[PHILTHY96]

Philip over here at FK Instruments, running into a issue on a part I just programmed & set-up, was hoping to get some help or guidance on how to attack this!



Material: 15-5 CG .375

Turning tool: DCMT-3-1-4 IC8150

Part length: 3.460"

Machine: Swiss Citizen L32



I'm currently running a part with a +/-.001 true position call out on an OD. I'm not sure what is going on with my part, as there's no consistency or repetition from part to part. I don't know if it's tool deflection, material whip/bend, or bad collets. I am maxed out on my guide bushing pressure, & both my main & sub spindle. The whole 3.460" part is turned on the front side, as there's a 2.00" tapered feature that needs to be done in one pass. I can't bring in the sub for support, I don't have tool clearance. My first turn pass, about .350" "Z" move, is holding a .0002-.0004" run out & that has repeated consistently. The next turn pass goes into the taper & this is where my issue begins every time. The taper is about 2.10" long gradually getting bigger, from .204 to .275. I have an "M1" after that turn to stop & check the run out. My part is about 2.500" out of the guide bushing now. Closest to the guide bushing, the part is holding true, only running .0002" as it should. When I put my indicator to the front & indicate close to the face of the part, it's .002-.010" never repeating & that's where my +/-.001 true position call out is at. This has to be tool deflection right? Or is it the material stress relieving? I'm stumped & need help!

[Cruzeguy]

If I'm correct you're using a .015R insert, I would suggest running the smallest nose radius you can get away with. Larger nose radius will increase contact area leading to the material "pushing off" or deflecting. I've had this issue in the past in softer stainless on parts with a thin wall I need to hold .0005" roundness on the ID, the larger nose radius was giving me out of roundness which transferred over into the ID, switched to a .004R insert and they're almost perfect now. The only other thing you can do is run an extended land guide bushing, split up the turning, use the sub as support and use a back turning tool, though, I'm not sure you can get a guide bushing that long.

If you figured it out already would you mind telling us what you did to fix it?

[servtech]

Philip over here at FK Instruments, running into a issue on a part I just programmed & set-up, was hoping to get some help or guidance on how to


Material: 15-5 CG .375

Turning tool: DCMT-3-1-4 IC8150

Part length: 3.460"

Machine: Swiss Citizen L32



I'm currently running a part with a +/-.001 true position call out on an OD. I'm not sure what is going on with my part, as there's no consistency or repetition from part to part. I don't know if it's tool deflection, material whip/bend, or bad collets. I am maxed out on my guide bushing pressure, & both my main & sub spindle. The whole 3.460" part is turned on the front side, as there's a 2.00" tapered feature that needs to be done in one pass. I can't bring in the sub for support, I don't have tool clearance. My first turn pass, about .350" "Z" move, is holding a .0002-.0004" run out & that has repeated consistently. The next turn pass goes into the taper & this is where my issue begins every time. The taper is about 2.10" long gradually getting bigger, from .204 to .275. I have an "M1" after that turn to stop & check the run out. My part is about 2.500" out of the guide bushing now. Closest to the guide bushing, the part is holding true, only running .0002" as it should. When I put my indicator to the front & indicate close to the face of the part, it's .002-.010" never repeating & that's where my +/-.001 true position call out is at. This has to be tool deflection right? Or is it the material stress relieving? I'm stumped & need help!

You need qualified material diameter,if the stock material diameter varies in diameter, so will the component, due to deflection.
Buy in qualified material, however it is more expensive.

[jreynolds5]

So here is a couple of things to consider.

Material:
With a swiss your part is only going to be as good as your incoming material. On average if your material has .001 of runout you generally will not be able to get any better than .0006 runout in your finished part. The same goes for material straightness. Your material could also be stress re-leaving a bit too.

Tooling and speeds and feeds

As the other person said you need to try a small rad insert. I would play with your speeds and feeds as well.

[servtech]

Philip over here at FK Instruments, running into a issue on a part I just programmed & set-up, was hoping to get some help or guidance on how to attack this!



Material: 15-5 CG .375

Turning tool: DCMT-3-1-4 IC8150

Part length: 3.460"

Machine: Swiss Citizen L32



I'm currently running a part with a +/-.001 true position call out on an OD. I'm not sure what is going on with my part, as there's no consistency or repetition from part to part. I don't know if it's tool deflection, material whip/bend, or bad collets. I am maxed out on my guide bushing pressure, & both my main & sub spindle. The whole 3.460" part is turned on the front side, as there's a 2.00" tapered feature that needs to be done in one pass. I can't bring in the sub for support, I don't have tool clearance. My first turn pass, about .350" "Z" move, is holding a .0002-.0004" run out & that has repeated consistently. The next turn pass goes into the taper & this is where my issue begins every time. The taper is about 2.10" long gradually getting bigger, from .204 to .275. I have an "M1" after that turn to stop & check the run out. My part is about 2.500" out of the guide bushing now. Closest to the guide bushing, the part is holding true, only running .0002" as it should. When I put my indicator to the front & indicate close to the face of the part, it's .002-.010" never repeating & that's where my +/-.001 true position call out is at. This has to be tool deflection right? Or is it the material stress relieving? I'm stumped & need help!

