Thread: 19" BS upgrade

I just did the sums on the linear band speeds and the new setup should be
3600 FPM @50 Hz (original setup was 3300 FPM)

So 20Hz should be 1440 FPM versus 1660 FPM on low gear on original pulley.

80Hz should be 5770 FPM - probably a bit fast although the Bandsaw mill I'm using does not much less than that.

I have the same BS as Bob and I too changed my motor to a 3kw 3ph but is a 2 pole (2850 rpm) and as yet I haven't gone down the VSD road yet so at normal motor revs my blade speed is around 6400ft/min on the large pulley and I can't remember what it is on the smaller pulley but faster, I used to change to the faster speed for the TCT blade but don't bother these days, both the bimetal and TCT do fine on the 6400ft/min. The faster blade speed was a vast improvement on the original setup.

I posted in another thread the faster blade speed increases the number of stress cycles in the blade with an increased tendency toward blade cracking, one reason I want to put a VSD drive on mine is then I can turn the speed down when those moments arise where you don't want to turn it off but you need a moment to think about the next operation, whether it saves a blade or not, Who knows? but has to help, and of course the blade braking feature.

All your stops and interlocks (door open) will just be in series with the VSD stop when wired up to the terminal strip connections.
I can't recall exactly but I don't think Bob put a limit switch on his braking system, If you haven't Bob Are you thinking you will?



Pete

Thanks for the info Pete.

Originally Posted by pjt

I have the same BS as Bob and I too changed my motor to a 3kw 3ph but is a 2 pole (2850 rpm) and as yet I haven't gone down the VSD road yet so at normal motor revs my blade speed is around 6400ft/min on the large pulley and I can't remember what it is on the smaller pulley but faster, I used to change to the faster speed for the TCT blade but don't bother these days, both the bimetal and TCT do fine on the 6400ft/min. The faster blade speed was a vast improvement on the original setup.e

Before I embarked on this upgrade I did some investigation on band speeds for wood and according to Cooksaws in the US the optimum speed for cutting is around 5500 FPM. Above that increases amount of motor power goes into friction which contributes to blade damage which is what you refer to below. If faster cutting speeds are required and more power is available they recommend using a more aggressive blade rather than more speed. My setup should hit 5500 fpm at 77 Hz.

I posted in another thread the faster blade speed increases the number of stress cycles in the blade with an increased tendency toward blade cracking, one reason I want to put a VSD drive on mine is then I can turn the speed down when those moments arise where you don't want to turn it off but you need a moment to think about the next operation, whether it saves a blade or not, Who knows? but has to help, and of course the blade braking feature.

Based on my experience with these HY VFD they don'y have much of a braking capability unless a braking resistor is used.
The HYs I have used work fine when braking smaller spindle machine machinery like a DP or lathes with small work on them, but machinery with significant angular momentum like (grinders Linisher and blowers) all trip out under braking (also the grinding wheels tend to untighten themselves) so I am assuming this will be the same for the bandsaw. So initially I will be setting up the VFD on the BS to use a coasting stop and will just use the footbrake for now. I may explore adding braking resistors at another time.

All your stops and interlocks (door open) will just be in series with the VSD stop when wired up to the terminal strip connections.

That would be one way of doing it but it that would then mean that when these switch were restored e.g. door closed, if the VFD motor switch was already closed the BS would start up again. The same would apply to any switch on the brake.
The switch box I have put together puts the the door switch and the brake switch in series with the power to a NV switch which in turn provides power to a relay. When the brake, door and NV switches are closed this closes the relay output allowing the VFD switch to be used to turn the motor on/off.
If either the brake, door or NV switches are opened the VFD stops and will not restart unless all three are closed. having to manual activate the NV switch prevents the BS from restarting.
The normal mode of operating will be to leave the usual VFD motor switch on and use the footbrake to turn off and the NV switch to turn on.

I can't recall exactly but I don't think Bob put a limit switch on his braking system, If you haven't Bob Are you thinking you will?

The switch on the brake has been excellent

Here is the circuit I've been working on.

Power comes in from the left

An emergency (E) latching switch in series with the keyed switch activates a 30A power relay which powers up the VFD.
The motor switching is then controlled by a NVS and a 240V relay.

This slightly more complicated setup also removes the need for HD (15A) switch gear




The E-switch will shut down everything while the NVS will shut down the motor run side of the VFD but leave the VFD itself running

Originally Posted by BobL

Here is the circuit I've been working on.

Power comes in from the left

An emergency (E) latching switch in series with the keyed switch activates a 30A power relay which powers up the VFD.
The motor switching is then controlled by a NVS and a 240V relay.

