BE CAREFUL - very thin tips


F’ing nice fit - thx again GP



Looks like your printer works well! Think I need to order one of those.

On my 3rd set of hoop connectors and they are all looking good. I also did some other printer mod prints before and they look great as well.
I found a site that sells a compatible auto leveling mod for this printer that I might do later. For now it is working fine.

Awesome…thanks!! :+1:

Important! Sorry guys but there is design flaw with my design created by the intended print orientation. I was hoping if I printed them solid that the layer adhesion would be strong enough but while removing the hoop I broke a tip (I leveraged on the tip too much with the hoop). It split through the layer lines like wood splits with the grain.

As a solution to prevent the others from breaking I installed a 1-5/8 inch long grabber screw.

I just pre-drilled and countersunk the holes rather than re-printing them but if you haven’t printed yours yet here are the files with the new holes:
Reinforcing Connector w Grabber Screw - Left Tip.stl (1.8 MB)
Reinforcing Connector w Grabber Screw - Left Center.stl (1003.2 KB)
Reinforcing Connector w Grabber Screw - Right Center.stl (1003.3 KB)
Reinforcing Connector w Grabber Screw - Right Tip.stl (1.8 MB)

This was the cheapest fix since grabber screws are pretty cheap.

Another option is to use longer bolts into the standoffs (M3 x 30mm instead of 12mm) and make the counter bore more shallow. This requires re-printing the tips (if you have printed them already) and purchasing 16 screws (80 cents each at my local hardware store adds up fast when you buy 16 of them).

Here are the files for that option:
Reinforcing Connector w 30mm Bolts - Left Tip.stl (1.7 MB)
Reinforcing Connector w 30mm Bolts - Left Center.stl (975.0 KB)
Reinforcing Connector w 30mm Bolts - Right Center.stl (975.1 KB)
Reinforcing Connector w 30mm Bolts - Right Tip.stl (1.7 MB)


I’m new to the 3D printer thing (just ordered my Prusa), but wouldn’t PETG be a better material for these? I understand you are prototyping solutions and PLA is easier to work with. I thought PLA would have issues with being exposed to the elements and PETG would be stronger.

What material are the OpenPPG printed parts made from?

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I use PLA Plus and I never have issues with exposure to the elements. If PLA is left in direct sunlight in a car it can get hot enough to get soft and distort but I keep my OpenPPG in the trunk so that hasn’t been an issue. And if a part ever did wear or distort… hey, I printed it in the first place so I can just print another one.

Yes, PETG has its advantages but regardless of which material you print with the layer lines will always create a weak direction and therefore the changes above are necessary for optimal strength. I’ve worked with PETG with my Prusa and have been satisfied with the results but I don’t have any red :joy:

Also, it’s not exactly prototyping if I never intend to make it with a mold later. FDM printing has become more and more a manufacturing process and not strictly for prototypes. All of the plastic parts on the Prusa are 3D printed but that doesn’t make them prototype parts. What it does do is give them the ability to constantly make small improvements to their product that with other processes could cost thousands of dollars to change.

Enjoy your Prusa and I hope you have good luck with it… have you ordered some red PETG to use with it?

I agree that the changes you made will provide better strength. I really like your solution for protecting the tips.

IIRC, the Prusa parts are printed with PETG. I did order a roll of black PETG, and I plan to use that for any parts I plan to fly with. I am looking forward to building the printer kit when it arrives.


Thanks for this, they printed perfectly and work great!

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Ok - so what is the final word on the best option – The new 30mm repint in PETG, solid fill?
I got no problems doing a reprint - thats why I got the dang thing anyway :grinning:
Anyone use the Amazon brand PETG - seems to be cheaper!!

I’m new to this, so bear with me. My reading so far has convinced me that PETG is the right material to use for 3D printed parts on OpenPPG. Supposedly, there is not much difference printing with PETG over PLA. That said, for dimensionally-correct parts, the shrinkage might be slightly different between the materials. It might be necessary to scale the part slightly in some of the dimensions to get the right fit.

PLA is fine as long as you use one of the new designs. PETG might be a little better but finicky to work with. You wouldn’t save much weight or cost doing anything other than solid infill with these small parts. I would prefer the longer bolts but I am totally happy with the grabber screw version.

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I think the default setting when i did mine were 30% in the Cura, will need to check that again. Ok buy me I will stick with the PLA for now. I like the 30mill design – the 2 evenly spaced bolts makes for more sense to me. I will print them solid.

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Can you confirm the bolts required are m3x30mm? Will order these parts on 3dhub

Yes, M3 x 30mm Cap Head

Too me it looks like you did not get enough heat. Correct me if I am wrong but to me the white spots indicate the material bonded very well? Where as, No White, the rest, did not bond at all.
The Cura slicer has the new Gyroid infill that is suppose to be very strong,as long as you are achieving good layer adhesion.

Good observations. Two settings that could improve layer adhesion are heat (like you are suggesting) and flow rate which would press the hot material better onto the cold material. Turning up either of those settings too much will mess up the quality and tolerancing of the print. I do have my heat settings higher than the default for this filament. I could possibly improve my layer adhesion more but it broke because I put too much leverage on it with the hoop and the layer lines will always be the weak link.

I just took a closer look at the picture and I believe the white actually indicates the point of initial failure. Notice the white is only on the top edge indicating that I leveraged downward with the hoop. So the white is a tensile break while the rest is a lateral break.

Nonetheless the new design will fix it.

I put my extruder heat in the middle of the recommended manufacturers range(Sunlu 205-230C) at 220. This is well above the recommended PLA setting of Cura…185 I think. No bed heat is listed on the box but everyone else seems to think 60 is a good setting.
I did slow down my print speed(40 I think) as well on the last batch and will do the same. I will also use 50% fill with the Cura’s Gyroid fill pattern setting - like you point out the failure was at the outer edge, so without good adhesion a solid fill is pointless anyway…well not pointless but not enough to matter.

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We only need to reprint the outside Left and Right pieces if we already did all the previous version?