How Are You Mounting Your Pm1340gt Lathe?

[sanddan]

Dan, is that sealant/RTV on the underside of the bolts/washers?

Mike.

Yes. I didn't on my other lathe and wish I had as that one leaks somewhere by the motor and ends up on the floor as it seeps through. I squirted it up into the hole after the bolt was inserted but before the nut was tightened.

 

[zmotorsports]

Dan, mine is mounted the exact same way.

I didn't use any RTV on mine but I did chamfer all bolt holes as they appeared to be punched rather than drilled and I noticed one looked a bit convex so I did them all.

I wonder if that could be part of RIO's issue, the bolt holes aren't allowing the lathe to bed down onto the cabinets properly.

Mike.

 

[sanddan]

I asked about the underside of the cabinet as I can feel the plates flex. If I hit the headstock similar to Reo's video I get a similar "ring" but not as bad. That got me looking for any gaps which I didn't see. I did notice how the underside of the cabinet was made, the weight of the headstock is out on the unsupported edge of the 2 plates. On my machine if I put my right hand on the plates and push on the top edge of the headstock with my left I can feel the plates flex. Easy solution, just requires me to do a lot of disassembly but it's just time and some steel.

 

[RIO]

Boys, I'm sorry for the silent delays. If I told you how crazy life is right now....nevermind.
Dan, et al, sorry I'm not replying to all you guys individually each time. You all are giving such great inputs, I just don't have time to reply.

Quick summary, then I have to get back to domestic duties:

1.) I realized that since I installed the Marathon motor, and had to buy a new drive pulley because it was 7/8" shaft, that I mis-matched sizes. I was running a Gates AX-25 because I got an AK series drive pulley, but the stock "driven" step pulley is B series. I just ordered a BX-25 belt and a new B series drive pulley for the motor (should have listened to Mark/Mike closer in the first place). When I get this new belt/pulley setup fixed this week so everything matches in size, I'll post pictures. Might make a big difference.

2.) I ordered a 1/2" steel plate, 15" x 66" to put between the chip pan and the stand. It will be a small chore just to drill the six bolt holes and the drain hole. I expect this plate install to really help, if not mostly fix the vibration. Dan, your inputs and insight on the issue with where the lathe bolts up to the stand confirmed what I was already thinking, and helped me decide to do this. In fact, I remember emailing Matt to address that issue a few days ago. Basically, I said "I think it might help a lot if that was one solid piece of steel across the top of the stand where the lathe bolts down to each section". I'm doing that and more by putting this [$70] steel plate all the way across the top under the chip pan. Can't wait to see what changes.

3.) I hooked up an A/C reactor in line on the load side. Couldn't help it, I was curious to see what it did. Mark advised me awhile back that it probably wouldn't help anything. He was right. I ran the motor, and noticed no change. Curiosity satisfied, I'm returning it.

I'm happy that for Mark, Mike and others that they got a stable setup first try. But for guys like Dan and I, it highlights a need to make some factory changes to this stand setup, because it seems to be about a 50/50 chance that the setup will work well the first try. And bolting it down still doesn't fix the problem, as I realized. I bet we really see Matt engage the issue with the factory in time to come. That's what we've all come to see and expect from him. In spite of the painful issues we're having, I think he's earning all our trust and customer loyalty.

Oh, by the way, Dan, mine looks just like yours too, where it bolts down to the stand. And I didn't use RTV or anything. Thought about that later, and probably will use that or silicone this time when I re-do the mounting, so I don't get cutting fluid leakage.

One more thing: I ordered all my belts/pulleys from Amazon. With amazon prime, it was cheaper than royal supply, after they added shipping.

More to come.
Thanks for all the input and help. Hope my (and Dan's) growing pains help somebody else in the future.
RIO

 

[mksj]

Rio et al,

I tried to look at what would be considered the resonant frequency of the system on my Pm1340 lathe, and also compare different chucks to see if it is a balance issue. I dialed up some 1" stock in the 8" QMT 4J independent chuck, measured the chuck run out and ran it carefully form 10-90 Hz, I also repeated it with my Bison 8" combo 4J which is about twice the weight. I had previously mentioned that the new Taiwanese QMT 4J was a significant improvement, and when I tried to measure the TIR of the chuck body with it mounted on the lathe it was under 0.0001", I actually did a double take because the dial indicator looked like it wasn't moving. Much lower TIR on the body than any of my other chucks. I then ran the lathe and could get some small vibration at ~620 RPM (~45.2 Hz in high gear low speed belt ratio) and around 1230 RPM. I reran the lathe with the Bison, and I encountered the same two resonant points within a few RPM. It was independent of gearing and also if I had the feed engaged or not. It did not change. The total resonant band was maybe 20-30 RPM, on either side this machine was absolutely smooth. Without the chucks, I really could not see or feel any resonant frequency no matter what I tried. So these are most likely the resonant frequency nodes for my lathe with the additional weight of the chucks, and normally one would not be seen these in the non-VFD version because they do not align with any of the 60Hz speed ranges. It was also interesting that it did not change with different chucks. The vibration nodes may not be the lathe per se, but the resonant point of the cabinets and flexing where it is mounted to the top of the cabinets or between the cabinets.