This slightly more complicated setup also removes the need for HD (15A) switch gear

The E-switch will shut down everything while the NVS will shut down the motor run side of the VFD but leave the VFD itself running

BobL,

What sort of VFD are you using ? Are you able to post a link to the supplier so we can have a look at the VFD specs ?

Thanks,

RoyG

It's a 3kW Huanyang single 240V to 3 phase 240V
This is similar to the one I purchased except I paid around $170 for mine
http://www.ebay.com.au/itm/4HP-3KW-V...item1e9bf6102e

I would feel comfortable using a 2.2kW VFD on this motor but the 3kW is a spare one I have on hand so that is why I am using it.

Originally Posted by BobL

Thanks for the info Pete.


So initially I will be setting up the VFD on the BS to use a coasting stop and will just use the footbrake for now. Yep, I was thinking about this when I woke up this morning, and that sounds good to me, I may explore adding braking resistors at another time. With the Zener extra circuitry is required for additional braking.


That would be one way of doing it but it that would then mean that when these switch were restored e.g. door closed, if the VFD motor switch was already closed the BS would start up again. The same would apply to any switch on the brake.
The switch box I have put together puts the the door switch and the brake switch in series with the power to a NV switch which in turn provides power to a relay. When the brake, door and NV switches are closed this closes the relay output allowing the VFD switch to be used to turn the motor on/off.
If either the brake, door or NV switches are opened the VFD stops and will not restart unless all three are closed. having to manual activate the NV switch prevents the BS from restarting.
The normal mode of operating will be to leave the usual VFD motor switch on and use the footbrake to turn off and the NV switch to turn on.

Are there options with the HY's re how they can be started? With the Zener there are programmable start options and also how they are wired will determine how and when they start, I usually select the fwd/latch option which means on reinstatement of a stop the VSD won't restart unless I push a start button, the Zener uses internal relay's to achieve this, from the looks of it you have done the same thing but external to the VSD,
As the old saying goes....there's more than one way to skin a cat....


Pete

Originally Posted by pjt

Are there options with the HY's re how they can be started? With the Zener there are programmable start options and also how they are wired will determine how and when they start, I usually select the fwd/latch option which means on reinstatement of a stop the VSD won't restart unless I push a start button, the Zener uses internal relay's to achieve this, from the looks of it you have done the same thing but external to the VSD,

The default setting on the HY VFD is that if the VFD itself is turned off and then back on the VFD wont restart the motor without a start button being pushed. But there is no option for this on the remote stop/start button. If there are multiple switches in series attached to the remote on/off switch (e.g. foot break, door switch and ordinary stop start switch) then the VFD has no way of know which one is being switched.

Motor, VFD and most of the working electrics are installed, well enough to see it running.
I haven't connected up all the interlocks or remote switching yet.

Here's the motor installed - not much to see there


The VFD hangs out from the back/side on a couple of Al brackets.
The vibe make the VFD wobble more than I like so I might need to add some braces to the brackets


The black cable coming out of the top is part of the remote motor switching circuit (it carries no power) and is not connected yet



Here's a close up of the electrical box
The keyed switch and the E-switch under the Box turns the power to the VFD ON/OF
The Yellow/red No Volt Switch turns the motor on-off via a relay connected to the VFD remote switch.
The door and foot brake are connected in series with the NVS.
1.4A free running current for the motor and the VFD - I'm happy with that - I

BTW, despite testing when I first received it and it worked OK,when mounted into the bos and first switched on the cheap V/I panel meter displayed the V but not the I.

On closer inspection the coil was OC and removing the tape quickly showed where the coil break was, across a sharpish outer corner of the ferrite core.
I'm pretty sure I stuffed the coil it into the box on and angle and some other wiring on the top must have pushed the ferrite core too hard across the coil and broken the wire.
The wires are quite fine so it does not appear much is required to break them
Undo one loop and resolder and cover join with a small piece of shrink tuning. recover the coil with several layers of teflon tape and all is good.

Interlocks and remote on/off switch and speed control are all working and a diagonal brace reduces the VFD vibrations.

A few final pics;

Here you can see the remote speed and stop inside a box attached by a strong magnet to the BS cabinet. The box can be moved so that it is closer to the operator.


While I had everything apart I finally put a coat of paint on the foot brake mechanism.
It's been paint-less for over a year now and was showing no signs of rusting probably despite the fat and marrow that sprays around inside the cabinet when I cut up dogs bones


Another shot of the remote.

Very nice work and nicely illustrated and explained Bob, - Thanks for sharing it with us,
Rob.