Newbie- Stepper motor size needed??

[btrager1978]

What power/ oz in, stepper motor would be best for direct drive on a HF 42827 model geared head mill drill conversion.
Thanks for any help.
Joe

[Crevice Reamer]

Two questions:

1. Do you already OWN this mill, or are you just planning to buy it?

2. What do you plan to DO with it?

CR.

[btrager1978]

I already own the mill, I would like to get some light to medium production work out of it, making small airgun parts, but for the most part it will be an educational stepping stone to a better machine.
I was looking at 2 kits on ebay, one consists of 425 oz in steppers and the other 1200 oz in steppers.
it would be nice if I could get by with the 425's because of price but also dont want to spend the money if they wo'nt have what it will take.
Thanks for your time
Joe

[Crevice Reamer]

It must be said that a round column mill is a poor candidate for CNC conversion. You might be better off in the long run to buy another mill--like a Grizzly X3 or SX3.

That being said, you need to estimate the force required to turn the respective axis cranks. For example, measure the radius of the X axis wheel and multiply that times the force necessary to TURN that wheel.

Stepper motors are measured by the peak torque, which is what the motor puts out to hold it still. As RPM goes up, torque falls off rapidly until, much too soon, the motor stalls under the load.

How fast do you want the axes to move in air from one cutting point to another? (rapids) How much force will you need to exert on the work during cutting? How do you intend to wire your motors? Bipolar parallel gives higher rpm. Bipolar series gives more low speed torque. Both are more powerful than unipolar.

Even as important as oz inch ratings is the POWER SUPPLY you intend to use. A good rule of thumb is to use a power supply about 20 times larger than the motor's rated voltage. Less, means lower speed and torque. Higher voltage (within the driver limits) charges the coils quicker so gives better performance.

So, for example, if you have a 425 oz motor rated at 4 volts and drive it with a 24 Volt power supply, you will get less performance than if you used a 200 oz motor rated at 1.5 volts with the same power supply.

CR.

[btrager1978]

http://cgi.ebay.com/3-Axis-Stepper-M...QQcmdZViewItem
theres the shortcut to the item I was looking at.
I'm not going to lie I know very little about this subject but I am very interested in learning and I have to start somewhere, and This seems to be the best place to start, hopefully that link works they have the specs listed, but I dont know enough to know if they are what I need.
Im not to concerned about speed and power just need it to work well enough so that I can get a good education out of the money I might spend on it.
Thanks
Joe

[jalessi]

Joe,

The kit you are looking at will work for your mill, you might want to upgrade the power supply to this model KL-350-48 it will double the performance of the steppers for a additional $30.00 .

You can use pulleys for the X and Y axis to double the torque go with 2 to 1 reduction.

The 425 oz stepper will be more than enough for the quill on your machine.

Jeff Alessi

[Crevice Reamer]

OK. You have to start somewhere. But you are not ready to consider steppers yet. How do you intend to MOUNT them to your mill. I don't know of anybody making conversion kits for that mill, so are you ready to fabricate mounts yourself?

Back to the Keling kit: These "kits" cost almost as much as the individual components. They are a good deal pricewise, but not performance wise--As configured. But, you can mix and match as needed and upgrade the price slightly.

Keling website:

http://kelinginc.net/

In order to get the full POWER out of the 425 oz (4V * 20 = 80 V) steppers--you would have to upgrade to the $190 72 volt power supply. But THAT would exceed the driver voltage. The 48 V Power supply would work with the drivers.

You would actually get more power by substituting the 282 Oz steppers which run quite well on 24 volts.

But you haven't determined the force requirement for the mill yet. No sense making mounts for Nema 23 size motors if you actually need Nema 34 size steppers.

CR.

[btrager1978]

nt

[jalessi]

Joe,

There is a company "www.microkinetics.com" that makes a retrofit kit for your mill that uses 2-470 and 1- 350 oz stepppers and 2 to 1 pulley reduction for X and Y axis.

They charge about $4,300. for the kit.

There are several people on the CNCzone that have made the stepper mounts etc...

Take a look at these images, they will give you some ideas to start with.

The last set of images is interesting also.

http://pashupatina.com/gen2/album/

http://ivan.pashupatina.com/cnc/cnc_2/images/

http://tinyurl.com/5d6yh6

[btrager1978]

Sure the mounts wont be a problem for me.
So looks like what my next move will need to be is to estimate the force needed.
One question, that is the force required to turn the shaft at the actual shaft dia and not at the outside handwheel dia right.
Thanks for all the info it is greatly appreciated.
Joe

[btrager1978]

Thanks Jeff
I'll check it out.
Everything helps to form the final plan.
Joe

[jalessi]

Joe,

This is a good read.

http://tinyurl.com/42rdao