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Old 10-14-2009, 12:13 PM
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allessence allessence is offline
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Default vertical bandsaw preference and VFD?

Hello all,

I am looking for a vertical bandsaw and have come to the conclusion that A Grob 18" or a Powermatic 18" (model 81 wood model single speed, model 87 varible metal saw) is more than likely going to be the dibbs. Though I do like the smaller Older Walker turner 16" models. Just can't find one around.


Who, prefers which model and why? I know everyone will have a slightly different thought on this and is the reason why I am posting here. The knowledge base is way cool.

Now for VFD's? Both 18" saws come with 2 or 3HP 3phase and I was thinking that if I am going to spend money on a machine then wouldn't I be better off buying a wood machine (which is constant speed) and using the VFD as the blade speed varible vs mechanically done with step pulleys and such?

On this page they offer 3 VFD's. with different pricing but the only difference I can see is 1 or 3phase in with 3 phase out. All control speed. http://dealerselectric.com/default.asp

Reason why a wood machine? Well, metal machines seem to take a beating and wood machines seem like they wouldn't get the surfaces beat up as much. Is my thinking on this correct?
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Old 10-14-2009, 02:02 PM
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Grobs are built like a brick house, IMO

Quote:
wouldn't I be better off buying a wood machine ... and using the VFD as the blade speed variable vs mechanically done with step pulleys
VFD's are best used as a fine tuning device, and as an easy way to get lower than normal blade speeds (plus higher than normal blade speeds if desired). They maintain constant motor torque BUT do not provide the torque multiplier of a step pulley or other mechanical system.

Say the saw comes with a 3 hp, 1725 rpm motor, which produces 9 #/ft of torque. Run the motor through a 2:1 step pulley & you now have 18 #/ft of torque available, at 862 rpm. Use the VFD & you can dial in 86 rpm for a low speed, 1300 rpm for a high speed, plus all the speeds in between.

Without the step pulley, you never have more than 9 #/ft of torque. And your low speed would be about 172 rpm, with a high of 2600 rpm. The range of speeds may work for you, but you will certainly miss the added torque. This also applies to lathes & mills, where the VFD is used to get the speed you need within each gear or step, while getting the added torque available only from mechanical reduction.

The Teco drives you link to will do a good job, but you should consider a sealed housing for the saw. My last two SMVector drives are totally sealed against dust, chips, coolant, and Bud Light (which is technically a coolant)
Price on a sealed drive is higher than on an open drive, but you can leave the machine outside in a rain storm & the drive will not care.
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Old 10-14-2009, 07:13 PM
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Quote:
Originally Posted by allessence View Post
Reason why a wood machine? Well, metal machines seem to take a beating and wood machines seem like they wouldn't get the surfaces beat up as much. Is my thinking on this correct?

A good quality metal bandsaw is built to take a beating. I'm partial to DoAll mostly because I have one and it is bullet proof. It was a wreck when I got it but it came back to life and will most likely last me until my son inherits it. It is a 1939 model and it's re-birth can be seen here http://www.shopfloortalk.com/forums/...light=band+saw

I think any good quality industrial machine would be a good choice.
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Old 10-14-2009, 08:57 PM
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I use a 2HP GS2 VFD from Automation Direct on my mill, and have been very happy with it. I mounted it in a NEMA enclosure to keep it away from swarf, dust, etc. The manual is well written, which is not true of all VFDs apparently. The display can be set to show a fixed multiple of Hz, meaning you could set it to show FPM.
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Old 10-14-2009, 10:17 PM
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Quote:
The manual is well written, which is not true of all VFDs apparently.
+1

I've read most of the manuals from most of the manufacturers who've made drives during the last 20 years. After you read a dozen or two, similarities start to show up, as well as how they differ.

Freq Drive Rule #1 - RTFM

Freq Drive Rule #2 - RTFM again

Freq Drive Rule #3 - If the problem persists after twice reading the manual, call tech support. The phone call is free. The support staff for every drive manufacturer is knowledgeable & eager to share their information. I've made more phone calls to tech support than I can remember - Siemens, Allen Bradley, Square D, Hitachi, ABB, Teco, ACTech, TB Woods, Yaskawa, etc. The questions are always answered quickly & correctly. The resource is there for you to use
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Old 10-15-2009, 03:47 AM
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A Delta is the basic standard machine. It is much cheaper and does a really good job and the gear box allows it to be changed from metal to wood pretty fast.

I do agree any of the professional metal bandsaws will be better, the inital price is a lot more.

I don't see a wood saw working without serious changes. The metal saw only runs about 1/10 as fast.
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Old 10-15-2009, 06:31 AM
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I love you guys!!!

I did check the specs via parts list on the model 81 and the model 87 and the only major is the gear drive parts. The drive wheels, housings, top doors, bearings are all the same part#.

So, I guess it is a metal machine for me.

I did look at the delta's, Cresents, and few other wood machines and the biggest deterrent was the problem with setting up a proper gear reduction. For the most part there simply isn't any room and instead of having a drive shaft that goes all the way thru the bearing spindle it stops just shy of the outside.

If I had a metal lathe I wouldn't consider this an issue as the shafting is very straight forwards. My problem is cost of machine, cost of new shaft. transport. etc.

I did look at the new Jet 18" wood and metal saw with VFD and it's 1800.00. Not a bad deal when you consider the size space take up wise and what others MFG's saws are going for. But then I get stuck with quality. I've never owned a Jet anything. And it's 1/3rd the size and weight of a true Doall, powermatic, Grob. Nice thing with the Jet is it takes the same blades as the Johnson. Which means only stocking 1 blade length.

Most people I take to say the Doalls are the bomb and usually are at a premium price.

I'm going down to Thomaston, CT today to look at a powermatic. I'll keep you guys informed.

Thanks again. Jennifer
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Old 10-15-2009, 06:34 AM
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Someone somewhere said that going a little larger size wise on the VFD isn't such a bad idea, Had something to do with Hz and heat in the motor or something like that???????
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Old 10-15-2009, 07:20 AM
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Quote:
going a little larger size wise on the VFD isn't such a bad idea
For 3 hp and under, it is size for size (3 hp motor takes a 3 hp drive, etc.)

For 5 hp and above, with single phase input, the VFD size is double the motor hp (5 hp motor takes a 10 hp drive, etc.)

These drives are designed to run for over 20 years, and that's 24/7/365. Which means they last almost forever in a small shop.

Look at a Grob if you can, although DoAll does build a nice machine. Leave the Jet in the showroom
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Old 10-15-2009, 09:28 AM
kvom kvom is offline
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I don't know how much sawing you are going to do, but if you get a saw that takes the same blade width as the Johnson (1" I seem to remember), then you can buy the blade material in a roll and make your own blades with a blade welder (which a lot of vertical bandsaw come with).

The saw at school is a Powermatic and is a really beefy machine. It and the Wilton horizontal both take 3/4" blades.
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