4th axis setup on a Haas VF2SS

KTM- · Oct 17, 2014

Hello,
So we just got in a brand new Haas with all the fancy bells and whistles... We are running two rotaries (Haas HRT160SP) as opposed to a rotary and a tailstock w/ brake (we have that setup on a Haas here as well and it presents us with some job specific difficulties).
Our goal is to run these two rotaries simultaneously. We have a 36" Bed, and with the two rotaries, the chucks, we are left with a maximum part size of about 16 inches.
That being said we are looking to do two things and I am just reaching out for some other opinions/maybe this has been done before.
We are trying to use some sort of 'slide' similar to a lathe bed on the rotaries to make them easy to slide to clamp on a part, as well as keep them lined up to reduce part set-up time.

I am currently thinking of using a lathe bed in some fashion with a fabricated adapter to mount the rotaries to it. However I haven't been able to find something in the 48" range that I'm looking for.
Also, are the tables on the VF2SS and VF3SS identical except for the length? If so, could a longer table be put on? Just a thought...

I'd appreciate any input!
Thanks!

jid2 · Oct 17, 2014

This sounds like crazy talk for a brand new machine. Not sure what two tables does unless they are running different operations.

Oldwrench · Oct 17, 2014

Sorry I don't understand exactly what you are visualizing but we have a VF3SS with multiple devices that we slide out of the way rather than hump them off the table with a crane. Your table should have fairly accurate T-slots if somebody hasn't buggered them up. Just key your 4th axis heads to the slots with long keys and make some matching long T-nuts. Break a few bolts loose, push, and presto, lots of room. You can make gages for repositioning the heads in X.

Larry Dickman · Oct 18, 2014

I believe the VF2 and VF3 have completely different T slot spacing

Dupa3872 · Oct 18, 2014

I'm not really sure I am picturing what it is you are trying to do but I'm pretty sure you are over complicating it with a lathe bed in a milling machine. We are all guilty of this at one time or another, Step back and think again. Maybe a sub plate with a slot milled in it much like the slots in the table. This could be keyed for both machines and have a common center line for both indexers.

Good luck Ron

HuFlungDung · Oct 18, 2014

Make or acquire a subplate long enough to hold your setup, without leaving yourself short on length due to table restrictions. Then attach a rail system to the subplate to permit sliding your indexers back and forth. I'd likely use a plain bearing system, something like bushings riding on induction hardened chrome plated shafting. This is because plain bearings are easier to keep cleaned of fine swarf.

dstryr · Oct 18, 2014

Build a sub plate for getting them out of the travel but as far as sliding them back and forth and keeping them aligned ...good luck. You have to keep them both on the same centerline and extremely parallel to each other or else your parts will come out wrong.

2outof3 · Oct 18, 2014

I hope the Haas salesman at least warned about the intrinsic issues of trying to time two rotary tables that are not actually the same as much as Haas wants them to be. I give them 6 months before they start fighting each other for positioning. Not that you will notice, they will just lose positioning accuracy as the worm gears tear each other up fighting for supremacy. You might get lucky and just get servo alarms and overheated motors.

Secondly, as much as Haas says maximum table weight is 1500 lbs that is a lot of weight for a small table on not that large of linear rails. Haas means maximum. As in turn down the rapids and go slow with everything centered. I only bring that up since you are asking about building some second set of ways on top of the table and then moving the weight of two rotary tables, the fixture holding them together and then moving that weight to one side or another.

A couple of alternatives.

Make a sub-plate like many here have suggested that has multiple positions. Just a 1.5 inch of steel that is ground with a couple holes to mount it to the table. You can then use some long tools to finish machine it on the machine. This is how most large bridge machines are finished. The table is final milled with the machine as the last step. Then you can make multiple holes and a T-Slot for the table to be repositioned as needed. You need to be aware of the weight distribution. You can also make space for a couple vises in the center for when you don't want to use the trunnion fixture between the tables.

HuFlungDung · Oct 18, 2014

I can't think of a reason why two rotaries would need to be live, on one part, on the one axis. Is it just that you need a chuck instead of a tailstock?

dstryr · Oct 18, 2014

2outof3 said:
I hope the Haas salesman at least warned about the intrinsic issues of trying to time two rotary tables that are not actually the same as much as Haas wants them to be. I give them 6 months before they start fighting each other for positioning. Not that you will notice, they will just loose positioning accuracy as the worm gears tear each other up fighting for supremacy. You might get lucky and just get servo alarms and overheated motors.

