Heavy Weight EDM Rotary Table

Hi all,

I've been tasked with finding a way to rotary some large parts on our wire EDM at work. For reference, I don't run the EDM, nor have I ever. I am very familiar with manual machining and CNC a little bit, but EDM is pretty far out of my league.

So the parts we are looking to rotary turn are about 8-9" in diameter, at up to 11kg. The largest machine is an AC progress VP3 wire EDM with a Hirschmann H80R.MNC. It is rated for 10kg. With the part and it's fixturing overhanging, that would be pushing over the limits. We has a tailcenter, but the operator doesn't want to use it to avoid the thrust load on the bearings.

So I'm looking for a heavier weight rotary table. I know that Hirschmann has them, but they're pretty expensive. This is the first time that something this big has ever needed to be rotary turned at my work, so it's not something that will see use often, like the smaller one which runs everyday. I'm sure you can see why we'd rather not drop 50-100 grand on something that gets used every couple of years.

So basically what I'm asking is if there is any budget options that won't be destroyed after a few days of running? We need rotary only, no positioning. No need for it to be controlled by the machine either, it can just be an external control with a speed pot. No need for crazy accuracy either, a regular vertex style would be plenty accurate. I thought about using one of those (maybe a super-spacer with a IP68 stepper?), but I figured even with marine grease and a rotating ground that it may have issues after hours being submerged. I wouldn't care if a $500 unit got destroyed, but it needs to be able to finish the job.

So am I crazy or on the right track? We could sub it, and that's probably what we should do, but the higher ups would really like to do it in house.

I appreciate any help.

Just my opinion.

I can understand the thrust load from the tail stock. So I would incorporate a sprung loaded centre or spring washer in to the tail stock to limit tail stock pressure.

ClappedOutBport,

The cost of EDM Rotary Tables have always come with sticker shock!

The reality is that the Rotary Table design and construction has to be very different for an EDM because of the fully submerged environment and nature of EDM machining. The key item on the rotary table is that its bearings have to be 100% electrically isolated, and they are usually made from ceramic for this reason. Using a Rotary Table from a Mill on an EDM will result in EDMing of the bearing race, and this gets chewed up quickly!

Hirschmann makes great Rotary Tables for EDM, but you can also take a look at MMK Matsumoto, and I believe their MDHWi100L table might suit your needs and has higher payload capacity. (MMK).

- Brian

We had 3r b axis rotary units...I believe they were over 20k each...and unrelable.

Brian Pfluger said:

ClappedOutBport,

The cost of EDM Rotary Tables have always come with sticker shock!

The reality is that the Rotary Table design and construction has to be very different for an EDM because of the fully submerged environment and nature of EDM machining. The key item on the rotary table is that its bearings have to be 100% electrically isolated, and they are usually made from ceramic for this reason. Using a Rotary Table from a Mill on an EDM will result in EDMing of the bearing race, and this gets chewed up quickly!

Hirschmann makes great Rotary Tables for EDM, but you can also take a look at MMK Matsumoto, and I believe their MDHWi100L table might suit your needs and has higher payload capacity. (MMK).

- Brian

Click to expand...

They do! It's a whole new world to me. Crazy. I'm begging for just a full sized knee mill instead of a minimill and a new lathe, and I could buy 4 for the price of some of the Hirschmanns.

I thought about the bearing component after doing some initial research. I do agree, that is going to put a stick in the spokes of anything non-EDM designed. That MMK does look like a good possibility. Thanks!

Luke.kerbey said:

Just my opinion.

I can understand the thrust load from the tail stock. So I would incorporate a sprung loaded centre or spring washer in to the tail stock to limit tail stock pressure.

Click to expand...

I could see that. Just leaving a reamed hole and having a center which just sat in the hole might work well. I dunno that I can get the EDM guy to go for it.

plastikdreams said:

We had 3r b axis rotary units...I believe they were over 20k each...and unrelable.

Click to expand...

Dang! That's a shame.

