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View Full Version : Just Curious, Rotary or Fixed GB??



PoiToi
04-02-2009, 04:54 PM
I'm just curious what you prefer and run on a day to day basis. My 2 citizens are rotary GB, and it seems to be a great system.
I honestly fail to see what advantages a fixed GB would have, except being able to make long parts in one chucking...

tobyaxis
04-02-2009, 11:54 PM
Voted the same as you, Rotary for obvious reasons. Rotary is just better in many aspects which you already know. Besides I only used Rotary with the exception of one Namura with 5 Slide tools. That was convenient because it was all open. No cover to lift to get to the Z axis spindle and guide bushing. the control was the size of a refrigerator and stand alone.

The other two were one Tsugami Panther B018 Mark 2 and a Star (can't remember which one:)). Neither were the best in their class, but both had Gang Tooling, Live Tools, and Sub-Spindles. Good enough for what we had to do.

Rotary or Nothing, LOL:D

MikeMc
04-03-2009, 07:55 AM
I have two Citizen B-12 machines, they are both rotary with a max spindle speed of 8000 rpm. If I were to go fixed GB I could turn at 12000 rpm.

I cut my teeth on cam machines, all of them were fixed GB. We had to use rotary GB units if we were going to cut stainless.

All the machines I have now are rotary, and I think the system is great! I am just really happy not to have to run cam machines anymore!

Shadow_CMA
07-16-2009, 11:05 AM
You CAN do longer parts on the B-12 using the rotary GB, it would just not be driven from the headstock as normal, a 2.5" stroke.
Non-syncronized rotary GB, works for stock larger than .25" but not anything smaller as the stock tends to twist inbetween the headstock & GB. That way you can use the full stroke of the headstock, all 5" of it.
The old advantage of the fixed GB was high rpm's, you can run 10,000 rpms on your B12 with the rotary GB, but you will be replacing GB bearings more often.

Shadow
CMA Service

extanker59
07-17-2009, 10:01 AM
We had rotary GB but in the training class they said that the advantage of a fixed GB was precision. With a rotary you have the tolerances of the bearings on top of the tolerances of the bushing.
I was surprised to read "The old advantage of the fixed GB was high rpm's" from Shadow. We were told that, with a fixed GB, you couldn't go as fast because of friction. Made sense to me but, again, I never ran a fixed GB.

tobyaxis
07-19-2009, 04:16 AM
I am just really happy not to have to run cam machines anymore!

I have one friend that loves those old CAM Swiss, but he may have fallen off the deep end IMPO, LOL.:D

petriej
07-28-2010, 01:11 PM
We run rotary. One "magic." We took magic off our other Star to install the bar gripper. I was told the same story on precision with the fixed.

steve3three
09-09-2010, 09:40 AM
fixed for the win imo. Rotary ftw only if you don't have skilled operators. Rotary is way easier obviously but to keep those tight tolerances I think it would make the most sense to go fixed with precision ground stock. if your running loose tolerances and are planning on buy loose tolerance stock (cheaper) then rotary is probably your best bet.

PixMan
09-24-2010, 08:50 PM
I vote rotary, with the caveat of using it on machines with servo-driven GB's. On machines with rotary GB's, you can usually run much higher productivity because you can run larger-diameter stock at higher speeds. I've had just a few too many burned-up fixed GB's trying to run heavy cuts at high speeds that are no issue on rotary GB machines.

dookie2022
10-19-2010, 07:27 PM
I did a job .2mm in diameter * 1.4mm long once and the only guide bush system that worked for this job was rotary guide bush and to most jobs rotary is much better than fixed.

Mountain_Hiker
05-23-2012, 04:53 PM
I know this thread is old, but I was wondering if someone could talk about the difference between a fixed guide bushing and a rotary guide bushing. I can already tell that there is something "fixed" about the one option.

Fixed, to me, could mean that the guide bushing and main spindle are "fixed" together, as in direct gear drive from one to the other. While rotary could mean a separate drive mechanism for the guide bushing apart from the spindle.

Or fixed could mean that the main spindle turns while the guide bushing is just stationary, which I think is what it really is. I think there may be different options on the kind of rotary guide bushing system you can get. I'm not sure. As in, you can have one with both straight geared together, or you can have a separate drive for the guide bushing, than the spindle.

What thoughts does anybody have?

MikeMc
05-23-2012, 05:22 PM
Hey there.....a fixed guide bushing is stationary, and does not rotate with the material. A rotary guide bushing rotates with the material. In our old cam machines, most jobs we did we used a fixed style guide bushing. The only times we would use a rotary is when we turned hex material, or stainless steel. Running stainless steel in a fixed guide bush would cause the material to gall and build-up on the carbide pads of the guide bushing. In the old days you also lost a lot of precision when using a rotary style guide bushing because of the deflection in the bearings.

