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Import mill, step pully or VS for the HSM?

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  • Buckshot
    replied
    ...........I'm sorry I haven't checked back sooner. Management took away the internet at work as I suspect the people during the day that have stuff to do were spending too much time on it instead of working. Myself on the other hand work at night by myself and have nothing to do! I don't spend much time on the internest at home as I'm busy doing other stuff.

    So anyway I REALLY appreciate the input you guys have given. What makes it even better is it's about what I wanted to hear, which always is a nice thing :-) So far I have a list with about $2K in tooling I want to order too, ha!

    Thanks again, Rick

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  • A.K. Boomer
    replied
    Originally posted by Bill Pace
    My mill does have the back gear, but I rarely use it --- stays set in the middle belt position and I'm constatly amazed at what it'll do at that setting, like tapping at 50-100rpm --- 1/4" and smaller... no prob, .


    A true Mechanic will get around electrical problems every time, even though my mill is rated at 240 RPM's (single phase but 120rpm's if i bought the 3 phase)
    I can get her down to about 30rpm's if I want, Put pulley system in low gear and leave belt all the way sloppy loose, drag brake accordingly (with third hand of course)

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  • Joel
    replied
    Another vote for step pulleys and a VFD.
    Almost all of these mills come with 3 phase motors, so you are probably going to need to convert from 1~ to 3~ anyway. Why not kill 2 birds with 1 stone and gain some other nice advantages while you are at it. I wouldn't worry too much about up-sizing the motor since few people (especially HSM's) push the machine very hard anyway - I really doubt it will be an issue.

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  • Bill Pace
    replied
    Originally posted by A.K. Boomer
    tell that I rely on my electrician brothers for stuff like this, True learning starts with a desire -- and iv never had it for electrical much...
    I can relate to that!! I kept seeing references to this "VFD" ?? -- what is this thing? So I went prowling and read quite a lot,-- finding out that I figured I wanted one. I didnt learn enough that I can get into the finer stuff (like Lazlo can) (and I also let my electrician buddy 'help' me install it),--- but, I can relate from experience.

    My mill does have the back gear, but I rarely use it --- stays set in the middle belt position and I'm constatly amazed at what it'll do at that setting, like tapping at 50-100rpm --- 1/4" and smaller... no prob, --- and the routine tools at the necessary higher speeds, ---EM's, drill bits, boring, etc that probably 90-95% of my work is done with, it handles it handles with ease,--- all with the turn of the little potentiometer knob. Course I will occasionally have to lower the belt position or run in back gear,--- but you would have to do that in the original setup.

    Like Lazlo says, the motor change shouldnt be too big a deal, 3ph motors are plentiful and suprisingly cheap compared to single phase, --- specially if you are a good scrounger. I got a 2hp for my lathe at the scrap yard for .50cts lb ($18.50), --- and I'm still in awe at the difference THAT change made.

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  • rkepler
    replied
    For a VFD solution I'd also suggest that you get a sensorless vector drive. They'll give you a lot better torque at low RPM than a VFD w/o the feature. I have a Hitachi SJ100 drive on my Lagun and seldom move the belt on the mill, just changing the frequency using the remote pad. I have it set to display the RPM on the drive unit, so it's easy to hit the sweet spot with a cutter.

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  • A.K. Boomer
    replied
    I dont have a backgear, just a reverse switch, I will say this, whithout any gearing my mill is very stable while cutting, I very rarely get any kind of chatter and I attribute this to there being nothing but a good mounted spindle and direct belt drive from motor to the cutter,

    thanks for the info, Im sure you can tell that I rely on my electrician brothers for stuff like this, True learning starts with a desire -- and iv never had it for electrical much...

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  • lazlo
    replied
    Originally posted by A.K. Boomer
    the only three phase they make for it is 1 1/2 hp just like my single and they are a special mounted motor but maybe i could go bigger and adapt a base plate
    That's what a lot of folks do: get a standard NEMA 56 motor, and make a new mounting plate. You can buy a nice new USA-made 3-phase motor on Ebay for a lot less than the dealer will charge you for the OEM motor.

    would be handy to have lower than 240rpm's and maybe higher than 1550?
    You have a back-gear, right? Generally, you get useful power on a VFD/Motor at 50% above and below the rated speed.

    So for your speed range, I'd get a 1750 RPM motor, and leave the belt on the 2:1 ratio. That would give you a 875 base RPM, which the VFD could drive as high as 1312 RPM (+ 50%) and as low as 438 RPM (- 50%). For lower RPMs, you'd want to engage the backgear, and then you still get the +/- 50% RPM range.

