[Geof]

We have some small parts that come off the lathe needing a clean-up and radius on the backside which was parted. It was a fiddly job loading two per vise on a Haas MiniMill with two vises so I made the rather complicated looking fixture shown below.

A long fixed jaw with eight semicircles is bolted to a base plate.

The eight parts are clamped in pairs by four moving double jaws.

To balance the clamping force between all eight parts there are two short balancing bars acting on each double jaw with a long balancing bar acting on the two short ones.

A locking cam acts on the center point of the long balancing bar.

The cam rotates on a boss that is eccentrically mounted so the center of rotation of the locking cam can be moved forward to adjust the clamping force and compensate for wear.

Springs acting between a spring block and the long balancing bar open the jaws with link pins connecting the balancing bars and jaws.

The link pins run in slots in a cover plate to keep eveything in alignment and stop the long balancing bar moving sideways as the locking cam rotates against it.

The entire assembly is held in a pair of Kurt vises and levelled up with the four leveling screws at the corners.

A single work zero is dialed in to a boss under the center bolt on the mfixed jaw and the program uses G52 to shift a secondary work zero to the parts.

[Caprirs]

Slick. How long did it take you to draw that in CAD?

[Geof]

Slick. How long did it take you to draw that in CAD?

Smart a**

[Caprirs]

Seriously, that is a nice setup. If you built a couple, you could palletize them and the operator could unload/load while the machine runs. Of course, he have to be built like Ahhnold to heft that mass every 90 seconds.

[Donkey Hotey]

Beautiful work, Geof. :cheers:

[WallyL7]

Geof - YOU ROCK! That is a sweet setup.

[Geof]

Seriously, that is a nice setup. If you built a couple, you could palletize them and the operator could unload/load while the machine runs. Of course, he have to be built like Ahhnold to heft that mass every 90 seconds.

Yes, 1" by 8" steel 16" long is heavy. We do have numerous multipart fixtures that are in pairs for external loading and some of these are heavy; my guys earn their money.

[tobyaxis]

Yes, 1" by 8" steel 16" long is heavy. We do have numerous multipart fixtures that are in pairs for external loading and some of these are heavy; my guys earn their money.

That is a nice well thought out fixture Geof. I have a few ideas running around in my head now for a few jobs that were done in the past. Only problem is that now those jobs are done and gone.

Thanks for sharing that.

[quadbob]

One quick question. What happens if one on the parts has a slightly smaller diameter? We did a similiar fixture a number of years ago,but if parts aren't within tow or three thousandths, one could pull up, or in your case spin. How do you compensate?

[Geof]

One quick question. What happens if one on the parts has a slightly smaller diameter? ....

That is what the balancing bars are for in the first picture. The locking cam acts on the center of the long bare; the long ends of the long bar act on the centers of the two short bars and the ends of the short act on the center of the moving jaws which each clamp two parts. This system can accommodate up to 0.05" variation between parts and can assure you we a a lot better than that.

This balancing action is okay on this part because the operation being done is simply a radius around the ID on the part; very little cutting load. It may not be suitable for more intensive machining because the clamping force applied by the cam is divided by eight at the parts; if you needed 500# to hold the part you would need to be a real gorilla tightening the locking cam.


We have numerous other parts done in multi-holders and I have shown them in some threads. For these holders we had to tighten up the tolerance on the part OD so the smaller ones do not spin in the holder. A variation of 0.002" between adjacent parts is okay so the ODs are controlled to +/-0.001"

My next multi holder project will be either hydraulic balanced clamping or elastomeric balancing with urethane as I mention in the last link.

http://www.cnczone.com/forums/attach...1&d=1176648481

http://www.cnczone.com/forums/attach...1&d=1176648481

http://www.cnczone.com/forums/attach...1&d=1176648481

http://www.cnczone.com/forums/showth...t=73902&page=3

[Vern Smith]

Back in the days of building race cars the biggest pain in the a** was figuring out how to hold onto the specialty racing seat and then figure out how to mount the seat to the tube frame. The second biggest PITA was the clutch linkage.

In the late seventies the Japanese auto manufacturers put hydraulic clutch systems in their roller skates. Bless their little hearts, this made moving the clutch arm a snap and of course a simple hydraulic line replaces all the linkage. The heart of all this were their very small ultra reliable slave cylinders that could be mounted to most anything. They used a piston with a concave socket on the end so you could get away with all kinds of misalignment.

