What About a Gang Lathe?

[BobWarfield]

Lots of mini-lathes being converted to CNC here, but I haven't seen a real good answer to the toolchanging problem. People do mount the cutoff tool on the rear, which I guess gives you 2 tools, and there have been some complicated looking rotary changers built, but it seems like gang tooling is the easy way out and I would expect to see more of it.

I first saw gang tooling associated with a product called the "Accu-Slide" that let you convert a Hardinge to CNC just by clamping the thing to the ways:



The idea on a gang lathe is to use a long slide, and let the machine's X and Z motions select the tool. To select a tool, the slide moves right to clear the workpiece (no tailstock used on a gang lathe!), the tool is selected by moving the slide in or out, and then the slide moves back left to bring that tool to bear.

Very simple! The key is going to be having long enough slide travel to carry enough tools. I learned a lot reading about gang lathes from manufacturer's web sites like Omniturn. For example, they use an 18" long slide with 10" of travel.

Along the way, I have also mused about converting Asian machines to use linear slides. A gang tool conversion is a perfect opportunity, because you probably need to fabricate a new longer slide anyway.

It turns out the Omniturn-sized slide would work well on my Lathemaster 9x30 lathe, so I did some sketches in Rhino to see how it might work:



The circles show swing over cross slide and swing over apron top. If I install a 1" thick aluminum gang slide with clearance for some 12mm linear rails, I lose about 1/4" of swing over the gang slide. Given how they're used, I can live with that. I would think some pre-ground tooling plate of 6061 (or preferably 7075/Fortal) would be ideal.

The drawing shows mounting the 12mm linear rails to the bottom of the gang slide, and then bolting the blocks to the apron. I would bolt them either side of the male dovetail, leaving that dovetail intact so I can go back to "stock" if desired. The ballscrew drives from the side, much like Ron111's Lathemaster conversion you see on another thread.

Toolposts are attached using the single T-slot that runs along the front of the plate. One could buy commercial QCTP's like Phase II, but that's way overkill. I would make them up in the AXA size, and just use a set screw to load the tool holder against the wedge. Alternatively, you can design the holders to go right to the T-slot, but you'd have to shim to get height adjusted.

This does not seem that hard to fabricate, yet would add tremendously to the power of you CNC lathe conversion by solving the toolchanger problem. Not sure why we haven't seen someone do it yet.

I will look into it further when I finish my basic Lathemaster conversion, but there's lots of folks on these boards who would probably turn out a finished result a lot faster than me.

Let us know how it goes if you decide to give it a try!

Cheers,

BW

PS I will be keeping my design notebook and eventually build log on my web site here:

http://www.thewarfields.com/cnccookb...GangSlide.html

[Al_The_Man]

To select a tool, the slide moves right to clear the workpiece (no tailstock used on a gang lathe!),

Bob
Would this not turn it into a variation of a turret lathe and defeat the purpose of purchasing a 30" lathe where you cannot use long material/tailstock
Al.

[lerman]

Bob,

Me too. I have a Rivett (very much like a Hardinge 2nd op lathe), and a Max Turn (15 x 30). The Rivett has a pneumatic collet closer.

I'd like to build something that could be used with either machine. Pick it up and move it from one to the other. I've been looking at the Omniturn website videos with envy. For my use, gang tooling is probably the way to go.

The "plan" is to first build the table and get it running with EMC for the control system. (I'm currently using EMC on my mill.) Then I'd play with the spindle. Add an encoder, at least, so I could do threading. It would be nice to put a VFD on it and be able to do constant surface speed machining. The best of the options would be to put a servo on it. That would give the best control and allow the use of a C-axis and live tooling.

If you look at the Omniturn site, you'll see the live tooling options they offer. Any small spindle could be mounted on the slide.

If you decide to go with off the shelf components (rather than off the ebay components), I might be interested in working on the project with you.

Ken

[BobWarfield]

Bob
Would this not turn it into a variation of a turret lathe and defeat the purpose of purchasing a 30" lathe where you cannot use long material/tailstock
Al.

Yes and no. You can't use the gang tooling with a tailstock, or at least not unless your tailstock is motorized and will get out of the way. On the Omniturn site they have an optional tailstock that mounts to the headstock instead of the bed.

My view is you could either start with the smaller 8x18 Lathemaster, or keep the 9x30 and use the tailstock w/o gang tooling. All you'd need to do is cut back the number of toolposts on the gang slide to 2 (one in front, one in back) when using the tailstock. When I think about how often I actually use my tailstock, this works for me.

Me too. I have a Rivett (very much like a Hardinge 2nd op lathe), and a Max Turn (15 x 30). The Rivett has a pneumatic collet closer.