------------------

I found this today at work: Wire EDM rotary table DPFP60 - Mecamag.com

It looks heavy duty and is manually indexed. I was thinking with a timing belt, a couple of cogs, an IP68 stepper, and a cheaper controller, we could a have a dumb rotary axis. It's 1/3rd the weight of the others, but it also doesn't have much going on inside. I sent a message inquiring about it, hopefully they write back. No weight limitations listed on their website, not much info in general. It also can be set up for ER50 collets, which would be well suited for larger, heavier fixtures. Thoughts, assuming it can hold the weight?

Hi ClappedOutBport:
Do I understand correctly that you want to do "Spin and Burn" and you do NOT want to do "Index and Burn" or "Turn while Burn".

For those unfamiliar with the difference, Spin and Burn uses a dumb spindle that rotates at relatively high speed and the wire EDM with this kind of unit functions effectively like a lathe doing single point turning but with a wire instead of a carbide insert.
The spindle just spins.

Index and Burn is as the title implies...the machine controller issues a command to the table, it indexes, then locks in position and a burn is done, then it indexes again, locks again and another burn is done.
The motion control can be either from a standalone box or from the machine control.

Turn while Burn is the process used for cutting spirals so the table rotation is co-ordinated with axis advance and is the most expensive of the three by far because it needs to interface directly with the controller so it will adjust it's rotation rate as the spark gap conditions dictate.

The distinction is important to you because each of these devices is totally different from the others, and you need the correct one to do your job.
Index and Burn as well as Turn while Burn tables rotate slowly, and a Turn while Burn table can be used for Index and Burn but not vice versa.
Neither works well for Spin and Burn because the spindle needs to turn at relatively high speed; up to 1500 RPM for small parts, where a typical Turn while Burn table might go 10 RPM.

From what you're describing in Post #1 you're talking about a "Spin and Burn" application.
Typically this technology is used to make tiny tiny things in hard materials with super long aspect ratios... the typical demo part to showcase this process is a carbide ball 3 mm diameter burned onto the outboard end of a needle maybe 0.75mm diameter and 20 mm long.

So I am unsure why you need this tech to make a large part, but I assume you have very good reasons to do so.
Also, it sounds like your EDM guys are already pretty familiar with this turf, so if I've been stating the obvious, please forgive me.

Anyway, if my understanding is correct, you're looking for something that can spin fairly fast, and what's been recommended so far doesn't appear to meet that need.

FYI, here's a link to an excellent overview of the processes of rotary wire EDM:
https://maroneycompany.com/wp-content/uploads/2014/02/TechnologySpotlight-RotaryWireEDM.pdf

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

implmex said:

Hi ClappedOutBport:
Do I understand correctly that you want to do "Spin and Burn" and you do NOT want to do "Index and Burn" or "Turn and Burn".

For those unfamiliar with the difference, Spin and Burn uses a dumb spindle that rotates at relatively high speed and the wire EDM with this kind of unit functions effectively like a lathe doing single point turning but with a wire instead of a carbide insert.
The spindle just spins.

Index and Burn is as the title implies...the machine controller issues a command to the table, it indexes, then locks in position and a burn is done, then it indexes again, locks again and another burn is done.

Turn and Burn is the process used for cutting spirals so the table rotation is co-ordinated with axis advance and is the most expensive of the three by far because it needs to interface directly with the controller so it will adjust it's rotation rate as the spark gap conditions dictate.

The distinction is important to you because each of these devices is totally different from the others, and you need the correct one to do your job.
Index and Burn as well as Turn and Burn tables rotate slowly, and a Turn and Burn table can be used for Index and Burn but not vice versa.
Neither works for Spin and Burn because the spindle needs to turn at relatively high speed, up to 1500 RPM for small parts, where a typical Turn and Burn table might go 10 RPM.

From what you're describing in Post #1 you're talking about a "Spin and Burn" application.
Typically this technology is used to make tiny tiny things in hard materials with super long aspect ratios... the typical demo part to showcase this process is a carbide ball 3 mm diameter burned onto the outboard end of a needle maybe 0.75mm diameter and 20 mm long.

So I am unsure why you need this tech to make a large part, but I assume you have very good reasons to do so.
Also, it sounds like your EDM guys are already pretty familiar with this turf, so if I've been stating the obvious, please forgive me.

Anyway, if my understanding is correct, you're looking for something that can spin fairly fast, and what's been recommended so far doesn't appear to meet that need.

