Change gears? ELS? Help!

[GunsOfNavarone]

I am using the servo/stepper setup (is this not a hybrid of the two?) Are you saying that the 2:1 pulley setup is a stronger/torquier setup? I'd rather make the small changes now before it all is put together in the machine. Sounds like I should also use a different pulley setting. I was excited for that 50 rpm threading speed, but I was kicking its butt at 130rpm

 

[RJSakowski]

I am using the servo/stepper setup (is this not a hybrid of the two?) Are you saying that the 2:1 pulley setup is a stronger/torquier setup? I'd rather make the small changes now before it all is put together in the machine. Sounds like I should also use a different pulley setting. I was excited for that 50 rpm threading speed, but I was kicking its butt at 130rpm

What is your lathe? Are you using the same hybrid motor tha Clough used? Using a 2:1 pulley arrangement will double the output torque but also double the required motor speed to obtain a given lead screw feed. Steppers typically have an inverse relationship between rpm and pull out torque but there is also a bit of a plateau at low rpm due to the limitation of drive current. Here is the torque curve for my stepper. If my stepper is running at 150 rpm, there is about 300 N.cm of torque. If I double the speed, the torque drops to around 260 N.cm but the 2:1 pulley reduction to give me the 150 rpm on the output doubles that torque to 520 N.cm for a 73% increase in available torque

https://www.hobby-machinist.com/attachments/24hs40-5804d-e1000_torque_curve-pdf.329472/?hash=81f2c37d2e375d08cb59db77348a4c0b

 

[GunsOfNavarone]

RJ, I have the G0602 as well, the stepper & driver are verbatim what Clough used. If there are logical/worthwhile changes I can make, now would be a good time. I have the launch board programmed and up and running. I have everything except one pulley and the encoder which are in route. Perhaps there will be no issues, but again, this would be the time before I start making mounting brackets and such....
What are you thoughts of belts/pulleys for the VFD? Like I mentioned I removed the ribbed belt from the motor and am using the center pulley from the motor to the spindle. What are your thoughts to improve torque?

 

[RJSakowski]

RJ, I have the G0602 as well, the stepper & driver are verbatim what Clough used. If there are logical/worthwhile changes I can make, now would be a good time. I have the launch board programmed and up and running. I have everything except one pulley and the encoder which are in route. Perhaps there will be no issues, but again, this would be the time before I start making mounting brackets and such....
What are you thoughts of belts/pulleys for the VFD? Like I mentioned I removed the ribbed belt from the motor and am using the center pulley from the motor to the spindle. What are your thoughts to improve torque?

Seriously, you will want to take a look at some of your overhead losses. If you haven't already done so, the half nut setting is a quick and easy fix. We had some communication on this back in November. https://www.hobby-machinist.com/threads/grizzly-g0602-half-nut-engagement.80832/#post-717716 If you find that you have torque issues, you can run the internal gear box in position IC instead of IA. This will double your servo rpm and double the output torque. You will have to change the thread pitch setting from 12 tpi to 24 tpi to compensate.

I would recommend mounting your servo motor under the lathe bed as I did with mine rather than Clough's location. I was able to fit a NEMA 24 motor in that space so a NEMA 23 motor will fit easily. I had to open up the opening some which took a bit of effort but it makes for a much cleaner install. My control box is actually quite similar to what Clough used. I just repurposed an old mains fuse box. I didn't use bulkhead connectors on the box as all the the internal connections are easily broken should the need arise.

I would recommend using the highest voltage power supply consistent with your driver. If you are using a switching powers supply, you should run a voltage about 10% lower than the maximum driver voltage. This is to prevent back emf from tripping the over-voltage circuit.

 

[GunsOfNavarone]

I will look at the half nut, honestly since it works, I have no way of deciding if it's tight or just right. Anyway of knowing/testing?
If I found that with Clough's ELS I need more torque, you're saying to run the gears at I/C but go into the code and change my lead screw from 12 to 24tpi?
I suppose you reason to go with the NEMA 24 not the 23 clough suggested was for more torque?
I know he said to keep things close (shorter wires) So I was going to try to use the empty space where the old contactor/capacitors were and even under the run/direction cover. I DO NOT want ANOTHER electronics box mounted by the lathe...space is limited. I just need to be careful with noise as I will have VFD and ELS now. Do you have pics of your complete setup? I have been having such problems with this site and the error messages (unsecure) its difficult to post...to like...to search, otherwise I'd try harder to find it. Every click here errors out.

