rotary actuator - was strip cutter

On the strip cutter that I am building from the previous post. The knife has to rotate to create a mirror image on the cuts. Meaning first cut is like this / and the next is like \.

The angle has to be adjustable for different products. In a production run though the angle does not vary.

How would you accomplish this? I was thinking something like a pneumatic actuator with some form of manually adjustable stop, but I suck at this so someone has to know better.

Thanks

Jason

A pneumatic actuator will be the cheapest by far. SMC has several rotary actuators that have adjustable stops and a degree scale built into the actuator.

SMC

If the angle doesn't need to be adjustable by the operator I'd go that route.

Stops are simlple to incorporate into a simple cylinder-crank arm arrangement as well. The stop could be a separate removable assembly you swap out for different products.

Chris

how about a V die? this would waste some material but it would be faster

surplusjohn said:

how about a V die? this would waste some material but it would be faster

Click to expand...

What does a V die look like? Would I be able to heat it as well? The material is cheap so not a big worry.

Thanks

Jason

if this is a hot cutting die, you would use two blades brass or steel, mounted in you heater block so each stroke would cut both angles, you would need a block for each variation.

I am thinking that the pneumatic setup will require adjustable stops to set the rotation angle.
You will need one for each direction. If this is something that must be set up with less than a maintenance technician level of support, it might pay to use a servo or a stepper to spin to the required angle. A PLC could have a display for the cutting angles, and the operator would just have to punch in the numbers off of the job tag.
Sure, it is more expensive, but it will allow the operators to set up the job an run, not a maintenance technician to fiddle with stoppers for every job change.

3t3d said:

I am thinking that the pneumatic setup will require adjustable stops to set the rotation angle.
You will need one for each direction. If this is something that must be set up with less than a maintenance technician level of support, it might pay to use a servo or a stepper to spin to the required angle. A PLC could have a display for the cutting angles, and the operator would just have to punch in the numbers off of the job tag.
Sure, it is more expensive, but it will allow the operators to set up the job an run, not a maintenance technician to fiddle with stoppers for every job change.

Click to expand...

I found these videos from a manufacturer. I would need to combine some features from a few different machines.

Sheffield Cutting Equipment - Hot and Cold Angle Strip Cutting Machine video.

Sheffield Cutting Equipment - Hot and Cold Automatic Angle Strip Cutting Machine video.

Sheffield Cutting Equipment - Hold and Cold Multifunction Line Marking/Hole Punch cutting machines.

I have never used steppers before. How are they used? Are there benefits over servos?

Thanks

jason

If you stay with air, I have a small rotary air cylinder, actually two cylinders with a rack and pinion in the center.
these are pretty nice cutters, I like the markers. the hot hole cutter is slick, is there simply a hollow hot punch or is it a solid hot punch? unless you can remove the slug in apositive manner, I would expect it to make a mess.

here is what i mean

Jason,

The first video is what I was thinking about.
They are using steppers, servos would work as well, or better.

Steppers are cheaper than servos, generally.
There is a stepper driver, and a motor. The driver may have the power supply already built in, or may require a separate power supply.

Basically, the computer, or the PLC sends a Step (pulse) and a direction signal to the driver. The motor will step forward or backward for every Step pulse it sees, the direction set by the Direction signal.
The computer or PLC cannot send the pulses too fast, or the motor will not keep up.
If the motor cannot keep up, or encounters too much load, the driver generally will not know it, and now the system is out of position.

You can hear the stepper motors moving in steps in the video.. It is a distinctive sound.

Servos may be a better solution, and may be competitive with electronics prices coming down.

I thought the biggest advantage to a servo or stepper would be the ability to program a new angle for today's job without a tech needing to fiddle with the mechanical stops, and the ability to have multiple angles for the job, in any pattern.

Here is a link for AutomationDirect.. for stepper systems.
Stepper Systems Products
Here is a link for servo systems.
100W Servo System (Low Inertia) Products

Automation4less has some integrated driver/motor packages too.
There are many others, and Ebay for the brave or experienced.

