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Cutting Multiple Sheets of Plywood Together - Motor Longevity

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Forum topic by Uriel7 posted 03-11-2016 04:07 AM 1306 views 0 times favorited 14 replies Add to Favorites Watch
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Uriel7

24 posts in 1976 days


03-11-2016 04:07 AM

At work our packaging department goes through stacks of 1/2” plywood building shipping crates. They just can’t cut enough plywood fast enough in a day. I was thinking they could cut 2-3 sheets of plywood at a time, but what about over working the motor? Their regular 3HP saw had to get repaired/replaced quite frequently and just upgraded to a 4HP saw. They were running a 10” plywood blade on the 3HP motor. The new 4HP table saw came with a 12” blade. We have two guys working the saw together and nice sliding table to manage the full size sheets. Since this stuff is for making shipping crates, perfect/clean edges aren’t a priority. All of this is in overseas where the standard voltage is 220v @ 50Hz.

Should I simply have them use the smaller 10” blade to prolong the motor’s life? I know we should be running at a lower rpm for thicker cuts, but how much lower for how thicker a cut? If I stack up 3 sheets of 1/2” plywood common sense says that it needs to be cut slower than 1 sheet, but by how much?. Most people seem fine only cutting one sheet of plywood at a time. I can’t find much info on cutting sheets of plywood together. Can you guys help me out with any tips or advice to cut lots of plywood fast and keep the motor in good shape?


14 replies so far

View pete724's profile

pete724

36 posts in 271 days


#1 posted 03-11-2016 04:25 AM

I’M no expert but;

More people and more saws.

Don’t stack!

What if the top sheet slips out of alignment with lower sheets?
Blade pinch. Kickback. disaster.

View JAAune's profile

JAAune

1640 posts in 1779 days


#2 posted 03-11-2016 04:51 AM

Sounds like you have the wrong saw. An Altendorf F-90 should do the job handily. If you’ve got the money, perhaps a beam saw would be even better. That’s an automated saw that can definitely handle stacks.

Stacking on a conventional saw would be suicidal.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View MadMark's profile

MadMark

977 posts in 915 days


#3 posted 03-11-2016 04:58 AM

Do not attempt to cut multiple pieces at once. This is a safety issue.

Get a panel saw:

-- Madmark - Madmark2150@yahoo.com Wiretreefarm.com

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Uriel7

24 posts in 1976 days


#4 posted 03-11-2016 07:33 AM

Don’t worry, this table saw isn’t your conventional table saw. It is more like the recommended Altendorf F-90 minus the automation. Infeed and outfeed tables were made to handle full sheets of plywood. Keeping the stacks aligned would be an issue, especially when most of the sheet has been cut up. This would explain why nobody talks about cutting stacks of plywood.

Even on a panel saw, won’t the same motor issues exist? From what I’ve seen in panel saws, they seem to have nearly the same motor as a circular saw, which seem to max out at about 3HP/2,200W. We cut one sheet at a time, and still have motors going every couple months. Sometimes it’s a motor bearing, sometimes the brushes. How many service hours should you get out of a decent saw? I was thinking at least 2,000 hours. They’ve used the circular saw bolted upside down to a table configuration and are now trying a belt and pulley driven system.

View Tony_S's profile

Tony_S

605 posts in 2545 days


#5 posted 03-11-2016 11:21 AM



At work our packaging department goes through stacks of 1/2” plywood building shipping crates. They just can t cut enough plywood fast enough in a day. I was thinking they could cut 2-3 sheets of plywood at a time.

You need a beam saw.
High production, repetitive, multiple sheet cutting is what they are manufactured for, and excel at.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

View rwe2156's profile

rwe2156

2192 posts in 943 days


#6 posted 03-11-2016 12:46 PM

I won’t be so presumptious to tell you need another method. And I assume you are screwing the panels together before sawing.

Sounds like you’ve got a good machine there.