FYI, here's a link to an excellent overview of the processes of rotary wire EDM:
https://maroneycompany.com/wp-content/uploads/2014/02/TechnologySpotlight-RotaryWireEDM.pdf

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Click to expand...

Hi Marcus, thanks for the reply.

Spin and burn is correct! That is a lot of what the current rotary table gets used for. All though for some reason the machinist never seems to go over about 60 RPM, which he said he uses the same speed for everything.

Would you really spin a 10+kG 9" diameter part that fast? Knowing the cost, fragility, and balance (tube shaped, so all the mass is at the outside), I would personally keep it pretty slow. Even on a lathe with big spindle bearings. We're burning tungsten, so it's not suitable for a lathe. I assume it could be ground, but I'm not sure if that would be any better.

I believe the current table can turn and burn, but has some sort of an angle limitation? It's a bummer, because we often get parts in with super mangly threads make from Tungsten or the like, and we could do a better job ourselves if that wasn't an issue.

Thanks for the link. Familiarizing myself will help a lot. Cheers.

Hi again ClappedOutBport:
With regard to your question about the spindle speed; no I'd freak out too, if someone wanted to spin such a large workpiece at those kinds of speeds.

Your application is really unusual for Spin and Burn...I've only ever done it on parts in the 1 to 3 mm diameter range and it seems from what I've read that it's used mostly for those tiny bits that are too long and skinny to tolerate tool pressure or are harder than a woodpecker's lips or both.

With a spinner, you don't need anything very elaborate if your roundness requirement is not too outrageous.
All you need to do is seal the bearing housing decently, introduce positive pressure air into the housing to keep out stray water drops, put an insulating plate between the chuck and the spindle and another between the housing and the wire EDM table, and put a rotating contact collar and contact finger on the chuck and connect it to the table
Then you can motorize it with any variable speed drive using belts to keep the motor out of the water.

I've used my Rotobore sinker EDM attachment successfully for Spin and Burn...that's basically all the Rotobore is...an electrically isolated, spinning spindle with variable speed you can put a chuck on and burn without fucking up the bearings.
But I do tiny stuff...not like you're doing.

BTW, you will not be able to burn threads with a Spin and Burn...you must have a Turn while Burn unit to make helices, and it will be incredibly slow and use up a Hellacious amount of wire.
Basically you need to first index and burn away the bulk of the material in staggered little U shaped nibbles, then you need to cover the whole surface with Turn while Burn passes...bazillions of them if the thread is coarse, unless it just happens to be a profile on which you can lay a straight wire and touch everywhere at the same time.

It's not like cutting a twisted planar surface...when you see the helical burning demos that's almost always what they're showing even if it doesn't look that way on first glance.
Attached is a picture of a rodent leg bone drill I made for a scientist years ago...it's three curved, twisted flat surfaces arrayed at 120 degrees to one another.
The shank was Spun and Burned, the head was Turn while Burned.
It doesn't look like flat twisted surfaces but it is!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

implmex said:

Hi again ClappedOutBport:
With regard to your question about the spindle speed; no I'd freak out too, if someone wanted to spin such a large workpiece at those kinds of speeds.

Your application is really unusual for Spin and Burn...I've only ever done it on parts in the 1 to 3 mm diameter range and it seems from what I've read that it's used mostly for those tiny bits that are too long and skinny to tolerate tool pressure or are harder than a woodpecker's lips or both.

With a spinner, you don't need anything very elaborate if your roundness requirement is not too outrageous.
All you need to do is seal the bearing housing decently, introduce positive pressure air into the housing to keep out stray water drops, put an insulating plate between the chuck and the spindle and another between the housing and the wire EDM table, and put a rotating contact collar and contact finger on the chuck and connect it to the table
Then you can motorize it with any variable speed drive using belts to keep the motor out of the water.

I've used my Rotobore sinker EDM attachment successfully for Spin and Burn...that's basically all the Rotobore is...an electrically isolated, spinning spindle with variable speed you can put a chuck on and burn without fucking up the bearings.
But I do tiny stuff...not like you're doing.

