Electric Wire Cutter

Can you cut and strip wire-wrap wires in pre-determined length? We would need a few hundred thousands of different lengths.

In the commercial ones I have used, the wire passes through a hole in a shear cutter. Once the proper length has been counted, the shear guillotines the wire off. The count mechanism is a simple rev counter on a pressure wheel feeder.

The thing is quite accurate, but slippage can be a problem on clear vinyl coated wires.

- Tim -

with a whole machine shop that shouldn't be too hard :) I image something like: small tube leading in between a plastic or rubber wheel driven by a steppermotor and a ball bearing this drives the wire forward then a small tube feeding the wire through a hole in a plate, on the other side of plate a disc also with hole in it that can be rotated with a strong (gear) motor, when the holes are aligned the wire can be feed through, when the disc is turned it cuts the wire.

makes sense?

-Lasse

Try to incorporate lasers, if at all possible. NASA has a laser powered wire cutter and stripper, for making the perfect joint.

Tim

-- Deep Friar: a very philosophical monk. Website:

First shot:

o Advance wire between rubber pinch rollers pinched from a printer, o Drive rollers with a stepper motor to produce desired length, o scissors-style cutter made of two HSS lathe bits, pivoted at one end, open at the other. o Perhaps a groove in the HSS bits to guide the wire. o Can drive the cutter with a "jack" screw type arrangement, motorized, on the open end. Strong, simple, and slow enough for safety.

Cheers, James Arthur

I had a piano wire cutter that was simply two holes drilled in a sock pliers-shaped thing (one in each metal half). Line the holes up, insert wire, squeeze, the wire was sheared off clean.

In your case, the feed half of the cutter would be a steel block with a funnel-shaped hole, say 1/4" inlet and 1/16" outlet. The outlet side has another plate with a 1/8" hole. Line holes up, feed wire, move second plate 1/8" to cut wire, reset, feed more... Works best if you have one die for each size, but should work for smaller wires than the die hole.

The second plate could have some slots cut in it to screw it to the first plate, perhaps with lock washers to act as springs to hold them together. A stock R/C servo should be able to operate it, assuming it has enough power to cut the wire. Note: the plates do not have to be thin! As long as fingers are larger than the hole size, you can't get hurt. Well, I suppose you could hit someone over the head with it. Never underestimate students.

A similar die with a keyhole-shaped hole (and angled sides) could pre-strip the ends too, or at least cut the insulation for later stripping. That would have to be wire-size-dependent.

As for the feed, another servo with the pot removed and a shaft encoder (or better, a shaft encoder on the other wheel, to sense slippage better) driving a pair of rubber wheels should do.

A brass tube between the two could guide the wire, assuming you hand-feed it at first to get it into the tube.

Of course, you could just connect a linear actuator to a pair of diagonal cutters ;-)

Nice cutter idea. Safe. Needs big torque, maybe a worm-drive on the circumference of a large-diameter cutter-wheel, with the cutting holes toward the center of the disk?

Cheers, James Arthur

drive cutter with a simple cam arrangement, more reliable.

There are some interesting mechanisms incorporated in punch presses and similar tools that convert the inertia of a rotating flywheel into a one-shot vertical motion (one cycle pr operator command). I don't have a description of the machine involved, but an old timer machinist could explain one to you.

If you scale something like this down, you could use a relatively small motor to spin the flywheel up and then engage the mechanism with a solenoid. The vertical motion will be used to operate a shear for your application.

Needless to say, all of the moving parts of this machine would have to be designed so that fingers cannot fit into any apertures while it is in operation.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
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Just an armadillo on the shoulder of the information superhighway.

Buy a bicycle digital pedometer for the lineal feed reader. A rubber faced drum (flat faced wheel), and maybe a lightly knurled drum to place against that. You also need a little set of wheels to "tractor" the wire through the system. Oh, and a solenoid actuated shear, essentially a hardened steel block with a nice 90 degree corner polished on it, and a hardened steel shear block with a wedge shaped face polished on it.

