# Regular Ripples w/ Power Feed on PM-1130v



## mikkmake (Jan 19, 2022)

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 (Jan 19, 2022)

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 (Jan 19, 2022)

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 (Jan 19, 2022)

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 (Jan 19, 2022)

KevinM said:


> 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 (Jan 19, 2022)

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 (Jan 19, 2022)

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


----------



## mikkmake (Jan 19, 2022)

KevinM said:


> 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 (Jan 19, 2022)

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 (Jan 19, 2022)

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.


----------



## mikkmake (Jan 20, 2022)

First of all, I'm unbelievably grateful to all of you for jumping on this problem with me. Thank you.
Here's where I'm at tonight.

Passes, Feeds, and Materials
Disclaimer: Many of these passes have crap finish for other reasons. I'm not talking about the overall finish here, that's a totally different topic; I'm specifically investigating the ever present, regular, ripples.

Boy am I blowing through bar stock on test bars. Gotta order more metal. Sticking with free machining steel and 6061 aluminum for now. If I ever get this resolved, I'll have fun with the brass (so pretty but sooo $$$).

Every pass used the same HSS tool. I've replicated this using some other off the shelf tooling with the same results.

500ish RPM, Manual Feed, 6061, .020 DOC -- Work piece was about .500
I'm not well practiced in manual feeding but it's clear that the pattern didn't show up. I did feel as the pinion transitioned from one gear to the next. This tripped up my smooth turning from time to time. Generally, OK.






500 RPM, .010/rev, 6061, .020 DOC





300ish RPM, .0025/rev, 12L14, .020 DOC





Here are two more passes on the 12L14 but I forgot to write down which was which on the feeds. Both were faster than the slowest which is .0025. As I see it, both of these also clearly show the pattern.








​Measuring the Ripples​I took this super lovely pass in 6061. It is glassy smooth to the touch apart from the ripples. I put a tenths DTI on the carriage and ran it over the surface. I measure between 5 and 9 tenths between the low and high spots consistently. I can repeat this measurement on the surface plate if we want to remove the carriage as a source of measurement error.  
	

		
			
		

		
	






Other observations and Feedback from Precision Mathews​At their suggestion, and in line with the post from "the other forum" I did some inspection of the rack and pinion while under power. I was unable to see anything visually wrong. I snuck an indicator in and was able to measure about 1.5 thou of runout/wobble on the pinion shaft about .25 from the gear. Hard to know if this is having an impact.

Applying pressure to the hand wheel either helping or opposing the direction of motion doesn't seem to make a difference.

EDIT: The pattern is apparent when power feeding away from the chuck as well. 
EDIT: Tail support also makes no difference. 

PM also suggested swapping out some change gears to see if there is some eccentricity in them somewhere. I'll try that when I get back next week.

One more test I should try out is a manual spring pass after a power feed pass. This just occurred to me as I was writing so I'll add that to the test list for the next session.

Here's a video running at .0025 in steel. The wine you hear is another annoying issue I'm experiencing with the VFD. That I've solved with ear plugs.





Your browser is not able to display this video.





I'll try just about anything at this point. I'm really impressed with this lathe all around but this power feed issue is really making life tricky. I discovered it during initial adjustment when I was working on bed leveling and tailstock alignment. Both are operations during which I was hoping to leverage power feed for consistent cuts.

That's all I have for now.
Regards,
Eilif


----------



## mikkmake (Jan 20, 2022)

Whoops, I forgot one pass. @macardoso here's the .005 pass. Not as prevalent but still there and can be felt. 
	

		
			
		

		
	





I'm generally expecting the finish to be kinda bad or kinda good but mostly random. The regularity is the most perplexing part.


----------



## macardoso (Jan 20, 2022)

Let me try and summarize. Please correct if I am wrong.

