Layer height and strength

Mostly Printed CNC - MPCNC Advice
#1

I’m working on printing the Parts for my MPCNC build and I wanted to run a couple questions on part strength past the community. My printer is working really well for me so far and seems to make really clean prints. Its a Maker Select v2. I’ve got it tuned where I am really happy with my prints with one caveat.

I see where the suggested layer height for printing the parts is around .26mm. My printer has a little trouble printing at .2 and above where occasionally a layer won’t adhere to the layer below it as well. I’m tweaking the settings to see if I can’t work out this issue. I understand why it happens, the plastic cools too fast and just doesn’t adhere as well is my understanding. I have also seen that thicker layer heights are supposedly stronger.

How concerned should I be with my layer height in regards to the strength of the parts and are there any parts in particular I should be careful with this about? I feel like my prints look better and seem just as strong at .15 or .1 but it seems like there is a lot of wisdom out there to tell me it really isn’t as strong. I don’t care how long the parts take to print as I’m not in a hurry to get my cnc done but rather I want to have a really solid build when I do get it done. Thanks in advance.

#2

I don’t feel as if there would be any issues. Layer height is dependent on your nozzle size. If you have a standard .4mm nozzle you really need to figure out what is wrong, I would say clogged nozzle, or your parts will be weak from under extrusion at any layer thickness.

#3

Makes sense. I’ll clean the nozzle out and tweak my settings some more. I feel like my prints look really solid all the way through up to about .18 or so on layer height so I know I can try printing them there to get as much thickness as possible if nothing else works. There are a few upgrades to the printer I can do that I think can help if I need to as well. Are there any parts in particular that get more stress on them than others?

#4

Yeah, with a .4mm nozzle that sounds like something is really wrong. With a .4mm nozzle you should get a free extrusion width of about 0.48mm which should give optimal layers at 0.25mm ( https://nathan7.eu/stuff/RepRapCalculator/RepRapCalculator.html#PrintSetup )

You want a width over height ratio of at least 2.0 for strength, but more than 3.0 will start to decrease detail in the prints.

Though your Z axis mechanics will play into optimizing that layer height as well: http://www.prusaprinters.org/calculator/#optimallayer

One of the best writeups I’ve seen about calibrating extrusion is here:


I started using the same method just before she posted those and finally got things dialed in to where I could do print in place designs in any material successfully. Now anytime I get a new roll of filament I setup a new profile for it in slicer and do a couple of quick single wall test prints to dial it in. Accuracy on my prints has been great since I started doing that.

#5

Thanks for this. I’ll go through these steps and then tweak my heating cooling again to see what I get. I’ll post back how this went.

#6

I worked through this. I had a minor clog that cleared up the issue. Thanks for the help on that. I also discovered there was a little z wobble that seemed to be making the problem look even worse just by introducing some irregularities. I did the z brace mod for the printer and it cleaned it up quite nicely. Thanks all for the help.