Fishmouthing Tubes from CAD

[RagingGrandpa]

I'm sick of grinding bars by hand for our '04 space frame. Some people in here mentioned that they have tube laser-cut and fishmouthed, using CAD of a bar 'unwrapped.' We can't find a lasercutting sponsor for this, but being able to unwrap a bar in cad would be helpful.

Anyone know how to do this? We use unigraphics....

-JLo

"...with powershifts and tiresmoke for all"

[RagingGrandpa]

I'm sick of grinding bars by hand for our '04 space frame. Some people in here mentioned that they have tube laser-cut and fishmouthed, using CAD of a bar 'unwrapped.' We can't find a lasercutting sponsor for this, but being able to unwrap a bar in cad would be helpful.

Anyone know how to do this? We use unigraphics....

-JLo

"...with powershifts and tiresmoke for all"

[fsae_alum]

A MUCH cheaper alternative to laser cutting is to use a hole saw and a tubing notcher tht attaches to a drill press. Very cheap, Very easy. Better have a good stash of hole saws though because you'll go through them fast. BTW, coolant helps in this. Make sure you have your RPM up real high when doing this too.

In spite of...

[Ben Beacock]

The other advantage to a tube notcher is that the angles can be determined from the CAD drawing and dialed right into the jig. Its a bit of a stretch to do some of the long angles, but we managed to get up to 60deg cuts. Compound cuts are also easy with a chart that measures circumference distance vs angle, so you can rotate the bar to make the second cut (or more).
We had a pretty basic notcher last year that we borrowed and we're buying a heavy-duty model in about a week from pro-tools.com

Ben Beacock
Co-Manager
2004 Gryphon Racing - University of Guelph

[RagingGrandpa]

Out team has played with the drillpress-style tube notchers and I'm not satisfied with the results on thin-wall 4130. (vs. grinding by hand)

Would still like to know how to represent a bar with a 2-D, unwrapped shape on the computer.

"...with powershifts and tiresmoke for all"

[Brent Howard]

You mean you want to basically weld your own ERW tubing?? Basically you would have to use something like the sheet metal add on in solidworks. You draw the part, put the bend in and then you can either surpress (flat part) or unsurpress (round tube) the bend in teh program. I'm not too sure what use this would be though. Maybe try milling the fishmouths rather tahn a tube notcher, just need to spend a lot longer jigging it.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[Denny Trimble]

Brent is right, in SolidWorks you can split your frame model apart into individual tubes, then split each tube lengthwise so it can be "unrolled", and print out the end details, then wrap those around the tube. I played with this, and it's no faster than the other ways (holesaw, or well-placed hacksaw cuts and finish-grinding). By the way, a holesaw mounted in a mill is a very rigid, accurate way to notch tubes.

I'm not sure how to unwrap sheetmetal curves in Unigraphics, but I know Pro/E can do it.

If you model a T-joint tube intersection, you'll see that the mitered tube has two straight-line edges when viewed straight on (looking at it like it's a letter T). You can cut these with a hacksaw and be 95% there, very quickly.

Hope this helps!

University of Washington Formula SAE ('98, '99, '03)

[fsae_alum]

Ragingrandpa, I have been using UG for the past 8+ years professionally (30+ hrs week) and have NEVER been able to do what you are trying to do with unwrapping a tube. You MIGHT be able to fudge it with the sheetmetal package. I'll see what I can do with it here at work!!

BTW, the tubing notcher has worked great for us. Again, make sure that you're running it at high RPM, and that you're using a good hole saw that has more than 3 teeth on it. Just take it slow on the cutting.

In spite of...

[fsae_alum]

raginggrandpa, I tried everything I could think of in UG and no success. Sorry!!!

In spite of...

[fsae_alum]

lasercutting?

Try: Kooima Company
2638 310th street
P.O. Box 156
Rock Valley, IA 51247
Contact: Jeremy Van Zee at (712) 476-5600
email: jeremy.vanzee@kooima.com

Hope that helps!

In spite of...

[RagingGrandpa]

Thanks for the SolidWorks suggestion. The bars that are really frustrating me are round mating with square, so unless you have a magical holesaw, the jigging and drillpress thing won't work for me. An end mill with insane jigging would work I suppose, but I could do it by hand on the grinder twice before I got it set up right on the mill.

"...with powershifts and tiresmoke for all"

[fsae_alum]

After talking to a co-worker he has told me that he knows of a way to unwrap in UG. I will see what he says and pass it along!!

In spite of...

[RagingGrandpa]

Thanks!

"...with powershifts and tiresmoke for all"

[RagingGrandpa]

find anything out fsae-alum?

"...with powershifts and tiresmoke for all"

[fsae_alum]

not yet...I'll ask the guy who suppossedly knows again today.

In spite of...