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Wondering if this would convert wood to metal bandsaw

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SubtleHustle

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#1

JimDawson

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I think a 40:1 gearbox might be a little slow for a band saw. 10:1 would be my first choice, then do the final reduction between the gearbox and the lower wheel shaft with pulleys and belt.

But first you need to do a little math. You want a speed range from about 60 - 400 FPM (Feet Per Minute) for metal cutting.

First let's look at the wheel diameter, you need to know the circumference of the wheel in feet, so, (Pi x dia [in inches]) / 12 gives you the circumference in feet. So let's assume a 14 inch wheel. (3.14 x 14 = 43.98 inches) / 12 = 3.66 feet. so if the wheel is turning at 1 RPM, the blade speed in FPM would be 3.66. at 10 RPM would be 36.6 FPM and at 100 RPM would be 366 FPM

Now let's look at the motor RPM, the motors that you would want to use are 1725 - 1750 RPM or so, but to make it easy let's use 1800 RPM because that is the synchronous speed of the motor. So with a 10:1 gearbox, the output shaft would turn 180 RPM So 180 x 3.66 = 658.8 FPM with a 1:1 ratio on final belt drive or 329.4 with a 2:1 ratio on the final belt drive.

Using stepped pulleys, you can get various speeds by changing belt positions. This is what I have.

A treadmill motor would be a good choice and there are controllers available for them on Ebay.

If I really wanted to do a Cadillac system. I would use a 3 HP 3 phase motor, a sensorless vector VFD, and a 10:1 C-face gearbox. This would give you a usable speed range of about 5 to 1300 FPM.

A C-face is a standard motor mount arrangement where the motor bolts directly to the gearbox.

1543767783169.png
 

middle.road

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#3
...........

If I really wanted to do a Cadillac system. I would use a 3 HP 3 phase motor, a sensorless vector VFD, and a 10:1 C-face gearbox. This would give you a usable speed range of about 5 to 1300 FPM.

............
Your Gearbox setup is Cadillac/Lincoln, a 3PH/VFD setup would be Bentley/Rolls level, IMO... :grin:
 

lordbeezer

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#4
I converted a delta 14" saw to metal cutting with a 6:1 gearbox.commercial treadmill motor and a mc60 controller.workedgood enough that someone else wanted it more than me..gotta do it again.
image.jpeg
image.jpeg
 

SubtleHustle

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Thanks guys, I am starting to gather enough info, from you and other reading, and I think I am getting a better idea of what I want to do. Thinking of a 1.5hp, 1750rpm, c face, 3 phase motor with a 5:1 c face speed reducer, and a vfd. Does this sound viable to you all? I am actually torn between 5:1, and a 10:1, but figured that paired with a vfd, the 5:1 would be able to get slow enough, and still have enough torque to do the job. Really want to do it as a direct drive, and still have the ability to speed it up enough to cut the VERY occasional wood projects. So running 14" wheels, is the direct drive a good idea, or should I still put a couple step pulleys between the gearbox and drive wheel? I am completely green to this, so if I sound like I'm talking gibberish, then tell me, cause I'd hate to think I'm getting a grasp, and I'm completely wrong. Thanks again for having the patience to lend your advise.

PS, cutting wood is only a secondary objective, if I can get to 100fpm, and leave it there, I'd be completely happy with that!
 

JimDawson

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You are on the right track. I'll say again what I said above: ''If I really wanted to do a Cadillac system. I would use a 3 HP 3 phase motor, a sensorless vector VFD, and a 10:1 C-face gearbox. This would give you a usable speed range of about 5 to 1300 FPM.''

Now with a 1.5 HP motor I would absolutely go with the 10:1 gearbox just for the increased torque. The sensorless vector VFD is important because that will give you 100% torque at 0 RPM, as opposed to a V/Hz VFD that causes the torque to drop off as the speed goes down. The sensorless vector VFDs are only slightly more money than the old V/Hz VFDs.

You can safely overdrive the motor to 3600 RPM (120Hz on the VFD).
 

SubtleHustle

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So using your "Cadillac ", could you just direct drive that, and have that speed range, or are you talking about with step pulleys? The vfd I currently have on my lathe, I am running in senseless vector mode, according to the parameter chart, and the setting I have chosen...
Screenshot_20181203-230931_Drive.jpg

00-00, setting "1" SLV.
Does this mean the same vfd would be adequate for this application? If so that's awesome, because I feel very comfortable with this vfd, and it's not very expensive, at about $150.
 

SubtleHustle

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U would obviously need one that could handle more than a 1hp motor, which is what mine is rated at, but I believe the same brand has vfd's that can support more hp, yet are basic as lily the same.
 

JimDawson

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That is assuming a 1:1 direct drive on the output of the gearbox, no step pulleys needed

Yes, that VFD would work great. Did you do the auto tuning when you set it up?
 

SubtleHustle

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I went through the manual, and set the parameters manually.
 

SubtleHustle

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At least for the parameters I could figure out, so that lo eft about 60-70% on defaults! :rolleyes:
 

JimDawson

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#12
Once you input the motor nameplate parameters, there should be an ''Auto Tune'' function you can run. That will automatically set up the SLV control parameters.

Yeah, I normally only set up a half dozen or so parameters. Most of them should be left at the defaults for most applications.
 
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