BTW, you will not be able to burn threads with a Spin and Burn...you must have a Turn while Burn unit to make helices, and it will be incredibly slow and use up a Hellacious amount of wire.
Basically you need to first index and burn away the bulk of the material in staggered little U shaped nibbles, then you need to cover the whole surface with Turn while Burn passes...bazillions of them if the thread is coarse.
It's not like cutting a twisted planar surface...when you see the helical burning demos that's almost always what they're showing even if it doesn't look that way on first glance.
Attached is a picture of a rodent legbone drill I made for a scientist years ago...it's three curved, twisted flat surfaces arraye at 120 degrees to one another.
The shank was Spun and Burned, the head was Turn while Burned

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Click to expand...

Okay, I'm tracking.

Yes, we do some unusual stuff.

Regarding your suggestions for a rotary table. Is that a list of what to look for, or are you suggesting to build something? Rotary ground is no issue, conductivity is no issue now that you have made that obvious ( ), air purge shouldn't be hard. But I'm not sure that we could seal up anything not made for EDM or at least IP67 applications.

5/8-18 was the thread in question. I'm sure we go through a lot of wire, the 3 machines run basically around the clock. It would have been better than the supplier using a die they probably grabbed from home depot. They were supposed to be class 3 threads. They came in as probably a class 1, then after coating the part and sending it out, it came back with the threads even more mangled and the coating chipped, probably well below class 1 threads. EDM may be slow, but I know it could cut class 3 threads all day long. The Hirschmann H80R.MNC. should be able to turn while burn, right?

HI again ClappedOutBport:
Sorry for taking so long to respond; I've been fully occupied bringing in and commissioning a new surface grinder so I haven't looked a PM for a while.
Anyway, to answer your questions, I looked up the Hirschmann table you referenced and it looks to me like it's a spinner and indexer, not a turn while burn table.

My machine has a turn while burn unit, and it has a motor in the unit, but the servo amp for it is built into the control, so the two are integrated, and were mated together by the machine builder on my machine.

Hirschmann must have a similar provision to integrate their turn while burn capable tables to whatever machines they are going to be run on...I don't think you can just buy one and bolt it to a machine without the interface kit to mate it to the control.

Turn while burn requires that the controller governs the rotary motion; this is because the rate of rotation has to be driven by the spark gap conditions in conjunction with the axis motion of the rest of the machine whether it's X or Y or U or V.

So sadly no, I don't think the table you specified can do that thread burning task.

If you looked at the article I referenced in post #6, you will see a thread that was burned using turn while burn, and that may have lulled you into thinking...well hey, here's an example of exactly what we want to do.

Unfortunately, that's not a 60 degree vee thread...it's a bastard thread. (It's on page 7 of the article)
If you look closely at it, you can see it's got a weirdo ellipsoid thread profile.
It was faked by tilting the wire to an angle other than the thread helix angle with the U axis, then driving a fine pitch helix with B and X (B is the rotary axis on my machine).

So the straight but tilted wire cuts the leading flank on one side of the wire, the root of the thread on another side of the wire, and the trailing flank on the third side of the wire, all in one pass.
Makes a pretty demo picture but is useless as an actual conventional threadform.

To cut an actual usable thread you cannot do a fake like that.
You can use the strategy to knock some of the meat out and rough the thread, but you still have to make a bunch of successive passes down the trailing flank, across the root, and back up the leading flank and they have to be spaced close enough together that the scallops from the 0.010" diameter wire are shallow enough not to matter.

You can imagine just how many passes that would take (a LOT), and you will always have a 0.005" radius at the junction of each flank and the root, which may or may not be acceptable depending on the application.

So when I said a Hellacious amount of wire, I really meant it: spools and spools of wire in the toilet just to make all those passes.

The 5/8-18 thread you referenced would take at least 12 hours of continuous cutting to finish cut a thread 2" long, so probably between 6 and 10 Kg of wire.
That's one expensive thread and it's a crappy thread too, with all the residual scallops and the root radii.

I've never tried thread grinding tungsten, so I don't know if it can be ground, but I'd sure look into it before I ever tried to cut that thread on the wire.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Brian Pfluger said:

ClappedOutBport,
Hirschmann makes great Rotary Tables for EDM, but you can also take a look at MMK Matsumoto, and I believe their MDHWi100L table might suit your needs and has higher payload capacity. (MMK).

- Brian

Click to expand...

