PLA or PETG for parts?

Mostly Printed CNC - MPCNC Advice
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I am about to start my build as soon as this week

I am planning to use PETG for corners as I can see those parts requires some tightening, tight it just right and crack the piece is sometimes only a quarter turn away :stuck_out_tongue:

but printing all parts with PETG seems time consuming because the slower speed (40mm/s vs 80mm/s)

this sound so greedy that I don’t want to double the printing time but still want the build as rigid as possible.

I really appreciate some advice that which PLA parts failed you and you have to do it with stronger filaments (PETG, PC+, PLA+ etc)

my current plan is to print feet and corners in PETG, anything else?

Thanks.

2

PLA is stiffer than PET, but PET can handle higher heat and is marginally stronger. My center section is all PET, but I think my tower parts are PLA, can’t really remember anymore. Either will do fine unless you have your cnc in an unheated or cooled garage and you get a lot of extreme temperatures. All the parts from the store here are PLA.

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actually I am planning to put that in my basement workshop, there is no heat in the winter, it’s about 10C at most, in the summer there is no window so no heat exchange, it’s about 23C

so I am thinking other than corner parts, the rest will be in PLA for now and see how they hold up, any broken parts will be replaced with PETG, PLA is way easier to print and faster.

 

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At what ambient temperature would you need to worry about PLA melting/deforming? I’m not sure how hot our garage gets, but I would assume 100F or higher might be possible on especially hot days.

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You are looking for the glass transition temp. 60-65C

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60C=140F. Yup, it definitely won’t ever get that hot in the garage.

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My shop here in AZ gets up to 120F+ in the summer when I am not in there with the A/C running. I have multiple printers and the MPCNC. I’ve only ever had one part deform that I would attribute to temperature and it was a tension lever for a customer extruder that was printed from PLA. The high heat and constant strain made it deform by about 2mm, but even that took a very long time at those temperatures. Other than that, no issues. I have steppers that get hotter than that with no ill effects on the PLA mounts.

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original plan was to print a PETG and PLA mix parts, but I think I will print them all in PETG with 30% triangular infill, hopefully that’s strong enough

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So a more flexible material and less infill? Might want to stick with the recommended infill or higher.

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well, even PETG is printed at 100% infill, the property of flexibility won’t be remove.

I have some parts in a d-bot printed with 100% infill PETG and, it’s still as flexible as it should.

came across this video on youtube

glad I use the triangular infill which actually fill about 45% when I tell S3D to fill only 30%, lol

but just in case, I’ve changed the perimeter to 3 and 4 bottoms and 4 tops, hopefully my printer will still give me a dimensional correct print :smiley:

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All my pet-g parts are 4 perimeter, 50% infill. Most of the printed parts on both my cncs are pet-g. Mainly because it will flex a little before breaking. Pretty sure the only pla parts left are the feet on the mpcnc. I just printed the new feet, also in pla, 3 perimeter, 50% infill.