The summer seems to have killed my MPCNC

I went to cut some plywood a few nights ago, my machine had been cutting fine previously.
When the job started I noticed the the endmill bogged down a lot at one side of the wood. It was visibly cutting deeper at one side than the other. I checked to make sure nothing was after getting in under the wood when I clamped it and it seemed fine so I decided to check the heights of all 4 corners of the machine to make sure nothing had gone wrong.
Sure enough one corner of the machine was around 5mm lower than the adjacent one. I was in a rush at the time so I didn’t check any further and just went back to the machine today.
I went to adjust the height of the corner in question and noticed that it was loose, then I saw that the section where the screw is was cracked. I checked the other corners, all cracked to various degrees.
I started to check over the rest of the machine and found cracks in lots of parts, all quite severe.
I hadn’t gone crazy on the tightening of these parts and the machine had been working ok. The only reason I can think of is that the machine had been built and tensioned at around 10 degrees celsius and temperatures have been up to 22 celsius here in the last few days with a lot of sun.
The machine is also in a room where it would have gotten quite a lot of exposure to the sunlight, so I’m guessing that along with the fact that the parts are black probably got them up to a temperature where they expanded and softened to the point that the cracks happened.
Pics of a few cracks below. I think I’m going to reprint in PETG filament to hopefully decrease the possibility of this happening again.

I had the same thing happen with a couple of mine. I just ran a self tapping screw through the plastic into the pipe. Will print better feet later.

I’ll have a look later and see if enough parts are ok to make it repairable. There’s a lot of parts after cracking though. There’s cracks in the corner pieces and the clamps on the rollers too. It might be too far gone.

I found that in PLA, a lot of the original parts are really easy to over tighten and crack. So I have been gradually replacing my parts with PETG (the cheap Microcenter Inland brand). My Z assembly is PETG with a bit of ABS. The PETG is far stronger than the PLA. All of my parts use 0.3mm layers.

Is that the Makita router or the Dewalt?


Ya I’ve found PETG to be a lot stronger in the past too for parts that will have stress on them. A little pricier but should be worth it.
Have you had any parts crack that were printed in PETG?
The router is a Katsu 101748. It seems to be a rebranded Makita RT0700, from what I can see it’s identical other than 1 part of the plastic casing on top.

It would be interesting to know if color/brand of filament have anything to do with the PLA cracking. Either way it could just be that the black color heats up a bit more in the sun. I am still in the middle of printing all of my parts to get mine up and running. I have been printing the majority of the parts off on an xyz davinci jr with hatchbox lite green pla. I plan to start a build thread to post my progress along the way. Take care,

Funny that you should mention that. My parts were actually printed from 3 different brands of PLA.
I know that while printing the feet that I ran out of PLA and switched to a different brand. The spindle mount that cracked was printed from a 3rd brand the brand I had been using was out of stock.
1 brand was from Craftunique that I got with my printer, another was eSun and the 3rd brand was Colido.
All 3 had quite different characteristics when printing. The Craftunique stuff had to be printed about 20 degrees hotter than the other 2 types and didn’t like to adhere to glass. The eSun and Colido printed well at similar temperatures to eachother but the bed adhesion of the Colido was fantastic.

The Inland(microcenter) petg is pretty much the same price per kg as their pla. Both are about $20 per 1kg spool, unless you get the fancy stuff.

That’s a great price, I can’t find anything quite that cheap over here (Ireland). The cheapest I’ve found is around $30-35 per kg shipped.
If I could get PETG for $20 per kg I’d probably use it exclusively.

I had a bunch of parts I printed with black esun fail. Some before I even put screws into them. They cracked just sitting on my desk unstressed :frowning:

That whole roll of black esun I had was junk. It would feel flexible and not brittle when I’d test it…but after every print it would snap an inch above my extruder and there’d be a few inches of brittle filament. Then after printing the parts would look ok…but a few days later they’d all be brittle and many broke in half just sitting there.

I ended up reprinting my whole machine in PETG since I have to keep it in my old office which is a free standing building in my backyard that I don’t keep air conditioned…and I live in the AZ desert (114f last weekend) so I figured PLA wouldn’t hold up. I followed the printing suggestions but added a 4th perimeter with the PETG to help make up for it being more flexible…but not sure I’d do that again as it made the feet very difficult to get on the conduit (everything else went fine.)

I got my PETG from Atomic and Maker geeks and love it. MG had a sale going with 2 rolls for $33 shipped but they pick the colors…thankfully they managed to send me colors I liked :wink:

Wow, PETG is really well priced over there, I couldn’t even get PLA that cheap over here. I’m reprinting mine at the moment in PETG, the brand is Prima. Cost around $35 per kg but as long as the machine is strong I’m happy.
I had the old corner parts and the old center parts in my machine before so at least I’m upgrading to the newer parts now.
I had one print fail earlier, the printer just locked up for some reason about a quarter of the way through the print so I used the failed part for strength testing. What was printed was about 5-6mm thick, I tried twisting and bending it as hard as I could and no way would it break or even crack. I’m quietly confident that the machine will be more than strong enough when printed with this.
I’m going to print some feet and clamp them onto a piece of conduit and leave it bake in the sun for a day to see if it cracks or deforms.

I have yet to put my mpcnc together so only time will tell. I am quite new to having a 3D printer of my own but so far I am really impressed with how the hatchbox pla feels vs the stuff that came with the machine (xyz davinci jr). the natural stuff that came with it printed well but feels much more brittle than the hatchbox material.

What about that tempered high temp PLA from protopasta? Looking to get some of that in the carbon fiber PLA to run off a batch of parts just for grins.

Just to follow up on this. Our temps here the past week have been hitting 115f. The other day I got in my car and it was reading 119f outside. So I’ve been torture testing a few extra/misprint parts from my MPCNC build. I have both PETG and PLA sitting outside in full sun. Around 3PM at full heat the PLA is soft and I can dent/deform it. Full (or nearly full) parts I can’t really reshape but I could slightly deform. Partial prints that aren’t as substantial (or something less 3D like the motor mounts) can easily be bent/reformed.

It seems that the extra perimeters and high infill give the parts plenty of strength even in temperatures high enough to soften the PLA. I wouldn’t actually run a machine in those conditions…and I’ve been keeping the AC in my shop on at 86 (the warmest it will go) when I’m not out there just in case. But I think when I start printing the new parts I’ll do so in PLA instead of PETG this time. Unless my next electric bill convinces me that even cooling the shop to 86 is too expensive as the temp in the shop gets higher than the outside temp when I don’t run the AC out there.

Oh - the PETG parts out in the sun…rock solid still. So they are far better suited for heat. But I’m not sure the slower printing and hassles of getting PETG dialed in are really worth it on this.

So far I haven’t had any issues with my petg parts in the heat. My barn is only air conditioned by fans, so no real cooling for inanimate objects. Just did a 20ish hour cut and nothing flexed or moved other than my dust collection bucket. Hit 100 here yesterday, and was in the high 90’s to low 80’s during the cut. Though the few parts that are still pla haven’t moved either. That would be the feet, and a couple of the leg parts I think. Oh, and the motor mounts are still pla. I haven’t noticed if the’ve warped or not, still run the router around, so I’ve not looked.

I had Australian heat kill my first MPCNC (printed in cheap PLA) so I re-printed in a combination of Taulman Tech-G and N-vent.

Huge improvement in rigidity/stiffness, and no cracking /deformation so far with several hrs of aggressive use.

I’m just about to do some testing on using it as a printer. I’m going to experiment with how far I can push the speeds and acceleration before inaccuracies become apparent. Will be interesting.