[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.

[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