Electronic Lead Screw on an Bernardo Profi 700 Pro

P

Poppey

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Hi
I´m planning to put an ELS on my Bernardo Profi 700 Pro lathe. This is the same lathe as Warco WM290V, Weiss WBL290 and PM-1130V
I plan to use
Clough42 display and controller and controller board as James described.
NEMA 23 Integrated Easy Servo Motor 180W 3000rpm
5:1 Worm Gearbox NMRVS30 Worm Gear Speed Reducer mounted direct n the lead screw with an adaptor that sits where the banjo was attached. Bothe the servo and the gearbox will be purchased from Stepperonline.
The servo will be driven at 48 VDC
As you see from the model the servo and gearbox fit nicely without modifying the cover.
Anyone that sees a problem with the use of a gearbox?
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I've been planning the same thing, using the gearbox on a Grizzly G0509G. My plans have not left the drafting table though. My only worry was the backlash of the [lathe] gear-train. It should not be an issue if always traversing in the same direction while cutting but if cutting in both directions, backlash might be an issue.

That would be a nice setup, well hidden.
 
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Thats pretty much how I did my PM 1130v. I found that the wire connectors for the servo would not clear the cover if I left enough room to be able to move the drive belt between speeds. I ended up mounting the servo horizontally instead. I do think the added drag in the worm gear box is an issue though. I am planning to remove the worm box and mount the servo between the motor and the lathe bed as others have done. Overall I am very happy having the ELS, it definitely took a decent machine and made it awesome from a useability standpoint.

KIMG0563.JPG
 
As far as backlash goes I figured the existing geartrain in the lathe gearbox already has backlash and the 1:5 wormbox doesn't add that much more. To me the wormbox does rob some power from the servo so have had some issues with fine feeds at pretty low spindle speeds.
 
Thank you,
Should I go for a 10:1 gear ratio? It seems like you have a lager spindel pully than I have (6") so vertical may fit well. Otherwise I can du as you have done. The Idler pully on mine is way lagrer. I´m planning to to make a boss and fit the gear box by the use the 40 mm banjo boss to lock the gear box. I will make sure it´s 100% centric to the lead screw
 
I see you use the banjo and a gear and pully to drive the encoder. I was planning to 3D print a pully that fit over the spindel gear. Or I may remove the spindel gear and fit a pully instead, that if I can pull off the gear on the spindel. But your setup looks nice and clean, so I may copy yours.
 
I think with 10:1 you will find that the servo cannot keep up with the spindle speed and will trip out. I used a plastic gear from a Grizzly G602 lathe to drive the encoder pulley to be quiet, the steel gear was noisy. Same ratio set up as Clough42 for both the belt and gears. The reason I did this was I can go back to the factory geartrain quickly if needed. My servo to drive the leadscrew is at 5:1 ratio with the lathe gearbox in its 1:1 position . If I go to belt driven it will end up at 6:1 like Clough 42 , being I have pulleys for that. I tried printing pulleys and gears to test everything and would have used them permanently if they were more concentric. The 3d printed pulleys for the encoder would probably work out fine I would think.
 
Thanks for good advises. You mentioned in an other tread that you may change to an 7.5:1 gear box du to problems at low speed, do you think that will work? Or should I just buy the servo with the 5:1 ratio? I dont think it will be a problem for me as I dont foresee treading with this low pitch at this low speed any way.
 
In my opinion, Any ratio above 5 or 6 to1 the lead and feed screw speeds will get to be an issue. I think the worm gear reduction box has enough rotational drag that it affects the servo by reducing the output torque available to do the actual work. I had thought about switching toa 7.5:1 box but when you start doing the math spindle speeds will be reduced due to the fact the servo will overspeed. My lathe has a 10tpi leadscrew. both the leadscrew and the feed rod are geared the same. I did do an experiment with 10:1, quite by accident and it had lots of power at very low feed rates but it could not support spindle speeds that were very fast at all. I have been hoping that the worm gearbox will loosen up after I use it for some time in the hopes that the low spindle speed and slow feed rate issue goes away. I would guess I probably have 15hours or so on it now. When I talk of slow spindle speed/feed its like 75RPM with .001 or .002 inch feed. Most of the turning I have done I have had no issues with that. 100 or so RPM and up it does not appear to be an issue. I have not had any issues threading course threads are no issue. the finest thread I have cut is 28TPI at about 100RPM and it worked well. I do know that I will not go back to change gears no matter what, as a matter of fact When or if I find a servo with a larger power output and the same speed range for a decent price that would also be a good option also.
 
Just looked at some pictures of your lathe, the spindle is driven much differently than mine. Your plan to mount the servo vertically looks like a winner! I do believe that driving the encoder directly from the spindle to the encoder would be better than the extra gear that I used, no backlash and be very quiet.
 
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