Thanks for the reply. And thank you as well for including suggestions for different temperature settings and layers.
Is there a formula that provides a good starting point for the relationship between layer height, filament temperature and build speed?
It took us a while of trial and error to arrive at the 205ºC/40mm/0.1mm value!
Edited by GuestThose are all good suggestions, and certainly the first place to start...
If you want to go a bit more advanced, you can look into the "olsson block"...
Originally developed by a UM2 user, but now fully supported and sold by Ultimaker (amongst others), its an alternative heatblock that lets you fit different sized nozzles which will allow you to finish prints faster (or make super fine detailed small prints with the small nozzles)
Edited by GuestOh yeah - I forgot to mention - use a .8mm nozzle and now your walls/shell will come out in one pass isntead of 2 and you can print with thicker layers because the .8mm nozzle has much less "resistance" than the .4mm (4X less of course - it's based on the area) so you can print with 4X volume.
Anyway just printing the wall in one pass instead of 2 will double the speed right there even if you don't thicken the layers also. Thickening layers to .3mm really starts to lower the visual quality quite a bit!
Multiply the speeds by the ratio of layer height to get tables for other layer heights.
Here are my recommended top speeds for .2mm layers (twice as fast for .1mm layers):
20mm/sec at 200C
30mm/sec at 210C
40mm/sec at 225C
50mm/sec at 240C
The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.
it might be more helpful to give you a table in cubic mm/sec. If you hover over the speed or layer height in cura it shows you the volume of PLA in mm^3/sec. You can use that number in this graph however the following graph is also different in that this is max volume and I recommend printing at half the max volume:
Above graph is PLA only.
Everything is a tradeoff - the max volumes in the graph above is what a perfectly tuned UM2 can do with brand new teflon part and so on. Notice that at 230C the max volume is about 8mm^3/sec although some people can achieve 10 or even 12mm^3/sec but with some minor underextrusion. Ultimaker tests every printer at 8 and at 230C before shipping (I was told).
However you also get better quality at the lower temps. PLA is more like toothpaste at 180C and more like honey at 240C. "Honey" doesn't print as well as it moves a bit after it is placed whereas the "toothpaste" stays where you put it long enough to harden.
Also if you always print at 240C but you print slow (say 1 cubic mm/sec) or don't print at all while the nozzle is at 240C you can bake the PLA into a clog. You want to keep things moving at that temperature. This is even more true with ABS I have done many prints at 240C no problem but stil...
Wow thanks for the detailed replies! I'll have to wait until my boss gets back to try find the larger nozzle.
I did try printing a raspberry pi frame at 1.6mm height and 210°c, but I got some underextrusion. Bumped the temp up to 212°C and it was a little better, however I did see the corners warping off the build plate.
I'll try the frame again tomorrow at 214°C, with more careful glueing and see how I get on. I don't recall setting the temperature as high as 240°C yet, so think we'll be OK.
It surprised me how minor the increase in print speed affected the large robot chassis print. Layer height definitely seems the place to get the pure speed gains.
Just a quick update. Printed a larger part with some 'quicker' speeds. Excellent results. Not as refined as the previous slower prints, but definitely impressive. Had a few spots of underextrusion, nothing major. Had to let the bed completely cool before it'd let me pop it off.
So this time I used 0.25mm layer height, at a temperature of 228ºC, all other settings stayed the same.
Thanks for the suggestions - particular the chart of related heat/speed relationships.
Nice. The last photo above shows some underextrusion on the walls - that pattern.
Regarding corners "warping off the bed" - this is a common problem and easily fixed but you have to know a few tricks. Basically you need to make it stick better. Much better. So well that you will then be asking me how the hell do I get parts off the glass? here is my standard cut/paste:
lifting corners, curling corners, part sticking to glass
1) Make sure the glass is clean if you haven't cleaned it for a few weeks. You want a very thin coat of PVA glue which is found in hairspray, glue stick, wood glue. If you use glue stick or wood glue you need to dilute it with water - about 5 to 10 parts water to 1 part glue. So for example if you use glue stick, apply only to the outer edge of your model outline then add a tablespoon of water and spread with a tissue such that you thin it so much you can't see it anymore. wood glue is better. hairspray doesn't need to be diluted. When it dries it should be invisible. This glue works well for most plastics.
2) Heat the bed. This helps the plastic fill in completely (no air pockets) so you have better contact with the glass. For PLA any temp above 40C is safe. I often print at 60C bed.
3) heat the bed (didn't I already say that?). Keeping the bottom layers above the glass temp of the material makes it so the bottom layers can flex a bit (very very tiny amount) and relieve the tension/stress. For PLA 60C is better than 50C. 70C is even better but then you get other "warping" like issues at the corners where they move inward but if you are desperate it's worth it. For ABS you want 110C (100C is good enough).
4) rounded corners - having square corners puts all the lifting force on a tiny spot. Rounding the corner spreads the force out more. This is optional if you use brim.
5) Brim - this is the most important of all. Turn on the brim feature in cura and do 10 passes of brim. This is awesome.
6) Squish - make sure the bottom layer is squishing onto the glass with no gaps in the brim. The first trace going down should be flat like a pancake, not rounded like string. don't run the leveling procedure if it is off, just turn the 3 screws the same amount while it is printing the skirt or brim. Counter clockwise from below gets the bed closer to the nozzle. Don't panic, take a breath, think about which way to move the glass, think about how the screw works, then twist. This may take 30 seconds but it's worth it to not rush it. You can always restart the print.
Good advice. I have had some good results printing with a brim, but for some reason I didn't use it this time.
With regard to the underextrusion, do you suppose knocking the temp up from 228ºC to perhaps 232ºC would sort it?
If anything that large print stuck on the bed TOO well! But it was just a matter of waiting for the bed to cool completely then it popped right off.
228C to 232C will make no noticable difference. You would need a very accurate scale to measure the difference in weight of the final print. Visually it would be very difficult to tell the difference. Now if you want to 245C that might help a noticable amount. Or if you print it at half speed.
Just print the part - and then part way through go to the TUNE menu and set the feedrate or whatever it's called to 50%. Maybe mark the part on the layer when you change it and notice the difference below and above the mark.
I think generally, we're happy with a slower print, but because this part was so large I wanted to ensure it would finish printing during work hours. We have previously had a couple of failed prints that we didn't discover until the next day.
I think res arching the Olsson block and an 8mm nozzle will be the next step.
I'm impressed at how easy it is to sand or file the plastic after which helps to smooth out the appearance.
Those are good results.
White PLA is tough to print, I have found 
I would definitely agree with that. It took us a while to find good settings for use with the White.
Thankfully now though we have a couple of nice Acura profiles setup for our machine. One is high resolution slow prints, one is lower resolution quick prints.
It also didn't help getting cheaper filament, but it's worked out OK in the end!
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You can probably speed things up a lot. Well it all depends on the print but often you can print with no infill. For parts shaped like a potato versus parts shaped like forest of trees you may get great speed improvements.
The obvious answer is to print thicker/faster/hotter. If you simply switch from .1mm layers to .2mm layers it will complete in half the time (11 hours versus 22 hours) but note that you probably have to increase the temperature. At your current speed of 40mm/sec and at .1mm layer height you want at least 200C. But at .2mm layers you want at least 225C. This will lower quality a bit but you will probably be fine with it.
or you can go somewhere in between - .15mm layers needs about 210C at 40mm/sec.
If your parts has lots of straight lines then speeding up print speed will also help but if it has lots of very short lines for example yoda or pretty much any sculpture (animal, person) then it probably won't print much faster with higher print speeds as it needs to slow down at every vertex anyway.
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