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dubtec

speed settings & layer height questions.

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I'm looking to speed things currently printing perimeters at 50mm/s and infill at 80.

I'm looking to speed things up a little:

what is the "Normal" movement speed for non printing moves?

also Z axis speed?

I understand that there might be a bug with retraction speed, is it half of what you set. and what would be a normal setting as cura shows 40 as default on fesh install, is this really 20?

I'm using a UM1 as standard. the extruder gear has two sets of teeth (not sure what type it is).

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Optimal layer height:-

I wish to use http://calculator.josefprusa.cz/ to find "allowable" layer heights, can we just confirm the leadscrew pitch is 1.5875? and 1.8 degrees.

as i want to find a happy height between 0.1 and 0.2mm without error.

any help would be much appreciated.

David

 

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Optimal layer height:-

 

You are talking about the error caused by minimal steps (max resolution of Z axis) but the resolution is so high that it doesn't matter. I looked into this about a year ago. .1 and .2 are fine. Don't worry about this - it's silly.

 

I'm looking to speed things up a little:

what is the "Normal" movement speed for non printing moves?

also Z axis speed?

 

Well - I usually do 150mm/sec because that's plenty fast for me and the non-printing moves tend to be rare - the long moves anyway. On the short moves it never gets up to 150mm/sec. Some people do 250mm/sec. I think the max speed is 300mm/sec. Before going that speed you should test the repeatability using prontrface which is free, and easy to use GUI, and you can do lots of 300mm/sec moves back and forth and see if you lose any steps. Probably you will be fine:

http://koti.kapsi.fi/~kliment/printrun/

 

Doing 80mm/sec for fill and 50mm/sec shell will lower the quality - speed change will result in over extrusion when it slows down. A little bit. But if you don't need "perfect" quality, and if you don't care too much about stringing, I can print at .2mm layers, 100mm/sec or maybe even 200mm/sec if you heat up the PLA to 240C. Here are some photos that explore the relationship between speed, temperature, quality:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

In general, "perfect" quality is around 30mm/sec. But you can do fine at 100mm/sec if you aren't picky.

Another huge speed improvement I have found with zero quality reduction is to not print any infill. The UM is amazing how good it can bridge openings - for example the top layer of a cube with no infill. This means however that you need the top/bottom thickness to be a layer or 2 thicker than if you use infill. Usually 4 layers is plenty. The latest Cura (14.02) is now very accurate about predicting how long a print will take. So you can fiddle with more top layers and less infill and see how much time you will save.

The strength of a part comes mainly from the outer edge - that's why bones are hollow and the wood beams in a house can be drilled only in the center (for plumbing/electrical) without sacrificing strength, etc.

Speeding up the Z axis won't print any faster but will print with better quality. I doubled the default Z acceleration and it changes layers twice as fast. Didn't need to touch the max Z velocity. This helps the Z seam quite a bit.

 

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Thankyou for such a helpful answer. I need to get this nailed as I now using two ultimakers in my shop.

So basically try and keep perimeters and infill the same speed. say 50 - 60 for "average quality"

Travel 150..

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two other questions -

Retraction 40mm/s ? at 4.5mm

does cura always Retract on layer change?

The reason for the questions, is I'm trying simplify 3d and very annoyingly all the settings are in mm/min

thanks

 

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So basically try and keep perimeters and infill the same speed. say 50 - 60 for "average quality"

Travel 150..

 

That's fine. Really every print has different requirements if you want to want to be fast and efficient.

 

Retraction 40mm/s ? at 4.5mm

does cura always Retract on layer change?

 

I find that 4.5mm is not enough distance for a stock UM - typically you need to either increase that to around 6mm or add this simple part:

http://www.thingiverse.com/thing:46157

 

40mm/sec is fine. If you have the old firmware (with a bug in retraction speed) this will retract at instead 20mm/sec which is a reasonable speed and if you have the latest firmware it caps at 25mm/sec. So 40mm/sec is recommended retraction speed for UM Original. 35mm/sec for UM2.

Cura usually does not retract on layer change. This results usually in what some people call a "Z seam" especially if you are printing at high speeds (like 70-150mm/sec and .2mm layers) because it stops while changing Z height and you still have high pressure in nozzle and you get a tiny blob. Usually in the same spot for many consecutive layers. You can improve the Z seam by doubling the Z acceleration that comes default with Marlin. Don't touch the speed - just the accelearation. You will get less noticable Z seam.

 

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