Thread: Material suggestion for a small gear?

I have an STL drawing, from which I hope to get a speedometer gear made - a helical pinion.
It's not under a great load, and I've seen such gears made from plastic in car speedo gearboxes.
Any suggestions for a suitable 3D printing material, that might make for a long lasting result?

What size gear are we talking about? Do you have a link to the STL?

Although 3d printing claims 0.2mm resolution, the reality is that even 3d printed threaded holes are a tough call.

On the other hand I have seen some great success stories 3d printing change gears for lathes.

If its an easily accessible/replaceable part then don’t bother with exotic materials or filaments and just PLA it.

Else PETG is fairly durable and has become a favourite for chemical, oil, UV resistant applications where PLA suffers. Mechanical resistance is slightly better than PLA (I say slightly because ABS is way better but warps on longer prints unless we have a heated chamber).

Plastic gears (when moulded or machined) are typically nylon or acetal. Depending on your printer, that may or may not be possible.

Michael

I printed small differential gears for my son's remote operated toy vehicles and my son has printed large gears for his 3D printers.
For anything that turns slowly and are lightly loaded even PLA works but eventually they do wear - if the gear is easily accessible then just print another.

I've printed a differential gear for my son using PLA, Carbon fibre impregnated PLD and ABS and they've all work but the last two were better for wear.

If you wanted longest life I would print with nylon but not many 3D printers can do this.

The gear is easy to remove, no problem to replace.
It's not on a vehicle that gets a lot of use, and doing it yearly is acceptable.

Size is about 22 x 12mm overall, with a 6mm bore.
I can't upload the .stl file here.

You can upload it to https://filebin.net/ and share the link here.

Looking at that overhang being at a 40 degree angle might be a slight challenge but if you have a dialed in printer then you can do it without supports.

If it’s easily replaceable then do print it in PLA.

I can try printing it for you in PLA and PETG (FOC offcourse) if you don’t have a printer and post it to you. Let me know, happy to help.

That would be a great help, thanks Kafie.

Filebin works very quickly. I'll be using it again I reckon.

The link number for the STL file is 92t2k9lr4357oog4

I will have a look at the file once I get home and run a test print in PLA first and let you know how it goes.

That is a fairly small part. What is it going to mesh with?

Printed one in PLA at 0.1mm layer height:

74B7C56D-6393-496B-BFBE-B8120568D6EE.jpg
311ED079-570F-476D-A3F2-C26412B5721B.jpg

These are fairly magnified images from my phone to show you the layers. (I have a 0.4mm nozzle on my printer.)

The design is definitely printable without supports and feels rigid based on my finger pressure however PLA can be scratched with a finger nail just to give you an idea on hardness.

I will print another one in PETG after this.

Printed another in PETG at 0.1mm payer height.

4E8061B4-D90F-471F-B1DC-3D2FD2E05E06.jpg

PM me your address so I can post them to you on Monday.

That was fast.
Thank you very much.

Here's the mating gear.

No dramas, Don’t mention it.

I think the real test is if these will hold in your application and it will be great if you report that.

Remember, grey is PLA and yellow is PETG both printed at 100% infill and 0.1mm layer height.

Plastic shrinks slightly and the internal bores on such small diameters need slight cleaning. Run a reamer or a drill bit by hand through the bores to clean them up slightly and don’t apply too much pressure. I didn’t know what your exact shaft dimension was else I could have done it.

If you wish to use a light grease on plastic (gears) something like a silicone based grease is most likely to be OK, Avoid using an ester based grease as it can slowly soften and eventually dissolve many plastics.

Originally Posted by BobL

If you wish to use a light grease on plastic (gears) something like a silicone based grease is most likely to be OK, Avoid using an ester based grease as it can slowly soften and eventually dissolve many plastics.

Thanks for that alert, Bob.

Kafie's printed gears turned up in today's post.

The yellow PETG one is likely to be tougher, but I'll try the grey PLA one first.