Mountain_Hiker
05-24-2012, 09:09 PM
Hmm, I have an interesting question. Is there a manufacturer that offers a feasible option for choosing one or the other on the same machine. I'm not literally speaking of choosing one option over the other, but am speaking of the interchangeability of each kind.

In simpler words, does any manufacturer make a machine so that you can install a fixed guide bushing when you need it, but also set up a rotary guide bushing when you need it? All on the same machine, and with an easy transition. It would seem like someone would as advanced as our machines are, and with the technology. It just make sense.

MikeMc
05-25-2012, 11:43 AM
They probably all do, as far as i know. I know my Citizen B-12s have the option of interchanging the fixed for rotary. Max spindle speed on rotary=6000, and on fixed=12000. Haebeggar used to make adjustable guide bushings with carbide balls on the inside surface and sold them as an alternative to rotary guide bushings for cam machines.

MCImes
05-25-2012, 11:56 AM
Both my tsugami's support a fixed bushing option. You replace the entire assembly that the bushing screws into. All it takes to change over is 6 large screws. They provide an identical assembly minus the bearings. My machines are a BS19-III (2004 year model) and a BX12 (1996 year model) panther. The 19 can also be run with no guide bushing. If you remove the GB assembly and turn on "GB less mode" in the custom menu the linear rails go far enough forward that you can get the collet face almost to the gang plate so it turns into a sliding headstock lathe with no bushing.

I have no idea when or why you would use this. Large stock, long parts with loose tolerance? might speed things up? Ive never used it though. Why use a swiss without a GB? why not just use a much cheaper normal lathe. Overall I despise the collar type sync that the B12 and both my Tsugami's use.

To all machine manufacturers: PLEASE use a G.D. jackshaft with 2 belts to sync the bushing. Screw servo motor sync. Screw collar sync. My tsugami's have 2.3" and 3.1" Z1 travel with the collar style bushing drive. That is a freaking joke. I do so many regrips its silly. Why even make a machine with <6" useable z1 stroke? The collar limits stroke. The servo motor I dont like for setup because you cant lock the GB with the spindle so you have to hug the machine and get a wrench on both sides.

* end rant*

If you cant tell I vote for rotary as well. I can hold +0-.0003 tolerance on 3" turns consistently. I feel that as manufacturing technology has evolved bearing runout and associated issues have become MUCH less of an issue.

g-code_junkie
09-14-2012, 07:21 AM
I have used both rotary and and stationary guide bushings. Today most machines come standard with a rotating gb.The one feature on some of the stationary gb's that l really liked, was the ability to adjust it's z position mechanically in order to reduce the gap between the gb and tooling. Today I have to order extended nose guide bushings when working with small parts.

steve3three
09-14-2012, 11:13 AM
I retract my previous statement. When the topic started I was under the impression rotary was self adjusting. My machines will only run rotary but the adjustment is not self adjustable.

jptech
11-02-2012, 06:35 PM
All 12 of ours are rotary. I've never used a stationary............John

z369
11-09-2012, 01:55 AM
One for fixed, every swiss I've ever ran was fixed except when running hex.
I really don't see the need to even run a rotary GB and never have. I've put some pretty crappy stock through solid carbide bushings before and it straightened out just fine, of course theres always the occasional hiccup/hang-up, but very, very few and far between (10 years on swiss and maybe once a year) It takes some skill to set them, but the gain is well worth it IMO.

Momchil
11-14-2013, 12:16 PM
Hello, everyone

I know this thread is old, but I've been reading for a couple of days for the types of guide bushing and I couldn't understand a couple of things.
1. What exactly is fixed guide bush.I have read that it doesn't move with the bar stock.Could some one provide a video or a drawing. I searched the internet, but couldn't find one.
2.How the guide bushing( fixed or rotary) clamps and unclamps the material. For exaplme: Citizen - M32Y Demo - YouTube (http://www.youtube.com/watch?v=fuBBjF4ViCI) this video on 2:13 minutes. The bar stock is moving through the guide bushing with no effort.I could not understand how to adjust the clamping preassure of the guide bushing.

Please, I would really appreciate all your answers.

Ned-Dragon
11-14-2013, 08:28 PM
A rotary guide bush rotates together with a work piece and holds the work piece for axial (z) sliding. A stationary guide bush remains stationary and holds a work piece and does not rotated, if you over tighten you burn it if i lose you will have problems with dimensions. I use rotary guide bushing and fixed stationary GB, I work with bushings for 17 years , both GB are good. If you not used to GB-s at all, go with rotary GB, other wise you will end up buying them by load. Fixed stationary GB will give you better T.I.R., or order Swiss machine with out GB, just collet and that is another story...

"Bushing is heart of Swiss machine program-cams are the brain"