I would think that’s plenty of power, especially using a 10” blade, but you could put an ammeter on the power supply and see what happens under load. If you’re exceeding or coming very close to rated amps for motor, its too much

Bottom line this is a lot of continuous work for any motor. Its possible 4HP may not even be enough.

You might also think about different blades like maybe a combination blade.

-- Everything is a prototype thats why its one of a kind!!

View JBrow's profile

JBrow

818 posts in 383 days


#7 posted 03-11-2016 03:16 PM

Uriel7,

I am not much on motors or electricity, but it is hard for me to believe that industrial machinery requires such frequent motor changes. Perhaps there is something not quite right in the power feeding the motor. If the voltage is not within the motor manufacturer’s specification, I suspect this could affect motor life. Also I notice your power is 50HZ. In the States the standard is 60HZ. A motor designed to run at 60HZ may not last as long at 50HZ.

Feed rate is too fast when the motor slows down. This is easily determined by listening to the saw. The maximum feed rate I use is that which just begins to bog down the saw. No doubt, the thicker the stock, the slower the feed rate required. But a 10” table saw should easily handle 1-1/2” thick stock. The cheapest way to prolong the life of the motor is to reduce the load on the motor by always using a sharp blade. Carbide blades last longer but do become dull. A 10” blade is cheaper than a 12” blade, so this may be a reason to change from a 12” blade to a 10” blade, especially if the added 1” depth of cut is not required.

I think you are on to something when suggesting cutting 3 pieces of plywood in one operation rather than 1. After all, production can be increased by almost 3 fold. However, shifting plywood during a cut would make for a bad day. It could tear up equipment and people could get hurt.

There are two ideas that come to mind that would allow 3 sheets to be cut simultaneously. Three sheets of plywood could be stacked and aligned. The three sheets would then be screwed together. Screws would be placed at all four corners. Of course the screws must never contact the blade. Also, additional time is required to stack and align the plywood, install and then remove the screws. Three sheets stacked together are of course three times heavier, making the job of moving the stacked plywood more difficult.

The other option is to use a different set up altogether, similar to a panel saw but cheaper. A track saw is used rather than the table saw. First a plywood cutting frame would be needed. The cutting frame would be a grid of construction lumber flush on the upper surface that is flat to fully support the plywood stack down the length and across the width. The surface on which the plywood sets would be at a comfortable working height. Plywood is stacked on the plywood cutting frame. It is aligned and the stack may have to be clamped together. Alignment could be automatic if the frame has edges that capture the plywood when it is placed in the plywood cutting frame. Then the track of the track saw is placed on the cut line and the track saw makes the cut.

The track saw method could be very efficient and superior to a panel saw. For example, if you needed to break down 4×8 sheets of plywood into 2×2 sheets. The cuts could be all made without ever having to move the plywood. Rather the track of the track saw is simply repositioned. Doing this multiple breakdown may require the plywood to be clamped to the plywood cutting frame, but may be not.

Replacing or repairing the track saw is an expense amortized over the number of sheets cut. This will either be too high and therefore not economically viable or the value of the increased production supports the method and makes replacing or repairing the track saw a small margin cost.

To determine whether production can in fact be increased, a time study would be required. For a given task measure the time required to complete by the two competing methods. The method that results in more product in a given time is the most efficient.

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MrUnix

4219 posts in 1661 days


#8 posted 03-11-2016 03:33 PM

Sometimes it’s a motor bearing, sometimes the brushes. How many service hours should you get out of a decent saw?

Bearings are a standard maintenance item, and should be inspected/changed at regular intervals. Failure to do so can cause catastrophic failure of the motor. Brushes are the same, but won’t cause damage when worn and simply need to be replaced (are you sure you have brushes? Are these not induction motors?). Depending on the motor type, capacitors and other start circuitry in an induction motor will also need occasional inspection/maintenance. However, as long as the motor has adequate overload protection and not allowed to over heat beyond it’s specs, with proper maintenance, the motor should last almost indefinitely.

