Fixture with soft jaws

tcncj · Nov 10, 2017

I'm making some small parts (100+ pieces) and it's a returning job so making a fixture is worth it.
It's a 2 side op part.

First top, switch part over and machine bottom.
For the first op I use a fixture with some mitee-bite clamps.
Just like this:

Before I leave work I fill the fixture and let the machine run while I'm gone.
But the bottom side of the part is a bit time consuming and I'm searching for some alternatives. At the moment I need to swap parts every 30 minutes.
It would be nice to let the machine run while I'm gone, just like the first operation.

The mitee-bite clamps I use for the first op will damage the part (because of the clamping pressure). That's a no go.
Some parts don't have a flat surface to clamp to.
A fixture with uniforce clamps could work if the stock (from the first op) or part doesn't sit above the bolt (of the clamp).
At the moment I use soft jaws in 4 vices. So I can make 4 parts each run.

I'm curious what you guys are using

lionelt · Nov 10, 2017

Do you have enough travel to move that fixture further to the left and another fixture to the right?

tcncj · Nov 10, 2017

Above picture is an example I found. Not my actual part.
But yes I have enough space.

Booze Daily · Nov 10, 2017

At 100ish pcs it hardly seem worth it to make high density fixturing even if it is a repeat job.
I'd be more inclined to use a couple double vises. Four 1st op. 4 2nd op. = 4 pcs complete per cycle.

I don't know if your machine has a 4th axis (doesn't have to be full 4th, could just be an indexer), but you could make a homemade tombstone and run 1st ops on one side and 2nd ops on another side. You could put your fixtures on subplates and run other jobs the same way on their own subplates.

gkoenig · Nov 10, 2017

Instagram

Hot swap vise pallets. I run an Orange, but my parts are small and I wanted something that gets in/out of the machine fast; these just locate into the standard vise jaws and repeat within a couple of tenths. Snagged the idea from Tim @ Autodesk. Op1 makes 6 parts from 2 pieces of stock using Pitbulls clamping into Talons. Op2 takes those 6 parts and finishes them using machineable Uniforce clamps. It's about a 20 second changeover time and about 10 minutes of cycle per pallet.

G00 Proto · Nov 10, 2017

If you really want to make a fixture (vs just running them in soft jaws and being done with it), you could do the same array as above with pockets to index the parts, and use an expanding mandrel in the bore of each one.

Hazzert · Nov 10, 2017

Copy the pitbull design out of mild steel/aluminum and machine the bore profile into the end so that when the clamps are tightened they push the parts into pockets in the OP2 fixture.

I thought carr-lane had machinable edge clamps but it looks like I was mistaken.

tcncj · Nov 14, 2017

I was thinking about the fixture idea some more. And maybe the best way is to make a sub plate.
On this sub plate I use 3 diamond pins and 3 round pins. This way I can place 3 smaller pallets on the sub plate.
I will put my vices on a pallet for easy and fast swaps.

For example today I was running some parts.
With the current setup the machine can run 30 to 40 min before changing parts. Besides I hate it to run to the machine each time, I have other stuff to do. The machine should work for me, not the other way around.
If I make a subplate with pallets I can let the machine run for 9-10 hours! Before I leave work I can fill the pallets with stock, put them on the subplate and run the machine while I'm home. It will save me a huge amount of time.

With the above setup I can machine those parts in 3 days, while I'm at home!

Booze Daily · Nov 14, 2017

I’ve run lights out many times. It’s awesome when you come in to bunch of finished parts.

It sucks big time when you don’t.

Things to watch for (also known as things I’ve done):

Don’t push feeds and speeds. You’re getting free parts, remember?

Make sure chips are cleaned out and fluids are topped off. It sucks to come in and find servos alarmed out from chips packing up. It sucks when the machine stops after one cycle from low way lube. It sucks when tools break from low coolant.

If you change to a fresh tool at the end of the day and op stop to check the size, don’t forget to turn op stop off. DAMHIK. It REALLY sucks to come in and find you only ran the next tool after you went home.