Brian, I contacted MMK today about that unit and they were quick with a quote. Looks like about $32k with a m-code driven basic controller which should work perfectly for our application. So thanks a lot for pointing that out!

implmex said:

HI again ClappedOutBport:
You can imagine just how many passes that would take (a LOT), and you will always have a 0.005" radius at the junction of each flank and the root, which may or may not be acceptable depending on the application.

So when I said a Hellacious amount of wire, I really meant it: spools and spools of wire in the toilet just to make all those passes.

The 5/8-18 thread you referenced would take at least 12 hours of continuous cutting to finish cut a thread 2" long, so probably between 6 and 10 Kg of wire.
That's one expensive thread and it's a crappy thread too, with all the residual scallops and the root radii.

I've never tried thread grinding tungsten, so I don't know if it can be ground, but I'd sure look into it before I ever tried to cut that thread on the wire.

Cheers

Marcus

Click to expand...

Thanks for the reply Marcus. Yes, I can see now how it would take a hellacious amount of wire. But, it was only a 1/2" long thread, so 4 hours of running doesn't sound that insane on a machine that probably clocks in 12 hours a day. I agree with you though that grinding is almost certainly the answer for that part. But I guarantee any solution would be better than what was sent to us.

At any rate, Mecamag didn't get back with me (I will try to call tomorrow morning) but the MMK is looking like the most promising option thus far if we're gonna do this in house. Thanks all for the help.

MMK has an 8-10 week lead time, which is too long.

But I don't think it matters, as I had a better idea. (I think)

I intend to mount the part between centers.

1. On the left end of the table where the rotary axis normally sits, I will have a riser with an Mt2 bore in it.
2. On the right end, I will have a long flat bar, maybe 1-1.5" thick to span the gap in the Agie table. On top of that, a riser (if necessary) then a tailstock off a lathe (like off a SB 10", widely available and cheap)
3. On both ends, use a hardened, non ball-bearing, live (sometimes called dead, but I digress) center.
4. On the part mandrel, bore out both ends to accept a plastic insert. I'm thinking Delrin, but maybe PEEK? That will then be centerdrilled. This will avoid making electrical contact through them and provide a friction surface. I know the guy here has an ordinary mt1 center he uses sometimes, but I can't see the ball bearings in there lasting long.
5. Mount a brush and brush holder to transfer the current.
6. Mount a timing pulley to the mandrel, run a belt to a motor sitting on the left end riser.
7. Buy or make a simple controller that can index and spin at a given speed.

I don't see why this wouldn't work, and given that the tailstock can be moved back, it should be capable of almost any part length that will fit in the machine. I intend to make the axis height to be 1/2 of the "swing" between the two heads unless I head otherwise. I'll talk to my guy here about that.

Thoughts anyone? I know it is unconventional, but so is our part.

Hi ClappedOutBport:
I cannot see any reason why it would not work.
So long as you have a connection between the table and the workpiece you should be able to cut it like you can cut any other workpiece.

However: (If your guys are experienced with rotary wire EDM, the following should be already well understood and obvious)

The rotation speed will affect the feedrate of the wire along the primary axis significantly, as will the depth of cut, and on a large diameter part it will matter much more than on a small diameter part.
If you imagine a large workpiece spinning fast and the wire is being asked to remove say 0.100" per pass, it effectively presents a huge amount of material to the zone where erosion takes place, and the erosion process will not be able to keep up.
The primary axis feedrate will slow down as the gap sensing circuit sees the gap close, and of course the gap continuously closes as the part rotates unless the erosion happens fast enough to keep up.
Remember erosion happens one spark at a time so there is a finite limit as to how much material you can present to the wire per unit time and still expect the sparks to gnaw it all off.
As a ballpark, a fast wire cuts at 25 square inches per hour, and the slot is typically 0.0135" wide so an MRR of about 0.3375 cubic inches per hour.
Compared to a lathe, that's pathetic!

Unlike with a stationary workpiece, the flushing does not normally limit the feedrate...your "slot" is nonexistent, so on a submerged machine the debris can be removed efficiently, but as you spin faster and increase the DOC it acts as if the material were thicker and thicker.

