What's new
What's new

Vari speed to VFD

adama

Diamond
Joined
Dec 28, 2004
Location
uk
Well finally had enough, had a vibration i just can't get rid off. have rebuilt my vari speed head about every 3-4 years now and its just had a couple of issues this year and thats it, tonight is its first night as no longer a vari-speed mill at least via reeves pulleys. The heat the vari speed use to generate made long runs in the summer miserable too. Im a very small shop to say the least.

Had some great luck and managed to score a truly lovely German 1.5Kw 90l iron framed 3 phase motor, final job of the reeves drive was to drill and tap the face of said motor to let me mount it to the plate i had laser cut last month.

Then Friday suddenly a gap in the work opens, despite having a lot of the bits too hand, i was not ready just yet, but today was a window as is Monday and Tuesday to get it done. I had the VFD drive, the speed control pot and the motor. Managed to also scrounge up some lovely L series timing pulleys and had ordered a belt to suit. Yeah one of the pulleys had the wrong size taper lock, £5.50 on ebay sorted that issue. Gear ratio is a fixed 0.75 and with a 1400RPm motor that gives me a nominal 1000RPM ish spindle speed, Vfd will happily drop that down and i had previously tested the motor upto 300hz, reality i will only run it upto 150hz for now on the mill, that will give me a top speed of circa 3Krpm, which is fine, i never really used the vari speed above 2.2krpm any how do to noise and im mostly milling steel or harder so loss of top ends no real concern.

Took a few goes to get belt alignment just right and it probably wants a nats more tension, squealed like hell being a new belt, but a quick squirt of silicone spray instantly solved that.

Temp hook up of VFD and she purrs, yeah motor fan is a issue at full wack, but she will have the shaft fan removed and a nice 6" powered fan made to fit should really reduce the noise. Vibration is gone at long last.

Hence its onto the control side, gutted the electrical cabinet, everything bar the isolation switch is out. New 12V supply to feed a good low voltage work light is in, VFD is in, New DIN rail is in for coolant relays. Temporary hook up to existing switches is wired, that will change though, but the switches are on a slow boat from china and hence will be a couple of weeks and i have holes to drill come Wednesday! Got a new Digital Tach that will replace the old speed dial on the head giving a real readout of spindle speed in high range, low range i will have to divide by 8 in my head.

Got the correct cable and glands to get tomorrow, then the final proper wire up of the power side and im back in business. Its just going to be nice not to have the uncertainty of things going wrong with parts i just can't easily and quickly get anymore.
 
Been most the day messing with things and wiring things up, Bijur is now powered through armored cable, VFD to motor is also in shielded armored cable. Invertec Optidrive E3 inverter is now nicely mounted in the OEM control box common on the side of the colounm of the mill as is common over here with all Bridgeport textron mills of the circa 1980 time frame.

Parameters on P15 is set to 11, so as to work with the Knee mounted momentary buttons for now, P17, bumped the switching frequency up to 16Khz and thats got rid of the annoying VFD buzz along with doing a stationary auto tune.

So far i have only drilled a few holes but what a diffrence, the stupid vibrations are gone, the noise whilst diffrent is but a fraction of the vari speed belt squeal. Outside the garage theres no audible noise now, the old single phase (cap start cap run) motor had a low frequency rumble that really transmitted through the solid brick wall (think washing machine like).

The original 50V AC work lights gone, now has a IP67 flood style LED 12V pond style head on it which gives a lovely wide flood of the work table and no flicker at all.

Future plans are to upgrade the controls to a box on the head, will have the tach readout, spindle controls and coolant controls all at eye level. No more bending down to work the too low controls on the knee. Cable and control box for that should be here later this week, Have also added what i can of the wiring for a foot pedal control for power tapping, this will be setup just like my lathe, switch the controls into reverse and the spindle runs backwards, press the pedal it switches to forwards and you can power tap away, lift your foot spindle reverses and out the tap comes, its one of the beauties of a VFD drive and its cheaper to go this way than a tapmatic which over here for a genuine one is now a multi hundred £££ item.

The motor fan will also be removed and replaced with a separately powered permanently on 12V cooling fan in a custom cowelling. Will help ensure a constant cooling air supply and also let me realy bump the motor speed with out sticking way too much power into the stock cooling fans which tend to get real power hogs and noisy at above 2 pole motor speeds.

Just wish i had gone this root 15 years ago when i got her, but back then funds were tight and i had nothing like the knowledge of drives i now do.
 
Well Just a update, power wise it seams plenty, not dropped it into low speed at all since the change, hence everything has been done in high speed and just the 0.75 pulley reduction. Drilled 1/2" holes in steel just fine, lots of boring and some power tapping upto M8 and no stalls at all. Also done so low speed face milling of Hardox 450 and with my 2.5" face mill even that showed no signs of bogging things down.

