Need advice for Bridgeport M head VFD

[techymechy]

I own a Hardinge TM milling machine and I recently purchased a Bridgeport M head for it. I have an older Allen Bradley 240V VFD on the main machine motor and it works OK. The VFD usable frequency range is from 0-120Hz and it supports a potentiometer, works well with the machines FWD/REV switch and fit's nicely into the electrical box on the lower right-hand-side. It also has a torque boost for the lower RPM's, which works fine.
I think I have my frequency range limited from 20-100 Hz. The AB conducted a lot of noise to the 240V main. I tapped off of 1 leg of my 240V so I would have 2 duplex 120V sockets on the side of the machine. My Servo X axis power feed is plugged into this box. The noise from the VFD caused my Servo feed control not to work. I had to put a line filter for the 240 V single phase going into the VFD.

I'd like to have a separate 120V VFD for my Bridgeport Head and set up the same as the Hardinge motor. I was thinking of using the original FWD/REV switch as a control and mount a small box adjacent for the potentiometer control. I'll have to mount the VFD externally to the cabinet and would like to have it run on 120V.



I see that the supply of VFD's is fairly limited now. I'm also just a hobbyist and this won't be used very hard and really don't need all of the bells and whistles that come on these things now.

What brand, model and size of VFD would you suggest for my M head? Do you have a suggestion on where to buy one? I'm torn if I should try to get a used VFD on eBay. Do you have suggestions on a good used VFD? I need to make sure that the VFD is fairly quiet so it doesn't feed back into my Servo X axis power feed again!

Thanks,

Dave

 

[DaveKamp]

I know it doesn't directly answer your question, but MY recommendation, and this is based totally on personal experience, is that regardless of 'hobbyist' status, the best move, is to remove the "M" head, and either find the Hardinge vertical milling adapter, or put on a Bridgeport "J" head.

You didn't identify your Allen-Bradley's type or model (1305? 1336S?) but the VFD's conducted noise backwards into the line is usually going to be quenched by applying an input inductor as identified in the A-B manual... but that doesn't assure that whatever is 'getting into' your servo axis is actually going to be resolved... typically, the problem is terminations and sheilding, proximity and switching frequency. Keeping the leads between the VFD and motor is absolutely necessary, as they're antennas for the VFD's HF switching 'noise'.

 

[techymechy]

Hi Dave,

Thanks for the reply.

I have the Hardinge vertical head and it is quite nice. It uses a 4C collet and it has a 3/4” max size collet. The main issue with the head is that it doesn’t have a quill.

In my opinion, the M head is a better fit for this mill. A J head would be too big. The mill only has a 2” overarm and weighs about 900 lbs. I think a J head is too much for the machine and it M head is better suited.

I used a 5 pole filter that decreased the conducted noise from the VFD to the mains power over 30dB. I don’t know what caused the noise in the first place. I was careful with my connectors, etc.

My AB VFD is an older unit: 160S-AA04NSF1. It seems to work fine. I have it running at 7kHz frequency.

Do you have a suggestion for a cost effective VFD that would work well with the M head motor?

Dave P

 

[jim rozen]

You solved the problem for the main spindle motor on the UM, why not simply connect the M head motor to that same VFD? This is how I did it when I swapped between my UM motor and the M head.

 

[techymechy]

Hi Jim,

Thanks for the reply. I was told that one doesn't want to add a switch between the VFD and the motor. Can you take a picture of how you did this? I think I'm missing the obvious.

I use the original FWD/OFF/Rev switch on the machine. My High/Low speed switch is not used. I wonder if I could use this to switch between the motor on the mill and the M head motor? Potentially add a 230V plug to the cabinet that I plug my M head into. This would allow me to remove the head when I want to run the horizontal set up or if I want to run the Hardinge vertical head. Then use a switch to flip between the VFD output to either the Mill motor or the plug? I can't see why that wouldn't work, but I remember reading where one shouldn't share a VFD between different motors.

 

[mksj]

Doesn't pay to share one VFD between two machines when the cost has come down, you need a VFD with dual motor paramters and the ability to switch everything between motors. A bit unclear if you want to run off of 120VAC or 240VAC. Boost voltage VFDD's are common up to 1 Hp (Teco, L510-101-H1-U 1 HP, 115 Volts, 1 Phase, IP 20) is under $200 and 166 in stock. You would need to call on the other two (Fuji FRN0005C2S-6U, Hitachi WJ200-007MF). They all work fine for mills with a basic setup, but do not plan on using a GFCI, as they will almost always trip. Do not use old switch gear used for higher voltages to switch low level signaling to the VFD, the signal voltage are only a few mA and I have often seen erratic signal conduction with any type of switch gear used for higher voltages due to contact resistance. On the mill, I prefer, and find it safer to use 3 wire control, basically momentary switches for the run/stop, and a sustained for reverse. Some VFD's also have 3 wire control for either direction (Invertek), in either case you do not need to stop the VFD to switch directions. Older motors do not do well running them hard, at low or high Hz relative to the base speed, and I like to keep the carrier frequency a bit lower. So figure maybe 30-75Hz, and with only a 1/2 Hp motor you are quite limited. I assume you have a pulley drive, if you have a Reeves drive then leave the VFD at 60Hz and adjust the speed by the mechanical drive.