You have to pause the feed during the shear operation,and re-zero the lineal counter, and increment the program (assuming PC control). The shear goes behind the feed tractor as well. The feed tractor goes right at the exit orifice.

It is fairly difficult because of the masses of all the wheels, etc. carry inertia and cause problems as you up the feed rate. Also, the mass of the actual wire spool can cause your tractoring system to slip unless you pre-feed that spool into the "cutter box". You could make one that operates fairly slowly, but a high speed cutter even takes the big boys a long time to perfect.

Sounds great though. You could program an array of different cut lengths, as opposed to n number of a single length, then step. With the PC control, you could cut any length in any order, or batch cut n number of all one length,then step.

Good luck.

Jeez... you are still doing wire wrap? You never heard of solderless insertion?

We are using them to patch PCBs. We got a batch of PCB where the solder does not seem to connect to the copper, just sitting on top of it. Since there are only a few connections, it would be cheaper to just patch some wires on top of the traces.

What

drill

each

The eyes have it. ;-]

*****************CAUTION - Commercial follows **********************

We are a cut/strip house that sells millions of kynar leads every year. I would guess about half of them are for wirewrap and many of the others are short and used for board fixes, jumpers, etc.

We stock 30, 28, 26 and 24 gauge in all 10 colors. We cut and strip them from 1/4" to over 60". Strips from .032" to 2"+. See us at

for all our wire products. Email: snipped-for-privacy@squires.com

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10 colors in Kynar, not TFE? Wow.

is it solid SPC?

I'll bet that a laser outfit for this task would be a good thing. We use one for labels at work, this seems just as important. I am sure a

40W range laser would "cut it".

Lots of commercial machines can do this. Many better machines can crimp connector pins on the end as well.

Alternatively, you may be able to buy the wires from a wire supplier pre-cut and stripped (or partial stripped) and bundled.

Best regards, Spehro Pefhany

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Since it's a robotics class, is length accuracy critical or is this more along the lines of teach the concepts?

Look at a mig welder for a pretty good example of a wire feed system. You could probably do something similar with a couple of knurled wheels and a similar spring lock mechanism. Weld one side of some wire cutters to a block and drive the other side with a solenoid or cam/arm arrangement. Heat/glue some plexiglas as a cover for the cutter. Chuck up a piece of metal in the lathe and make a funnel guide for the down stream cut side. Maybe a couple of rubber clamping blocks and a spring to tension and then pull the cut wire.

--
Joe Chisolm
Marble Falls, TX

In a past life, I used to babysit a production wire stripper. I forgot the name. The feed was the hard rubber feed roller and pinch roller combination. They were about 1" diameter and had a small grove in the middle to get more contact surface area. The feed roller was made from some kind of rubber or fiber, impregnated with metal "dust". The idea was to get as much traction as possible on the wire insulation. There were different rollers for different types of wire.

The cutter was two "V" blades against a backing plate. The idea was to NOT bend the end of the wire, which is what will happen if you use an asymmetrical guillotine style cutter. A similar blade was used in the wire stripper section.

You might want to look at commercial products:

As long as you only need to cut the wire, and not strip it, a roller and guide tubes should be sufficient. Partial insulation stripping is a different problem.

The cut and stripped wire was ejected using a 2nd set of rollers. I would think a pneumatic ejector (blow the wire out the guide tube) would be equally effective.

Remember, you have but one life to give to your profession.

Heh. I'm sure you and your students will resist the temptation to "see how fast it can go". My guess is your upper speed limitation will be the inertial load of the wire supply spool.

Put all the controls on a control box with a long cord. That way, you can stand back when some PIC register overflows and sends the machine into overdrive.

An exacto knife blade is probably too fragile to work.

"V" blades are self centering.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Get a windshield wiper drive motor from a junkyard.

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Paul Hovnanian	paul@hovnanian.com
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Have gnu, will travel.