I can't help but think a bunch of these, or their modern equivalent, lined up on a fixture plate and plumbed to one el cheapo automotive master cylinder could securely clamp most anything against most anything.

Vern

[tobyaxis]

Back in the days of building race cars the biggest pain in the a** was figuring out how to hold onto the specialty racing seat and then figure out how to mount the seat to the tube frame. The second biggest PITA was the clutch linkage.

In the late seventies the Japanese auto manufacturers put hydraulic clutch systems in their roller skates. Bless their little hearts, this made moving the clutch arm a snap and of course a simple hydraulic line replaces all the linkage. The heart of all this were their very small ultra reliable slave cylinders that could be mounted to most anything. They used a piston with a concave socket on the end so you could get away with all kinds of misalignment.

I can't help but think a bunch of these, or their modern equivalent, lined up on a fixture plate and plumbed to one el cheapo automotive master cylinder could securely clamp most anything against most anything.

Vern

Indeed they are a resourceful people. If only US manufactures would learn from their ways and stop pointing fingers at who is to blame.

Explains why most of the CNC's I like are Japanese made.

[Geof]

Hydraulic brake components are being considered.

First I want to get an idea of the clamping force needed for the various parts. At the moment we use 3/8"-16 bolts that clamp two parts at a time, the bolts are torqued to something like 15 lb-ft and things do not shift during machining, but what is the vertical clamping force arising from this torque value. In between other things I am bulding a little test rig to directly measure the force.

Another thing that I have to determine is the resistance of brake system seals to water based coolants because this is what I intend to use for the hydraulic fluid. I have found some rubbers swell tremendously in the coolant.

[tobyaxis]

I have found some rubbers swell tremendously in the coolant.

I buy new shoes every 3 to 4 months because of the coolant. The oil from the swiss was a lot worse, but I no longer work with swiss.

Are you going to post your findings here or will they be Top Secret?

[Geof]

I will keep tacking things on here or my other thread or may start a new one. All this is going to take months.

[Vern Smith]

If your plan to use coolant as the hydraulic fluid is to prevent contamination due to a leak we never had one of these systems leak. I "think" most contemporary automotive hydraulic systems use Teflon based seals which will usually stand up to panther p*ss.

Testing for force requirements is an excellent idea. If I remember correctly hydraulic force is the force applied to the master cylinder times the volumetric difference between the master cyl. and the slave cyl. The only limiting factor is structural failure. Now this could lead to some serious contamination.

"my other thread" this is ungentlemanly obfuscation.

Vern

[Geof]

....."my other thread" this is ungentlemanly obfuscation.

Vern

Sorry, this is "my other thread":

http://www.cnczone.com/forums/showthread.php?t=73902

The force difference is dependent on the areas not the volumes. It is unlikely I will be able to get away with using a thing like a master cylinder because I will need a reasonable stroke on the fixture cylinders to allow easy removal of the parts and with many parts the displacement needed on the master cylinder would be very large.

What I have in mind experimenting with (of all things ) is a paint sprayer. Relatively low cost, made to pump a water based liquid emulsion, capable of developing up to 2000 psi and they turn the motor off when they reach pressure and just cycle when the pressure drops.

[One of Many]

You might also consider a system like the Kopal self compensating hydraulic vice jaw. No pump required in this captive fluid system.



You can custom create your own with a bit of ingenuity and some Screw in cylinders or create your own cylinder within the jaw manifold for a compact design.

DC

[Geof]

Yes I have seen those or something similar but we are trying to get away from reloading individual parts in the vises with the machine idle. Gradually we are moving to mini-platen systems with one being reloaded while the other is machining.

[tobyaxis]

Yes I have seen those or something similar but we are trying to get away from reloading individual parts in the vises with the machine idle. Gradually we are moving to mini-platen systems with one being reloaded while the other is machining.

That is definitely the way to go Geof. I use to do this with slide-in-vise-fixtures.

While one fixture was in the machine, the other was being reloaded by the operator at the bench. There were 50 parts being done in each load and I used a tensioned spring load on the right side to seat the fixture against the stop. The operators were slamming the fixture in so locations were being lost. The parts were for fishing reels and there were lots of 5000 per month. Brass Job!!!!