I have been researching various ways to add a variable speed spindle motor to the Taig mill, both the manual version and the CNC mill. One of the drawbacks to the mill is having to change the belt ratio and the difficulty of keeping it aligned properly.

I looked into various 56C frame motors to replace the existing motor in the stock location but came back to the fact that we would still be left with a huge motor hanging off the side of the machine, and likely the same hassle with belt alignment.

My research did reveal the ideal types of motors to use so I went looking for a manufacturer of small but powerful, 1/4 HP continuous rated DC motors. I know folks have tried all sort of surplus motors from treadmill motors to golf cart motors but always run into problems as they are not built for continuous duty as a spindle motor. Well, not only did I find some nice motors made in the USA, I found some that were small enough to be mounted behind the spindle! They could also be mounted very close to the lathe spindle for a nice small, neat arrangement.

So, we would need maybe only two belt ranges at most (0-5000, and 5000-10000) and could have a completely variable speed control either manually or with a 0-10V signal. The motor would tuck behind the spindle instead of being cantilevered off the side.

The upside and downside is that these are custom made motors. In small quantities it would cost way too much to be a viable option. I would like to be able to offer a complete retrofit kit for the Taig mill for around $250, of course motors would be available separately too. If there is enough interest in such a kit I'll move forward with getting some prototype motors made up for testing. It would likely take 8-12 weeks to get them through prototype and have the first production motors.

Here is the deal. If your interested in such a kit please let me know. Getting a bunch of these motors made up is a huge investment so I want to ask you all about your level of interest. Anyone that expresses interest ahead of time will get a really good discount, I'm not looking to make a bunch on these but I would like to cover the cost of getting the motors made. So if your interested just let me know that you would be interested in a mill kit, a lathe kit (designed after mill kit is done) or just a motor.

I would like to have computer control of the RPM on my mill. If you haven't seen, I'm in the process of replacing the Taig motor with a Keling servo motor. I've been dragging my feet (to say the least) but a couple days ago I finally got around to wiring it up. I'd say it looks pretty promising, but I haven't actually used it for any real milling yet.

So, count me in as "interested" but not "confirmed to buy".

Being able to mount the motor behind the spindle would be nice for sure! Using a USA made motor that is rated for constant duty would be nice too.

I know very little about motors so I have a couple questions...
Lets say I tell the spindle to spin at 4500 RPM and start machining. If the end mill hits a tough patch will the motor somehow increase the juice to put more power to the spindle or is it likely to stall?
I get the impression with a servo in this scenario the driver will give as much power to the motor as possible to keep it spinning at the speed it's suppose to.

Also, if the servo gets stalled the driver can send a signal to the BOB to tell the computer to stop too. I'm guessing a tachometer would have to be installed to get a similar "e-stop" signal from a regular DC motor, is this right?

Can the motors you've found be used like servo motors? In addition to the above a servo would be able to stop quickly, spin in reverse, and it would also know the position of the bit.
Stopping quickly would be a good safety feature. I'd hate to need to hit the e-stop button only to have to wait a couple more seconds as the spindle spins down.
I don't know if the Taig mill is capable of tapping, but if it is: it seems like being able to turn in reverse and knowing the position of the bit would be very important.

Well I had almost a whole response typed up and the power went out

Basically a servo motor is any motor with feedback to an active controller. The controller uses the feedback (encoder, resolver, tach) to control the position/velocity/torque of the motor. Some type of motors work better than others for this and the design is usually optimized for use as a servo motor.

Servo motors are also not usually rated to constantly deliver 100% of their rated power. So using one as a spindle motor would require careful selection.

The DC motors I'm having made will have double shafts so a tech or encoder can be mounted. I was thinking of this primarily for using a tach with a DC speed controller. Doing so will give you speed regulation to +-1% and provide about 90% of the utility of a servo type spindle motor (on a mill, a CNC lathe could really benefit from a servo type spindle.) A DC speed control will also work on a manual mill but a servo control would not.

After I considered it a bit I realized that the difference between the two comes down to a bit more expense for a servo controller and a power supply. (The DC speed control hooks directly to the main voltage.) So it would certainly be a possibility.

If there is interest in a servo version I'll look into offering that as an option as we could use the same motor.

Jeff,

for $250, I don't think that's too bad at all to get a complete package that you could end up with a Mach 3 controlled spindle and a tach reference in Mach 3 as well.

I would definitely be interested in such a package as long as the moter was not larger/taller than the original Bluffton gray motor.

Dave

Hello Jeff,

Sounds like a good idea.

I'd be interested in a motor and probably the conversion for a mill, assuming the DC motor isn't larger or heavier than my existing AC gray motor.

Regards,

Chuck Kuhn

Any word on this setup, Jeff?

Dave

I'm finishing the design of a new 4-axis drive box/kit at the moment. The variable speed kit is next on the list. I already started making a mock-up of the motor so I can work on the bracketry while awaiting the first prototype motors.

Thanks, Jeff-

Dave

Jeff,

Please put my name on the list as a purchaser for the kit. Will this include a controller or just the equipment to mount the motor?

Rick

It will include the speed control as well. You will need a way to generate the 0-10V input control signal from Mach. The G540, some BOBs etc will give you the correct signal from Mach.

Jeff, I'm interested in just the motor. I've been looking for a small motor to replace the kind of bulky treadmill unit I use now. Can you tell us the diameter and length of the one you have in mind?

Thanks,

Dean

Are there any updates on this? After I couldn't get my spindle motor to spin as fast as it should (a couple months ago) I pretty much stopped using my machine all together. I guess it was just too much of a letdown.

I'm going to try a SmoothStepper with it, if it doesn't solve my problem I will probably start chomping at the bit for something like what you're proposing.

Jeff,

How is the it going with the kits/motors? Do you have any idea when they will be available?

Rick

Sorry Rick. This project has taken a lot longer than I planned. I have an update in a few weeks.

Now I know Its Crude, but I have seen one of the 4th axis steppers set up in a plate with a electrical dimmer switch next to it, between these was a rubber drive belt and both had similar v-groove pullies on them, this allowed the operator to control this 4th axis stepper and by calibrating it control the voltage (AC) going to the Drive motor, I realize this would not give the best control but thought it was innovative use of the "spare" stepper motor he had and since he did not use 4 axis machining it worked well for him. He tended to cut lighter things so I guess a reduction in motor power that I assume would come from using a dimmer type switch was a acceptable trade-off.




But I am interested in what Jeff is building!

Hi guys,

I have been working on the variable speed kit slowly but surely. This summer was a tough one personally and that has no doubt had some effect on my progress. I also recently finished up and released a 4-axis drive system.

One thing I want to try and do was to be able to design the motor mount so that the spindle motor was centered behind the spindle, that way if someone just wanted a better motor mount they could just get that part. While a standard 56C frame size motor can be mounted that way, the Taig pulleys just take up too much room. So, the variable speed kit motor mount will not be usable with the stock motor/pulleys. With the variable speed motor two pulley selections would be plenty though.

In a few weeks I'll have the mount done and be starting some testing.

Jeff,

Are the motors available now for use on the lathe?

Rick Kernell