First off, I know there are a ton of threads on this and I didn’t really want to make a new one. But reading them made me even more unsure.
Has any one who started with PLA and switch to PETG or vive versa have any strong options on which is better?
Or did you start with one and never look back? Regret it?
I hear people switch to PETG because the PLA cracked too easy (or melted). And people who switched to PLA because the PETG wasn’t rigid enough for this application.
I’m leaning towards PLA since rigidity seems more critical from what I’m reading (and just make sure not to over tighten the bolts). But I wanted to ask the community one more time before I go and tie up my printer for 60+ hours.
I will admit i have not tried both, but being very familiar with both my thoughts are stick with the PLA. i think most of the people who had the PLA crack probably did not have well printed parts (maybe they used cheap/old PLA or their temps where off or some other defect causing the PLA to be weaker then expected). i do think melting of the PLA is a concern if you plan on having your CNC somewhere where it gets above 110’F regularly, but since you should not be leaving the machine alone while it is running (and there should be almost no stress on it when not running) i would think if it is that hot in your shop you should find a way to cool down your shop rather then print in PETG (at least i am not going to sit in a 115 degree shop for 6 hours for a CNC project, maybe you are ok with that).
Yeah, that makes sense. I also noticed some of the pictures of cracked PLA had the layer lines going in a direction that is not ideal too. I have no intention of letting it get to 115 degrees so the heat one is not an issue for me
then i strongly recommend printing with a good PLA brand, it will be easier and cheaper. if you feel like going the extra distance turn on the “alternate extra wall” setting in Cura. i find that adds quite a bit of extra strength to most prints
Consider Ryan’s no slacker when it comes to updating/improving his designs when there’ll be meaningful change yet throughout it all the recommendation for PLA remains.
Since the layer direction is determined by the slicer settings I in no way meant that as a criticism of the design. More a comment on how some people who build the MPCNC may just put the print on their bed and not put much thought into how the layers line up vs where the stress will be.
To be fair, right after the recommend PLA the instructions say:
PETG is also acceptable, if your dimensions are verified good and you are willing to sacrifice some rigidity
And it is clear a bunch of people here did choose to go the PETG route for whatever reason.
But going with PLA, thanks for the feedback. Wish me luck.
I’ll update this thread in a month or two with the outcome to help out future web surfers
No worries, I didn’t think you did. I have a burly which works quite well and I’m sure the primo required much work in design/testing yet now we have it. I spent a lot of time fooling with bikes/cars in my misspent youth and have been down the road a few too many times where what you’re promised and what you get are sometimes not even in the same zip code so dealing with V1 has been a pleasure as things are as promised if not better.
Ryan also considers the direction of printing. I don’t know how often this is said (could probably be said more), but don’t rotate Ryan’s parts. They are oriented in their strongest way, to solve the machine’s constraints.
IMO, PLA should be everyone’s first choice, unless you really like PETG and in that case, use a lot more perimeters. Don’t overtighten anything. The bolts are way stronger than they need to be just because we can, and it makes the BOM simpler.
It is not a direct experience with the MPCNC but I have my LR completely printed in PETG. If I had the chance to come back I’d do it in PLA (maybe with a nozzle bigger than 0.4).
PETG is really less rigid, even with 4/5 walls and an high infill percentage.
The first set failed because it was hands down the worst filament I’ve ever tried to use. I had ordered Hatchbox from Amazon and was sent eSun, decided to try it since some people spoke highly of it. Every part printed in that eSun filament failed. Most while just sitting on my desk with no stress. They would just suddenly crack and split. And not with the layers - right across the layer lines. Just horrible fillament.
I reprinted all my parts in PLA. And built my machine up as 2’x2’. But my plan was to build it large enough to do 20"x30" foam board…so that was only temporary. And once I saw how big the 2’x2’ version actually was I realized there was no way I could put my final machine in my house and it would have to live out in my shop. I live in southern AZ in the sunniest place in the US, we regularly have weeks of 113f in the shade. My shop has AC…but at the time I only ran it when I was going to be out there.
So…I reprinted everything a 3rd time out of PETG.
My machine is now way outdated. I built it in early 2016 and Ryan has released 3 major redesigns since then. My machine still works though due to some life changes it doesn’t get used nearly as much right now. But…it also doesn’t get used as much because at the size I built it 3’x4’ and with PETG and the old design it just isn’t rigid enough to do a lot of what I’d like to (and was able to do when it was 2’x2’ PLA.) It does work great for cutting foam…but it takes up way too much space to use it just for cutting foam…and it’s ability to cut wood and plastic is nowhere near as good as it was as a 2x2 PLA machine.
I had a few failed prints so Put some of the PLA and PETG parts in my truck to test how they’d handle the extreme heat. I’ve baked cookies in my truck more than once during the summer…so I knew this would be a good heat torture test. Both parts held up really well. With all the walls and infill that Ryan recommends the parts are solid enough that even when they soften they don’t deform much unless they’re under stress. But even the PETG parts got soft enough I could deform them after a day in my truck. Though - I also found that the parts did anneal and after a few days in the truck they help their shape even when they softened. Though the PLA annealed more than the PETG.
So I want to rebuild it again as a Primo with 1" tubes instead of EMT…and since I’ve given in and now run my AC all summer in the shop anyway after seeing the results of my heat test…and I’ve learned that running the AC out there doesn’t impact my electric bill as bad as I feared it would. So when I do get around to rebuilding again it will be PLA this time…though I’ll also splurge on some really nice PLA (probably from Atomic since I used their PETG and really like their filaments.)
For me the ultimate for structural parts is ASA, it provides the strength of ABS but without the warp and dimensional issues. The downside is I’ve only ever found it in black, grey and natural - so much choice for colour contrast.
True, but for anyone looking at using an engineering plastic to make their machine, ASA is a great choice and at around $42 au per kg it’s only $10 per kilo more expensive than PLA in my country.
“ASA matches or exceeds
the mechanical properties of standard
ABS and has greater heat resistance.
Moreover, ASA demonstrates
exceptional UV stability and, with its
matte finish, offers the best aesthetics
of any FDM thermoplastic”
I’d never heard of ASA until reading this thread and haven’t been tempted to try ABS because of its warping tendencies. ASA sounds kind of interesting. Maybe a good material for those talking of replacing belts with racks and pinion gears?
If I build another machine I might try HIPS, not generally chosen as a primary filament. But it is as rigid as pla, affordable, and has a higher operating temp.
It behaves very much like abs, and is a popular choice as a support structure filament for abs because it can be dissolved. So there is some concern about warping, but it is generally regarded as mildly easier to print then abs.
Again pla would be my first choice. But I think as a higher temp alternative hips would be a great choice. And if I ever reprint I would give it a shot if for no other reason then I’m curious XD