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  • A.K. Boomer
    replied
    You make allot of sense Lazlo, I was wondering about the low end grunt and how they handle that, I did not know I can do away with a RT and stuff, nice bonus, I guess a motor could be adapted to my mill --- the only three phase they make for it is 1 1/2 hp just like my single and they are a special mounted motor but maybe i could go bigger and adapt a base plate, just kicking it around -- would be handy to have lower than 240rpm's and maybe higher than 1550? Thanx

    Leave a comment:


  • lazlo
    replied
    Originally posted by A.K. Boomer
    I can get a factory 3 phase motor it would be 1 1/2 HP, besides the cost of the motor what then would i be looking at to go VFD? PS, I dont have 3 phase at home so whould have to go static or rotary...
    An induction motor on a VFD has constant torque, but power is proportional to the base (60 Hz) frequency, so as the VFD varies the speed above or below the nominal motor speed, the power drops off. So on a VFD conversion, people usually step up the motor horsepower by 25 - 50%. So if you have a 1 1/2 HP motor on a step pulley, you'd want to go with around a 2 HP motor on a VFD conversion.

    Also, you don't need 3 phase power to run a VFD -- it does the 3-phase power conversion for you. You just need 220V power, which you can pull off of your electrical sub-panel.

    A 2 HP VFD runs between $200 and $300.

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  • A.K. Boomer
    replied
    My friends sharp is taiwan and is V/S head and has held up to many, many years (15+) of almost daily production, Hell, some of the parts you can probably make yourself,

    My mill is step pulley so I am interested in what some of you guys are saying, I can get a factory 3 phase motor it would be 1 1/2 HP, besides the cost of the motor what then would i be looking at to go VFD? PS, I dont have 3 phase at home so whould have to go static or rotary...

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  • Steve Steven
    replied
    I have a friend who is a senior machinist at the Naval Shipyard here, he is 2nd shift supervisor in the Tool section. He is strongly against the vari-speed pulley heads, he says they wear out too soon (they are used a lot there) and are noisey. He bought a step pulley head for his shop at home. I would think a 3 phase machine with a VFD would be the best to get, and about the same price.

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  • lazlo
    replied
    With the advent of modern VFD's, there's not a lot of reasons left for a mechanical vari-speed system, as long as you have a mechanical back-gear for a torque multiplier at low RPMs (like when using a large facemill or flycutter).

    I would get the step pulley machine with a VFD -- that gives you nearly infinitely variable speed via the VFD, and you'll never have to change the belts.

    The step pulleys also have more efficient power transfer: there's around a 25% power loss on the mechanical vari-speed systems, which is why the Bridgeport Vari-Speed ship with 2 HP motors, while the same mill with a Step Pulley ships with a 1 1/2 HP motor.

    I have the step-pulley/VFD setup on my Burke knee mill, and it's fantastic.

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  • Forrest Addy
    replied
    If you are concerned with parts availability in the future, buy the ones you need now. When I bought my lathe in 1971, I bought cross slide and compound nuts as spares. First thing I did is make a complete set of lead screws. That's been 36 years ago. My lathe is holding up well OHT its been babied for all that time. I Still have the nuts and the lead screws. Note to self: dig out the screws and check for rust; it was a wet winted around here.

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  • bob308
    replied
    i bought an enco vari. speed mill 10 years ago never had a problem. i hate changing the belts on step pully mills. also for most of the work i do the step pullys seam to never be the right the right rpm eithr too high or too low but never right.

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  • Nutter
    replied
    Another good story about Enco.

    I picked up a basket case Enco 10x54 VariSpeed for $200 last fall (with working X axis power feed and 2 axis DRO). The VS parts were apart and some were missing. This was a mill made in 1995 and it had the old style pulley on the motor, missing many parts. The good thing was that the spindle pulley was complete and already upgraded to the newer style with the nylon wear inserts. Enco set me up with all the parts for the upgrade on the motor pulley plus all the other small stuff that was gone for around $400. Their tech support was really good to work with and knowledgeable.

    I've sold it since, but it seemed like a decent quality machine when I was using it. I got very familiar with the vari-speed setup and I would not hesitate to buy a newer Enco VariSpeed mill. The nylon wear inserts are the only thing that will wear and they are not difficult to replace and only about $25 for a whole set.

    Also, if you have room you might as well get the machine with the 10x54 table. It fits your budget at just under $7K on sale. It's more than just a bigger table, the whole machine is more stout, weighing in at close to 3000 lbs. You can never have to much table space or too rigid of a machine

    With all that said, the mill I kept is a Gorton Mastermil with a step pulley head because it is quieter and even more rigid than the big Enco.
    Last edited by Nutter; 06-01-2007, 09:31 AM.

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