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Correlating Print Speed to Layer Height

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My understanding is that the lower the layer height you select, the slower your print should be if you want an accurate model. However, I'm sure there is a point of diminishing returns where slower speed for a given height will no longer yield a better print, just a longer print time.

Has anyone figured out a rule or thumb or a general range of print speeds for certain layer heights?

For example, how slow should one go for .06 mm layer height to maximize accuracy? What about .1mm?

 

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Well I think this is on each printer. A lot of issues with speed have to do with the flow rate. and each printer can be its own beast.

I've made something here http://umforum.ultimaker.com/index.php?/topic/7262-flow-rate-vs-speed-calc/

But what you are talking about is slightly more complex since you're getting into accuracy not flow restriction. But doing he print test and using those flow rates seems to work overall as a guide.

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it also has to do with the complexity and the size of your model. If your model has mostly straight walls you could for for a higher layer height, say 0.15-0.2.

If your model is very detailed, or organic with lots of curved walls, like a scan, smaller layer heights are better, like 0.06.

I believe that going lower than 0.06 doesn't show much difference, but I could be wrong… it ads a lot of time indeed.

 

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It works by determining how much material volume your printer can move. So you do the test to see how well your printer is. Then this will make sure you're not pushing the printer too hard, keeping it In a flow volume the feeder likes to move. :)

 

Thank you for the link, I will definitely give your calculator and that thread some attention. I am very new to 3d printing, so forgive my ignorance, but is flow rate a parameter we can control through cura or the ulticontroller? If not, is it preset by the firmware?

 

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I found the opposite. The thinner the layers the faster you can print but it's more complicated than that...

There's a few things to understand:

1) Printing too fast. If you are printing at the limits of what the extruder can push out you can of course print faster with thinner layers because there's less thickness to the layers - less plastic.

2) 90% of the quality issues (but not all!!!) are related to the bowden springiness. The pressure in the head can be very high - typically 20 to 100 psi. Similar to pressures in a bicycle tire. When the extruder stops, the pressure is still there because the bowden tube stretches when printing and shrinks when you stop. Actually you don't have to stop to create a problem - simply slowing down printing will cause some overextrusion at first before the pressure balances again and speeding up initially will cause underextrusion. That is why corners on cubes tend to bump out a bit - over extrusion followed by underextrusion at the start of the wall.

The fix is to never stop printing - always print at a constant speed. The "jerk" setting is 20mm/sec and the acceleration defaults to 5000 mm/sec (awesomely fast). If you always print at 20mm/sec the printer will never stop (except level changes and retraction hops) and you get amazing quality. Even 35mm/sec is slow enough that you get good enough that you probably can't see any over/under extrusion caused errors.

So there is no need to go slower than 20mm/sec no matter how thin your layers are.

3) Bridging - bridging works much better with thicker strands of pla (this includes top layers over infill!). Thin strands break. So there is some point where you just can't go thinner and still get higher quality. To me it's silly to go much thinner than .1mm anyway without going for a smaller nozzle hole - go for a .3mm nozzle and holy crap you will see better quality but you will have to print 2X slower to get plastic through that tiny hole.

 

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Cleven I read the thread you linked and inserted the values I am using for my nozzle size, layer height, print speed and left the values you had inserted for max flow and SF. The calculator gave me a flow speed of .05.

What does that mean, what should I do with that information to improve my prints?

Also what is the 10mm3 test?

Nozzle size = .4

Layer height = .06

Print speed = 20

Flow =.05

Max flow = 10

SF = 1

Max speed = 417

Max layer = 1.26

 

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Gr5

How do I determine the degree of my Bowden springiness, if its too springy how would I correct it? My quick coupler broke and I replaced it by combining parts from the two designs below, not sure if that would effect Bowden springiness:

https://www.thingiverse.com/thing:17027

https://www.thingiverse.com/thing:65838

Also I'm still hung up on knowing how much my printer is extruding? Is Cleven's calculator is telling me my printers flow speed when I put in my values into it for print speed, nozzle size, and layer height?

 

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Flow is the volume of material moving at that print height. If you wanted to achieve the max flow possible of 10mm3/s then you would need to set print speed near 417mm/s which isn't really advised or possible. If you did the print test then put the value you were able to achieve it could be 7-10mm3/s. I was able to get 10 maybe you get less or the same.

Overall this Basically is giving you the flow rate so you know that your feeder can handle the volume you are asking it to push.

In the right corner you set yhe max volume your printer can handle. Then when you set your layer height and speed etc it gives you the volume flow so you are not pushing any limits. I would only set the value to like 7 where I was able to get a perfect print even though I was able to get 10.

Play around with it you'll see with a few tests. Read gru's notes it will help you too

 

Cleven I read the thread you linked and inserted the values I am using for my nozzle size, layer height, print speed and left the values you had inserted for max flow and SF. The calculator gave me a flow speed of .05.

What does that mean, what should I do with that information to improve my prints?

Also what is the 10mm3 test?

Nozzle size = .4

Layer height = .06

Print speed = 20

Flow =.05

Max flow = 10

SF = 1

Max speed = 417

Max layer = 1.26

 

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Gru replied above. I was referring to that.

Here is the forum on the flow test.

http://umforum.ultimaker.com/index.php?/topic/4586-can-your-um2-printer-achieve-10mm3s-test-it-here/?hl=10mm&do=findComment&comment=39458

The file is here:

http://umforum.ultimaker.com/index.php?app=core&module=attach&section=attach&attach_id=809

Print at 230c read the forum post above for more info and what others have said. But this is just more a guideline. I never try to print at max rates. It just isn't worth it as too much can happen :).

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