Using a CNC machine as an automatic hammer

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Using a CNC machine as an automatic hammer

Postby wolvescaptain » Sun Jan 20, 2013 6:58 pm

I am wondering if I can get a CNC to work as a hammer.

Do CNC machines have enough strength and speed on the Z axis to hit strong enough?

Currently I am manually hitting large sheets of metal with a round-ended hammer endless times to give them a voronoi-like texture (something like this http://www.cruxdelux.net/index/wp-content/uploads/2012/02/voronoi_scales2.png).

I would really like to just use a CNC as a hammer that will do this automatically, since it takes hours upon hours of patient hitting for every sheet.

If a CNC can't do this, do you people have any ideas as to what can?

Thanks.
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Re: Using a CNC machine as an automatic hammer

Postby kbob » Sun Jan 20, 2013 7:04 pm

It seems like you could replace the spindle in a CNC with a solenoid with a weight on its shaft. You would have to fabricate a little and program a little, but it's certainly doable.
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Re: Using a CNC machine as an automatic hammer

Postby wolvescaptain » Sun Jan 20, 2013 7:10 pm

While I don't really have any idea what's the meaning of what you wrote (I don't really know anything about CNC's, but might get access to one), it's good to hear this is possible.

I will try to get access to said CNC and google all the information I need.

Thanks!
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Re: Using a CNC machine as an automatic hammer

Postby macona » Sun Jan 20, 2013 10:32 pm

Yes, a cnc machine could do it. Also a non-cnc machine could do it. You could build something with motor driven pawls to index at a fixed rate.

But it will take a very heavy machine for working metal. This is not something you can buildout of extruded aluminum.

An average solenoid will not have the power to do much, either. I would look at either something like an air hammer or maybe something like a spring loaded trip hammer.
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Re: Using a CNC machine as an automatic hammer

Postby Fred » Sun Jan 20, 2013 11:05 pm

Nobody will give you access to their cnc if you intend to use it like a hammer! You could perhaps modify or build one to cope with hammering but most machines - no.
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Re: Using a CNC machine as an automatic hammer

Postby Kellerkind » Sun Jan 20, 2013 11:53 pm

it probably depends on the material, if you work on cooper you could just push it with the machine and stay within the machines force limits. Even though a home brew solution should work out too, you dont need any accuracy at all for this task and could use a cheap selfmade x/y mechanics and a spring charged hammer
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Re: Using a CNC machine as an automatic hammer

Postby canadianavenger » Mon Jan 21, 2013 1:32 am

Note that CNC will probably work against you in this application, as the resultant pattern will likely become too regular. Because it is normally done by hand, that texture takes on an organic feel.

I do agree with the other sentiments that it can be done by a machine, as is probably best served by a purpose built one. [certainly no sane CNC owner will let you repeatedly crash the Z stage into a piece of sheet metal - it is not designed for those kinds of forces]
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Re: Using a CNC machine as an automatic hammer

Postby wolvescaptain » Mon Jan 21, 2013 4:56 pm

It is intended for silver and brass sheets, most of them between 0.6 and 0.8 millimeters.

About it not being random, I figured it shouldn't be hard to add a tolerance factor to a prefixed grid of points so that it will look random (using any random number generator).

I don't really know anything about mechanics or building machines, will it be hard to build this alone? (and will it cost a lot?)
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Re: Using a CNC machine as an automatic hammer

Postby cvoinescu » Mon Jan 21, 2013 5:31 pm

If you want to build it, I suggest a ShapeOko. It's probably the least expensive Cartesian robot you can buy. It's also easy and inexpensive to enlarge, if you need more than the stock working area (a little more than 200 mm x 200 mm). If you're in Europe (and not in a hurry), the eShapeOko may be cheaper for you, and it has an A4-sized working area.

Disclaimer and/or shameless plug: I sell the eShapeOko (here).
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Re: Using a CNC machine as an automatic hammer

Postby metalman » Thu Jan 24, 2013 12:26 am

For what you want to do you should first try a pneumatic planishing hammer. Harbor Freight sells a cheap one for about a hundred bucks. http://www.harborfreight.com/pneumatic- ... 94847.html They do about 1000 -2000 hits per minute and have several interchangeable hammer heads for different size impressions. I built one from a cheap air hammer with a modified hammer head and some 1-1/4 pipe for about $30. Then I graduated to a CP sytle hammer once I saw how much better they were. But I still have and use my original home built hammer and a HF plashing hammer plus a couple mechanical hammers too. A boy never has enough toys or hammers...

If that isn't fast enough for you then you can add a CNC X/Y table later. For sheet metal work, normally the metal is held by grippers on the X axis gantry and the hammer is stationary. My big mechanical hammer weighs between two and three thousand pounds and has a 48 inch throat. The X/Y table has to be fairly heavy too to stand up to the pounding that the sheet will receive.
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