Cheers,
Brad

PS: Don’t forget that the saw itself will need attention as well – inspecting/replacing arbor bearings, cleaning and lubrication of wear points and gear interfaces, etc… Lack of maintenance on the saw will have an impact on the motor as well. In a production environment, you should have a well defined maintenance schedule for those machines with planned downtime for service.

-- Brad in FL - To be old and wise, you must first be young and stupid

View Ger21's profile

Ger21

1047 posts in 2594 days


#9 posted 03-11-2016 05:01 PM



Even on a panel saw, won t the same motor issues exist? From what I ve seen in panel saws, they seem to have nearly the same motor as a circular saw, which seem to max out at about 3HP/2,200W. We cut one sheet at a time, and still have motors going every couple months. Sometimes it s a motor bearing, sometimes the brushes. How many service hours should you get out of a decent saw? I was thinking at least 2,000 hours.

Motors in industrial saws should last at least 10-15 years with nearly no maintenance.

In 20+ years in cabinet shops, the only failure I’ve seen were the arbor bearings in a 15+ year old Streibig panel saw. And that was due to not being greased according to manufacturer recommendations.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

View dschlic1's profile

dschlic1

330 posts in 1432 days


#10 posted 03-11-2016 05:41 PM

A couple of comments. First you stated that you are using a blade made for plywood. These are usually high tooth count ATB to achieve a smooth cut. Try going to a general purpose blade or better yet a rip cut style blade. These should achieve a high cut speed.

The second point is to check the motor protection. In general it should trip out before the motor is damaged. Are you having frequent protection trips?

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bigblockyeti

3668 posts in 1183 days


#11 posted 03-11-2016 05:57 PM

If they can’t cut through 1 1/2” of plywood with a 3hp saw and not tear it up, either the saw is setup incorrectly, they don’t know how to properly use the saw, or it has the wrong (or dull) blade installed.

View MrUnix's profile (online now)

MrUnix

4219 posts in 1661 days


#12 posted 03-11-2016 06:05 PM


If they can t cut through 1 1/2” of plywood with a 3hp saw and not tear it up, either the saw is setup incorrectly, they don t know how to properly use the saw, or it has the wrong (or dull) blade installed.
- bigblockyeti

Gotta agree… My 3hp Unisaw came out of a boat building factory where it was used to cut plywood panels day in and day out, for over 20 years with, AFAIK, little or no maintenance. When I got it, I opened up the motor and, while the bearings were starting to leak grease and needed replacement, they still had quite a bit of life left in them. The arbor bearings were pretty well shot though. The saw was used enough to have worn down the blade elevation gears, but the motor still ran just fine.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View Uriel7's profile

Uriel7

24 posts in 1976 days


#13 posted 03-12-2016 02:54 AM

Thanks for all the feedback guys. I’m working in China and all our equipment so far is domestic which means a new low in quality. Even if your saw is made in China and it is exported, it is still not the same saw we can buy in the mainland. The woodshop has one guy that knows what he’s doing around a table saw, but his “assistants” are another story. To answer some of your questions, yes 50Hz power messes up electric motor intended for 60Hz, but all our stuff wired for 50Hz. The motor(s) does not trip off although it probably should be.

How often do you find you have to clean your blades? I just asked them yesterday to clean the blade and I got a lot of puzzled looks. I figure this is at least part of the reason.

View JBrow's profile

JBrow

818 posts in 383 days


#14 posted 03-12-2016 04:04 AM

Uriel7,

If my vision of your operation is correct, a lot of plywood is cut in a day. Cleaning the blade daily would be ideal, but perhaps impractical. Weekly at a minimum; but these are guesses. But to be sure, inspect the blade for pitch build up on the teeth. When pitch is present, some benefit can be derived by cleaning the blade. It is easier and faster to clean a blade if the blade is not allowed to accumulate a lot of pitch.

Since I started cleaning my blades, bits and cutters after completing every project, they seem to cut better and cleaner and it does not take much time since there is not much pitch to remove.

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