Electronic Lead Screw

[weston1968]

I can confirm an oversized motor is not a good idea. I put a 2hp motor on my Logan 10" with a quick change gear box. It was designed for 1/2 hp. I did something stupid and when I ran into my tailstock I snapped the shaft in my gear box.

 

[gerritv]

I have a 1022 lathe (King KC1022ML=G0602) with now a Rocketronics ELS 4 Pro. Prior I was using the Russian Electronic Guitar 7e2.
I haven't seen any mention in the posts above about your step rate.
I can tell you from experience that a 2.8nm NEMA 23 stepper motor is fine on the leadscrew, if driven 1:1. The problem with 2:1 drive is that you are doubling the number of steps to move x distance. High step rates result in less torque. Add in runing high microstep rates and the problem gets worse.

 

[RJSakowski]

The "issue" is that an attempt is being made to connect the motor through an additional gearbox, and cross feed unit, operating at 32F which is an additional motor load. My original design drove the lead screw directly. It's quite possible that a simple gear reduction could be satisfactory fix, with an appropriate accommodation in software.

The 602 still uses the gears to obtain the 1:1 output. there is no direct coupling between the input and output shaftin the gearbox. I am using a gear reduction for my setup.

 

[RJSakowski]

I have a 1022 lathe (King KC1022ML=G0602) with now a Rocketronics ELS 4 Pro. Prior I was using the Russian Electronic Guitar 7e2.
I haven't seen any mention in the posts above about your step rate.
I can tell you from experience that a 2.8nm NEMA 23 stepper motor is fine on the leadscrew, if driven 1:1. The problem with 2:1 drive is that you are doubling the number of steps to move x distance. High step rates result in less torque. Add in runing high microstep rates and the problem gets worse.

I had thought this as well but the mechanical advantage of using gears outweighed the torque loss of the higher stepper speed. This was verified by actual measurement of the force applied to the carriage drive.

 

[RJSakowski]

I can confirm an oversized motor is not a good idea. I put a 2hp motor on my Logan 10" with a quick change gear box. It was designed for 1/2 hp. I did something stupid and when I ran into my tailstock I snapped the shaft in my gear box.

One upside to an ELS is the drive force to the carriage is limited by torque capability the stepper motor. It makes no difference what the spindle motor size is. On a gear driven lead screw, that 2 hp motor will push until something gives, as you found out.

 

[RJSakowski]

This can do imperial threads according to the video I saw. Like most Chinese stuff there is not enough documentation before purchase for me to really feel comfortable. One interesting thing I saw in the video is that I can specify the length of the thread. Using a stepper makes that possible and allows me to thread closer to the end than I felt comfortable with before.

When it arrives I will scan and post all of the documentation. I figure about a month.

Can you post a link to the video? I am looking forward to reading about your experience.

 

[WobblyHand]

The 602 still uses the gears to obtain the 1:1 output. there is no direct coupling between the input and output shaftin the gearbox. I am using a gear reduction for my setup.

True. I am using a 1:1 connection from the stepper to the input of the gearbox and adjusting the gearbox settings to get the correct output. I had assumed that one of the settings of the box was 1:1. Even so, the lathe has cut what I have asked from it. This class lathe won't peel off huge chunks like a bigger heavier machine, but it is fine for me. I have not noticed any reduction in capability with my implementation. Perhaps, that's because I don't push it too hard, but more that I don't like to break things. I call it mechanical empathy. For myself, even if there was a slight reduction in capability, I don't mind, since the value of the convenience of an ELS is very high to me. I'd feel different if I had a production machine, but as a hobbyist, an ELS is the greatest thing since sliced bread.

@ivel03 is using a different lathe (but same class lathe) which has two lead screws. One powers the threading lead screw. I know the other powers his cross feed, and possibly the carriage feed. The load is different than the G0602. In addition, this lathe is in a shed which does not have heat at times. So he (and I) are pioneering "retrofitting" for his lathe. Been an interesting experience for both of us. Frustrating at times too, but in a way very satisfying, because (besides this "torque" problem) everything works, including the Z & X DRO integration. I think to be able to move on, there needs to be some real testing, like cutting metal, so the nature of the problem can be characterized. Once that is known, a solution can be appropriately determined. It might be as simple as reducing the gearbox ratio and speeding up the motor. But the first question really is, does it cut metal without a problem?

 

[WobblyHand]

I can confirm an oversized motor is not a good idea. I put a 2hp motor on my Logan 10" with a quick change gear box. It was designed for 1/2 hp. I did something stupid and when I ran into my tailstock I snapped the shaft in my gear box.

Overkill design is not always the best. As you found out with your 2hp experiment, the weak link became the (1/2 hp) shaft in the gearbox... Breaking stuff is not terribly convenient, to say the least.

 

[weston1968]

Overkill design is not always the best. As you found out with your 2hp experiment, the weak link became the (1/2 hp) shaft in the gearbox... Breaking stuff is not terribly convenient, to say the least.

The only good that came out of it was that I learned how to machine a replacement part. Lathe out of service for over a week.

 

[RJSakowski]

True. I am using a 1:1 connection from the stepper to the input of the gearbox and adjusting the gearbox settings to get the correct output. I had assumed that one of the settings of the box was 1:1. Even so, the lathe has cut what I have asked from it. This class lathe won't peel off huge chunks like a bigger heavier machine, but it is fine for me. I have not noticed any reduction in capability with my implementation. Perhaps, that's because I don't push it too hard, but more that I don't like to break things. I call it mechanical empathy. For myself, even if there was a slight reduction in capability, I don't mind, since the value of the convenience of an ELS is very high to me. I'd feel different if I had a production machine, but as a hobbyist, an ELS is the greatest thing since sliced bread.

@ivel03 is using a different lathe (but same class lathe) which has two lead screws. One powers the threading lead screw. I know the other powers his cross feed, and possibly the carriage feed. The load is different than the G0602. In addition, this lathe is in a shed which does not have heat at times. So he (and I) are pioneering "retrofitting" for his lathe. Been an interesting experience for both of us. Frustrating at times too, but in a way very satisfying, because (besides this "torque" problem) everything works, including the Z & X DRO integration. I think to be able to move on, there needs to be some real testing, like cutting metal, so the nature of the problem can be characterized. Once that is known, a solution can be appropriately determined. It might be as simple as reducing the gearbox ratio and speeding up the motor. But the first question really is, does it cut metal without a problem?

You are right on. The proof of the pudding is how the lathe performs. I struggled with a way ro evaluate that perfo4rmance because there was no previous metric on the actual force needed to make a particular cut. An experiment to that effect would be in order. I would set up some stock and a depth of cur and increase the feed rate until the stepper stalled. The number will be dependent upon the diameter of the stock as that is proportional to stock removal rate and to spindle speed as the stepper torque is dependent upon stepped speed. A family of curves would be generated for a particular material and tool.

At a 5mm feed rate (the highest my ELS will go), that is screaming at 300 rpm. 50 rpm is more reasonable. In that case my lead screw is turning at 6x the spindle or 300 rpm. The stepper is turning at 2x that or 600 rpm. From the torque curve for my stepper, it is generating about 1.4Nm of torque.