Information needed for cutting device

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Thread Starter

Peter Cauchy

What size/type of stepper motor would have the power to drive a cutter to cut a 14ga piece of wire? The cutter is driven on a threaded rod to use mechanical advantage. I have a mock-up of the system, including small steppers and control software. The steppers are currently controlled by 2 5803's, with input from a PC via parallel port. The 5803's will only carry 500mA per phase, so I am pretty sure I will need a different controller. Any suggestions would be appreciated. Peter Cauchy
 
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Cameron Anderson

Peter, from what you explained and how I understand your application, the cutter assembly is mounted to a lead screw system and you move to a position to cut the wire. There are a more few bits of info you will need provide before we can pick out a motor size: 1. Weight of cutter assembly? 2. How is cutter supported? Bearing Type? Coef. friction if known? 3. Move profile - How many inches in how many seconds. Not velocity, looking for a distance in a time. 4. Screw Diameter 5. Screw Length 6. Screw lead or pitch 7. Acme or Ball Screw? Explain more about your application. Why are you moving the cutter head? Is the wire constantly moving? Doing a Flying Shear/Cutoff? If the wire isn't constantly moving, then look at doing a nip roller system and keep the cutter stationary. I would suggest you take a look at these 2 sites for good stepper drives/contorls and motors. <a href=http://www.idcmotion.com>http://www.idcmotion.com</a> and <a href=http://www.superiorelectric.com>http://www.superiorelectric.com</a> Cameron Anderson Senior Motion Control Specialist
 
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> What size/type of stepper motor would have the power to drive a cutter to cut a 14ga piece of wire? Shear strength of copper wire:25-33k lbs/sq.in. Dia of 14ga: 0.064in Area: 1/250sq.in. approx. Therefore shear FORCE=25000/250=100lbs. This of course assumes a 'perfect' cutter. Power=Force x Velocity so 'how fast' determines power needs. Don't forget screw mechanical advantage & the overall system efficency. (screw=0.8; dull cutter=0.5; motor=0.7; variation of the wire=.6 ==17%). Looks like around a 5 times multiplier. How about using a solenoid and lever arrangement? I've done that in the past but it is NOISY.
 
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Peter Cauchy

> 1. Weight of cutter assembly? approx 6-8 oz. carbide tipped blade > 2. How is cutter supported? Fitted to screw with a key slot follower on a support. > 3. Move profile - How many inches in how many seconds. Not velocity, looking for a distance in a time. 1/2 inch, no length of time, as the wire is stationary when being cut. > 4. Screw Diameter 3/8-16 std, acme or ball would be better I know. > Explain more about your application. Why are you moving the cutter head? Is the wire constantly moving? Doing a Flying Shear/Cutoff? If the wire isn't constantly moving, then look at doing a nip roller system and keep the cutter stationary. < The device is taking a helix, and severing 1 winding, then pushing said winding till it meets the previously cut end, then returning to the home position. Thanks for the input. Peter Cauchy
 
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Peter Cauchy

The solenoid would be a possibility, since it would allow me to force the end of the ring up into the previously cut end. Unfortunately I have just started in the realm of motion control and am unsure how to implemement something like this. I would be happy to hear any suggestions for implementing this. Peter Cauchy
 
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Peter, It's hard to say without knowing more. How fast do you want to cut it, how are the blades arranged, what is the friction component of the cutter, what are the accuracy requirements.... Does the mockup work, or does it just not have enough power? I like to use ST (www.st.com) for stepper and other power driver chips. I think they have some that will carry 4 amps. If that isn't enough, there are some discrete MOSFET drivers available from them, too. I've had good results over the past years being able to get their chips consistently. Regards, Willy Smith
 
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Peter Cauchy

Thank you for all the response, to answer some of the questions, the mock-up does work, but will not cut thru the wire. Since I am using stepper motors from old floppy drives to power the mock-up, this is no suprise. I am also using a very basic driver circuit where the PC has to send all of the pulses to the coils, not just a step and direction. Thanks again for the advice. Peter Cauchy
 
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