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Todays plasticworking

Today I got tasked with making new gripper jaws for an assembly cell. I saw the email before I made it into work while drinking coffee eating breakfast.

I'm using some 3" square 95A Shore urethane to make some vee shaped grippers that hold a round part we clamp onto and then torque 6 fasteners to about 36 foot pounds.

I knew it was coming since I figured out what durometer material was being used. Quality had a shore hardness tester.

Anyway, I took my high priced 3x3x36" chunk of urethane and made a test cut in the band saw. Sliced off a 1/8" piece nice and square. Cool. Make a mark at 7.5" and take another cut. I get a crooked cut, thankfully the crooked made my part longer at the bottom so I didn't waste the urethane.

Okay, I'll change the blade, it looked okay but I've seen the saw cut crooked when someone else ruined the blade. Medium horizontal saw, 12'6"x 1 variable pitch.

Take another test cut on end of remaining stock. Nice and square.

Cut another chunk for the other jaw, just as crooked and I even slowed the cut down to nothing and even lifted out of the cut a few times. I was even running coolant.

I do not know what is going on there. I can cut a chunk of steel just fine and square.

To save time milling this crap (trust me, this stuff stinks to machine), I used the vertical metal bandsaw to wack off 3/8 inch down a side. Other than the drift angle being about 25 degrees to cut a straight line that went well.

Now clamping it in the vise hard enough that it would not pull out, raises the material

0.10" or so. I learned to clamp it, face it, measure it, reclamp it putting the vice handle at the same angle. Putting the counterbores in the right place might take some thought or bigger holes ;)

I would have liked to try a dry ice and alcohol bath to make this stuff hard but no one knew where I could get dry ice. I did put the two chunks in a freezer in the lunch room to cool them. I'm not sure that made them more machinable but I figured it can't hurt.

Due to the milling I have to do, I fabricated a plate that I can screw the part to since there is no other way to machine it.

Tomorrow I'll fight with it again. I had to order a counter bore. At least it will be sharp, you need sharp with this crap.

I *really* want to get my wood shop set back up so I can make a mold for using castable urethane to avoid much of this.

Wes

Reply to
Wes
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used. Quality

when someone

angle being

You used to be able to get dry ice at Baskin Robins and other ice cream places.

That was only about year 10AN* -- it's 50AN now, so they may be protecting you from getting hurt now.

  • After Nader
Reply to
Tim Wescott

almost every supermarket around here has a dry ice cooler next to the bagged ice cooler.

Reply to
chaniarts

I'm getting tired of being protected. Since I repair things that are 'protected', the protection starts to become a safety hazard for me. I have to figure out how to defeat it to see what is wrong inside a protected machine. Lots of trip wires there.

Btw, I noticed today, the Servo brand power feed for bridgeports really has some torque. You don't want to get between the X axis handle and the power feed body. It doesn't want to stop and it is a pinch point. Not an accident, just an observation since I was making a lot of passes on some urethane and had lots of time to notice things.

Wes

Reply to
Wes

Charlie,

I've kept my eye out for dry ice for years. Never seen the stuff in super markets. You in the USA?

Wes

Reply to
Wes

phoenix area. we have lots of boaters who use it in their coolers to go to the lakes. ice doesn't last long without it out here.

Reply to
chaniarts

If you have a machine shop, you can use metal working tools on wood without too much grief, or just make the mold out of aluminum.

Reply to
Roger Shoaf

I'm near 45N latitude. I bet dry ice is popular in Arizona.

Wes

Reply to
Wes

You can make your own, all you need is a CO2 cylinder with a dip tube, or invert a non-dip tube cylinder. Run the liquid hose (get a Stainless steel wrapped hose designed for liquid CO2, and be sure never to trap the liquid in the line between valves) into a tightly built wood box with a UHMW (or similar) lining. The hose should be run into a T fitting with the side to the tank, bottom into the top of the box, and top having an adjustable relief valve. Shoot small bursts of CO2 into the box, each burst will create a layer of 'snow' and many layers will pack into a solid brick. a 2x3x8 inch brick will be about a pound of dry ice. Build the box so it can be easily unclamped to allow removal of the CO2(s).

Stuart

Reply to
Stuart Wheaton

Are you closer to Salem or St. John?

Reply to
Tim Wescott

That's funny. I crossed 45N twice this weekend. Ca to Wa.

Reply to
Jim Stewart

Only one that carries it in our town is Krogers.

Reply to
cavelamb

The whole time I was reading your post, I was thinking casting, casting, casting :-). Make the mold from aluminum so you get to do metalworking, and cast the jaws.

----- Regards, Carl Ijames

Reply to
Carl Ijames

The Fred Meyer Store (Kroger) in Redmond, Oregon has a locked chest just outside the do-it-yourself check out counters. I bet if you asked any employee at a Kroger chain market, they could tell you where the locker is located.

Paul

Reply to
co_farmer

that hold a

used. Quality

in the band

crooked when someone

and square.

drift angle being

the material

but no one

the lunch room

can't hurt.

part to since

it will be

using castable

I see Dry Ice in Publix and Winn-Dixie Supermarkets. You have to show that you're 18 to buy it.

Reply to
Michael A. Terrell

Mitten State.

Reply to
Wes

to defeat it

doesn't want

was making

You want to get one of the safety handles fitted where you have to twist the handgrip to engage a drive pin, a standard BP part. I fitted one when I added a power feed to my BP because I knew getting a hand trapped would not be pleasant.

Reply to
David Billington

I saw the email

ers that hold a

g used. =A0Quality

ut in the band

at 7.5" and take

rt longer at the

oked when someone

fine and square.

e drift angle being

s the material

tting the vice

might take some

ard but no one

in the lunch room

d it can't hurt.

e part to since

t least it will be

using castable

It's probably extruded so you're fighting built-in stresses in the longitudinal direction. No stress while crosscutting. Only way I can figure to fight that problem is the cold solution and gnaw away from both sides to get the required thickness. Same problem as with cold- rolled. Got a wood planer? Might be easier to do it that way than try to mill it.

Kroger around here has dry ice, Yellow Pages might turn up something for your area.

Stan

Reply to
stans4

Try asking at Meijer. I saw a note/reference to it (dry ice) when I was checking out ~6 months ago. Keep forgetting to ask one of the cashiers we're friendly with about it...

Reply to
Leon Fisk

some torque.

doesn't want

I was making

I'll look into that. We have a Series II Special with bigger table and bigger power feed, it has that push in to turn handle on it.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Reply to
Wes

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