 

[GunsOfNavarone]

Found your pics @RJSakowski looks clean. In that thread, the great old one said he had issues running at high rpm and errors, and though I won't be threading at 2000 rpm, I will be using it for feeding the carriage. DO you have anyone power feed issues?
Also, do you know if its possible to buy a generic touch screen and use it in replacement of the control box?

 

[RJSakowski]

I will look at the half nut, honestly since it works, I have no way of deciding if it's tight or just right. Anyway of knowing/testing?

I used a small torque wrench to evaluate the torque required to turn the lead screw. If you don't have one, it is fairly easy to make a torque gauge. Turn a small pulley from a convenient material. Wood will work. Thread about 6 ft of line through the hole and wrap it around the pulley. The pulley replaces the input gear on the gear box. Attach a pull scale of appropriate sensitivity to the line. As you pull on the scale to rotate the input shaft, the scale reading times the radius of the pulley will be the torque.

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I used my 20 fish scale with .1 lb resolution on a 3" diameter pulley to measure up to 480 oz-in of torque with a resolution 2.4 oz-in.

I first measured the torque required to turn the lead screw with the half nuts disengaged. Then I engaged the half nuts and noted the increase in required torque. Then I advanced the set screw as I watched the effect on the torque. The half nuts in an as shipped condition are clamped tight to the lead screw with no clearance. Adjusting the set screw will back off the half nuts, reducing friction. It will also increase backlash in the lead screw but this isn't a huge deal as threading and power feeding are done in one direction only. As noted in my post, I decreased the required torque to half of the original.

If I found that with Clough's ELS I need more torque, you're saying to run the gears at I/C but go into the code and change my lead screw from 12 to 24tpi?

That is correct.

I suppose you reason to go with the NEMA 24 not the 23 clough suggested was for more torque?
I know he said to keep things close (shorter wires) So I was going to try to use the empty space where the old contactor/capacitors were and even under the run/direction cover. I DO NOT want ANOTHER electronics box mounted by the lathe...space is limited. I just need to be careful with noise as I will have VFD and ELS now. Do you have pics of your complete setup? I have been having such problems with this site and the error messages (unsecure) its difficult to post...to like...to search, otherwise I'd try harder to find it. Every click here errors out.When I originally did my search for

When I originally did my search for a suitable motor/driver package I stumbled on the StepperOnline site and the NEMA 24 motor. The 602 oz-in. of torque was better than Clough's motor spec and the same as on my Tormach x and y axes and the cost was about half of what Clough paid. I also determined that I could fit a NEMA 24 motor in the cavity under the lathe bed. Those were my reasons for going that route.

As to mounting your electronics in the lathe housing, I think you may have a hard time fitting it all in. I would also have some concerns about any power switching that you may still have in that enclosure. I mounted my main enclosure on the back of the backsplash with the power switches mounted to that and my display above that. The box is only 3.5" deep so it doesn't take much room and if I need to work on anything, three nuts hold the entire assembly to the backsplash so I can easily move the assembly to a convenient location for service. Here are some photos.

 

[kb58]

Keep in mind that if you go with a commercially available ELS, there will be additional expenses for the stepper/servo motor, gears, and belts. The Clough42 approach ran me about $350, complete.

 

[GunsOfNavarone]

@kb58 I'm already in fully as far as having every part Clough recommended. I guess I just want to know what my possible issues could be and how I might go about fixing them. If I knew anything about this stuff, I would have made changes based on the issues I could see in the setup. I considered stronger stepper, but I didn't know what it would take to take it work. This way, if I do everything Clough says and purchase the same items, it should be as close to plug and play as you can get.

 

[jlesser27]

[mention]GunsOfNavarone [/mention] I’m in the same boat no pun intended. Waiting on a few more parts from the big candy mountain but followed Clough42 verbatim. I have a Weiss WBF250 which is almost an exact copy of the PM1030. I think engaging the internal gearbox will be my first try if the torque doesn’t work out.


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