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VFD, 1hp, 4.2A, 115VAC, Single Phase Input, 230VAC, 3 Phase Output, Compact Micro Drive, Easy To Use, Optional NEMA 1 Kit: NEMA1-C2-205 and Optional DIN Rail Mounting Adapter: RMA-C1-2.2 Available to Order Separately

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VFD, 1hp, 120V, Single Phase, Sensorless Vector, I

VFD, 1hp, 120V, Single Phase, Sensorless Vector, IP20, High Starting Torque

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[jim rozen]

Mine was switched by changing plugs between the receptacle. The UM motor is 3/4 hp, the M head motor about the same, right?

 

[DaveKamp]

M-heads are usually only 1/2 or 3/4hp, only belt reduction, no backgear, no power downfeed. The weakest part of it's original configuration, is that to get maximum reduction, one has to run the smallest motor sheave and largest spindle sheave, which means you have very little tractive surface on the motor side, and that's where power limitation starts (belt slip on the smallest radius). At least with a VFD, one can use the greatest-belt-traction position (middle-middle) and dial the frequency down to get a slower speed, but the lack of backgear really limits the M-head to very soft metals, wood, and plastic. What one COULD do (and I have), is remove the step-belt arrangement, and fit in a toothed-belt drive system with a fair reduction (3:1) so that the TE limitation of belt surface leaves the equation... it also allows lower belt tension, so less overhanging load on the motor and spindle bearings.

The other M-head limitation, is the spindle taper. Mine was #2 Morse with drawbar, but more often they have a B&S or other similar 'small' taper... so collet choices can be a bit challenging.

All my VFDs are older, secondhand pull-outs, most are Allen-Bradley 1305 or 1336 drives. Larger than any moderns, and they're probably older than your 160S.

VFDs at this application size don't 'like' to run multiple motors much, but some have the ability to have multiple motor 'personalities' as noted above. What you do NOT want to do, is disconnect the VFD from a load, or connect additional load, while the VFD is running. As noted by another above, using a corded plug is one way to accomplish it, and while it's not 'pro', it does work, and will be safe if done responsibly.

 

[techymechy]

Howdy,

Thanks for the advice. The M head motor is 1/2 HP and the UM motor is 3/4 HP. The Allen Bradley VFD currently used for the UM motor is 1 HP. I currently have the original switches being used as a 2 wire control for the UM motor (FWD/OFF/REV) and a Allen Bradley Potentiometer being used to control the speed. This is actually working quite well. The switches that Hardinge used for this mill are excellent quality as is the AB Pot.

In order to open the power cabinet, all power is disabled at the heater disconnect. I think that adding a 3 pole/double throw on-on switch on the inside of the cabinet down stream of the VFD will allow me to use one VFD for both motors. It will insure that power would be off to the VFD before I could switch between the motors. I will then add a box on the outside of the cabinet that has a 230V/4wire socket so I could plug in my M head to the socket. I want a plug so it is easy to remove the head if I decide to run the mill in the horizontal orientation. One concern is the Full Load Amperage of the 3/4 HP motor is more than the Full Load Amperage of the 1/2 HP motor. The M head motor Full Load Amperage is 1.9A. The FLA for the 3/4 HP motor is 2.8A. This is a setting in the AB VFD parameters. I believe that it is more of a concern to protect the VFD rather than the motor but I'm not sure. I can't see myself stalling out a motor though.

I could purchase a new VFD for the unit that has dual motor parameters. I'm not too sure how important the Full Load Amperage parameter is though. I am currently running the frequency range between 20-100 HZ, but I rarely am below 30 Hz or above 90 Hz. I certainly won't be running this mill for extended periods of time.

Do you think that I need to get a new VFD that has multiple set up's for the two motors?

Dave

 

[mksj]

Do you think that I need to get a new VFD that has multiple set up's for the two motors?

Dave

I see no reason to use one VFD for two different motors, and have to switch everything between motors. As I mentioned, at the end of the day it is a real PTA, vs walking up to one machine, turning it on and doing what you want. In some case say a H/V mill with two separate motors that would one would operate only one at a time in the same machine, then it may be warranted. As I indicated, I do not care how well made the switch is, once the contacts have passed current, they do not work well then using them for low voltage/low current applications. I had quite a few people have intermittent contact issues using there mill F/S/R switch for operating the VFD contacts after they were already crispy from previous years of switching the motor. My perspective is do not cut corners, do it right the first time.

 

[techymechy]

Hi MKSJ,

It's good to hear from you and thanks for responding to my thread.

