Fixture advise...

[peter.blais]

Hello guys.

I would like some advise or thoughts on how to go about making (cnc milling) this part. Machine is a haas vf2.

It is a .230" thick part, made from 6061. It's a rounded off diamond shape- 1.89" x 1.00". It has a 2 bolt pattern approx 1.65" apart lined up with the long axis of the diamond. They are two x m6 clearance holes.

On the top, it needs a chamfer and an engraving. On the bottom, an O ring groove, and a small chamfer to debur.

Top and bottom must be face milled to excellent surface finish so they are ready for sale right out of the machine.

Here's the catch- not the end of the world, but quantity is high, I'd like to do runs of 300-500pc, and it's an ongoing thing- so a little $$ spent on fixturing wouldn't kill me. Particularly if some of the parts could be used for other thin / small items in the future.


Here's what I was thinking:

Make two steel "soft jaws" which are quite long- enough to go across 3 vises. Machine a step into those, perhaps even cut a half a tooth form into them to give it some bite. I would make them deep enough so that basically all the stock is supported from the bottom when clamped.

Start with 2" x .375" stock, grab long pieces in the vises using said lonnnng soft jaws. Machine 24" strips of parts leaving a carrier on the back. Machine the OD, engraving, top chamfer, profile, bolt holes, etc all in this step.

Step 2: make a large fixture plate which holds the strips. Machine the outside profiles into the fixture with .003-.005" clearance. Use either machineable pitbull clamps, or possibly machineable uniforce clamps- to grab them.

- Then machine off the carrier, put the o ring groove in, and whack a small chamfer onto the bolt holes & outside profile.



What do you guys think? I'm running low on these and need to run more pretty soon, but don't want to spend ages dicking around with fixturing which doesn't work.

TIA - Pete

[christinandavid]

You could cut your lengths to long enough for 3 or 4 compts - stick one in each stepped jaw vise. Face the strip minimum cleanup, do the work on the top and cut the profiles just deep enough to put the chamfer on. Spot drill holes in components to create a chamfer. Put in four nice holes at opposite ends of each strip as a register for the second op.

Second op would be a tapped plate, on which you locate the 3 strips using opposing pins/bolts thru four tooling holes. Face the strip to size, stick holes in components and clamp thru holes. Finish work on top then cut out components.

DP

[Geof]

Your first operation idea is the way I would approach a part like this, actually it is the way we do several parts.

For your second operation make soft jaws that grip the profile, this is a much faster way of holding things rather than bolts or clamps. What you do is machine the jaws to grip a pair of parts which means you can load six parts total. The reason for this is that if you try to hold more than two parts in soft jaws the middle one does not always get held firmly, with pairs there is enough wobble in most movings jaws that the clamping is equal on each part. Of course you have to saw cut the machined parts from the first operation into pairs.

Incidentally duolock vises are excellent for this kind of stuff. In one set of jaws you hold your starting bar stock and in the other the profiles from the first operation. The advantage to this is that six finished parts come off the machine every cycle which is handy if you practise just in time manufacture.

[ctate2000]

Use .250 stock. Cut to near net shape. First hold is in a vise with standard jaws. Face mill .005-.010 and machine all geometry other than profile. Transfer to second vise with soft jaws. Install a 6mm pin in each jaw making sure the pin is below the .230 dimension. Use the pins to grip the drilled holes; then mill the profile and face mill the part to .230 dimension. Not counting the vise, this rig would be $20. You also do not have issues with changing profiles and proper fit in machined jaws.


I do not like to mill long thin pieces in any set up. Just my opinion, which is not worth much

[peter.blais]

Originally Posted by Geof Your first operation idea is the way I would approach a part like this, actually it is the way we do several parts. For your second operation make soft jaws that grip the profile, this is a much faster way of holding things rather than bolts or clamps. What you do is machine the jaws to grip a pair of parts which means you can load six parts total. The reason for this is that if you try to hold more than two parts in soft jaws the middle one does not always get held firmly, with pairs there is enough wobble in most movings jaws that the clamping is equal on each part. Of course you have to saw cut the machined parts from the first operation into pairs. Incidentally duolock vises are excellent for this kind of stuff. In one set of jaws you hold your starting bar stock and in the other the profiles from the first operation. The advantage to this is that six finished parts come off the machine every cycle which is handy if you practise just in time manufacture.

Thats why I was thinking these:

http://www.miteebite.com/products/m_uniforce_m.html

I could basically make a plate with like 10 "mini" double vises- and make batches of 20pc.

They are a little spendy but this is our product and I will do 3-4 runs like this a year for the forseeable future.

At the moment I'm the only one running the machine and I like to do long cycles so I can let it work and come up front to do design work / g code work. If I have to tend to the machine all day it will sit for a day or two after the run is over.

[Geof]

Those uniforce clamps are a good idea and one of my guys used a similar priciple for a small part fixture; it was just as economical as buying them.