A Nice Gear Tutorial #1

Thank you for sharing the info.. I would like to make a replacement set of gears for my S.B. 9 inch.. Still trying figure out which way to go, single point, hobb, or a set of cutters. But spring time is a ways off yet, and I need to wait on warmer weather.
 
Ray C said:
I'm going to make some gears soon and came across this while brushing-up and refreshing my memory. Of course, the Machinist's Handbook has it all but, this is a very nicely authored and to-the-point tutorial. This is based on Diametral Pitch and not the Module method. I have some other guides based on Module method but need to check the copyright information.

Enjoy...

Ray
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I have just noticed some "plastic" gears being sold on eBay for SB lathe. Just started to dabble in plastic 3D printing and am having a hard time believing a plastic gear could hold up. Wonder what plastic they are using if indeed they work?
 
@Hit-N-Miss Tom POM / acetal / delrin is common for cut gears, and I've heard of more people lately printing it, though I've also heard that bed adhesion can be tricky. It's on my list to play with but I haven't ordered any yet. I've heard of and seen ABS for printed change gears, which is fine, but you may want to account for a bit of shrinking. Some of the modified PLAs (like PLA+) are probably a reasonable choice too. ABS typically shrinks more uniformly than PLA; PLA tends to shrink differently in Z than in X/Y but for a gear that's actually not a big deal.

I used PLA+ to print some bevel gears. I used 0.1mm layers for the bevel gears for a smoother bevel, but for spur gears I don't think that's valuable. Thinner layers aren't necessarily stronger. I think that 0.3mm layers with a 0.4mm nozzle is common for spur gears for change gears, if memory serves.

Annealing PLA will cause substantial changes, if I remember right it will typically shrink meaningfully in X and Y and expand in Z. This can be measured and pre-scaled against. I've seen multiple reports of annealed PLA being strong and heat-resistant, neither of which is a characteristic I normally associate with PLA. But I'd think that with PLA+ you would be fine without annealing.

For change gears, they shouldn't be under tremendous load. You typically have a clutch or shear pin to protect steel change gears; with essentially disposable plastic gears they will probably fail before a shear pin but should be fine for driving a lead screw.

OpenSCAD's MCAD collection has an involute gear module.
 
mcdanlj said:
@Hit-N-Miss Tom POM / acetal / delrin is common for cut gears, and I've heard of more people lately printing it, though I've also heard that bed adhesion can be tricky. It's on my list to play with but I haven't ordered any yet. I've heard of and seen ABS for printed change gears, which is fine, but you may want to account for a bit of shrinking. Some of the modified PLAs (like PLA+) are probably a reasonable choice too. ABS typically shrinks more uniformly than PLA; PLA tends to shrink differently in Z than in X/Y but for a gear that's actually not a big deal.

I used PLA+ to print some bevel gears. I used 0.1mm layers for the bevel gears for a smoother bevel, but for spur gears I don't think that's valuable. Thinner layers aren't necessarily stronger. I think that 0.3mm layers with a 0.4mm nozzle is common for spur gears for change gears, if memory serves.

Annealing PLA will cause substantial changes, if I remember right it will typically shrink meaningfully in X and Y and expand in Z. This can be measured and pre-scaled against. I've seen multiple reports of annealed PLA being strong and heat-resistant, neither of which is a characteristic I normally associate with PLA. But I'd think that with PLA+ you would be fine without annealing.

For change gears, they shouldn't be under tremendous load. You typically have a clutch or shear pin to protect steel change gears; with essentially disposable plastic gears they will probably fail before a shear pin but should be fine for driving a lead screw.

OpenSCAD's MCAD collection has an involute gear module.
Click to expand...
I made my South Bend 10K spur gear out of ABS, not that I needed it, but to see how, or if, it would work. Took 3 tries to get the size right due to shrinkage, but finally got it. So far it has been holding up great. It seems the shrinkage was greater on the inner than the outside dimensions. What came to mind was a foundry ruler that compensates for metal shrinkage. I have taken design measurements then compared them to plastic printed part and so far have not come up with a "constant-factor" for shrinkage. Perhaps too many variables involved.
 
Glad you got it to work!

If you don't have a heated build chamber, ABS will warp and shrink inconsistently as you print it. I should have mentioned that. The heated build chamber I made wasn't great, which is related to my having done more with other filament types. :)
 
mcdanlj said:
Glad you got it to work!

If you don't have a heated build chamber, ABS will warp and shrink inconsistently as you print it. I should have mentioned that. The heated build chamber I made wasn't great, which is related to my having done more with other filament types. :)
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Read somewhere that ABS should be printed on a Raft. Once I did that on the 3 tries I did get a consistant flat print. I set Tevo Tornado to .15 layer, 240 on the hot end and 95 on the build plate, fan 30%.
 
Ray C said:
I'm going to make some gears soon and came across this while brushing-up and refreshing my memory. Of course, the Machinist's Handbook has it all but, this is a very nicely authored and to-the-point tutorial. This is based on Diametral Pitch and not the Module method. I have some other guides based on Module method but need to check the copyright information.

Enjoy...

Ray
Click to expand...
Fantastic! Thank you for posting!
 
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