Issues with printing circles and calibration blocks

[BobD1001]

I recently purchased a CTC dual extruder printer. Right out of the box it is making some great prints with just a bed level and an upgrade to Sailfish.

I am having some trouble printing circles and calibration blocks if anyone could help me. The 20mmx20mm calibration cubes come out to nearly exactly 20mm on the x-axis sides, but the y-axis sides are always a bit under, coming in around 19.60. Circles also seem to have perfect dimensions on the x-axis sides, but on the y-axis sides (towards to front and the back of the printer) the side flatten out a bit. They may be slightly oblong, I cant quite tell. At first I though it may just be a stepspermm issue which I could modify, and perhaps it still is, but when I printed the double-values-square-calibration object, the one square in line with the y-axis was 20.05mm, while the longer side came in at 39.65mm. Can anyone offer advice on what may need fixed or modified?

Here is a picture of whats going on:



You might be able to see that the fill material didnt quite reach the one side of the calibration L either.

My goal is to print fitting parts to prototype parts for my machine shop, and unfortunately it couldn't quite print the working nut/bolt combo.

[jfkansas]

If it is consistent over many prints, it wouldn't be hard to figure a distortion factor in to your Y axis. I would just print out something 100mm x 100mm also to check if the percentage is right. At 39.65 you are only off by .88%. Run your y axis at 100.88% in the slicer then print a 100mm x 100mm by 10mm box and check that. It's also possible that the material is shrinking front to back a little more because of some sort of cooling effect.

To change this in the firmware might be a possibility, but you want to check if the error is the same on different filament brands and colors.

[BobD1001]

Thank you for that, I believe that test has now eliminated it being a steps/mm issue. I created a 100mm square in SolidWorks and the x-axis side was at nearly 100mm on the nail (about 99.98mm), but the y-axis was again off by the same ~0.4mm. So I'm assuming something mist be amiss somewhere in the y-axis. 0.4mm of backlash (at least that's what we call it in the shop). Can anyone provide pointers as to typical issues?

[jfkansas]

It is tough to say on that, if it were a percentage thing the error should have been 2.5x as bad at 100mm which says the part should be 99mm or so.

I would hop on the Flash forge google group, there are some very knowledgable guys on there that will be able to tell if this is a software error thing maybe in acceleration or something more mechanical.

I think a taller 100mm test object would help to see if it will get smaller in size in one direction further up the print.

[BobD1001]

Thank you for the responses jfkansas, I think it may actually be the Y-axis rod bending under tension, in which case the pillow block upgrades may sort this issue out. Fingers crossed!

[jfkansas]

Ya, Pillow blocks helped on earlier flashforge wooden printers, but the creator X and Creator Pro already have pillow blocks. Not sure where the CTC printer fits in there, I guess it depends on how old it is. The CTC is a clone of the Flashforge which are both clones of some older model Makerbots.

[jfkansas]

Thank you for the responses jfkansas, I think it may actually be the Y-axis rod bending under tension, in which case the pillow block upgrades may sort this issue out. Fingers crossed!

What machine type do you have selected in the profile?

[sasabs]

I have solved several mysterious problems by tightening the set screws on the idlers and especially the motor pulley. If slightly loose the motor pulley might have to rotate a fraction before ir grabs.

[BobD1001]

Thank you all for the input, I think I was able to finally isolate the issue. The belt driving the y-axis off the motor was slightly loose, so I loosened the floor bolts holding the motor, and adjusted it to tighten the belt. After this my calibration cubes were within 0.08mm on both sides. I just printed the pillow block bearings also, do that should further improve the quality. I truly appreciate all the help you all have given me.

Also what do you all recommend using for the slicing profile?