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eldrick

"Magic" layer heights?

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Each 3D printer has a set of layer heights which, determined by the lead-screw pitch and number of "starts", along with the steps/rotation of the stepper motor and its micro-stepping settings, determines what layer heights come out exactly "even", i.e. don't require a "catch-up" step every N layers.

These are the "magic" layer heights that should always be used; if non-"even" layer heights are used, you may see regular banding in the finished prints, where the slicer/printer has to add a layer to make the piece height come out correct.

On my last 3D printer, the "magic" layer heights were divisible by .05mm, i.e. .10mm, .15mm, .20, .25, etc.

Can anyone tell me the magic divisor for layer heights on the UM2? What are the layer heights that exactly match what the z-axis leadscrew can do, so that the layers are exactly matched to what the UM2 can physically print?

 

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I've wondered this as well myself, but have never bothered to figure it out other Mathematically. The NetFabb defaults for the Ultimaker use a layer hight of 0.08 for the 'Ultra' quality and multiples thereof for lower resolution prints... And I've played around with this quite a bit trying all sorts of odd and even layer heights but I have always found the best results to be divisible by 0.08 on my machine. I get far better results at 0.08 than I do at 0.06, and similarly I get nicer results at 0.160 than I do at 0.1.

Regards,

Troy.

 

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So multiples of 0.001875mm ?

I don't know if this is still accurate but this information says:

https://groups.google.com/forum/#!topic/ultimaker/rDneN2H0ixQ

"On Saturday, February 23, 2013 10:24:05 PM UTC-5, wil21...@maricopa.edu wrote:

2. The lead of screw is 3mm, but I don't think this is a good choice. When the screw makes one rotation of 360°, the Z-plate rises up 3mm. The step angle of stepping motor is 1.8°, this means 0.015mm is the minimum step distance. So it is hard to reach the common layer height such as 0.1mm, 0.2mm. Perhaps, 2mm, 4mm or 5mm for lead of screw is better.

The Z screw is pretty much the element with the highest resolution in the whole system, about 7x better than the XY. The Z stepper is driven with 1/8 steps, not with 1/1 steps as you mentioned above, so it has 200*8 steps / 3mm = 533.333 steps/mm or 0.001875mm per step (8 times better than what you mentioned above)... so, why is the 3mm acme screw a bad idea? and how would a 2mm, or a 4mm, or a 5mm lead screw improve anything?

 

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. so, why is the 3mm acme screw a bad idea? and how would a 2mm, or a 4mm, or a 5mm lead screw improve anything?

 

It's for the number freaks... ;)

Some people find a number to be more aesthetic if it has less non-zero digits.

However, I tried today 0.09mm vs. 0.1mm. I really coulnd't see any difference which could be related to the fact that 0.09mm is exactly 6 full steps of the z motor. 0.09mm was a bit better in quality but I think it's mostly related to the layer thickness itself. A 0.08mm print later on was even better.

I do still see some tiny regular pattern in z direction. But I know it is coming from non-contrenticity of the z screw and the coupler.

 

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So multiples of 0.001875mm ?

I'm not sure but isn't that the UM Original? Eldrick was asking about um2 which has double or triple helix threads (much higher than 3mm pitch I think).

 

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For the UM-Origonal it is 200*8/3 steps per mm.

For the UM2 it is 200 steps per mm.

So you would want multiplies of 0.001875mm for the UM-Origonal and multiplies of 0.005mm for the UM2.

However, there is microstepping in the mix. And microstepping is not perfect we discovered recent tests. The size of each steps follows a small sinus wave. So, with the x8 microstepping that we have, you would want:

Multiplies of 0.015mm for the UM-Origonal and multiplies of 0.04mm for the UM2. For the best magic layerheights.

(For the number freaks that is. And maybe for the really thin layers, also Cura as an internal accuracy of 1 micron)

 

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