Also, count on scrapping a whole nights worth of parts. It happens occasionally. How fast can you get replacement matl? If you can get it before you run out of the stock you have left, fine. If not, the machine sits until the balance comes in. Now you didn't really save much running all night.

Good luck.

mhajicek · Nov 14, 2017

A little probing and tool breakage detection can really help lights-out. It adds cycle time, but like you say the parts are almost free compared to fully-attended machining.

tcncj · Nov 15, 2017

Thanks for the useful information!

At first I was thinking making the sub plate out of Aluminum. But it will cause lots of corrosion on the table and sub plate. Unless you hard anodize it.
Steel would a better option? Which kind of steel? The sub plate will be 30" x 12".

Rstewart · Nov 15, 2017

Unless You gonna have that aluminum plate on your machine for A Long period of time I wouldn't worry about it. A little bit of grease will do the trick.
I've made many fixtures just like what Gkoeneg has pictured above, always works really well.

Just don't spend too much time building an elaborate fixture only to find out you could've already been done with them using a few vises....

tcncj · Nov 15, 2017

Good point about the time it takes to make a fixture. I think it will take me an hour to draw and make it. The fixtures itself are pretty simple.

With a double vise setup I can make 6 at the same time (only 3 vises fit my travel range)
I would need 3 new vises 3.000+ usd and I need to make 12 softjaws for each part.

With a fixture setup:
I can machine 24 parts at the same time with all my machine workspace being used.
+/- 200usd on mitee bite clamps (I already have them) and 3 pieces Aluminium stock to make a fixture (+/- 70usd)

I was thinking to make a sub plate. But maybe it's easier to just drop them in my vise like you and Gkoeneg.

Bobw · Nov 15, 2017

I've said before, and also recently that I've screwed myself several times trying to get fancy
with fixtures and pallets..

The picture in the OP... Nice and fancy, 16 parts per run... You have to cut and then set
16 pieces of stock, and then tighten 16 screws (that's a pain in the ass)..

I would have cut the stock into strips 16X longer (you just saved saw time) and then slammed
that strip across 2 or 3 vises, and now you just saved screwing around clamping time, and you've
only had to touch ONE piece of stock, not 16.

Even if you have to split them and run the last op or 2 piece by piece you are saving a ton
of handling time, AND you don't have to mess around with allen wrenches and stupid little clamps.

Examples: Years ago had a job, 1000's of parts, simple little things. 1/2" x 1.25" x 2.25" long
aluminum. 2 ops. We had a new auto saw, so cutting the stock up was no big deal.. I made a
slick little pallet thing that fit in a single vise. Pallet held in with 2 De-Staco clamps, so
change out was FAST, and used mighty bites in the pallets.

I had 3 pallets, and 2 operators on that job.. The machine was still sitting in between cycles,
it took so damn long to play with all the stupid little clamps.. It was a pain in the ass..
If I had to do it again, I wouldn't go with the fancy fixture, I'd just run them in vises and
strips...

Granted, I had a lot of fun, and learned a lot setting that job up and making the fixtures, but
in the end I know I wasted a lot of time.

tcncj · Nov 15, 2017

Maybe it depends on the parts you're making?

I don't saw the stock. The supplier does it for me.

I prefer to tighten 12 bolts for 24 parts (mitee bite uniforce clamps on both sides) and let the machine run for 6-8 hours while I'm gone.
Compared to tightening 3 vices with 3 parts (or 6 if I buy new double vices)

Maybe personal preference haha.
I'm a one man shop. I don't have employees to to run the machine for me. While the machine runs I can do other stuff. If I need to load new parts every 30min / 1h I'm distracted from the work I was doing.

Rstewart · Nov 15, 2017

tcncj said:
Maybe it depends on the parts you're making?

I don't saw the stock. The supplier does it for me.

