AC gear motor reversing cycle with trip switches

shortbus

Joined Sep 30, 2009
10,044
1. The purpose of this cross cut saw is to facilitate the cutting of same size panels usually 16" x 16" or less from pre-cut runs of the appropriate width stock. For example if I'm making 16 x 16 inch panels, I'm feed 16" wide runs of 96" material into the saw. These runs are stacked, 3-4 sheets high. Keep in mind the sheets are 3/8" thick.
So your saw will also move down the length of the 96" panel for each cut too?
 

Thread Starter

JeffN

Joined Dec 14, 2021
14
So your saw will also move down the length of the 96" panel for each cut too?
No, that is not correct, sorry. The 96" runs will be pre cut on another saw this new set up is for cross cut only. Longest cut being 24" most often, 16" or less. I just ran a test on the saw motor power, etc it works just fine with a stack of four pcs. 3/8" thick, total of 1.5" thick cutting depth. I running a 10" saw, 15 amp. Used often to cut 3" lumber, I'm at half that thickness.
 

Thread Starter

JeffN

Joined Dec 14, 2021
14
Have you performed a time study on the activities? Working on similar, but larger scale work centers, I had found that efficiencies aren't gained on the saw cut, because it is what it is due to blade and feed rates. The largest gains come from handling the product into and out of the the saw cut. One place I worked cut 'books' of OSB as web for I joists. Pallets of OSB were raised on a hoist, and a stack of 10 were pushed off by a carriage, squared, then advanced through the saw. Fully programmable to account for a variety of joist widths and maximize yield. Fine tuning and some modifications to the hoist/carriage made substantial gains, while the saw cycle itself was allowed to slow somewhat to extend the life of the 32" blades, which would drift as they dulled.
I would seriously be looking at auto feeding the stock, manually stroke the saw, then auto cycling the feed. Once that was perfected, I'd auto cycle the saw stroke. That approach would then deploy a PLC , micro, or computer for a range of products. Add a printer for part ID and your on the heels of mass producers.
Im meeting with a fellow next week who is setting up his cabinet shop. Should be interesting to see what he has and where he wants to go with it,
I appreciate the feedback and experience you have. Automating the saw stroke is mainly to address operator fatigue. However I will run a number of tests without the automated saw stroke just to see how things work out. Your note about that not being where the time is saved is noted. Good point.
 

LowQCab

Joined Nov 6, 2012
3,952
Can you work out a schematic for the set up without lifting the saw? I've run some tests and will run more, but the current saw seems to work fine. I've run a production shop for 30 years, I don't overkill my motors and though this is a prototype, and I will learn even if the idea ends up not working, I want to give it a try.

Perhaps my use of "quick" implied faster than the saw can handle, I'm not going to do that.
Pulling a Saw backwards through the Work is just asking for a disaster, rails or not.
Leaving the Saw running between cuts is equally as bad.

This whole arrangement is starting to sound like a bad idea the more I think about it.

At the minimum, I would want "Bump-Bars" extending-out past the front and rear edges of the
Shoe of the Saw which would be tied into the same Electrical "Safety-Loop" as the Kill-Buttons.
But this wouldn't do anything about the dangers of moving material around a running Saw.

Have You considered that, without a much more powerful, variable speed, Gear-Motor
the return-to-home motion will be the same slow-speed as the forward-cutting-motion ?

The Electrical-Circuitry is the easy part,
but all of the mechanical and safety considerations must be worked-out first, in every detail.

OSHA would do screaming-back-flips if they knew what you're up to.
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GetDeviceInfo

Joined Jun 7, 2009
2,190
I agree with the previous post in regards to drawing the saw back through the work piece. The majority of saws I've worked on retract the blade into an enclosure, allowing them to safely run continuously, for repeated cycling. Starting the arbor for every cycle will affect maximum cycles per hour.
I will however volunteer a circuit, only because I like a puzzle. I do recommend you allow it to evolve in response to critique.
Referring to the circuit, LSS allows the start (hold start to overcome), while LSH breaks the cycle. MForward and MReverse drive the motor. I don't know enough about reversing your motor and others are likely better with that. Manual forward can be eliminated, but manual reverse will get you home if stopped mid cycle. Limit switch layout below. Double start for two handed.

saw_circuit.png
 
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Thread Starter

JeffN

Joined Dec 14, 2021
14
The point of drawing back the running saw as dangerous is a valid one. I need to think that through more. My initial thoughts are since the material being cut has a fence both on the leading edge and trailing edge, the material is not free to be cocked sideways into the running blade which would cause a jam and who knows what else. If the material is also prevented from sliding into the running blade that would also prevent a jam. The cut off piece will be dropped away from the blade before the return to home stroke, so that cannot cause a jam either. I appreciate the feedback.
 

LowQCab

Joined Nov 6, 2012
3,952
Never forget Murphy's-Law .........
If it's "possible" that the Saw can run without the Clamping-Fence secured,
then it's going to happen at some point.