Ripples present when power feeding carriage
Ripples present at any tested power feed rate. (0.0025"/rev and up)
Ripples present in all tested materials
Ripples are between 5 to 9 tenths in amplitude
Ripples are NOT present when using the threading leadscrew to power feed
Ripples are NOT present when manually turning a fine finish
Absence of ripples is a requirement for proper operation of the lathe
You lathe has a 3 phase spindle motor.
Here are a couple random thoughts

Ripples are likely NOT caused by variations in the ways
You'd see them
Ripples are not caused by manual or leadscrew feed

Ripples are likely NOT caused by any gearing in the headstock
Those gears power both the leadscrew and feed rod. You'd see issues in both.

Your lathe is equipped with a 3 phase spindle motor and VFD. This *should* resolve any harmonics issues people complain about with single phase motors.
Try and snug up on the carriage gibs. It should have a light drag to it but not be tight. If this is loose, there might not be much keeping the carriage from bouncing around. Don't forget to oil all sliding ways including the ones on the bottom side of the bed. Lathes have a lot of ways.
Try and snug up on everything on top of the carriage. Make the setup as rigid as possible.
Cross slide gibs
Cross slide locks
Compound slide bolts
Compound slide gibs
Compound slide locks
Tool post mounting
Tool mounting
Minimize tool overhang

The passes you are taking seem light. This seems to indicates the issue is not with rigidity.
Can you measure the pitch of the crests of the ripples? This might help indicate where in the gear train the issue might lie.
Measure the travel of the carriage after exactly 1 handwheel revolution.
Try to measure the travel of the carriage after exactly 1 feed rod revolution. Disconnect the lathe from power and rotate the feed rod manually while carriage power feed is engaged.
I still think the most likely culprit is something in the apron gearing, but I don't think we have tested enough to eliminate all other possibilities yet.


----------



## Christianstark (Jan 20, 2022)

"Here's a video running at .0025 in steel. The wine you hear is another annoying issue I'm experiencing with the VFD. That I've solved with ear plugs."

Can you share your programmed settings in the VFD? Is it Hitachi? There may be a very easy fix for this.

Edit - Also, is there a repeatable cadence to the ripples? Are they always the same length or does frequency change depending on feed rate?


----------



## mikkmake (Jan 20, 2022)

Christianstark said:


> "Here's a video running at .0025 in steel. The wine you hear is another annoying issue I'm experiencing with the VFD. That I've solved with ear plugs."
> 
> Can you share your programmed settings in the VFD? Is it Hitachi? There may be a very easy fix for this.


It's straight from the factory. I have a VFD manual that came with the lathe but I didn't program anything myself. Here's exactly what I know about the drive system so far. https://www.precisionmatthews.com/shop/pm-1130v-lathe/ 

The booklet that came in the crate with the lathe says it's a Delta (not the delta woodworking tool brand), MS300. I don't have any more information as I'd have to lift and rotate the lathe to see the back. There appear to be parameter settings available in the manual but I don't know what any of it means.


----------



## Christianstark (Jan 20, 2022)

mikkmake said:


> It's straight from the factory. I have a VFD manual that came with the lathe but I didn't program anything myself. Here's exactly what I know about the drive system so far. https://www.precisionmatthews.com/shop/pm-1130v-lathe/
> 
> The booklet that came in the crate with the lathe says it's a Delta (not the delta woodworking tool brand), MS300. I don't have any more information as I'd have to lift and rotate the lathe to see the back. There appear to be parameter settings available in the manual but I don't know what any of it means.


See if the booklet has an option to view and edit "Carrier Frequency", and if so what is it set to currently? A good place to try to get a reduction min whine is 12kHz.


----------



## Illinoyance (Jan 20, 2022)

If the feed pinion does not engage the rack properly the feed rate will be irregular resulting in banding.  The pitch of the banding would be the same as the pitch of the rack.  Quite common on older machines with worn beds.


----------



## Christianstark (Jan 21, 2022)

Can you hold a banded piece up to the rack? Do the bands exactly match the stagger of the feed rack?


----------



## mikkmake (Jan 21, 2022)

Thanks everyone for the ideas! I'll hold off on messing with the VFD until the ripples get sorted out. 


