Dadio's 3D Printing Stuff

[Dadio]

Took about a minute to strip the first two gears so i rebuilt the box with just the diff and idler gear in resin and ran again with no holding back and got another 5 min before they failed , still no use at all but it was an interesting experiment , i have some Siraya Tech Blue engineering resin coming so i'll try again when it arrives , the cool thing about these Siraya Tech resins is you can mix them to change the properties so the fun will go on !

[XLR8]

Good info, thanks for posting.
With how much power? What motor were you running when the gears failed?

[Dadio]

It was running a 17.5 t BL sensored system with a 21 tooth pinion and 2s lipo on grass with high traction , pretty quick by vintage standards ,mild by modern standards , with a 27t stock vintage motor and ni-cad/ni-mh then they might surive a 5 min run or two ,maybe more ? I guess I should try it for due diligence but from printed parts I'm always looking for something I can abuse , I can use genuine parts if I baby them !

[XLR8]

Okay, well that seems respectable. I thought maybe you were still running one of those cheap chinese brushed motors. 17.5 brushless is respectable power and running the car in grass will exert maximum loading on the gears.
I think you were wise to start with gears. I'd reckon that suspension arms and gears offer the greatest test for 3d printed parts. Find a material that survives as a printed arm or gear and you can use it everywhere else.

[Dadio]

The new resin arrived this afternoon so i'm running a test print to check settings , this is a you tube channel CNC Kitchen (excellent channel) testing the blue resin and comparing it to 3d printed filaments . https://www.youtube.com/watch?v=Yjm7aRKISMI

[Dadio]

Had my first print succeed with the new resin , this is Aria-the-dragon by Loubie off Thingiverse .

then i had a partial fail , all my own fault , apparently with resin printing its normal to manually place your own supports , i didn't know this and used auto supports , they were so dense they trapped resin between then and made a solid mess , i was able to sand it flat but its ugly on the bottom .

the other side is ok and i can still test then ok .

so its build the gearbox and test in the morning again , wish me luck !

[Dadio]

When I tried to fit the gears only one was actually useable , the little one so its in there for testing , I have another set printing .

[Pyxster]

This thread is making me want to get a resin printer.

[ROH73]

Me too!! Some great info, Dadio!

[Dadio]

Right now for this hobby I think an FDM printer is still most useful but the big advances in resins are worth investigating , at least for me .

[Dadio]

More good and bad today , firstly the good news is that i got a 5 min run till the battery went flat with the single resin gear in the gearbox , so the battery is on charge and i'll go again , i wasn't holding back either , i was jumping it and even had a front shaft pop out and lock the transmission , again on grass so its looking better with the new resin .
Now the bad and its probably my fault again , i manually placed supports and that worked well but i ran the print late last night and it finished about midnight and i left it till morning to clean it up , i think the long wait till clean up is the problem , some of the resin had pooled between the bottom gear teeth as it hung over night and seems to have partially cured cured there , i'm not sure yet why it cured as it was not exposed to light , it could be the way i've printed the part that's to blame , this is a transparent resin so potentially the pooled resin could have been cured from light spill from the next layers , this did not occur with the grey resin so i don't know yet how to solve the issue ? I'm printing a single gear now that I've used slightly shorter exposure on the layers and I'm planning on taking out the moment it finishes to see if that makes a difference .
meanwhile i was able to clean up the latest gears by using a metal pinion gear and using the edge of the teeth to carve out the pooled resin between the teeth , laborious and i don't want to do it again but i think it worked .
next is to put a whole pack through the gearbox with the single resin gear in it , if it stands up to it then i'll rebuild with two or three gears in there , i'll leave the diff for now as its a ball diff and more involved to swap about .

[Dadio]

After another run of nearly 10 min the single gear failed so I'm going to put this on hold for a bit , my feeling is that I need to learn (mess about) more and come back to it , I've only had the printer a few days so I'm very green about the whole process .

[XLR8]

Hmmm, I'm sorry. That's very disappointing but maybe there's a way.

For what it's worth... I'm really not qualified to comment on this topic but I'll toss this out there for consideration.
What about using the printer to make a mold to cast the gear from some kind of high strength chemical cured epoxy plastic?
Again, I have no experience with casting plastic but maybe it's worth consideration?

[Dadio]

Been playing again , i decided to try doing the gears flat with manual more minimal supports with one gear and flat onto the bed without support , i used 75% ABS like resin and 25% blue engineering resin for these prints .
Firstly this is the gear printed flat with supports , the first picture is of the upper surface as it prints and the second is of the bottom , the teeth are perfectly formed and the bottom is perfect like an injection moulded part but the top surface is a little less defined but tolerably formed . If it were strong enough then this would work .


Secondly is the gear printed flat on the bed without support , again the first picture is the top surface that faces the bed and the second picture the bottom . again the bottom face is like an injection moulded part and the gear teeth are 95% perfectly formed , the top/bed face exhibits elephants foot , this is where the bottom layers spread out and you lose fine detail and at this point only the teeth lose their shape , its only affecting 0.25 mm and would clean up with a little work .


So what we learn from this is that printing flat with supports although it leaves the top cosmetically less than perfect overall it could be used functionally but the unsupported gear would need some clean up .

[Dadio]

I fitted up the gearbox again with two resin gears , the first gear and the third , the second gear that i printed un-supported just would not clean up and run smooth but i had printed the third gear a knuckle and a top arm so i fitted the gear and other parts . I also de-tuned it to run with a brushed silver can that I've had kicking about for 35 years , some bald tires and ran it on road ,so far I've had two 5 min runs and still going strong , i did jump it off the kerb into the road a few times as well .



Its much less stressed now on the transmission and the top arm and knuckle have had no mishaps yet so I'll keep running it till bad things happen .