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Functional Differential Gear System

by Thing-O-Fun Sep 24, 2011
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How many prints per part?
Does each STL only need to be printed once? Or some of them need to be printed twice or three times?

Great model. Had to sand the hole on the "side" piece. Printed it in PLA on a Prusa Mk2s. Nice little learning project. Only change I did was to mount a second planetary bevel gear, just to get the model complete. It was a little tight to screw it together, but no big problems.

Fantastic model!

The hole in the 'Side' piece was a tad too small (though I think I may be overextruding slightly, so...), but a circular file took care of that in short order. I also used a 3mm tap to put threads in as many pieces as made sense, and used a workbench vise to press the shafts into the handles. (The ends of the shafts actually left dents in the plywood I'm using to face the vise jaws; very impressive.)

Which kind of bolt did you use? Thanks.

Very cool model! Minor sanding necessary but good fitment!

Great model. I had some problems with fit between the knobs and shafts. Had to do quite a bit of shaving down with a knife for them to fit.

Really great model, professionally done!

Do i need to make threads in the parts?

thank you for sharing solidworks files

Agree on the 11mm Side Plate for the Gear Case. I made two spider gears and filled the centers. This allowed screwing the spiders to the spider shafts from the outside. Oh, I just read hahcutt's post doing the same thing. I couldn't find M3 screws. I used #4 sheet metal screws and cut them to length with a Dremel. Great model to demonstrate how a differential works. Printed perfectly on a Flashforge Creater Pro.

The inner hole for the "side" piece should have a diameter of 11mm, not 10. That would make it match up with all of the other holes that the shafts go through, and would give it clearance to fit the 10mm shaft.

This is quite a good model. I printed it in ABS using a SeeMeCNC Orion with gcode done by Simplify3D. After printing and assembly it became clear why the design shows only one spider gear. The way it is designed, it is impossible to assemble the second spider gear. Thanks for including the SolidWorks models. I modified the spider and shaft models so the screws come form the outside allowing the use of two spiders. Also, I don't like to use machine screws in plastic. I used torx head sheet metal screws found at McMaster Carr ( p/n 90925A115). I had a lot of difficulty getting clean prints of the side gear and spider gears. I intend to do some further redesign of these gears to get cleaner prints. This model is great for showing people how a differential works. I am a retired automotive design engineer with 26 patents is a few fields and am really enjoying this kind of project. thanks again for the model.

Thanks for posting this print, I have really enjoyed printing it on my Afinia H800 printer. The only problem I'm having is the M3 screws are to small for the holes in the parts. The M3 screws fall into the holes that they should thread into. Maybe I did something wrong, I'm new to this 3D printing. But I'm having fun. Can anyone tell me what screws they used to finish the project.

very usefull model i`m using it for an electric generator :)

Hello, I'm new to 3d modeling and I'm just wondering what program did you use to create this?

Excellent model.
I made mine in Diamond Age PLA on an Ultimaker 1.
I found the wheels a very tight fit on the shafts - had to assemble with a hammer.
On the other hand the through hole in the crown wheel (the big gear as I can't read the given name in the parts list) seems far too big.

What screws/nuts/bolts are you using? I'd like to have a go, but I'm horrible at guessing mechanical components.

The exploded view which I printed out but can't spot in the list of files calls for 13 M3 screws .
I didn't use any screws to hold the wheels on as they were a very tight fit on the shafts. Elsewhere, from memory, I used M3 x12 except for the Input pinion where I used M3 x 16 (I think).
I used button head cap screws.

and how come everyone else seems to know?

where does the m3x12 go? Cant seem to find the location on the exploded view

I built one. The TWO m3x12's (or you could use m3x10's) are used on the two spider gears.

Wish I could help, but I was wondering the same thing. Also, I only count 15 screws used in the drawing, but the part list shows 16 - m3x16mm. Now we have two unaccounted for. lol

I'm still going to print this thing. I'm sure it will become obvious if a shorter screw is needed.

Would you please post the hardware needed again? The thingiverse website update did away with your part list and screw size.

Has anyone had problems with the side plate hole being too small?

Yeah, I had to sand that a little bit

any chance you could upload the slidworks files?

How have you guys printed the Shaft?

Also Thing-O-Fun, if you're going to do any updates to this, could you maybe give the stand rounded ends instead of corners to reduce warp for those of us not using HBP?

I added Stand3.stl which is a copy of Stand.stl with mouse ears at the corners to help with warp. The current ears are set at 6mm diameter with a thickness of 1mm.

The shaft should be printed in the orientation I have shown. If you do not have a HBP you might want to print this component with a raft to ensure that it does not move during printing.

I know this doesn't answer your question, directly, but if you can afford it get a heated bed. Since I started using it I don't need to use "brims" at all.

ah cool.

with the shafts I'm printing all three at once in the poition you've now got it, sliced with slic3r and using 5skirts 2 layers thick and at 0mm away from the part.

Finally finished it!


photo here does not really do it justice. gears are in gold/bronze, stand and shafts in black, and handles in Kawasaki green.

this is all Vik's (diamond age industries) PLA.

Any suggestion how to set GCode to print the shaft with correct cylinder inside ?I always get an oval :( - TOM MK7, 0.4mm nozzle, fill 1.75mm, GEN4, firmware 3.0 - SF 35 Thingomatic-ABP-MK7.