> Ripples present when power feeding carriage
> Ripples present at any tested power feed rate. (0.0025"/rev and up)
> Ripples present in all tested materials
> Ripples are between 5 to 9 tenths in amplitude
> ...



Correct
Correct -- Only tested .0025, .005, and .01, the feeds that are set up as standard.
Correct
The amplitude does seem to vary a bit. I can explore more here. I took an objectively WAY TOO heavy cut and the ripples were significantly less present. 
Correct. 
Very likely correct - I'm crap at manual feeding. 
For a brand new lathe, I expect the power feed to function successfully, yes. Can I make parts using entirely manual feed, yes.
Shop power is 120VAC single phase. I know very little about motor control. If the VFD is turning that into 3 phase? IDK



> Ripples are likely NOT caused by variations in the ways


Agreed. This lathe is brand new. Ways look pristine. 



> Ripples are likely NOT caused by any gearing in the headstock


I agree but I haven't actually changed out any gears yet. Was hoping to get the lathe adjusted in and gain some experience before messing with the change gears. 



> Try and snug up on the carriage gibs. It should have a light drag to it but not be tight. If this is loose, there might not be much keeping the carriage from bouncing around. Don't forget to oil all sliding ways including the ones on the bottom side of the bed. Lathes have a lot of ways.


This is going to sound silly but I can't actually find any carriage gibs that appear adjustable. The carriage lock grips the ways from the underside. Can't tighten this or I'd break everything. 

While I'm here...
The cross slide and top slide don't seem to have the usual gib adjustments I've seen before and the adjustments do not match the photos in the manual. There are two gib retaining screws on the end of each slide that seem to move the gib slightly but don't appear to be cams by design. Tightening the daylights out of them does stiffen the slide a bit. 
The top slide has a single screw and pin which does tighten up the slide. The cross slide may have a similar screw and pin but it is obscured under the linear scales for the DRO. These may be the slide locks but if they are, they are very coarse or, in the case of the cross slide, inaccessible. 

The exploded diagrams in the manual show the lathe as delivered while the photos do not. 
Am I missing something on slide adjustment? 

Here's a photo of the retaining screw on the cross slide. A similar screw can be see in the top right of the photo for the top slide. 







> Can you measure the pitch of the crests of the ripples? This might help indicate where in the gear train the issue might lie.
> 
> Measure the travel of the carriage after exactly 1 handwheel revolution.
> 
> Try to measure the travel of the carriage after exactly 1 feed rod revolution. Disconnect the lathe from power and rotate the feed rod manually while carriage power feed is engaged.


These will come in the next update tonight or tomorrow. 

The hunt continues!
-Eilif


----------



## mikkmake (Jan 21, 2022)

One more thing!
A camera on the pinion did not show anything obvious -- it's moving fairly slow. I put an indicator on the pinion shaft as close to the pinion as I could. I measured about 1.5 thou of eccentricity on the shaft.


----------



## mikkmake (Jan 21, 2022)

Clarification on the Gibs and the obscured lock pins from Precision Matthews.


> for the gibs, you loosen the screw at one end, and tighten the other to move the gib back and forth. It's one long wedge, so one way will tighten, the other will loosen. The screws just need to be snug once adjusted. They break easily if tightened down too hard. The gibs should be adjusted just enough to keep the slide from wiggling or moving in any direction other than the one intended. More than that will just wear out the gib.
> The lock pin is used to keep the slide from moving. Don't use it to adjust the motion of the slide, you'll just wear out the center of the gib. However, when making a powered cut there's every reason to use the lock to keep the slide from moving.
> The cross slide does have a lock screw that is indeed hidden behind the scale. I don't know why they do this, but they do.


Still hunting for the carriage gib on the exploded diagram. It's gotta be somewhere. 

Mike at PM votes carriage rocking. He makes a compelling argument.