One immediate thought is that for consistent results on a machine with guide bushings is to use qualified bar. If not, the bar diameter can vary considerably along its length, allowing deflection.

[deadlykitten]

One immediate thought is that for consistent results on a machine with guide bushings is to use qualified bar. If not, the bar diameter can vary considerably along its length, allowing deflection.

sometimes, even with good material, the guide bushing will fail - solution to this is adjustable guide bushing, like air driven ones, etc

[jreynolds5]

We used to use an adaptive guide bushing on our swiss because we make a long ball screw that is has a rolled ball groove. This part has 2 cross holes thru it with a tight true position. We used to fight it like crazy, then one day after we had tried everything else we decided to change over to a standard guide bushing and haven't had an issue since. We found that the double contact of the adaptive guide bushing was causing any differences in od to multiply and make the part deflect. We now just use a rally tight standard guide bushing.

[deadlykitten]

We found that the double contact of the adaptive guide bushing was causing any differences in od to multiply and make the part deflect

hy jreynolds, please, can you develop a bit about inner working of the adaptive bushing, the double contact that you did no like? i have never had the ocasion to inspect the inner mechanism

indeed, as being more complicated than the regular guide bush, may be less consistent when you really need that 'extra' precision

This part has 2 cross holes thru it with a tight true position

those holes where intersecting, thus locating at same z ? do you have a part drawing, please, i wish to understand better your case

ps : i just found this, don't know how relevant it is

www.youtube.com/watch?v=pEu393ww9lQ

[servtech]

hy jreynolds, please, can you develop a bit about inner working of the adaptive bushing, the double contact that you did no like? i have never had the ocasion to inspect the inner mechanism

indeed, as being more complicated than the regular guide bush, may be less consistent when you really need that 'extra' precision



those holes where intersecting, thus locating at same z ? do you have a part drawing, please, i wish to understand better your case

ps : i just found this, don't know how relevant it is

www.youtube.com/watch?v=pEu393ww9lQ

The idea of a guide bushing is to negate the need for a steady and machine the bar in one direction only, cutting close to the bushing supporting the bar. Longer workpieces can be supported by a running centre or sub spindle. In the case of longer workpieces the machine geometry is vital, it must be dialed in to specification or workpiece errors can occur.

I would get a service tech in to check and realign the machine where required.

[jreynolds5]

So the system we were using is the Adaptive Guide Bushing sold by Citizen. It utilizes an air clamping system with a double taper guide bushing that can be clamped and unclamped with an M code. The issue we were having is there are 2 separate carbide contact areas inside the bushing, and when we would drill the cross hole sometimes it would be out of true position because when the guide bushing would re-clamp there was enough difference in the material that it would cause it to deflect coming out of the guide bushing. Since we removed the AGB we have not had any more true position issues in thousands of parts ran. I will say that the Magic Guide Bushing looks to be a much better set up then the AGB.



Attachment 490604

[ToolHIT]

Cruzeguy is right on, the .015" radius insert creates a lot more surface contact and the tool pressure is most likely causing the material to deflect. I would look to bring in a .008" or .004" Radius insert. Also, the insert you are using is Molded and a Ground Insert will give you a sharper cutting edge to reduce the tool pressure, which can also help.

A ground insert with positive top rake in the .004" or .008" radius should solve the issue and allow you to see if it is the tool or not. If it does not solve the problem then it is the stock or the guide bushing. Any ground positive insert with the smaller radius should work, I really like the SK/SKS Chipbreaker in the PR1535 Grade from Kyocera for 15-5, it has been my go to to reduce tool pressure in Swiss Applications:
https://www.toolhit.com/products/tlc03461
https://www.toolhit.com/products/tlc40018
*Run at 200 SFM (130-260 SFM is the Range) & .002" IPR (.001"-.004" is the range)

It doesn't have to be these inserts, you most likely have a good option on hand. I just really like these and have had luck with them.

Hopefully this helps!

Mike

[deadlykitten]

It utilizes an air clamping system with a double taper

hy jreynold, please by double taper you mean like in attached image left ? or inside is cilindrical, but you reffer to outside tapers, like in the right side of the image ?

The issue we were having is there are 2 separate carbide contact areas ... when the guide bushing would re-clamp there was enough difference in the material that it would cause it to deflect coming out of the guide bushing

I will say that the Magic Guide Bushing looks to be a much better set up then the AGB

so you consider that the "Magic Guide Bushing" is more reliable, because of having only a single contact area ? so, in other words, when material is not uniform, it will be clamped in a more tilted state ( more erorr ) by the double contact, because the double contact makes kind of a lever(too much tilt), for example, if the material is much more less uniform in the back, then the double contact will be affected by touching the material there, while the single contact (Magic Guide Bushing) is not influenced, simply because it makes contact with the material only towards front ?