Let us know what happens next.

Thanks for the direction. I was going to use a servo for the payout potion of the rig. Thanks to Motion Guru I am into the Emerson app Power Tools for programming. I wanted to use the encoder for measuring length. I saw this setup, but with my limited knowledge I think the separate encoder up top might be less desirable. Is this right?

CuttingVelcro.mpeg - YouTube

I am willing to try a stepper for knife angle. any reason that a stepper cant be mixed with the servo?

Thanks

jason

The Stepper won't know or care that you are cheating on it with a younger, stronger servo....

There might be an advantage to having the same servo and driver for the feed and the swivel. One less controller type to program, spare parts to swap, etc..

Steppers are cheap and simple. You will need a way to re-zero it or reference it.
Either drive it into a hard stop on power up so you know where it is at, or an optical switch it will sweep past to find it's reference point.

The servo has the encoder to find it's reference point with.
---------

I suspect that the encoder on top of the belt may be for one or more reasons..
The belt drive may be driven by a motor without an encoder.
The amount of crush on the drive rolls may affect the feed per rev of the motor. ( I don't know?) The encoder measures the Actual amount the drive belt moves, regardless of what the drive rollers are doing..
It may have been added as an afterthought/retrofit.

If you have the encoder on the servo motor, it might be all you need. If there is a difference in the drive roller to servo revolutions, (will there/can there be. MotionG.?) you could compensate in the programmed distance before the cutter hits it.

---------------

Also, back in the mists of time, there was a cutter on a veneer line, that would measure the time for the clipper to stroke..
It used that information to adjust the next stroke timing to match the line as the line sped up or slowed down, and the clipper speed varied as the air pressure in the plant changed, and the grease etc. changed. It was calculating the line speed, the cliper speed, and the distance to the next clip... All BEFORE processors, and software..
It was all done in big racks of electronics, Up/Down counters, shift registers, Rate multipliers, and banks of thumb wheel switches. Sorry, no memory chips, other than shift registers...
With TTL it was a BIG rack of circuits, and many amps of power, and air conditioning for the big rack of electronics...

We thought we were being REALLY clever, with a switch to CMOS, and higher density logic....
Massively smaller, cooler, less power, less boards in the system, more reliable..
What's not to Love?

The customer went NUTS!!! How in the HELL can I sell this little box for $100,000 ???????

It was ugly, and tense... Fond memories.

Thanks for the direction. I will keep it servo all the way around. Since I want to keep the unit pretty portable, so that it can move to the workstation that needs it that day, I was looking at the HMI's that have the PLC's integrated into them. Is this a good or bad idea?

Any reason to or to not to use the combo units?


Thanks

Jason

I like these Unitronics units.
They have the HMI and IO all in one package.

They come up cheap on occasion. Watch Ebay.
Maybe stick with the Vision line instead of the Jazz line.

If I wasn't so many 100 miles behind right now, I'd pack one up for you to play with.

unitronics | eBay

Thanks for the direction. I dont mind buying new since i know I am a major pain on the tech support people. I gotta pay to play on these things. I figure i am paying for my education.

Jason

Another question - is there a way to incorporate the heating control within the PLC or does it have to be an independent process control unit like this:

1/16 DIN Size (SL4848 Series) Products

Thanks

Jason

A Vision 120 has a PID control already in it, depending on the model. They can take several types of temp probe/thermocouple inputs. All programmable/settable with jumpers.

Unitronics - Vision120

Click on the different model numbers for all the input/output options.
Also, there are simple expansion modules that plug in if more IO is needed.

The screen has a nifty graphics package you can create the screens for your product, and have several options come up on the screen.
It only took an hour or so to have it displaying different screens and options. Good support in the editor.

There certainly might be other PLC's out there. I seen these at a trade show, and liked how they have most everything already in one handy little box.

Thanks again! Production on this should begin late next week.


Jason