> The carriage is clamped to the lathe bed in the front and back with a gib strip in the back. If any of those are loose, this could also allow the tool holder (the whole carriage actually) to rock, so it's worth check those too.
> The fact that the lead screw doesn't show this effect argues for this being the cause. The half-nut clamps firmly around the screw and would prevent the carriage from moving in an odd direction. A bent feed rod would contribute as well, but once again, if the carriage is properly secured, it wouldn't cause an issue.


So tonight is gib night now that I understand how they work on this machine.


----------



## Christianstark (Jan 21, 2022)

mikkmake said:


> Clarification on the Gibs and the obscured lock pins from Precision Matthews.
> 
> Still hunting for the carriage gib on the exploded diagram. It's gotta be somewhere.
> 
> ...


I would tend to agree with carriage rocking. What causes it is another mystery.

I will ask again, can you take a piece of rippled stock and match it up to the tooth pitch on the carriage feed? If the tooth feed is a direct match, you may be experiencing rocking as the pinion riding along the carriage feed lateral gear maybe tightens and loosens agains the teeth. pulling the carriage down and the tool slightly away from the stock. As the tooth moves further, that pressure is relieved, causing the carriage to rock back.

That being said, I do wonder why that might only be during power feed, so maybe the issue is with some eccentricity or poor gear mesh of the gear that drives the pinion during power feed.


----------



## mikey (Jan 21, 2022)

mikkmake said:


> Thanks everyone for the ideas! I'll hold off on messing with the VFD until the ripples get sorted out.
> 
> 
> Correct
> ...



Seems to me that if the lathe finishes/turns clean when manually feeding then the issue has to be with the power feed rod or gears that drive it. The periodicity of the problem would point to the gear that drives the hex shaft in the head stock or the drive gear in the saddle. I don't see how it can be anything else given the responses you made above. 

I would look to see if the gear that drives the hex shaft is tight and is in good shape. If it is, then I would pull the hex shaft and check it for straightness. Then if that fails, I would pull the saddle apart and look at the drive gear in there.


----------



## macardoso (Jan 21, 2022)

Alright, I don't own a PM-1130V so I'll be including pictures of my lathe (an ENCO 110-2033, 12x36) but mechanically they should be similar.

*Saddle Gibs:*
My lathe has fixed gibs on the operator side, behind the apron, and adjustable flat gibs on the rear of the carriage.

Image 1: Headstock side fixed flat gib, located behind apron. Rides on ground underside of Vee way. Verify fully tightened.






Image 2: Tailstock side fixed flat gib, located behind apron. Rides on ground underside of Vee way. Verify fully tightened.





Image 3: Rear adjustable flat gib, located on the backside of the carriage. Rides on ground underside of flat way. Loosen the jam nuts, snug the adjustment screw, then tighten the jam nuts. You should feel a light drag on the carriage while sliding on well oiled ways.





Image 4: Same as the above the picture, but zoomed in on the adjustable gib.





*Cross Slide Gibs:*

Image 5: Cross slide tapered gib adjustment screw, operator side. There are (2) gib adjustment screws, one on the front operator side of the cross slide. Loosed the one in the rear of the lathe, then snug the front one up. There should be light to medium drag on well oiled ways. Lightly snug the rear screw. Do not over tighten as this can warp the gib.





*Image 6:* Compound slide tapered gib adjustment screws. Loosen this screw. Then snug the front one up. There should be light to medium drag on well oiled ways. Lightly snug this rear screw. Do not over tighten as this can warp the gib. 





Image 7: Front side tapered gib adjustment screw on compound slide. Tighten to increase friction/rigidity.
*



*

Lock the cross slide and compound slide locks.


