[airbrush]

Anyone had any experience with the chinese ones like this?

CNC Router Rotational Axis, the 4th Axis, A axis for the engraving machine 1650 | eBay

-already have a nema 23 275oz motor to use.


Any other suggestions on where to get one?

thx

[gregoose]

You can try automation technology, I've bought some stuff from them and most around here believe they're reliable. I haven't had any issues with the drivers I purchased. Most of their stuff is what the Chinese manufacturers try to copy.

High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin
High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin plus a chuck from grizzly.com would probably be inexpensive.

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[airbrush]

they do list these ones from the their site....looks the same as stuff listed on aliexpress...strangely enough its much cheaper than from ali

High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin

[gregoose]

yes, not sure why its cheaper, shipping maybe. Im not sure the taxes for Canada either. If im not mistaken the company used to be called Keling. I would almost prefer ordering from that site over anything on ebay anymore except where ebay or ali is cheaper. But, thats just my two cents, and Im no expert in the matter.

[asuratman]

Do you think 100 mm is enough size to carve some thing like table leg ?

[whimsical]

Maybe fine if you only turn reasonably small diameters.
Given a stepper has 200 steps per revolution and that axis thing is 6:1 so 1200 steps per rev. If your diameter is 4" that is a circumference of 12.56" so 1 step would give you 10 thou resolution. Microstepping can make an improvement but not huge maybe 1 thou. As the diameter goes larger the resolution obviously decreases.
That is why I make something a lot better as i want to turn 12" to 15" diameters.

Mike

[johncarpenter]

The Chinese harmonic drive 4th axis will give you 50 or 100 to 1 reduction. That will increase your resolution and torque. You need to make sure that the 6 to 1 reduction has sufficient holding torque for your system if you go with that type. Or build your own. Here is my DIY 4th axis from a harmonic transmission. Has a 200 to 1 reduction with no backlash. Cost me about $250 plus the machine work. If I did it again the stepper would be mounted on the side with a belt connection. That would be a lot less work.

[gregoose]

This one is similar with a 47:1 reduction.

High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin

[jfong]

If you are considering a DIY, here is my small rotary made with a planetary gear head bought on eBay for cheap.

CNC Rotary Axis

Even though it is made by Harmonic Drive, it is the HPG planetary version which has some backlash. Less than 1arc-min. I'm not sure what that translates as far as steps but it is minimal. 11:1 ratio doesn't seem much but I can't easily rotate the chuck by hand when the stepper is powered up. Good enough for engravings.

However....
I found these two zero backlash true harmonic drive gear heads for about $60 on eBay. 80:1 with brushless servo motors. Probably end up making a rotary for my gantry router with one of them. This should give much more rotational torque. If you look long enough on eBay, a inexpensive harmonic drive gearhead can be found.

[johncarpenter]

If you use a planetary gear make sure to check the advertised backlash against how much you can stand. Planetary gears with small backlash tend to be expensive.

[Devastator]

I picked up a 5 phase harmonic drive plus separate driver for under $150 for both. Super high resolution zero backlash. They are used for high end telescope positioning.

[johncarpenter]

Nice!

[jfong]

I picked up a 5 phase harmonic drive plus separate driver for under $150 for both. Super high resolution zero backlash. They are used for high end telescope positioning.

5 phase steppers are getting pretty rare now. I had a old 5 phase Berger Lahr stepper that was driven by a Vexta driver. It was exceptionally smooth running.

[Devastator]

5 phase steppers are getting pretty rare now. I had a old 5 phase Berger Lahr stepper that was driven by a Vexta driver. It was exceptionally smooth running.

Not really. They are $29.99 ea. "Buy it Now". Vexta PK564BUA 5-Phase Stepper Stepping Motor NEW | eBay

Trick is finding them with the harmonic drive on them, but they do show up from time to time under $100.

[jfong]

I guess a lot more in the surplus market since the last time I looked. I wouldn't recommend them unless you can really get them cheap with compatible drivers.

[airbrush]

the harmonic drive idea looks great...its just a lot more DIY than i was wanting...was hoping to find something more ready to go or somebody that was making and selling their own 4th axis solutions...


Also alot of the ebay/ali ones give options for 3 or 4 jaw chuck...which is preferable, and what does each kind benefit for holding?

[johncarpenter]

If you get and use the Chinese chuck you probably want the 4 jaw. That way you can compensate for any inaccuracies in the chuck. That comes at the expense of having to set the 4 jaw up everytime you mount something.

[airbrush]

okay...but i was thinking more in the way of how it holds stock...for example i would think that a 4 jaw chuck would be able to hold square stock if desired? or do you typically always hold the stock to a cylindrical end.
say for example my stock is square, i could always just cut some short pieces of dowel and screw that into the ends to hold in the chuck....

whats your typical workflow i guess....

[Devastator]

A four jaw holds square or round stock. A three jaw holds round or hexagonal stock.

[airbrush]

right...which is why i was thinking a 4 jaw may be more beneficial for me, keeps my options open at the expense of a little more setup time...