You are exactly correct - this is a horizontal/vertical machine with two motors and I won't ever be running them at the same time. The disadvantage of getting two VFD's is to find a place for them on the machine that is clean and secure and then having two set's of controls. Having two VFD's, a DRO, and my power axis feed will get really busy. I don't have room in the electrical cabinet for two VFD's. I really don't think the effort to unscrew the two bolts to get inside the cabinet and flip a switch is that big of an inconvenience relative to taking the Bridgeport head apart and removing it from the machine. I believe that the Bridgeport M head weighs in excess of 100-120 lbs and I can't safely manhandle it (by myself) in one piece when mounting and dismounting from the machine. When I split the head and motor, I can manhandle the pieces individually. I really should make a simple gantry crane, but that is for another day.

I expect that I'll run the Bridgeport head on my machine 95+% of the time. Horizontal milling has it's place, but almost all of it can be done on a vertical machine with a few exceptions (but I'm still rather new to this and I could be wrong).

I haven't had *any* issues with using the switches on my machine though.

Dave

 

[jim rozen]

I re-did an M head, never used it much. The UM gets run a lot with end mills in the collet.

 

[Greg Menke]

Plenty of toggle switches to select either motor, just dont flip.it while the motor.is running. Perhaps mounted in a conveniently located box. I power the shaper and j head motor with a single vfd that way.

 

[techymechy]

I just bought most of the parts to get my Bridgeport head running. The Hardinge TM has an electrical cabinet on the lower right-hand side. I have the VFD in the cabinet. I’ll mount the ON-ON switch on the three phase end of the VFD and run the wires to the mill. This way I can use the same controls for both motors.

There is a interlock on the electrical cabinet so if I get to the switch, power will be off. I think that this is the safest way to do this.

Jim, do you mean you use end mills in the 5C spindle collets or in the Hardinge vertical head collets?

 

[jim rozen]

Right in the horizontal's 5C spindle. Horizontal machine is the same as a vertical, you just have to think sideways a bit. =)

 

[techymechy]

Hi Jim,

I’ll have to give this a try. I really like this mill.

I tried to IM you but I don’t think that you rea my messages.

 

[jim rozen]

hardly ever use PM feature here. Only issue if you really push an endmill hard in a 5C, it can suck out of the collet. Tighten them hard and keep your eye on the stick-out.

 

[DaveKamp]

I'll second Greg's opinion- with the motor sizes you're running here, as long as you don't switch between the two while running, it should be fine.

The FLA params in the A-B are with regards to MOTOR PROTECTION... which means, the smaller motor won't have overload protection. Considering the size of the motors, and the loading limitations you're gonna be facing, there's no significant loading that won't give you plenty of obvious feedback (if the belt is even capable of bringing enough load to the motor).

For handling the head install/removal, fabricate a swinging bracket that will allow you to disengage the head physically from the face of the mill, and swing it around back, like the 90 degree adapter setup that MAHO and others use... and include a socket IN that bracket that will accept a pivoting jib arm suitable for picking up your milling vises, divider head, workpieces, etc. from your rolling tooling and transport table. Some use a cheap harbor Freight electric hoist, but a hand-op, or hoist made from a garage-door opener, bicycle derailleur, and junk cordless drill will work, too.

 

[techymechy]

I just got my M head powered up on my Hardinge Milling machine.

I am using the AB VFD that I originally set up to power the Hardinge motor. I used an ON/ON switch right off the VFD to either switch to the Hardinge motor or to the M head motor. This way, I can use the same controls and VFD for either motor. I placed the ON/ON switch in the cabinet so I will have to shut down all power to the mill (it is a safety interlock) before switching between motors.

I have included some pictures:

1. The mill with the M head functional. I raised the mill about 5 inches and it's a lot easier to work on.
2. Using the Hardings FWD/OFF/REV switch to control both motors
3. An AB potentiometer to control motor speed, located on the belt access panel
4. SHCS with a tapered end to align and locate the overarm bar
5. The AB VFD, ON/ON switch, and filter (on top of the VFD used to minimize noise back into my AC)
6. Wiring of the Harding Switches for FWD/OFF/REV and using the switches to wire the motor in the high speed configuration. Note the wires going to the external boxes.
7. External boxes: One for power on the mill and the other is the M Head drop cord.

This seems to work pretty well. I have my VFD operating between 30 and 90 Hz. The M head is quite a bit noisier than the Hardinge motor/belt drives but this could be due to the M head being right by my head. I think most of the noise is coming from the sheaves/belt. The motor seems quiet enough and the spindle bearing seem fine.

Thanks all who gave advice on this activity.

Dave

 

[jim rozen]

Nice. As you can tell now the major disadvange of the M head/UM combination is lack of daylight between the tool and the part. Par for the course, you learn to live with it. You'll need to tram the head in no matter what, even with that keyway in there. It will get you close though! Much of the rattle noise from the M head (if that's what you're hearing) is from the splines, many of them are pretty worn over the years.