----------



## pdentrem (Jan 21, 2022)

Does your handwheel disengage from the rack or is it always in turning when power feeding?
I found that if I maintained a constant tension on the handwheel there is a difference. My handwheel will slowly turn until the handle is at the top and then suddenly start down the hill, putting tension on the gear rack and change the amount of backlash present in the system. Try power feed but put a light drag on the wheel as it turns and see what happens. A dial indicator will show a speeding up and slowing down that is timed with the handwheel.
The only fix is to tighten the gibs on the carriage to add a little no drag to maintain the backlash that was taken up when the powerfeed was engaged.
Pierre


----------



## mikkmake (Feb 18, 2022)

I don't want to let the thread go too cold. 
I've tried a million and one things. The thing that appears to have an impact was tightening the carriage gips. Man, that was a pain in the butt. They are very inaccessible. Thank you @macardoso for your detailed guide on that process. Someday I'll take off the back splash guard and adjust the gibs without screwing up my back leaning over the lathe. 

I can still sometimes see the ripples in surface finish but they are no longer measurable. The jam nuts aren't as well adjusted as I would have liked so I'll revisit the gips every few months. 

For the question of pitch, here is the ripples compared with the rack. 





There is no tightness or disengagement as a turn the carriage hand wheel. After watching Quinn (Blondihacks) crash and repair her pinion shaft I think it's very unlikely mine is bent.


----------



## bretthl (Feb 19, 2022)

Sounds like you have chased down a lot possible adjustment issues.  Have you tried changing your tool grind?  I seem to remember having the same pattern on steel stock using a HSS tool bit with too sharp of a nose radius.  Not saying that is the cause, just something to check out.  Figuring out HSS grind, feeds-speeds-DOC by material was a steep learning curve for me (and I'm still not there).


----------



## tweinke (Jun 11, 2022)

mikkmake said:


> I don't want to let the thread go too cold.
> I've tried a million and one things. The thing that appears to have an impact was tightening the carriage gips. Man, that was a pain in the butt. They are very inaccessible. Thank you @macardoso for your detailed guide on that process. Someday I'll take off the back splash guard and adjust the gibs without screwing up my back leaning over the lathe.
> 
> I can still sometimes see the ripples in surface finish but they are no longer measurable. The jam nuts aren't as well adjusted as I would have liked so I'll revisit the gips every few months.
> ...



Did you ever come to a resolution on the ripples


----------



## Winegrower (Jun 11, 2022)

As another random opinion, and though it might be a problem with the photo, those rack teeth seem poorly formed and not identical looking.  It’s possible whatever tool made the rack had some periodic error in it…maybe inducing a slight velocity variation in the carriage Z travel which could create a varying tool load with slight X axis deflections.  Some gib looseness would make this more noticeable.    This defect would support the no ripples manually, yet ripples under power feed.

Can the rack be replaced separately?


----------



## Jake M (Jun 12, 2022)

I see this is an ongoing issue, have you solved it?  One thing I notice, you were  seeing a regular "amplitude", or height for the variation, but I don't see where you've measured a wavelength.  Can you get a dial indicator on the carriage to measure carriage travel, to get a distance from high spot to high spot?

I was lead (almost immediately) to this for several reasons.  Because you have no issues with the lead screw, and no issues with hand feeding, you can rule out a lot of things.  In particular, the carriage slides along the ways just fine, without the undulations.  Unless it's in one particular drive mode.  And because you tightened the gibs, and WERE able to reduce the undulations, but not eliminate them.  That just screams that something is acting on the carriage, forcing it to move in ways it otherwise doesn't.  And, because you said at one point, something to the effect of you could feel the pinion gear switching from tooth to tooth (or something to that effect).  That (probably) shouldn't be the case, but I dunno.....  However, the feed shaft drives the carriage a given distance per revolution.  With that information, the "wavelength" of the undulations in the work could be compared to the pitch of the rack/pinion gears, and/or "math'ed" a little in proportion to the gear ratio(s?) for the feeding mechanism inside the apron, and narrow the causes down to the items which are capable.  Or, if you were to determine that the "wavelength" of the undulations changes with the feed rate you've selected, you could actually rule out the carriage/apron area and you'd be able to see if it were something back at the headstock end of the feed shaft.  Although with the gib tightening results, I'd bet it's at the carriage area, because your evidence really points to something applying force to the carriage assembly in an unusual/abnormal way.


----------