There is one other possibility which has to do with an oscillation between the belt vibration and the mass of the chuck. Looking at your video, you can see the belt walking back and forth (wobble) on the pulleys, and up and down in the grove. The pulleys look like they are running without any wobble, and the TIR reported was fine, which would indicate that the pulleys are running true.

Having a more rigid mounting base, should go a long way to preventing any flex, and it might be a bit more noticeable on your lathe because of the additional motor mass hanging off the back. But it did not appear to be chuck, gear or feed dependent on my machine. I think it is worthwhile to note that there is always resonant frequencies, nodes that mechanical systems will vibrate, this is a big issue with VFD drive systems. Regarding the new Taiwanese QMT 4J, I am impressed with its quality, the casting/finish, jaws and mechanics are top notch (world of difference from my Chinese one). I do not feel this is a factor in this issue, but try different chucks. Look forward to your update.

Agree, with you on Royal supply shipping costs, and I had to do a second order for the larger size belts . The belts are cheap relative to the packing/shipping costs of most vendors, so you do need to shop around.
Mark

 

[qualitymachinetools]

Hey guys, I have been quiet on here for a bit, but I have been looking hard in to some options. Mostly different pulleys today, but looking at the stands too. It is tough, these 2 are the only issues that anyone has ever really brought up about them, but I am always open to improvements. Especially with something as easy as that.

I am still curious though where that 15 second rattle ( or whatever you would call that) is when the machine is not running. Something has some sort of tension on it and is not sitting right somewhere. There are 4 bolts holding the headstock end down and 2 on the tailstock end, So that should not be it. Its almost like there is some sort of tension somewhere, I am not even sure how to describe it. Try some wooden wedges under all of the cabinet corners real quick, just tapped in a little bit to tighten it up, if you have some scrap wood and a saw laying around, to see if that gets rid of that vibrating in that video. That steel plate is a good idea, but what its doing should not be happening without that plate. Can you see whats shaking on that when that happens? Something is different there, none have ever done anything like that before.

The little bit of shake at a certain speed with the VFD on is one thing, but that rattle is another. Check the welds in the stand on that top plate, it almost seems like one is broken or missed where those top pieces go on if thats where it is coming from.

The good news is that for how smooth its running without a chuck, I wouldn't do too much more with that. The only issue it is moving when you push on it.

Just have to find that rattle and you will be set.

I will have more to post as I have any updates on things. Always trying to improve things, if there is a problem with anything, I try to eliminate it.

 

[qualitymachinetools]

Great post Mark, that must have been posted after I started typing the last one. (Started at 8am and finally posted after 5!)

 

[stevemetsch]

I run the supplied bolts down the threaded holes to level the lathe, then went around and balanced the torque on each front/back pair. Lathe is solid. Heavy steel plate epoxied to a CLEAN concrete floor will do a good job of replacing drliled anchors.
Steve Metsch in dry Santa Barbara.

 

[joshua43214]

@qualitymachinetools
Matt,
I will bet you almost anything that when they assemble the stands, they are not making sure the punch-outs are facing down.
If the top support plates is flipped over after being punched, it will result in the lathe not bedding down to the firmly. It will be sitting on a little hill around each bolt hole. Simple enough to fix with a ball peen hammer if one is looking for it.

Might no be so easy to get them to put them in right though. Hard enough to get factories in the west to face washers or snap rings the correct way...

 

[sanddan]

Matt,

The primary improvement to the stand that I would suggest is to make the mount plate on the top of the column one piece instead of 2 piece. The weight of the lathe is on the unsupported edge allowing it to flex. The "ring" Reo and I get could very will be as you suggest, a raised area around the holes. I will look for that when I pull the lathe off the stand. I ordered up two 1/2" thick plates that I will add to the top of the columns, this will eliminate the flex. I'll also deburr the holes before installing them. Reo's solution of a one piece plate is also a good solution. The stand on my other lathe is also sheetmetal construction but the top is one piece, not 2 piece. It is only made out of the same thickness material as the rest of the stand but doesn't seem to flex at all. Hitting the top of the headstock only gives a dull thud, much like zmotorsports described. The rest of the stand is pretty crappy, no shelves for storage or even a bottom plate. Getting the flex out of my setup is the goal at this point, hopefully that will solve the shake issue.

For you tech geeks, here is a screen shot of an FEA analysis of the 2 piece mount plate. It's anchored on three edges and a load of 440lbs applied over an area simulating the lathe casting. The screen shot shows the deflection, the scale is magnified as the max deflection is about .010". Note the deflection near the bolt holes is about .004".

Modeling a one piece plate give about .002" deflection near the bolt holes. This is a good way to compare 2 different designs but keep in mind it is still a crude estimate of the actual system as it ignores the clamp force of the bolts. Also it is a static analysis just using the weight of the lathe for inputs. Still is shows that the one piece design is much stiffer.