Was concerned that the 1.5Kw of motor would have been lacking, but its turned out to be just great in practice. Hence if your contemplating a retrofit to VFD, no need to go more than a real 2Hp industrial motor, yeah that may be the same as a consumer grade 5hp tread mill or similar motor but a real 2hp seams a good fit to the original 2hp motor and the VFD or at least the one im using seams to do well enough keeping the torque high enough the loss of the vari pulley reduction is not turned it into the gutless wonder i feared it may have become at lower speeds. Certainly torque wise it has not been at all lacking so far and i have gone lower than what the vari speed turned all the way down in high would get speed wise.

Motor has not even got warm as yet either, shaft mounted fan is not proveing a issue.

The smooth vibration free power seams to have given a noticeable improvement in finish both milling and especially when boring holes.

Of cause if you geared it high to suit more top speed - alu type work this may change, But its probably fair to say at least based on what i have so far found, going 1:1 spindle to motor would still be very acceptable. Hope that helps someone make a better descion from the start than i did some 18+ years back when i got the single phase motor and made that work.
 
Maybe I'm a little slow, but I've read through this several times and don't see a mention of what machine you're doing this on. Since there aren't any pictures, if I was a newby, I'd be lost. Somebody doing a search and looking for infor wouldn't find this. Just saying!
JR
 
Nicely timed post adama.

My Bridgeport 2J2 Varispeed head has picked up vibration and a mildly scary low speed setting rattle from the Varidrive area. Wasn't looking forward to mechanical rectification. Doing it once about 10 years back was quite enough "fun" for one lifetime! Reverse engineering the formed in place varidrive bushes being less than amusing. A year or two younger and it would have had simple plain glue in ones. Sigh!

Most of the makings in stock. Big drawerful of pulleys so should be something close enough once I dig out some info on shaft sizes. Also a nice Siemens VFD in stock, got when I first thought about getting something better than a single machine rated rotary converter. But one of those whole shop plug'n play VFDs from Drives Direct appeared at a better than good price avoiding any need to dig into wiring. Hafta say it works a treat.

Hopefully the stock 1.5 HP motor will be powerful enough for what I do.

Clive
 
Sorry yes its your bog std 2hp constant 3hp peak varispeed bridgeport head. Mines a 1986 ish if memory serves bridgeport textron uk made machine.

Front vari drive pulley shaft is 35mm od but mines the newer one with the glued in pulley sleeves Clive so may be different if i remember correctly that shaft - motor shaft diameters are different between the 1.5 and 2hp heads??? Stripped all the vari speed top pulley off and put the 1" wide L series taper lock timing pulley about a 1/4" up from the fixed vari drive pulley - all in one spindle brake drum. just gotta split the head caseing to do it, so its not hard, just a disassemble and reassemble.

Don't know what to advise about the original motor, my mill when i got it had a rewound motor on it with no low voltage tappings and questionable bearings back then i was not as VFD savy and equally only 440V windings made that far from easy option wise. Hence i replaced it with a single phase 2hp twin capacitor motor with a custom shaft extension to take the vari speed pulley setup off the original motor, that bit had a lot of care put into it and a lot of trial and error static then running balancing to get it smooth as in zero feel able vibration.

Never realy could trace were the vibration in mine came from, it did vari with speed, but whilst a new belt and new glued in pulley sleeves helped, it just was never nice. Now its lovely and smooth.

Various numbers i found online seamed to recon that a vari drive sheave arrangement typically consumes about 1/3rd the power transmitted through it in friction, seams a bit excessive, but the alu part of the head use to get hot to bloody hot to the touch on a long run, now it noticeably does not! Not sure your 1/2 less hp will be much of a issue in typical use if you tune the drive properly.
 
Gear ratio is a fixed 0.75 and with a 1400RPm motor that gives me a nominal 1000RPM ish spindle speed, Vfd will happily drop that down and i had previously tested the motor upto 300hz, reality i will only run it upto 150hz for now on the mill, that will give me a top speed of circa 3Krpm, which is fine,

1K nominal and over 3K top speed. I could live with that for over 90% of what I do. I understand that. There are a lot of people that have really grown to hate the BP vari-drive system. I've never had a problme with the BP, it's my Clausing that is a PITA.
JR
 
Thinking about this last night after the meds kick in.

Why hasn't somebody come up with an "electronic drive" kit for 2J heads? I'm thinking double serpentine belts would handle the horsepower. A good, VFD rated motor, a VFD, and a control panel. Should be able to do it all for less than $1K USD. A couple of well balanced drive pullies and a spring or gas tensioner would be so quiet. You've got the Hi/Low range so the speed selection would be about the same. Or, you could offer a high or low speed version. Put a nice digital read out on the panel so when the hobiest calculates his RPM to 962.5, he could set it exactly.

OK, there's the money making idea. You heard it first right here. This is just like my Z drive for the drill that I gave away and people are now selling.
JR
 
Why would you want to limit to 1k rpm?

