Punched tin on ShopBot?

[robert_cheal]

I have had this question in the back of my mind for a while now.

Has anyone rigged their ShopBot to do punched tin patterns. If so it would be interesting to hear if could work.

Thanks,

Robert Cheal

[myxpykalix]

This was not done on a shopbot. I made this in 8th grade. Is this the type of design you are talking about, or something like the designs you would see on the doors of a pie safe? If you notice all the punches in the indian would (maybe) be done with some type of drilling toolpath? Maybe using some type of blunt tip like you have on the shopbot probes.

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[donchapman]

I have not done so, but it seems like you could grind a drill bit to whatever punch tip you want, place the thin copper or tin upside down on some sort of cushioning substrate like HDU, and run a drill pattern file with the router turned off.

[Brady Watson]

Sharpen (or not) the tip of a spring-loaded centerpunch & use a drilling toolpath. You'll have to come up with a mount for the punch, as the shock from the centerpunch's hammer is not good for your router or spindle bearings - so don't try to chuck it in a collet.

Trupan works well for this sort of thing. It will hold the metal down while being punched and resist pulling the metal up when the Z/punch retracts.

-B

[robert_cheal]

Thanks for the ideas so far. It seems if the tin or copper was thin enough that a spring loaded punch could punch through the material. I dont know how much pressure the Y- and Z axis could take by punching. I guess it could be drilled first then punched to give it that conical indent.
Perhaps something along the lines of these.

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[jeffreymcgrew]

We actually just used a 1/16" solid carbide 2-flute cutter & a drill routine to do this very thing. You'll need a jig behind the tin so it doesn't buckle. It worked fine. Wore out the bit a little, but we ran a number of them before that happened. You might look into a tiny spiral endmill from McMaster or something more metal-machining-ish.

[robert_cheal]

Jeffrey,
Thanks for the idea I have some project ideas in my head but it might be this winter before I get to try them. I will certainly post any results when I do.

Thanks, Robert

[don]

If I were going to be doing a lot of these,
I'd get a carbide drill blank and have the end ground with a cone of a 150 degree.
Different size blanks should give you a different effects.

[robert_cheal]

Don,
Thanks for the idea I will ask a local shop that sharpens and also makes custom cutters. I am sure they could come up with something. I guess it would stand up to a moderate plunge if the base material was the right density.
I guess I had better get my designs & tool paths worked up so I try this.

[Gary Campbell]

Robert...
If you are looking for a way to punch tin, you may want to look into an air cylinder. They are threaded on the end so you can attach a collet or chuck to hold your tool., You may even be able to get away with grinding the end to a point to punch soft materials.

You will be able to control the speed and pressure of the plunge using flow controls.

You could toolpath your designs using the PRT drill PostP and that would work the cylinder. Offsets would be handled just like those of a drill.

Gary

[robert_cheal]

Gary,

That is an interesting idea. I do have some smaller air cylinders about 1.5" D.
I am not sure if I understand how to activate
them, I am not familar with PRT drill PostP.
I will have to look into that.

Thanks, Robert

[Gary Campbell]

Robert...
You will need a way to mount the cylinder very firm. The 1.5" cylinder may give more pressure than needed, and move slower with low volume of air than you would like.

Look the the Sbparts\Custom files at "Custom 8" This is the file that the PRT Air Drill used to operate the drill. If you use the correct postP, you will get a 2D jog/move file to the center of your circular vector. Then "C8" is called. If you read, as possibly modify the timing to suit your needs, A punch operation would occur.(with correct pneumatic valving)

I would use a single solenoid, 4 or 5 port valve. This will allow a single momentary "on" signal to plunge and then return when off.

Depending on your software version, you should be able set the X & Y offsets in the my_variables file and have a relatively simple way to toolpath and punch the tin.
Gary