Cura Calibration

[3dtopo 0]

I am attempting to print pieces for a new and improved extruder, but I am getting ovals instead of circles on critical pieces.

I assume it is because the belts are not exactly the same tension. I understand that I cannot input calibration factors for the XYZ axises in Cura.

So how does everyone else get the much sought after circles?

Thanks!

[joergen 2]

I am attempting to print pieces for a new and improved extruder, but I am getting ovals instead of circles on critical pieces. I assume it is because the belts are not exactly the same tension. I understand that I cannot input calibration factors for the XYZ axises in Cura. So how does everyone else get the much sought after circles?

You really have to get your mechanical parts in order before you can expect getting something like proper prints out of your UM. if everything wobbles and has slack, please have a look at the assembly instruction again: http://wiki.ultimaker.com/Ultimaker_rev.3_assembly:_Extrusion_head

[Daid 306]

Calibration on X/Y/Z will not improve your ovals, as the reason for ovals is slack in one of your belts.

You'll have to make sure that:

1. The short belts have enough tension by pushing the motors down. (This usually has to be done once again after a few hours of operation, but then never again)

2. The long belts have enough tension, by adding belt tensioners.

[3dtopo 0]

OK, so I have the belts "singing" just like the video now.

But I am still getting ovals. Two different size circles I get:

20.20mm x 19.77mm

8.03mm x 7.73mm

So is there anyway to enter calibration data in Cura? Or any other suggestions?

[Daid 306]

Maybe thermal shrinkage is causing your slight oval circles?

[SandervG 1,521]

Are all your pulleys screwed on tight?

Have you tried printing these objects on a different place on the build platform?

For example in the middle, front right corner somewhere at the back?

[3dtopo 0]

Hi,

Daid: I don't think it is possible for the plastic to know to cool differently on the X and Y axises.

SandervG: My pulleys are as tight as I can get them with the included screwdriver. However, there are no flat ends on the motor shafts which means they could still slide (which I found rather strange).

However, I don't think it is slipping because all of my layers are practically perfectly lined up, see attached images. If it was slipping, I don't think this would be possible.

In my experience with my CNC machines that are belt driven, it is critical to calibrate the axises as slightly different belt tensions will cause the axises to move slightly differently. I don't see why the Ultimaker would be any different in this regard.

[Daid 306]

Different shrinkage in X/Y could happen because the PLA starts to cool as soon as it is deposted, and the order in which it's deposited defines the direction in which it moves.

If you think it's the X/Y movement that is wrong, attach a pencil to the printerhead and plot a line and measure it. You can change the X/Y calibration with M92 X... Y... a value of 78.7402 is the default.

[3dtopo 0]

I attached a pen, and I still get an oval. The oval is essentially the same shape that I am getting in plastic. See attached images.

It seems that the smaller the circle, the more noticeable it is oval.

[joemirror 0]

I too am having the same problems with a .5-inch square being 6-thousands short on the x and 10-thousands short on the y. And I too have other cnc machines where I have to adjust the steps per inch slightly different on the x and y axis to make things come out correctly. So, can you give us a screen shot and some instruction as to where you use the m92 code to adjust the steps per inch or centimeter.

[Daid 306]

You'll have to add the M92 X... Y... to the start code, as first line with do. The default X/Y are 78.7402