So our Pierson
Fixture Friday series highlights the best practices for building fixtures.
But in this video, we're covering what not to do.
So your pallet fixtures don't suck.
OK, so we've shown you plenty of examples from our own production,
as well as some really great examples from our customers.
But let's talk about what
not to do when designing a fixture into one of our pallets.
Now, even if you're going against some of these points and disagree with me
it's really just a matter of time where some of these problems will pop up.
And I want to spare you that grief.
So starting off, we're all familiar with these style of rocker clamps,
which in my opinion, are the best choice for small clamps,
because not only do they have high clamping force for their size,
but they also apply downward pressure.
Keeping your part flat and secure.
So here's what not to do when using these.
Number one, don't use the wrong size.
Now, these come in sizes from three eighths inch wide all the way
up to inch and a half wide.
So which one do you use?
Well, I recommend starting with the three quarter inch size.
The half inch size is tempting because
of their lower price and decent holding force.
But for 50% wider of a clamp,
you get nearly two and a half times more holding force.
That's why I say don't start with the half inch width
or eventually you might throw a part and wreck your day.
Number two, don't create slots for these clamps.
To sit in.
Now, I've seen examples from the manufacturers of these using slots,
but in my suspicion it's that these photos were originally taken
with clamps and slots, just because in the days of manual machines,
it was so much easier to create a slot than it was to create
a nice machined pocket for the clamp.
To sit in.
However, like I've said before, slots weaken your fixture significantly
and a pocket leaves remaining material to strengthen it.
For example, our pro pallets off the shelf are inch and a half thick,
but if you were to put a slot in it, that's about a half inch deep.
You've a essentially thinned out your pallet to only one inch thick.
Now, if you have multiple rows and you tighten down all the clamps,
the cumulative clamping force will absolutely bow
the palette and throw off your repeatability in Z.
Pockets, not slots.
Number three, don't get Mickey Mouse with your pockets.
Now, what do I mean by this?
Obviously, you can't create a square corners with round and mills,
so there has to be some type of radius in these pocket corners.
Now, common practice is to put a relief,
a little bit larger than the diameter of the mill.
And that's where you get the name Mickey Mouse just because of the appearance.
Now, this is fine, but just make sure that this relief
is not cutting into the back side support edge of the clamp.
You want the entire width of that back edge supported.
If it's not fully supported, it will prematurely deform.
And where the back edge and your clamp will not contact your part correctly.
Even worse, the clamp will shift far enough from the part
where you will get a false clamp against the opposite side of the pocket.
Number four, don't use them for what they're not meant for.
Now, what do I mean by this?
Browsing online.
I've come across pictures that have clamps on opposite sides of the part.
So why would we not do this?
Well, think about it.
These clamps are not secure edge
sops, and they can float one way or another.
If the clamp torque varies, or if the order in which you clamp them
changes, it's the same reason devices have a fixed jaw and a sliding jaw.
You want that consistent clamping surface,
or else the clamps will be fighting against each other.
Instead, use a fixed edge like the edge of a pocket like we do,
or the use of an aggressive, fixed edge clamp insert
commonly known as talons or piranha strips.
And finally, number five, don't use the wrong quantity
So earlier I mentioned not using the half inch with,
but if you've got a small, delicate part, that's fine
since high clamping force isn't needed
Now, on the flip side, you don't want to use my recommended
three quarter inch size with a large steel part
clamping on only one long edge The formula I recommend
is to multiply the width of the clamp by three.
That means you need a three quarter inch wide clamp
for every two and a quarter inches of edge.
Or if you're using a half inch wide clamp, you need one clamp
for every inch and a half of part edge.
And of course, if you're using a one inch wide clamp, obviously you need
one clamp for every three inches on the part edge and so on.
Now, after the rocker style clamps, the next mini clamp,
I would recommend are these aluminum channel clamps.
Now, I recommend these
because they also apply downward holding force when tightening.
They come in a machine wheel version so you can match the shape of your part
just like you would with soft jaws and vice Now, the downside of these clamps
is they have much lower holding force than the rocker style clamps.
But I would recommend them for second operation work
because they don't tend to mar the machined faces
of your part like the rocker clamps do.
That's what makes them great for second operations.
So here are a few don'ts when using these types.
Number one, don't clamp using only the top edge.
If you take a close look at the top edge of
these clamps is not even supported.
And cutting forces or clamping forces alone
can easily compromise your work holding security.
You want to sink your parts deep down into a pocket
so that the point which the wedge contacts the inside of channel
is in line with your part.
This line is where the clamping force will be highest.
Number two,
as I mentioned, with the other style clamps Don't put these in channels.
Pockets with proper clearance is best.
Also, keep in mind to not create your pocket
to the seam with this a clamp because these have a lot more throw
and you might create a false clamping sense if you've expanded them
to touch the edge of your pocket and not the face of your part.
And finally, number three, use the right quantity.
Keep in mind that these have much lower clamping force than rocker clamps.
So my formula for these is to multiply the width of the clamp face
by two to find out how many you need This means one inch wide
clamps is going to only be sufficient for clamping on two inches of material.
Now, let's talk about some other styles of clamps,
and this might be my most controversial point, but here we go.
Don't use other types of clamps.
There I said it.
Now, why would I not recommend other styles?
Well, let's break some of these down.
cam style clamps have always been popular and I see them often,
but machine strategies have changed over the years.
The old school machining strategy was to take the diameter of the cutter
and go 50% axial and 50% radial engagement.
This has been replaced with the superior
high speed machining approach, which means maximum axial
length of the entire flute and only ten
to 15% of radial engagement.
This strategy greatly increases metal removal rates
and extends cutter life significantly.
However, the axial engagement causes cutting forces
to want to pull up on the part rather than to shift it sideways.
Now, cam style clamps don't apply downward pressure when tightening them.
So this means that your part can be lifted up along with the body of the clamp.
Now you might not notice your part being pulled up,
but it's too late when you catch it in inspection.
Now, I've seen different versions of these clamps
that use an A centric counter sunk head that does apply downward force.
But the reason I don't recommend these is because it places
all of the clamping force sideways
on the thread of the fixture.
Now, threads are really meant for axial loads, not radial
and you'll quickly deform your threads to where they're sloppy and unusable.
No one likes sloppy threads.
Now there are a lot of other great clamps out there that I would approve of,
like OK vise, Dyna Force and ID expansion clamps, to name a few.
But theyre a lot more expensive and you can often
get away with the first two styles I mentioned earlier.
Again, I approve of them, but don't use them
if keeping down the cost of your fixture is a main concern.
So if you want to design money making fixtures.
Dig in with this playlist.
The entire Pierson Fixture Friday series and if you want to take your production
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So until next time, go innovate your production.