Secondly, as much as Haas says maximum table weight is 1500 lbs that is a lot of weight for a small table on not that large of linear rails. Haas means maximum. As in turn down the rapids and go slow with everything centered. I only bring that up since you are asking about building some second set of ways on top of the table and then moving the weight of two rotary tables, the fixture holding them together and then moving that weight to one side or another.

A couple of alternatives.

Make a sub-plate like many here have suggested that has multiple positions. Just a 1.5 inch of steel that is ground with a couple holes to mount it to the table. You can then use some long tools to finish machine it on the machine. This is how most large bridge machines are finished. The table is final milled with the machine as the last step. Then you can make multiple holes and a T-Slot for the table to be repositioned as needed. You need to be aware of the weight distribution. You can also make space for a couple vises in the center for when you don't want to use the trunnion fixture between the tables.

I agree with this except I'd make the table out of aluminum just to save weight. I have had a plate on my one doosan for over 4 years and it has held up fine.
Another thing you have to consider is going to be the thermal growth of the ball screws when you load up the table with all that weight. I learned the hard way about C-frames and a large weight on the ball screws.....

2outof3 · Oct 18, 2014

dstryr said:
I agree with this except I'd make the table out of aluminum just to save weight. I have had a plate on my one doosan for over 4 years and it has held up fine.
Another thing you have to consider is going to be the thermal growth of the ball screws when you load up the table with all that weight. I learned the hard way about C-frames and a large weight on the ball screws.....

Aluminum is great for sub-plates. You just have to go thicker if you are going to hang over the edge of the actual machine table. We use both steel and aluminum depending on the needs of the job. If you are making t-slots, I would rather use steel for wear.

KTM- · Oct 18, 2014

Hey guys!
I appreciate all the input! I have a bit more time to type this response up, I left out quite a bit on the OP...
This is the machine as it sits:
http://i.imgur.com/60BFcpU.jpg

The rotary on the left is the style we are going to use (HRT160SP), the right is being sent back to Haas. The parts are in the picture to show what our difficulty is...
The machining we are doing leaves sacrificial tabs in place on either end to hold the part. This is to allow multiple machining angles from one setup. When machining parts out of machinable foam (The yellow round stuff) or bone implants being held with bone screws, the inertia of turning a tailstock breaks or misaligns these tabs. (Clean and greased bearing, it's simply the inertia from the mass of the chuck) [we are also going to be machining 3D printed titanium and steel parts that will be held similarly to the bone implants]

This is why we need to run a second rotary.

That being said there is an issue of just using a long subplate. We had this in our old Fadal that this new Haas is replacing. Our old setup was this:
http://i.imgur.com/mYzp3OM.jpg

Headstock (not shown), tailstock, big sub plate. All was well and good when doing aluminum or steel because the tabs were strong enough. However, there is also too much friction between the tailstock and the table to slide it easily. This is an issue because when you go to move the tailstock and you slam into a part that is held by bone screws you risk them becoming misaligned or breaking the implant. Also the 3D printed parts already have a lotttt of $$$$ into them.

Anyway... the rationalization between a lathe bed-like setup is that they are hardened and have small points of contact so sliding a heavy rotary would be much easier. And it is a tried and true way of keeping 2 things in line.
What I didn't take into consideration is the weight of a setup like that... you all make a good point of it rapidly approaching the max weight capacity of the table.

Any other ideas to throw at the wall?!

PS - we have a haas mini mill with this setup in it as well:
http://i.imgur.com/6OhF88e.jpg

^ (rotary, tailstock, sub plates)

2outof3 · Oct 18, 2014

KTM- said:
Hey guys!
I appreciate all the input! I have a bit more time to type this response up, I left out quite a bit on the OP...
This is the machine as it sits:
http://i.imgur.com/60BFcpU.jpg

The rotary on the left is the style we are going to use (HRT160SP), the right is being sent back to Haas. The parts are in the picture to show what our difficulty is...
The machining we are doing leaves sacrificial tabs in place on either end to hold the part. This is to allow multiple machining angles from one setup. When machining parts out of machinable foam (The yellow round stuff) or bone implants being held with bone screws, the inertia of turning a tailstock breaks or misaligns these tabs. (Clean and greased bearing, it's simply the inertia from the mass of the chuck) [we are also going to be machining 3D printed titanium and steel parts that will be held similarly to the bone implants]

This is why we need to run a second rotary.

