Like a lot of people, I’m having trouble printing circles with my CTC Bizer dual head printer.
I thought I’d lost some things I have tried and am going to try in the hope that it may help the head scratching/hair pulling process.
ive tried lowering and raising the temperature - problem still exists (PSE)
changing the steps per mm in Simplify3D - PSE
making various z axis stabilisers - PSE
Things I’m going to try…
better cooling using a printed cooling system from thingiverse. It holds a fan and directs the air directly onto the printed surface. A friend who has been printing for years suggested this as it may be a problem with dragging hot material.
random layer start points setting turned on in simplify3D. In conjunction with better cooling this will at least be useful to see if it is a dragging problem. If the deformity comes out none uniform, that at least rules out x y axis problems.
aluminium pulley wheels and better quality timing belts incase it is an issue with the cheap ones it comes with.
failing all that, selling it and buying a flash forge creator pro 
please add add anything you think of or have tried.
If circles are coming out as oval, I’d first check the belt tension to make sure they’re all tight. Id check the stl files also and make sure the dimensions are correct. If its oval then it means one axis is out of whack. Print a square and check the measurements but mark the orientation. If one side is shorter than the other, then you can work out if that axis is off.
Hi Daz,
Thanks for replying.
whats actually happening is its printing perfect circles with flats on. I’ve done several square and cube tests and they’re bang on.
there is no play on any axis and everything else prints well. I am now thinking it could be the firmware. I tried changing to sailfish but could not for the life of me get it on there.
Let me know if you think of anything else.
Sam.
Hey Sam, Have you tried printing with makerware? If the CTC is mechanically true/tight it produces great prints on par with a real replicator or flashforge. I used mine with out of the box firmware for a few prints and than upgraded to sailfish, however I did not notice the behavior you are describing before upgrading to sailfish either. Do you have any photos of the problem prints?
Hi SEngineering,
Thanks for replying.
I’ve not tried printing with makerware yet. I’ve tried simplify3D and replicator G. Both produce exactly the same flats on the circle in exactly the same location.
I presume yours prints circles perfectly. Do you have more information about your printer and software setup?
Mine is the CTC Bizer Dual head, I bought it about a month ago. I have noticed that mine is only reliable over USB.
Here’s a photo of what is happening…
Hey Sam, Looks familiar, mine did something similar out off the box. The solution was multi faceted and I’ve listed them in order of severity: 1) the X axis was not perpendicular to the Y axis. 2) The Y axis had uneven belt tension with respect to right and left side as well as top and bottom of pulley (Removing the Y belt tensioners helped too ) 3) The Y axis rods needed pillow blocks. If you print really slowly like 20 mm/s and the problem gets better than the issue is probably more related to belt tension, if not than its probably more related to X vs Y skew.
You sir, are a star! I’ve just tightened the small Y axis belt like a banjo string and it has reduced the problem a fair amount. It’s pretty late now, but I’m going to do what you suggested with respect to binning those stupid clothes peg spring tensioners and manually tighten both long Y belts and try another print.
The difference that tightening the small Y axis belt has made is the most encouraging thing I’ve seen so far.I think the reason I thought it couldnt have been belt tension originally, is the uniformity of the error on every layer and across several identical prints. Hopefull people who are experiencing this will read this and learn to never assume to understand the dark magic that fuels the 3D printing realm!
I’ll let you know how it goes tomorrow. Cheers!
Awesome, glad you’re on the right path now. I tell people to treat the CTC printers like kits. You may get it fully built but expect to have to at least partially reassemble it before you will get quality prints. 
Well I’ve tightened the belts, squared up the axis, rebuilt the print head with new extruders and a cooling fan, soldered on a new mosfet to control the cooling fan, added a sheet of glass with special plastic on the heat bed, played around with settings and speeds and swapping stepper motors. Everything I have done has improved the overall print quality, but the flats on the circles (although significantly reduced) still exist. I’m considering buying a Flashforge Creator Pro and cutting my losses with the CTC. For what I’m printing, I need circles to be circular.
Did you ever add pillow blocks to the Y rods? If not, it’s quite likely that is where the last little bit of non-linearity is that is preventing perfect circles. Pillow Block CTC Flashforge Replicator by kyuzumaki - Thingiverse
I haven’t tried that. I was going to have a go at changing the steps to try to compensate. Pillow blocks seems like a better first go though, cheers. I’ll give that a go first. What’s your real name if you don’t mind giving it? I feel weird getting so much useful help from someone who’s name I don’t know.
Oh I just clicked on your profile… A good solid name
Hi Sam,
I got exactly some problem when printing circles
I almost get mad to correct this problem
I am happy to have found this thread
I will follow it and let you know
Regards from France
Sam, I’m having exactly the same problem as your image above and the ovalness is always in exactly the same position as your picture "5 to and 25 past as clock. I’ve tried belt tensions, axis squaring, steps adjustment, bed levelling… etc…
Did you ever find a definitive reason/fix for the problem of repeated ovalness?
How tight should the belts be on a Bizer?
Where did you get the bearings for pillow blocks?
Any help or guidance greatly received. Cheers!
