Designing a cycloidal gear for 4th axis

[Azalin]

Hi,

I wanted to open my own thread for this one. Like the title says I'm designing a cycloidal gear to use in 4th axis on my mill. I'm not after high gear ratios but what I want is low backlash as possible so kept the pin number as high as I could.

This is the first version of the design:

- Diameter of the wheel is 100mm
- Pins are 5mm hardened and ground steel
- Number of pins: 40
- Eccentricity of the wheel is 1mm
- Thickness of the wheel is 10mm (or maybe 15mm. I don't know yet)

Notes:
- I'll be using a Nema 34 stepper motor to drive this gearbox.
- I think I'll use 2 wheels.

I'm in the beginning of this so I'm sure I'm missing some important details. I welcome your thoughts and recommendations.

Similar Threads:

• 4th axis gear ratio ?
• Australia Looking for advice re gear cutters for cnc router with 4th axis
• Need Help!- making a ratcheting Gear w/4th axis
• Need Help!- Creat cycloidal gear
• Need Help!- USING TIMING BELT FOR 4TH AXIS INSTEAD OF WORM GEAR

[Azalin]

By the way I guess having the wheel 100mm diameter is a little too big.

[Azalin]

New version. To make it a little smaller I reduced the pins to 30. That gives me 67mm diameter on the wheel. So the diameter of the housing will be roughly 80-90mm. Considering the 4th axis will have a 125mm chuck, is the design good? What do you think?

[RCaffin]

Photos of progress, please!
I think 10 mm thick should be plenty.
For two reduction, the first could be even a bit thinner imho.

Cheers
Roger

[Azalin]

It's a single stage reduction. The second wheel is just for the balance.

[Azalin]

Anyone knows what this bearing is? Some kind of needle roller? Looks like a good one for the eccentric.

[Azalin]

The output bearing is a CSF-32. It is specifically made for harmonic drive but I already have it so I decided to use it.

[mactec54]

Anyone knows what this bearing is? Some kind of needle roller? Looks like a good one for the eccentric.

That is just a custom made Roller Bearing, a regular Roller Bearing would be fine in your design

[mbello]

Anyone knows what this bearing is? Some kind of needle roller? Looks like a good one for the eccentric.

These bearings are now standard bearings you can buy from a few suppliers.
I found them on AliExpress from many sellers already, but from brands/sellers of unknown quality.

https://www.aliexpress.com/item/4000...rch-mainSearch

Also, they trend to be bigger than I would like. I believe they are made as spare parts to commercial eccentric cicloida lreducers from sumitomo and others.

[mactec54]

These bearings are now standard bearings you can buy from a few suppliers.
I found them on AliExpress from many sellers already, but from brands/sellers of unknown quality.

https://www.aliexpress.com/item/4000...rch-mainSearch

Also, they trend to be bigger than I would like. I believe they are made as spare parts to commercial eccentric cicloida lreducers from sumitomo and others.

Yes, the only problem would be the eccentric would have to match the design that is being made, the problem with what you can buy would be the offset.

This one would be better if the offset would match, https://www.aliexpress.com/item/4000...mend-recommend

[Azalin]

Hi,

I cut the first disc from mild steel. It is also the first job of my mill. I used a 6mm 4 flute end mill and lost a flute during the cut but looks like the rest 3 flutes did the job well. Surface finish looks good and measurements are correct. I think I can use it.

[RCaffin]

Lost a flute?
What sort of cutter?
I have broken a few cutters, but I've never lost a flute.

Cheers
Roger

[Azalin]

An ordinary 4 flute end mill. The cutting tip of the flute got broke about 1mm.

[Azalin]

Hi,
I made new discs but this time I added ten 10mm roller holes and a much larger eccentricity hole. Thickness is 6.5mm.

Sent from my MI 5s Plus using Tapatalk

[mactec54]

Hi,
I made new discs but this time I added ten 10mm roller holes and a much larger eccentricity hole. Thickness is 6.5mm.

Sent from my MI 5s Plus using Tapatalk

Looks Good

[Vitali-M]

Hi,
I made new discs but this time I added ten 10mm roller holes and a much larger eccentricity hole. Thickness is 6.5mm.

Sent from my MI 5s Plus using Tapatalk

Hi Azalin, any progress on this project?

I'm working in a custom cycloidal gear for my project,

I'm studying a lot, the concepts, reading a lot of articles and drawing and drawing for days... it would be nice to have someone to talk and exchange insights


I have a Spark Erosion and Wire Erosion

[Azalin]

Hi,

I nearly finished it but the geometry wasn't perfect because the backlash in the X and Y axes. So I stopped there and started to upgrade my mill. I installed DFU ball nuts thus backlash minimized. I also changed my cycloidal design a bit. Will start on machining this week.

[joeavaerage]

Hi Azlin,
great thread, looking forward to how it goes.

I considered doing the same but I came to a different conclusion to you, I thought I could buy an acceptable solution for very much less than I could make something.

I bought this off Ebay. It has a 6.75:1 reduction, <1 arc min backlash and up to 10hp input, for $180USD new-old stock.

Craig

[deadlykitten]

hello only now i had time to look over this; can i help with something ?

the gear is simple ... trials may be needed to get it to right size, so to fit into existing reducer with low play

as for excentric bearings, if you can't find proper ones, you could modify a standard one and adapt design

last but not least, what joe did with 180$ seems a good deal, especially on time saved ... depends if you allready have the reducer and only need the gears, or you have to craft the entire reducer / kindly

[joeavaerage]

Hi,

what joe did with 180$ seems a good deal, especially on time saved

That was what swayed me this way. It would be good to make a cycloidal gear reducer as Azalin is, a lot of fun and great learning opportunity, but I wanted something
in fairly short time frame. I already have another servo reducer from the same company, Atlanta Drives, it is the next size up, (63mm cf 50mm) and has <2 arc min lash and 19.5:1
reduction. I use it for my fourth axis. Its great and that experience led me to seek something the same for my fifth axis.

The reducer I've got already has all the bearings and seals and all of that. I can install my fifth axis platter directly in its output bore and rely on the bearings of the reducer.

Craig