Since we removed the AGB we have not had any more true position issues in thousands of parts

please, do you somehow remember, what was the material roundness error ? or it's diameter was ok, but instead of straigth, it was curved ?

or to rephrase, material was ok, like normal calibrated for a swiss ( < 0.01mm diameter deviation for small ones, <0.03 for bigger ones, etc ), but your drawing conditions where really that tight ?

i try to understand if your issue was with material, or with clamping repetability, considering that you had to " clamp-cut 1st hole - feed z - reclamp - cut 2nd" ( thus 2 clamps / part ); for example, do you believe that there is a better quality material, that if you would have used it back then, it would have worked with your adaptive system ?

please excuse all this, i simply try to narrow down some details, as i have had experienced something opposite, like reaching the need to use an adaptive, and seing that the adaptive does not always work, i simply try to understand the inbetween reasons

some years ago, i used the gang with good material, but after a month of a long setup, dimensions started to vary with 0.01-0.02mm, very little; it was within drawing, thus part was ok, but till that day, all variations where <0.003 ... after some long inspection days and trials, we discovered that the normal guide bush simply got loose, and back then, i was offered an adaptive system, as a solution to this issue, because setting a normal guide bush is time consuming / kindly

[jreynolds5]

What I mean is it is like the bottom right picture with a double taper on the OD and it had to separate cylindrical pads on the ID both identical sizes. This system uses a pneumatic clamping system that pushes forward from the back of the guide bushing effectively creating 2 separate clamping surfaces inside the guide bushing. The material is a roll formed ball screw so there is quite a bit of inconsistency. The cross hole had a .002" true position call out. We were holding it for the most part but we would have the occasional 'flyer' that would be out of tolerance. It equated to probably a 4-5% scrap rate. But these are 26" long parts so material wise that is a good bit of scrap. And like I said once we went to a standard guide bushing we no longer have issues.

[deadlykitten]

hello again maybe you could have solved it by simply grinding away the 2nd contact area, thus 'forcing' the collet to only rely on one zone instead of two but also, this aproach, could have make the collet behave much more worse

bottom right picture with a double taper

just informative, i found this ( video below ) :
... double taper ( double contact ) collets are used in "Double Cone Guide Bush System"
... single taper are used in "Pull System Guide Bush System"
what i like about those, is that the collet is changed fast, there is no need to dismount like for a regular guide bush

cross hole had a .002" true position
26" long parts

pretty long please jreynolds, i have few more questions :

i have only worked on citizen l12, thus gang lathe for dia12max, and i found the spindle's collet ( not guide bushing, but left and right spindles ) settings really timeconsuming; the clamping range was like 0.15 .. 0.3, something like that, and in order to clamp on material o10, somewhere near the range middle, i was using some rods like 9.8 9.9 10 10.1 10.2 10.3, etc, and with those i was setting the machine so to clamp the material at midd range ... such a time waste; please, do you have some ideas how to adress that ? i believe that bigger gang lathes have more range, so there are less such worries with bigger materials

---

back to adaptive bushing, please check attached : that is a wide-range collet, made of 3 independent parts, with little springs in between; such a construction may not have high repetability when clamping, thus it's center can shift

a collet, made of a single part ( integral ), is much more rigid, and has much more clamping repetability

the adaptive collet that you used, was made of independent parts, or was integral ?

---

through jbs documentation, i found attached about how a diagonal thin slot will make a more performant collet ... far as i know, top quality collets have thin slots, but i can not understand how the slot position, instead of longitudinal, being diagonal, will actually improve performace ? kindly


www.youtube.com/watch?v=gXIeActAe9Q

[jreynolds5]

So yes the Double taper bushing is like your bottom picture. Ours were 2 pcs with springs between and rubber rings in the 2 od grooves. Due to the way these clamp with the double taper they are made to work by equalizing the clamping force both in the front and back of the bushing so if you were to remove material from one set of pads it would just clamp more on that end and equalize the clamp force. I have only used 20 and 32mm machines. I don't believe there is a difference in clamping range due to the size of the machine, I believe that the smaller the bore of the collet the smaller the clamping range. As you probably have noticed I am in the us so I use SAE. Generally speaking I have never had more than a +/- .0025" (.0635mm) tolerance which is more than covered by your .15. We also do a few parts that a thin walled brass that have a +/-.00015" (.038mm) tolerance and can crush very easily and we also have to do some sub work on so they have to be clamped tight enough to hold them for the sub work but light enough not to damage and we don't have any issues with it. I am personally no longer on the operator/machinist side of things and am on the programming/engineering side, but I am the only one here that knows anything about swiss above a machine operator level so I still am involved in it pretty deep.