That being said there is an issue of just using a long subplate. We had this in our old Fadal that this new Haas is replacing. Our old setup was this:
http://i.imgur.com/mYzp3OM.jpg

Headstock (not shown), tailstock, big sub plate. All was well and good when doing aluminum or steel because the tabs were strong enough. However, there is also too much friction between the tailstock and the table to slide it easily. This is an issue because when you go to move the tailstock and you slam into a part that is held by bone screws you risk them becoming misaligned or breaking the implant. Also the 3D printed parts already have a lotttt of $$$$ into them.

Anyway... the rationalization between a lathe bed-like setup is that they are hardened and have small points of contact so sliding a heavy rotary would be much easier. And it is a tried and true way of keeping 2 things in line.
What I didn't take into consideration is the weight of a setup like that... you all make a good point of it rapidly approaching the max weight capacity of the table.

Any other ideas to throw at the wall?!

PS - we have a haas mini mill with this setup in it as well:
http://i.imgur.com/6OhF88e.jpg

^ (rotary, tailstock, sub plates)

Really slick set ups. I would say the friction between the tables on the Minimill is probably causing you issues you don't see but you seem to have been doing this a while so you at this point are the expert. Everything you are trying to do is going to give you some issue. It is just a matter of what issues are you willing to work with. After seeing your set up, I still would work at some sort of trunnion with none locking side support, instead of two tables. Maybe a very strong cage to machine through instead of a bottom plate.

As far as sliding the table and support , just build a linear rail table on your machine using the lightest weight components you can find. Ground aluminum plates with as much weight taken out of it with pockets on the underside. Then attach to linear rails and trucks. you can find them at McMaster Carr or other suppliers.

McMaster-Carr

Weasel · Oct 18, 2014

I'm surprised it works, but since you have proven it on the Mini, more power to you.

At 90lbs each on the rotaries, as long as you don't go crazy on the sub plate/dovetail carriage weight, you should be fine.
What I am picturing is that you want to be able to have length adjustment on the gap between the two that you can control to a fine degree, is that right ? The Setco stuff that Doug posted looks interesting ( if it is accurate enough), and maybe instead of one long 48 inch base, you could put each unit on a shorter base and move them both in or out as needed.Lots of alignment/ rigidity issues to work around of course.
Or you could just cannibalize an old lathe.

John Welden · Oct 18, 2014

Seems like a mazak integrex style machine would be ideal.

Mounting a 4th on linear rails wouldn't be hard. I don't see any point in going with a dovetail set up. More friction and more weight.

Zahnrad Kopf · Oct 18, 2014

KTM- said:
When machining parts out of machinable foam (The yellow round stuff) or bone implants being held with bone screws, the inertia of turning a tailstock breaks or misaligns these tabs. (Clean and greased bearing, it's simply the inertia from the mass of the chuck) [we are also going to be machining 3D printed titanium and steel parts that will be held similarly to the bone implants]

I've done some very similar stuff and have experienced the exact same issues. I was able to work around it with some careful forethought and planning, but it does add time and effort. Basically, instead of a center or a driven rotary, consider machining a bearing journal and stop ( wall/flange ) that interfaces to what amounts to a fancy pillow block. This worked for me in both Titanium and glass filled Nylon of a part that was VERY similar to the bone model you show.

m98custom1212 · Oct 18, 2014

John Welden said:
Seems like a mazak integrex style machine would be ideal.

http://images.caeonline.com/im.php?id=%20282748[/G]

Mounting a 4th on linear rails wouldn't be hard. I don't see any point in going with a dovetail set up. More friction and more weight.[/QUOTE]

I was just thinking that John..

Look at that Mazak or the DMG Mori NTX

HuFlungDung · Oct 18, 2014

I think you need to devise a rack and pinion manual positioning system to bring the one indexer carefully up to the workpiece, no 'shoving' required. There are plenty of linear guideway systems out there (Essentra, formerly Reid Supply) has tons of stuff in their catalogue which might not show up online. No need to use an actual lathe bed, and there is certainly no guarantee that stick and slip won't affect your sliding baseplate exactly the same on a lathe bed. You simply need to improve the mechanical advantage of your 'approach' system.

dstryr · Oct 18, 2014

m98custom1212 said:
I was just thinking that John..

Look that Mazak or the DMG Mori NTX

lol they bought the solution that costs sub $100k...you guys tell them to buy a $400k machine?

m98custom1212 · Oct 18, 2014

dstryr said:
lol they bought the solution that costs sub $100k...you guys tell them to buy a $400k machine?

Not 400K and you could go used also.

4th axis setup on a Haas VF2SS

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