Without "being-there" it's hard to say how I would go about
installing a Safety-Switch on the Clamping-Fence,
but I'm sure it could be done, and it needs to be done.

I just can't see that "Universal-Series-Brushed-Motor" in that Saw,
lasting for more than a Month under continuous mass-production conditions.
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shortbus

Joined Sep 30, 2009
10,044
No, that is not correct, sorry. The 96" runs will be pre cut on another saw this new set up is for cross cut only.
I understand that the 96" is a "pre-cut". What I was asking about is the removal of the cut off pieces and advancement for the next set of small panels.
 

shortbus

Joined Sep 30, 2009
10,044
One other thing I just thought of. Have you considered doing this on a table saw using a moving sled to hold the material? This would keep the blade farther away from the operator durring the loading and advancing for the next cut. And with the way a tables saw blade turns the blade teeth will also be helping to hold the work down. With a little more work the blade could even be made to drop below the table/sled surface on the return stroke.
 
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MaxHeadRoom

Joined Jul 18, 2013
28,528
. MForward and MReverse drive the motor. I don't know enough about reversing your motor and others are likely better with that.
It appears to be a PSC Permanent Start Cap motor, both windings equal, if so it just needs a SPDT switch/relay to reverse with controlled RPM on the cut stroke, full voltage for return.
1/10hp motor with 40:1 ratio GB
 

Thread Starter

JeffN

Joined Dec 14, 2021
14
Never forget Murphy's-Law .........
If it's "possible" that the Saw can run without the Clamping-Fence secured,
then it's going to happen at some point.

Without "being-there" it's hard to say how I would go about
installing a Safety-Switch on the Clamping-Fence,
but I'm sure it could be done, and it needs to be done.

I just can't see that "Universal-Series-Brushed-Motor" in that Saw,
lasting for more than a Month under continuous mass-production conditions.
.
.
.
The fences are not quick release, they are bolted in place. Yes, I guess you could make the argument that someone would try to remove one and run the machine with out it. But one could also remove whatever safety mechanism is installed as well. That goes for any type of deal that could be attempted to be over ridden. I don't hire people who do that kind of thing. As as a small production shop it's me and a helper. Small foot print, keeps things simple.

I don't have continuous mass-production conditions either. So that's not really an issue. This is only one of several product lines we have and as such is used within a team of machines.
 

GetDeviceInfo

Joined Jun 7, 2009
2,190
It appears to be a PSC Permanent Start Cap motor, both windings equal, if so it just needs a SPDT switch/relay to reverse with controlled RPM on the cut stroke, full voltage for return.
1/10hp motor with 40:1 ratio GB
Thanks for that. I remember some of this in school, but to be honest, over my career, single phase motors were rarely encountered, at least where it required design or modification.
 

Thread Starter

JeffN

Joined Dec 14, 2021
14
One other thing I just thought of. Have you considered doing this on a table saw using a moving sled to hold the material? This would keep the blade farther away from the operator durring the loading and advancing for the next cut. And with the way a tables saw blade turns the blade teeth will also be helping to hold the work down. With a little more work the blade could even be made to drop below the table/sled surface on the return stroke.
Thanks for that. I remember some of this in school, but to be honest, over my career, single phase motors were rarely encountered, at least where it required design or modification.
Getdeviceinfo any you would be willing to send me an email and we can chat a little bit more about your circuit that you drew up?
<snip>

Moderator edit: email address removed to prevent spam.
 

Thread Starter

JeffN

Joined Dec 14, 2021
14
Thanks for all your suggestions. I'll keep seeking the solutions to this. I realize there are a lot of ideas about this, some positive some very concerned. I also realize that from a "distance" even with pictures it is difficult to see the practicality of this. I have cut over a thousand of these various size panels on a sliding table saw. It's pretty labor intensive moving the slider back and forth.

I don't want to dedicate my slider for just this single operation because I use if for other purposes. The danger of kick back on this new machine is forestalled because

1. I'm not cutting small pieces that could get jammed by bouncing around.
2. The fences are bolted down and not easily removed. Therefore the material is always square to the blade.
3. The cutoffs are removed from the passing of the reverse moving saw, before the saw is moved.


Tests I've run by hand show this to be quite a workable machine. I just was looking for help with the circuit. Thanks to "Getdeviceinfo" for your drawing. I don't find a way to email directly members with questions like on some other forums. No worries.
 

shortbus

Joined Sep 30, 2009
10,044
I don't find a way to email directly members with questions like on some other forums. No worries.
Like most forums that is done with something called "personal messages" or PM for short. Here you can only do it after 10 posts or that was the time frame. You click on the persons name that you want to message and choose the "start a conversation" block to click on.
 

Thread Starter

JeffN

Joined Dec 14, 2021
14
Like most forums that is done with something called "personal messages" or PM for short. Here you can only do it after 10 posts or that was the time frame. You click on the persons name that you want to message and choose the "start a conversation" block to click on.
Thanks for the help.
 
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