Recommended Lathe X & Z Axis Inches/Minute

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762x51
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Recommended Lathe X & Z Axis Inches/Minute

Post by 762x51 »

I'm working on the conversion layout of my Dyna Myte DM-3000 and have a question regarding axis movement.

What would be the suggested maximum inches/minute for axis that have 2.5mm (0.098")/revolution lead screws?

The existing Z axis stepper has a max RPM of 1500 and the lead screw is driven by a 10:1 ratio gear assembly.
Wouldn't this would be (1500/10) * 0.098" = 14.7"/min?

Is this a reasonable speed or a slow speed for a small lathe's axis travel rate? I'm going to use ClearPath servos and I could double the rate but I'm concerned that in doing so may cause the gear train to be damaged. I do think that increasing the speed by 25% would be OK - maybe.

I'd like to use the existing gear train as the conversion would be MUCH simpler that changing over to timing belts.
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by DICKEYBIRD »

I'm wondering why there's such a high reduction between the stepper & screw. That will make the stepper have to spin very fast & steppers do lose a lot of torque at high speeds. The stepper setups I've seen mostly are around 1.5:1 to 2.5:1. Where are you getting the 1500 rpm stepper spec. from? Seems kinda high unless they are very low inductance motors with a high PS voltage?...but then again, I didn't sleep in a Holiday Inn Express last night!
Milton in Collierville, TN

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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by 762x51 »

Hi Milton,

All of the specs I mentioned in the initial post came from either original drawings or the spec sheet for the stepper motor.

The Z axis P852-508-B stepper motor spec is attached. The X axis is a much smaller stepper but if I can get the Z axis right then the X axis ClearPath will be easy to size.

Orin
escapmtrs.pdf
(1.29 MiB) Downloaded 135 times
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by martyscncgarage »

Dyna got away with using tiny stepper motors, I think they were about 28 oz. in. I *believe* they also dynamically switched between parallel and series winding depending on whether or not it was in a rapid move or a cutting move.

So, if you were to keep the 100 tooth nylon gear and the 10tooth steel pinion that went on the stepper, you would have to be sure you put a motor on it with similar torque to the original. Thinking about it, put on Clearpath's smallest NEMA 23 motor which has 64oz. in, you would be over doubling the peak torque would you not?

This is one of the reasons we chose not to use the original nylon 10:1 reduction system in our DM3000 conversion. That and the nylon gear were problematic As they aged they would crack at the mounting holes (if memory serves). I think timing belt drive is a better option but harder to implement.

On my Dyna DM2400's mills, I designed a mount that would allow direct driving the screw. Fine on a mill, but not on the lathe because you can't close the door on the lathe

I'm just thinking out loud here. I would abandon the use of the original gear set in my honest opinion. With their age, they are already weak. Add a motor with more torque and I think they would be finished off...first crash. :oops:
Marty

Couple DM3000 pics: (This is my friend Dan's handy work)
DM3000a.jpg
DM3000b.jpg
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by 762x51 »

Hi Marty,

Thanks for posting those photos and I agree, using the existing gears would probably be a problem and at some point would have to be changed out to a timing belt design. I started working on that layout last night and determined that a 4:1 ratio was about the highest ratio you can get and have everything fit in the available space. I'll post renderings of that layout once I finish the design.

I still wonder what would be a good axis inch/min for this layout would be. Would you mind contacting your friend that did the conversion and ask him to share the model # of his ClearPath's, the ratio, and the max inch/min travel he uses.

Orin
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by 762x51 »

Here are the renderings of the Z Axis assembly. The ClearPath servo mounting plate is new along with the timing belt and pulleys.
The timing belt assembly ratio is 3.6:1 with a 20 tooth pulley on the ClearPath and 72 tooth pulley on the lead screw.
I laid it out this way so I wouldn't have to modify the existing lead screw mount. This appears to be similar to Dan's layout shown in Marty's post.

Image
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Image
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by frijoli »

Nice work!
I can't wait to come by and see it!
Clay
near Winston-Salem, NC
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by martyscncgarage »

Very nice CAD work Orin.
Marty
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762x51
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by 762x51 »

Thanks guys -
I'll have to get the motor mounts made as my mill is in pieces and will be my next project after the lathe is up and running.
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Re: Recommended Lathe X & Z Axis Inches/Minute

Post by 762x51 »

Here is my proposed X Axis design

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