I'd like to build something that could be used with either machine. Pick it up and move it from one to the other. I've been looking at the Omniturn website videos with envy. For my use, gang tooling is probably the way to go.

If you look at the Omniturn site, you'll see the live tooling options they offer. Any small spindle could be mounted on the slide.

If you decide to go with off the shelf components (rather than off the ebay components), I might be interested in working on the project with you.

As long as the mountings line up on both lathes, there is no reason you couldn't move the slide back and forth as needed. If I had a big lathe, like your Max Turn or a 14x40, I would be real tempted to do both axes in an Accu-slide like setup, and then you can bolt it on to run CNC and remove it for big manual jobs.

I did see the live tooling options and found that interesting. Live tooling really benefits from being able to run the spindle as an indexable axis. More research needed there.

I am pricing out off-the-shelf components to see. Ballscrews are pretty cheap from McMaster-Carr and other sources. The linear rails are a lot more money. I did find some HiWin rails on Technico that were more reasonably priced. We'll just have to see. I have a lot else in the queue ahead of this, but thought I'd start the discussion while I'm in the design phase.

Best,

BW

[gridley51]

We call them platen lathes over here.I don`t have one but have been looking for one for a while.Just missed a Wasino with motorised milling head a while back.I would tend to agree with Al and say they are not a lot of use for long parts as even with a tailstock you would only be able to access two tools.Ideal for short work on a series of parts.On some machines you can take the top of the slide complete with toolholders,this lets you keep plates ready set for repeating jobs,just change the collet,change the tool plate,call up the programme and of you go,no setting needed.
The other advantage has been already mentioned in that it would be simple to mount motorised attachments to a slide which does not revolve.
I doubt that I would ever convert a machine to platen style but if I did I would start of with a capstan (turret) lathe as they usually have a reasonably long substantial cross slide.

[wizard]

Years ago I used a specialized lathe for optical work that was more or less a gang tooled lathe. The problem I see with this approach is the very limited range of usage for a general purpose lathe. It would be one thing to set up a lathe like this for a specific production operation or task it is another thing to expect the lathe to be continued to be used as a general purpose machine.

Nothing bad about that of course as many a shop machine has made the transition to a tasked machine. As to your approach I don't see anything specifically wrong with it other than the aluminum and possibly the placement of the stationary bearings. The preference would be for cast iron, maybe even steel over the aluminum. You might also want three cars per side to better support the plate. These are really quibbles though.

What is really needed from the standpoint of this hobby is a really nice indexing tool holder that is either easy to build DIY style or could be delivered at a reasonable price from a vendor. Four or five tools ought to do it. I can remember from the days just after high school coming into contact with a manual Bullard VTL which could index it tooling turret with a single gear motor. Wish I had paid more attention to what was happening there, sometimes though the secretary walking up the steps to the office was much more interesting. 25 years later I think more about indexing tools than err lubing tools.

In any event you would think that there ought to be a low cost approach to a tool indexer for this market. Especially if a machine from the 40's or 50's could do it with a single gear motor.

dave

[RotarySMP]

Hi Bob,

I like your web site.

Do you have any real production runs lined up? I see from your web site you are a Hobby CNC guy like me. On my CNC'd mini lathe, I have a single wegde type AXA tool post and about 17 tool holders (they only cost about $15 from Shars, so I get a few each time I come to the states). Once you have your offsets set up, tool changing is only a couple of second. I can see it being a PITA on a production run, buit for hobby stuff it is not such a big deal.

[lerman]

If you have a 2nd op lathe that you want to convert to cnc, the issue is pretty simple. My Rivett turret lathe starts with essentially NO axis. It has a manual cross slide and a manual turret. So, to convert it to cnc, I have to build two axes.

If I go with gang tooling, I still have two axes to build. The X axis is just a little longer. If I used a turret for tool changing, I would have to add a third axis -- the rotating turret. That seems like a lot more work.

It seems to me that if I have to build two axes anyway, I might as well go with the gang tooling approach.


Ken

[BobWarfield]

If you have a 2nd op lathe that you want to convert to cnc, the issue is pretty simple. My Rivett turret lathe starts with essentially NO axis. It has a manual cross slide and a manual turret. So, to convert it to cnc, I have to build two axes.

If I go with gang tooling, I still have two axes to build. The X axis is just a little longer. If I used a turret for tool changing, I would have to add a third axis -- the rotating turret. That seems like a lot more work.

It seems to me that if I have to build two axes anyway, I might as well go with the gang tooling approach.


Ken

Ken, you've captured the logic that I find compelling for gang tooling perfectly. You get toolchanging simply for the cost of a longer axis, with no muss or fuss to speak of.