So your erosion settings need to take this into account and they will typically be set as if the material were thicker than the height of the contact zone would require if the part were not spinning.

All of the above is why a spin and burn strategy normally includes a roughing step in which the part is indexed and burned first; chopping as much of that material away in slabs as possible, so the finishing passes don't get bogged down by the huge amounts of material to cut if you just start spinning and profiling from a cylindrical lump.

So if your shape includes significant profile contours, you might want to add a manual indexing setup, with a pin and a bunch of holes like a dividing plate.
Nothing need be accurate...you just need to index often enough that the height of the peaks between flats is small enough to avoid bogging down the wire as you go from index and burn to spin and burn.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

implmex said:

Hi ClappedOutBport:
I cannot see any reason why it would not work.
So long as you have a connection between the table and the workpiece you should be able to cut it like you can cut any other workpiece.

However: (If your guys are experienced with rotary wire EDM, the following should be already well understood and obvious)

The rotation speed will affect the feedrate of the wire along the primary axis significantly, as will the depth of cut, and on a large diameter part it will matter much more than on a small diameter part.
If you imagine a large workpiece spinning fast and the wire is being asked to remove say 0.100" per pass, it effectively presents a huge amount of material to the zone where erosion takes place, and the erosion process will not be able to keep up.
The primary axis feedrate will slow down as the gap sensing circuit sees the gap close, and of course the gap continuously closes as the part rotates unless the erosion happens fast enough to keep up.
Remember erosion happens one spark at a time so there is a finite limit as to how much material you can present to the wire per unit time and still expect the sparks to gnaw it all off.
As a ballpark, a fast wire cuts at 25 square inches per hour, and the slot is typically 0.0135" wide so an MRR of about 0.3375 cubic inches per hour.
Compared to a lathe, that's pathetic!

Unlike with a stationary workpiece, the flushing does not normally limit the feedrate...your "slot" is nonexistent, so on a submerged machine the debris can be removed efficiently, but as you spin faster and increase the DOC it acts as if the material were thicker and thicker.

So your erosion settings need to take this into account and they will typically be set as if the material were thicker than the height of the contact zone would require if the part were not spinning.

All of the above is why a spin and burn strategy normally includes a roughing step in which the part is indexed and burned first; chopping as much of that material away in slabs as possible, so the finishing passes don't get bogged down by the huge amounts of material to cut if you just start spinning and profiling from a cylindrical lump.

So if your shape includes significant profile contours, you might want to add a manual indexing setup, with a pin and a bunch of holes like a dividing plate.
Nothing need be accurate...you just need to index often enough that the height of the peaks between flats is small enough to avoid bogging down the wire as you go from index and burn to spin and burn.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Click to expand...

Well that is very comforting to hear that it's not totally illogical.

The EDM operator told me he cuts everything at 60RPM regardless of size (for 0.3 to 100mm he said). This was illogical to me, but when pressed he couldn't explain it, so I'll just have to take his word.

I asked him about chop cuts, he said he normally does 15 degree increments. I recommended pro doubling that due to the size of the parts. That was something I considered when thinking of the setup, which is why I am opting for a timing belt over a round one. The basic controller should be able to index and spin.

Well, I'm off for two weeks, but after that I'll get going on it. This will be my first project as a full time engineer. Wish me luck. And a big thanks to all of you for your mentorship.

Hi again ClappedOut Bport:
I was thinking casually about your project again, and offer the following thought.

In your first post, you commented you already have a Hirschmann rotary, and that your EDM guy doesn't want to use a tailstock with it for fear of overloading the thrust bearings with a tailstock center.

So why not build a tailstock that works like a trunnion support and does not axially load the thrust bearings at all?

It's a simple build, it takes advantage of what you already have, it's cheap and quick to implement and it'll work like a hot damn.

You talk about mounting the part on a mandrel anyway...just turn a nice cylindrical bearing journal on the outboard end, bolt the near end to the rotary table faceplate and prop up that outboard journal with a vee shaped cradle to support the weight of the part.
If you're clever with your rotary table mount, you can make it so the tailstock is in place, before you mount the heavy piece, and you can just hang the mandrel and workpiece into the rotary and tailstock so the rotary never sees any cantilevered weight.
You need nothing fancier than a vee block bolted to the faceplate and a stub shaft on the inboard end of the mandrel to achieve that.