It sounds to me like you may need to review your bots axis calibrations, belt tension and speed settings. One of your two axis could be traveling further than the other which would cause an oval pattern to be printed rather than a circular pattern. Also, if your belt tension is not optimal you could end up with excess slop in one direction or the other when switching directions. The speed used could also influence this. There are many good tutorials (as well as schools of thought on doing it correctly) available online and in the makerbot forums.

I verified the file to be correct and should result in a circular pattern. Hopefully this helps.

That was a fun print!! Excellent design!!

I give up... I have tried and tried to print the small gears and have had no luck. What is the trick to stop them from curling up and looking like crap. I have tried teeth up and teeth down. No luck... slow fast hot cold... help! The large Casing gear came out perfect. :'(

Uploaded gears without back cut. Haven't printed these myself but there look to be no interference issues on the assembly. Hopefully these help.

That did the trick! I could always grind down the bottom to put the back cut back in. Thanks for the change!

Looks like RonG has you covered. Check out his version and maybe it will help. I'll see if I can put up some files that don't have an angled back cut.

Any chance we could get the solidworks assembly?

Has anyone successfully printed this on a Cupcake (Gen3/mk6, specifically)? Wondering if I should attempt it.


Yes, definitely it can be printed with CupCake just fine. I printed it with CupCake Gen3
amp; MK5 (DC) and it works great ! More photos from http://www.flickr.com/photos/yty/sets/72157627825253937/http://www.flickr.com/photos/y...

I printed it in Glow In The Dark - it's quite industrial looking thing when in the dark :)

It's on my list. Should be able to start with it this week now that I have RobG's new ugly cable hack in place on my Gen3 board. I'll post back and let you know how it goes (if you don't start before I get done :) )

Just printed it. Thanks for uploading the design.

Just a few notes on possible improvements.

Tolerances are rather loose and the shafts need a busing/ washers for it to run nicely, as the spider gears wont mesh fully without washers pushing the two axle gears in.

The main shaft gear needs to be better supported if you plan to run it at speed (i
did with a cordless drill) as it is currently unbalanced, a flange would work.

An additional spider gear is needed in the schematics. Although most depictions of the differential only has one spider gear, in production differentials, there's 2 to spread the load.

Thanks for printing and posting :)

I think you will find the tolerances loose if you have a higher tuned bot than I do. I based the clearances and tolerances off of the results I got from printing various elements (columns, holes, gear teeth, etc) that all relate back to how repeatable and precise the printer is. Unfortunately I am a little bit impatient so I also run my bot a bit faster than I probably should which doesn't help things. ;)

I found the tolerances to be very good on my print. I used two spider gears rather than just one as is shown. The mesh is very good on all gears. I did have to do some sanding to enable them to move freely.

Hmm, openscad does not want to import them.

Can you put them in the correct direction for printing? ie facing down

Awesome piece of work! :)

This works well. The handles were a very tight fit, and didn't need bolts! Thanks.

Am I missing something or are most of these upside down or on their side?

You can rotate them once they're finished printing.

can you post an stl of the Differential fully assembled?

thank you!

It's almost perfect!!, you only need to share the source code, and then it will be really perfect! :-P

I'm not having success generating Gcode for the stand. RepG gives tons of errors. Tried many times, ran through NetFabb, edited in SketchUp, rebooted, and still I cannot get it to work. Aside from redrawing it, I am out of ideas.

Is it just me?

From what I can tell, this is a warning more than an error. I have gotten these errors before on other items I have designed. Being the originator and having more faith in the native modeling software (SolidWorks) than I do in RepG I was willing to push on through it. I totally understand not wanting to start a multi-hour print from a file with warnings in it, I will watch more closely for this in the future. I tired exporting again with some different settings and RepG still threw some errors. I found that RepG doesn't like the rib features so I uploaded a file with them removed. The original file worked for me but it did throw up warnings. This new file generated for me in RepG without issues.

Hope this helps.

Sorry, forgot to include the warning that I have been referring to. Let me know if you were seeing something different.

This should never happen, there is a hole in the triangle mesh, each edge should have two faces.
1367 [676] [674, 701]
Something will still be printed, but there is no guarantee that it will be the correct shape.
Once the gcode is saved, you should check over the layer with a z of:

I've seen that on a lot of objects, both that I've designed, and that I've downloaded. There's a tutorial somewhere (Makerbot blog maybe?) about running objects through blender to remove non-manifold objects which may be related to this.

Think I found it:


Looks like a lot of manual manipulation. Don't know that it would be feasible to correct a large number of vertices on a complex part using this method.

It wasn't just a bunch of warnings, it failed to generate the toolpath no matter what I tried.

The no-rib version works just fine. Thanks!

An update, I encountered the same errors on a couple other parts. Eventually I changed the infill from 50% to 45% and the errors went away. Coincidence???

will it fit in the turtle shell racer?

I am not sure, the casing is currently 81mm in diameter so it is quite large. During my experimentation, getting correctly formed teeth on a bevel gear with a metric module less than 2mm was difficult for my printer and having fewer teeth than 13 on a pinion would start to result in binding due to undercut issues. Long story short, its big. :)

Beautiful. This is going on my desk, and may be even more played with by visitors than the corner cubes.

Three very impressive designs, in double quick time and nicely printed too! I look forward to the next... :)

The end plate of the casing seems to be absent.

Sorry, found the problem. I uploaded the SolidWorks model not the .stl. Should be fixed now.