Not limited to 1K, just torque optimized to that lower speed range. AC induction motors are pretty constant hp devices above there rated speed. Bellow there rated speed tourque drops off. At 500 spindle rpm i effectively have only 1hp of power being delivered (its a bit better than that do to drive magic, but not vastly so) At 2Krpm is still have my full 2 hp, but have electronically geared the tourque in half to double the speed. Obviously again there's losses with higher speeds on even a VFD rated motor. Hence with a VFD you want to ideally aim to gear it to give the sweet spot torque wise - base frequency speed were your using it most - need it for me that's 1k rpm with what im cutting 90% of the time (think milling steel and drilling around the 1/2" range) My products are just not made from aluminum its as simple as that.

Well actually i probably would have bought pulleys - aimed for base motor speed to give me more like 800RPM but the pulleys were free minus the one - correct taper lock adapter and like most things, theory gets you so far, having a real world bench mark - Just try it gets a far better solid proven idea of things.

Various threads in the past have made mention to needing 3 or 5hp motors and matching drives, this whole post is about the fact that you realy don't need that kinda power level and a real industrial 2hp - 1.5Kw seams to work well, which is a lot easier for most people to setup as at least in most of europe - places outside a std 3 phase supply much over this and your into larger power leads and also far greater drive costs. Equally much bigger weight than a 90L motor frame size and your rely pushing your luck with those head tilt gears.
 
JR theres a company in the US offering a complete head upgrade for bridgeports, VFD and a far more robust feed gear setup i believe, forget the name and don't have it bookmarked, but cost is well and truly up there (5K ish rings a bell). I believe they offer a lot more than 2hp too.

Not sure i see the point in more than 2hp as i have always found my bridgeport and any others i have run rigidity wise to struggle with just the 2hp, though maybe at higher spindle speeds in alu were there's no greater torque thats not a issue and you can use it?
 
Uh just a update, for the first time since the swap i had to drill and ream some 16mm aka 5/8" holes in mild steel. Previously to get the needed spindle speed would have dropped it into the higher end of back gear. Cobalt HSS stub/screw length drill in a ER32 collet. just slowed it down to a visually about right speed (gotta fit the final controls + tach read out to her still been busy) Fully expecting to simply stall out the motor.

Well regardless of how hard i lent on it i could not get it to bog at all in high speed. Think i probably need to gear things up a little higher, theres no reason this should not have been a back gear job. This also massively outperforms the torque delivered at such low speed compared to the Siemens G110 1.5Kw drive and motor combo on my lathe. The opti drives sensor-less vector clear is doing its job!

Hence when time allows, i think im going to probably jump the gear ratio back to either 1:1 or maybe go a smidgen more. Hell maybe try reversing what i have so base speed becomes more like 1.8Krpm, this would reduce the motor - fan - noise at the speeds im normally running at which would help as less noise means i can use it later with out disturbing anyone.
 
JR and Adama the company is All Machine down in Tennessee. We have done multiple of their systems on mills, mostly the Series II heads.

Servo also makes one as well.

Jon
H&W Machine Repair
 
^ What did you think of them? The pics look good as does the specs on there WWW, but do they make sense - are worth the cost when your hands on with them?
 
So we have installed more of the kits on the 4HP head and then did one on a rigid ram BP (an old Boss retrofit). The installation was easy and I like the other All Machine stuff (we install ALOT of the Maxi-Torque Rite power drawbars) however we dont operate them except to ensure that they function before we send them out. So TBH, I can't give any insite into them except for how easy they are to install and how we don't have any complaints from the ones we install.

I have never installed or seen one of the Servo ones. I think their basic version has a better price point than the All Machine one, but again, I cant talk about how well they operate or install.

Re-reading that, I totally sound like a politician lol

Jon
H&W Machine Repair
 
Thinking about this last night after the meds kick in.

Why hasn't somebody come up with an "electronic drive" kit for 2J heads? I'm thinking double serpentine belts would handle the horsepower. A good, VFD rated motor, a VFD, and a control panel. Should be able to do it all for less than $1K USD. A couple of well balanced drive pullies and a spring or gas tensioner would be so quiet. You've got the Hi/Low range so the speed selection would be about the same. Or, you could offer a high or low speed version. Put a nice digital read out on the panel so when the hobiest calculates his RPM to 962.5, he could set it exactly.

OK, there's the money making idea. You heard it first right here. This is just like my Z drive for the drill that I gave away and people are now selling.
JR

Home - All Machine Parts, Inc. :rolleyes5: :D :cool:
 
OK, finally had a chance to look at that site.
1. Single V belt ~ not serpentine
2. No read-out for speed, just load meter.
3. No price. Why do the site and not have "Starting at $995"
4. They don't say if they have any Marines working (or putting in their time) there.
JR
 
@JR lol most people dont wanna brag about having devil dogs doing all the leg work. Most people cant handle that much awesomeness. :D

We sell them for $2,395 (the ones that are "3hp" motors that fit on most knee mills). You do bring up an interesting point, I dont know if they have an encoder or something on the spindle for RPM. I think it just translates what the inverter tells it.

Jon
 








 
Back
Top