Now your EDM guy can do his magic on a unit he already understands how to run, and all will be well without you having to build a mechanical monstrosity for this one job.
You can adapt this setup for any future part that the table can swing, just by making a new mandrel to fit the new part.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

If you have the option to build your own solution I've been thinking about the design for a while. I'm working on adding turn and burn functionality to a DIY EDM machine, BaxEDM. I have the advantage of complete control over the structure of the machine, including the water bath infrastructure and motor placement.

As far as I can tell EDM rotary tables have two components that make them expensive to build -
1. IP68 motor.
2. Electrically isolated bearings.

I think I can do two things to build a less expensive table -
1. Move the motor outside of the water bath, this eliminates the IP68 requirement.
2. Use a "normal" stainless table and replace the bearings with ceramic bearings and use waterproof lubricants.

I've ordered some rotary lip seals, I'm hoping I can mount the motor to the outside of the water bath and make a waterproof connection that way. I'm aiming for a 6" table with ~5 lbs of carrying capacity. If this all works expect I can keep my costs < $3K.

implmex said:

Hi again ClappedOut Bport:
I was thinking casually about your project again, and offer the following thought.

In your first post, you commented you already have a Hirschmann rotary, and that your EDM guy doesn't want to use a tailstock with it for fear of overloading the thrust bearings with a tailstock center.

So why not build a tailstock that works like a trunnion support and does not axially load the thrust bearings at all?

It's a simple build, it takes advantage of what you already have, it's cheap and quick to implement and it'll work like a hot damn.

You talk about mounting the part on a mandrel anyway...just turn a nice cylindrical bearing journal on the outboard end, bolt the near end to the rotary table faceplate and prop up that outboard journal with a vee shaped cradle to support the weight of the part.
If you're clever with your rotary table mount, you can make it so the tailstock is in place, before you mount the heavy piece, and you can just hang the mandrel and workpiece into the rotary and tailstock so the rotary never sees any cantilevered weight.
You need nothing fancier than a vee block bolted to the faceplate and a stub shaft on the inboard end of the mandrel to achieve that.

Now your EDM guy can do his magic on a unit he already understands how to run, and all will be well without you having to build a mechanical monstrosity for this one job.
You can adapt this setup for any future part that the table can swing, just by making a new mandrel to fit the new part.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

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kfjkgfkjfkjfskj said:

If you have the option to build your own solution I've been thinking about the design for a while. I'm working on adding turn and burn functionality to a DIY EDM machine, BaxEDM. I have the advantage of complete control over the structure of the machine, including the water bath infrastructure and motor placement.

As far as I can tell EDM rotary tables have two components that make them expensive to build -
1. IP68 motor.
2. Electrically isolated bearings.

I think I can do two things to build a less expensive table -
1. Move the motor outside of the water bath, this eliminates the IP68 requirement.
2. Use a "normal" stainless table and replace the bearings with ceramic bearings and use waterproof lubricants.

I've ordered some rotary lip seals, I'm hoping I can mount the motor to the outside of the water bath and make a waterproof connection that way. I'm aiming for a 6" table with ~5 lbs of carrying capacity. If this all works expect I can keep my costs < $3K.

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Thank you both for your posts. I'm exploring a hybrid mechanical monstrosity now. I do agree with you Implmex on keeping the Hirschmann as the drive. But it's not tall enough and would have to be raised and knowing the operator, he'd be uncomfortable with that anyway. So what I'm considering doing now if taking both of your suggestions into account.

1. Build my risers and towers basically the same.
2. Instead of using centers, use ceramic pillow block bearings. These seem like a good option: S-UCP205C-16 (1") by Boca Bearings :: Ceramic Bearing Specialists I would probably use a differential size so the whole thing can be slid in from one side. This would also take some of the precision out of the jig as everything would be somewhat adjustable.
3. Run the shaft out long to the left and mount a timing belt pulley on it.
4. Run an identical timing pulley on the Hirschmann. Now I have an indexable motor control that is already hooked up and the whole system can probably be installed in 1/2 a day. The Hirschmann could stay in place removing the requirement to re-align everything when finished.
5. Should be cheap as chips.