Regular Ripples w/ Power Feed on PM-1130v

[mikkmake]

Hello everyone.

When running the power feed, the lathe creates regular ripples on the surface that are measurable high spots. When feeding using the lead screw, the ripples are not present. I've tried a wide range of speeds, feeds, DOC, tool geometry, and two materials (12L14, 6061 AL). No matter what, the ripples have persisted.

PM replied that it must be user error and told me to post here so here I am. I was really hoping PM would have more insight. The "less friendly forum" has a thread on this topic. Not sure if I'm allow to link to it here. I sent PM that link and they told me the pinion issue was unlikely.

To be clear, I'm not talking about the difference in surface finishes common with speeds, feeds, and tool geometries. These ripples are regular at the same spacing for all cutting conditions under power feed. When feeding with the lead screw or by hand the finishes are great and no ripples are present.

Any guidance of suggestions would be appreciated.

Powerfeed, .0025/rev (slowest), 6061 AL

Leadscrew, .004/rev, 6061 AL

 

[macardoso]

Hmm. Perhaps a bent feed shaft? I definitely think you're onto something here.

• Bent feed shaft
• Eccentric Worm gear on backside of apron
• Eccentric Gear on carriage power feed pickup
• Bent shafts/eccentric gears for carriage power feed inside apron
• Bent shaft/eccentric gear driving on carriage rack

Can you add a 3rd photo for comparison using you best attempt at constant feed using the carriage handwheel? This uses many of the same geartrain components as the carriage power feed.

EDIT: This could also be an issue that the gearing (when in power feed) syncs with the single phase motor and generates surging. I'd expect the same behavior on the leadscrew, but maybe it is a different ratio.

Can you also post photos of other feed gear ratios? Perhaps .004-.006"/rev

 

[mikkmake]

Thanks @macardoso! I'll conduct a series of cuts in the permutations you mentioned in 12L14 steel and/or 6061 AL and post all the photos as soon as I can.

 

[KevinM]

My lathe is a PM1022 which is identical to yours except the length. I have the same issues at times but not nearly as pronounced as yours.
Contact PM technical support, their service has been fantastic for me. Let me know if you come up with a cause and/or solution.

 

[mikkmake]

My lathe is a PM1022 which is identical to yours except the length. I have the same issues at times but not nearly as pronounced as yours.
Contact PM technical support, their service has been fantastic for me. Let me know if you come up with a cause and/or solution.

Thanks Kevin. I contacted them and they told me it was user error. Sent me here.

 

[mikkmake]

Minor Update: In addition to the cuts suggested by @macardoso and at PM's suggestion, I'm going to put a video camera to watch the pinion as I feed both under power and manually.


Also, the 1130v has a lead screw and an independent power feed shaft rather than a keyed lead screw. One of the reasons I went for this model.

 

[KevinM]

Ooops, my lathe is not the same as yours. By a large margin.

 

[mikkmake]

Ooops, my lathe is not the same as yours. By a large margin.

It's alright! I originally ordered the 1022 but supply chains and temptation got me to upgrade. Happy to have any thoughts from anyone!

 

[Liljoebrshooter]

I noticed my lathe, a Jet 1340 did something similar to this. I found that the handwheel was going past 12 o'clock and would spin counter clockwise from the backlash in the gears. By holding lightly on the wheel while it feeds along would eliminate it. Can't say that this is the issue you are having but something to consider.
Joe

 

[7milesup]

I have heard of single phase motors causing issues with cutting that show up as ripples due to the phasing. Your issue is very pronounced so not sure if phasing would cause that stark of an issue.