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Coilgun Powerhammer [Sep. 13th, 2011|02:01 pm]
Doug Ayen
I took yesterday evening off from the forge to let things heal up and to avoid repetitive stress injuries. However, I did come up with an idea for a power hammer: a monolithic slab of steel with an openwork coilgun moving a ram.





On top of the ram assembly is a removable stop so you can change out the ram if needed. It is hinged so that the ram can be floated out if it needs to be changed.

The ram is steel, slotted to accept a standerd die size. It is long enough to be rigidly stable at full extension.

The column itself is lined with either teflon or if that's not strong enough high-density low-friction plastic of some sort. It's held very rigidly to the back column, but is adjustable so it can be re-straightened if it goes off true. It has sensors along its length for feedback/control. It is attached to the back plate at a 45 degree angle to allow for pass-through work.

The base has the anvil and backplate attached. It's solid steel bolted or welded (now, that's a weld) to the other elements. Needs enough mass, along with the anvil, to keep the weight ratios at least 20-1. More is better, but this should be tied into a foundation in any case.

The backplate is solid, thick enough to withstand the forces involved. The posts connecting the backplate to the ram assembly are angled to the 45 degree angle to allow pass-through work. I'm thinking the posts should be fairly massive, probably with adjustment slots to allow for minor adjustments -- nothing more than a degree or two to allow for warpage/abuse.

Control is via a foot pedal. This feeds a computer which controls the hammer head -- ideally this can be changed out. Square cross-section rather than round will allow for greater control, stability, and the ability to control orientation. Sensors in the ram column keep track of the location of the hammer head, the less pressure the lighter the taps, from just barely tapping to full power.

Speed (BPS) needs to be controlled somehow. Initially via computer interface, maybe a dial or lever on the final. If there isn't any reason not to, this might be useful for sheetmetal work (rapid relatively light blows), heavy work, and everything in-between.

Can one be built that would act as a press as well? Controls for that mode then -- possibly an extreme speed setting?

My main questions then become: can regular house current handle this sort of load for, say, a 50 lb ram? Would cooling be necessary? How much force can this thing generate -- enough to make it "jump" unless unrealistic mass is used for the anvil? (insert mad grin). Base stability -- how big? Noise? Is this thing going to need huge-ass capacitors, or can this run more like a linear motor?
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Comments:
[User Picture]From: dcseain
2011-09-13 06:56 pm (UTC)
Yes, i think it could be built to act as a press as well.

I'm thinking likely 240 rather than 120 for power.
Cooling would depend on how much use it gets, and testing with prototypes wil be needed.
Prototyping also needed for the noise/jump/size of base question.
Single- or multi-stage coilgun will be part of what is needed in terms of capacitors, no?
Acknowledging that this is a rough draft, you'll need a safety to keep hinged part closed under most fail circumstances.
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[User Picture]From: blackanvil
2011-09-13 07:33 pm (UTC)
Yeah, I have 50-amps of 240 in the shop. The frame would only take a day or so to assemble -- if I buy pre-cut steel ($$$$).

The "hinge" is at least 25mm round, maybe more, and the latch would be similarly beefy, possibly even multiple 25mm bolts.

Sadly, I don't know enough about coilguns/linear motors to know what the specs would be. Fortunately, there's this Internet thing out there.
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[User Picture]From: chocorua
2011-09-14 03:00 am (UTC)
You don't give any dimensions, but if your drawing is roughly to scale and you're planning on direct-acting magnetic drive accelerating a 2 kg ram back and forth peaking at 5 m/sec, you are looking at some serious power electronics. This is more of a handwave, but I wouldn't be surprised if everyone on your transformer (or maybe your leg of the 3 phase) will know when you're running it.
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[User Picture]From: blackanvil
2011-09-20 06:20 pm (UTC)
Yeah, I did the math over the weekend, and since it's a 50lb ram to replace my existing power hammer, I'd need ungodly amounts of power on tap to run this thing. Still, a decent enough though exercise. I'll stick to a rotating cast iron wheel powering transmitting power to the ram via two linkage arms with a spring rebound, even if it was designed and built in the 1920s.
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