You can still use your tailstock, and the only cost is that for jobs that use the tailstock, you can only use a front and rear tool, which leaves you no worse off than otherwise.

The rotary toolchanger sounds great, but this is not going to be a simple thing to build and get working well, whereas gang tooling can be.

I don't really see it as an issue of production only. I see it as a case where if I am not using the tailstock, I get to have a toolchanger. As I look over what I do in my shop, other than cases where I have the chuck or die holder in the tailstock, I'm not using it very often, so this is a great solution for me. In addition, I've got to undertake machine work anyway to apply a ball screw to the slide, much as Al and Ron111 are doing. Once again, with just a little more work, I get my tool changer.

I think if you want to use something like this for real production, you'd need to line up a bar feeder or puller and a pneumatic chuck. Also doable, but not my cup of tea at the moment.

One last advantage is that I believe it will add substantial rigidity and perhaps precision to my little Asian lathe.

Best,

BW

PS The choice of aluminum stems from not wanting the metal to move after machining as steel or CI can. One could certainly have a go with CI. I rather like the way the material machines, and use it for my chuck backplates. If so, I would be tempted to look into having it stress relieved.

[lerman]

Well, I already have a pneumatic collet actuator, although last time I tried it it didn't open real well. I suspect it is an o-ring or seal issue that I'll address when I get a chance.

A bar puller is a very simple DIY item. A pneumatic bar feeder also seems like it should be a reasonable DIY task. Even with a manual collet, gang tooling should improve productivity tremendously.

Since most of what I'm machining is brass or aluminum, an aluminum baseplate seems pretty reasonable. It would certainly be easier for me to build with.

I've written to Omniturn to try to get the dimensions of their Tee slots and tooling plates. It seems reasonable to try to be able to use their tooling. There seems to be multiple vendors that supply compatible tool holders for that system. Unfortunately, Omniturn never replied to my email.

Ken

[RogerH]

Another small gang machine is the GT-27 from SNK. http://www.snkamerica.com/prodigy/prod/27.shtml/

Kia also makes some very reliable large machines.
http://www.kia-hyundaimachine.com/TurnList.htm

Gang tool machines are much faster for small parts than turrent machines. The moves are often much shorter and there is no lost time while waiting for the next tool to rotate into position. There also has to be enough space between tools so that one tool doesn't hit while the active tool does it's job.

RogerH

[handlewanker]

Hi all, In the shop where I used to work in the 90's we had 2 Mazak CNC's and they both had the "gang" tooling method of tool holding.
We were given them by another subsidiary of the company, and they were considered too long in the tooth for the then present day methods.
If I remember rightly the whole headstock moved in and out, on it's own slide, and the tools on the crosslide just moved across and back, also no tail stock as all the end work was done from the crosslide.
What a lot of people fail to realise is that these methods are geared to PRODUCTION machining, and when you come to apply it to general everyday turning and low volume work it doesn't work.
Take a capstan lathe for example, unless you are getting 200 batch runs, it is not economical to set up and make the parts. It don't pay, and nobody will pay your labour rates at the end of a short part run.
The same goes for CNC set-ups, if you're just having fun making parts using sophisticated state of the art technology, don't expect to compete with anyone running an old capstan lathe with form tooling and low overheads.
The point is, if you are seriously making parts to sell, then the set-up and make time will kill you if your act is not up to it.
There is always someone out there, with time on his (or her) hands, that will make parts for pocket money, and just likes to pick up the low volume jobs that no one else can make pay.
When it comes to the crosslide versus rotary magazine set-up, then the crosslide will come out tops as it's so much easier to make in the home work shop.
Provided you can tie the tools down to the crosslide, and space them out to miss each other, then the method of holding them just becomes a number of open sided tool posts with a bolt hole through the middle for a tee nut and hold down bolt.
The problem of using alluminium for the crosslide is that the tool holders will soon indent the top surface.
Using alluminium, I would fit a top piece of cast iron or steel with a long tee slot to offset the wear and abrasion.
There is no reason why any centre lathe could not be adapted to use a long crosslide for gang tooling, (incorporating collets and a bar feeder set-up),just don't expect to use conventional turning methods like supporting long work with a tailstock.
If your work load is long shaft work then the whole design takes a different turn and the gang method is unusable.
Many years ago I had a tool that was held in the 4 way tool post, and had a rotary tool magazine that rotated on it, in the vertical plane, with 6 tool slots.
This allowed 6 different tools to be selected and the magazine was just rotated manually to get the next tool required.
They have one for the tailstock too, like a capstan lathe, that holds six tools, mostly drills, reamers and taps etc.
Ian.