I prefer to tighten 12 bolts for 24 parts (mitee bite uniforce clamps on both sides) and let the machine run for 6-8 hours while I'm gone.
Compared to tightening 3 vices with 3 parts (or 6 if I buy new double vices)

No, you use bar stock held between three vises. You could make possibly 15 parts in one strip, either saw them apart or flip the whole bar over (into soft jaws) for op two.

cwtoyota · Nov 15, 2017

Bobw said:
I've said before, and also recently that I've screwed myself several times trying to get fancy
with fixtures and pallets..

The picture in the OP... Nice and fancy, 16 parts per run... You have to cut and then set
16 pieces of stock, and then tighten 16 screws (that's a pain in the ass)..

I would have cut the stock into strips 16X longer (you just saved saw time) and then slammed
that strip across 2 or 3 vises, and now you just saved screwing around clamping time, and you've
only had to touch ONE piece of stock, not 16.

Even if you have to split them and run the last op or 2 piece by piece you are saving a ton
of handling time, AND you don't have to mess around with allen wrenches and stupid little clamps.

Examples: Years ago had a job, 1000's of parts, simple little things. 1/2" x 1.25" x 2.25" long
aluminum. 2 ops. We had a new auto saw, so cutting the stock up was no big deal.. I made a
slick little pallet thing that fit in a single vise. Pallet held in with 2 De-Staco clamps, so
change out was FAST, and used mighty bites in the pallets.

I had 3 pallets, and 2 operators on that job.. The machine was still sitting in between cycles,
it took so damn long to play with all the stupid little clamps.. It was a pain in the ass..
If I had to do it again, I wouldn't go with the fancy fixture, I'd just run them in vises and
strips...

Granted, I had a lot of fun, and learned a lot setting that job up and making the fixtures, but
in the end I know I wasted a lot of time.

When you are stuck using the little mighty-bites and other multi-screw setups, get your hands on a cordless 1/4" impact tool plus a set of quality 1/4" drive hex-keys and Torx bits. I use the DeWalt 20V impact gun for breaking down setups. A cordless drill would work too, but not nearly as well as the little brush-less impact.

tcncj · Nov 30, 2017

Thanks for all the info so far!

I've ordered some stock the last week and made some fixtures with the mitee-bite clamps.
I placed the fixture plates in a vise.
In the Y there is a height difference (measured the top) ranging from 0,05mm to 0,09mm depending on the vise.
In the X there is almost no difference.
The difference in height in the Y axis could be caused by the moveable jaw of the vises.

I think it's better to make a subplate and face the top.
Buy some locating pins (round and diamond pin) and on top of this I place the fixture plates.
The vises will also be placed on a fixture plate.
That should be more accurate if I'm right.

THCustoms · Nov 30, 2017

tcncj said:
That should be more accurate if I'm right.

Not necessarily.

If you machine (face) the vise's fixture plate at around the same ambient temp and with the same amount of clamping force on the vise you'd expect when machining the real-part, then there is not much that can horribly go wrong. Maybe in the range of 0.03~0.02mm, but max I'd say.

Permanent fixture plate are advantageous but only if you plan on keeping it there forever. Once this moves it brings you back to that 0.03~0.02mm inaccuracy range anyway.

To minimize this, take note of the torque (and temp) you've put on each of the joints when machining the fixture (your chance to own a Snap-On Torque Wrench!). Once you have this data, even if you move out the plate you'll be able to replicate 'roughly' the same accuracy later on. E.g. use the same bolts, same location, same torque!

Machine/material temp is vital

tcncj · Jan 15, 2018

I did some machining with the fixtures but not that happy with the accuracy.

I had a fixture for first op parts using the Pitbull clamps. Works great.
But the fixture for second op is giving me a headache. I used the Uniforce clamps. Problems I encountered is that it's hard to see if the part gets pushed up.
Sometimes I had accuracy issues, and I could throw away 2 - 3 parts out of 10. I didn't want to set work offsets for each part to maintain accuracy. Or check if the part is clamped correctly.

I bought a second vise where I can clamp 2 parts in. I machine some soft jaws and let the machine run.
Accurate and much faster. I have to walk to the machine more times. But it's easier and faster in the end.

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