Inaccurate dimensions in Z axis - prints too tall
Hey y'all, not sure if this is a new issue or not because I haven't been printing anything with a critical Z dimension until lately. Prints are spot on, except for them being a bit too tall. I first noticed a few days ago when printing something at 2.2mm that came out at 2.39mm and wouldn't fit into the slot it was intended for.
After that, I printed a few calibration cubes and here's how they came out:
(mean of 3 caliper measurements across the bottom, middle, and top of cube faces)
20mm Cube
X - 20.01
Y - 20.01
Z - 20.16
40mm Cube
X - 40.01
Y - 40.03
Z - 40.25
Cubes were printed on mks3+ in Hatchbox 1.75mm PLA using the stock `0.300mm DRAFT` slicer profile.
I don't expect perfection and I can surely adjust my models to compensate, but this seems a little too off imo. I looked around and could mostly only find mention of inaccuracies in X/Y, or prints that are too short. Can anyone point me towards what could be causing this?
RE: Inaccurate dimensions in Z axis - prints too tall
not enough information. It's simple addition. What is the layer height, what is the first layer height, and how many layers. It will always been within a layer height of Z. If you want perfection, do the math, adjust the layer thickness to get within .01
RE: Inaccurate dimensions in Z axis - prints too tall
First of all, if you're going for accuracy in the Z dimension, the .3mm 'draft' profile is not the one to use. Resolution in that axis will be multiples of .3mm at best.
RE: Inaccurate dimensions in Z axis - prints too tall
I first noticed a few days ago when printing something at 2.2mm that came out at 2.39mm and wouldn't fit into the slot it was intended for.
Z measurements must be at the nearest layer height.
Cubes were printed on mks3+ in Hatchbox 1.75mm PLA using the stock `0.300mm DRAFT` slicer profile.
And draft is meant to be quick, not accurate.
Can anyone point me towards what could be causing this?
Assuming a 0.2mm first layer your layers will be at 0.2mm, 0.5mm, 0.8mm ... 0.2+(0.3xN) where N is the number of layers.
With a 0.15mm layer height it is 0.2+(1.5xN) so 0.2. 0.35, 0.5, 0.65 ...
And all this assumes you have a precisely calibrated live Z position.
Cheerio,
RE: Inaccurate dimensions in Z axis - prints too tall
Oh yeah whoops what I said was confusing. The actual part was printed at 0.2/0.2. I printed the test cubes at 0.3 to be quick but that was dumb in this scenario. So since the the final height is supposed to be 2.2mm...the math should work out.
I just checked in slicer to be sure and it is indeed 11 layers at 0.2 for first and all layers.
RE: Inaccurate dimensions in Z axis - prints too tall
@dpow
Are you sure of the layer count after slicing? This sounds like one extra layer, which could easily be triggered by a tiny overcalculation in the design when, say, an exact calculation just missed the nearest binary equivalent so overstepped into the next layer...
Try reducing the part Z by 0.01mm to make sure it doesn't trigger. Then the remaining error comes from the accuracy of your live Z and the precise size of the nearest microstep in the Z axis motors.
Cheerio,