long as it works. Cheers. Ian
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Fair enough, I have reverted to using the probe offset in firmware.
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Instead of starting a new thread with the almost the same subject, I hope it's OK to fill in this thread!?
I'm printing this delta calibration model: http://www.thingiverse.com/thing:745523
I have adjusted the diagonal rods so that I´m getting 50.99mm in Z (It should be 60mm), but both X&Y are off about 0,2-0,5mm.
Is there any way to adjust Y & X size separately?
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My understanding of delta kinematics is that there is not, since x and y movements are intrinsically linked to one another, unless its being caused by something mechanically off on one tower, that is okay on the other two, play in a joint, a slight twist etc…
How does adjusting the rods change the Z? Since Z is generated by moving all three tower carriages by x steps then as long as your steps/mm is correct, moving the nozzle to 60mm it should have exactly 60mm below it (+/- thickness of a piece of paper if you use that test to set nozzle gap).
X and Y scale is determined by your rod length setting in firmware. Longer rod setting means smaller objects and vice versa.
You can scale the object when you slice it but that's a pain in the a**.
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DjDemonD is correct. The Z height is determined by your steps/mm, and diagonal rod length affects the XY scaling. However, if you change diagonal rod length in an attempt to compensate for geometrical errors in your printer, then you will find that printed lines that should be straight will come out bent.
I suggest instead that you:
1. Correct geometrical errors as far as possible. See https://duet3d.com/wiki/Calibrating_a_delta_printer#Make_sure_your_build_is_accurate.
2. Print pairs of parallel straight lines from one edge of the bed to the other at different angles, each line half a bed diameter away from the centre at its closest point of approach. Then check that the lines are parallel. If they bow inwards or outwards, adjust the diagonal rod length and recalibrate the printer. Repeat until the lines are straight.
3. Use the M579 command https://duet3d.com/wiki/G-code#M579:_Scale_Cartesian_axes to correct any scaling errors.
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DjDemonD is correct. The Z height is determined by your steps/mm, and diagonal rod length affects the XY scaling. However, if you change diagonal rod length in an attempt to compensate for geometrical errors in your printer, then you will find that printed lines that should be straight will come out bent.
I suggest instead that you:
1. Correct geometrical errors as far as possible. See https://duet3d.com/wiki/Calibrating_a_delta_printer#Make_sure_your_build_is_accurate.
2. Print pairs of parallel straight lines from one edge of the bed to the other at different angles, each line half a bed diameter away from the centre at its closest point of approach. Then check that the lines are parallel. If they bow inwards or outwards, adjust the diagonal rod length and recalibrate the printer. Repeat until the lines are straight.
3. Use the M579 command https://duet3d.com/wiki/G-code#M579:_Scale_Cartesian_axes to correct any scaling errors.
While reading your section on building an assembling a precise Delta/Kossel/Rostock I was researching how to ensure everything is accurate.
I found replacements for my injection molded corners without me having to CNC mill my own (which I know everyone may not be able to do).
http://www.robotdigg.com/product/395/Metal-Corner-for-Kossel-of-2020-Profile(They also have corners for 2040 and 3030 as well as for nema 17 or nema 23)
I have MGN12 linear guide rail coming so there is less slop on each movement and already have the aluminum effector from robotdigg (rails are from robotdigg)
Do you have anywhere to get delta rods that are assembled so I do not mess them up? I hesitate using magnetic rod ends.
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I use those Robotdigg corners in my delta. I've switched to magnetic rods now, but previously i made rods myself using Traxxas and Igus rod ends. It's not hard, here are some tips:
- use a jig to get them all the same length. The jig is just 2 screws the right distance apart on a price of extrusion.
- if using Traxxas joints, buy 24 not 12, assemble them all using the hot/cold method, then pick 12 with no slop and use those
See https://miscsolutions.wordpress.com/2015/06/01/building-a-large-delta-printer/ for the original version and https://miscsolutions.wordpress.com/dc42s-large-kossel-build/ for the current version of my printer.
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Do you have anywhere to get delta rods that are assembled so I do not mess them up? I hesitate using magnetic rod ends.
Haydn Huntley on Google groups deltabots forum. Order them slightly longer than you think you'll need.
