How is the Kg/mm (oz-in) generated by rotary?

[finsel]

I'm trying to discovery all description about my rotary. I have:
Makita GD0600
400watts
25000RPM
1/4''
____
I trying to get the final result to buy the correct SCREW.
I got this result:

CV=0,00136*RPM
CV=0,54CV

Kgf.m=(716,2*CV)/RPM
Kgf.m=0,015584512

Nm=Kgf.m*9,806
Nm=0,152821725

Kg/mm=Kgf.m*100*10
Kg/mm=15,58

This final result is correct?
With this I can match with the power force generated by my stepper motor and choice the right Screw.

Any answers would be greatly appreciated! Thank you!
Frank

[Boort]

Frank,

I'm not sure what you are asking here. I looked up the Makita GD0600 and found out that it is an AC/DC powered die grinder. Cool tool! Are you planning to use this as your cutting spindle? or to drive the screws to move your axis?
(I ask because your calculations appear to be determining the torque provided by the tool while asking if this will drive the lead screw. so I'm a bit confused.)

Regards,
BoorT

[finsel]

oh, right, sorry.

This makita is the rotary to cut the stuffs only.
I just tried to check with you guys if my calc is correct... and maybe establish some discuss for about rotary capacity, types, etc.

I tried to determine the rotary performance. And so, based in this performance we can compare with the stepper motors. Then, when we have the performance (torque) of the stepper motors it should be possible to match with the rotary torque and then determine which is the best Lead Screws to use... for that environment.

For example, choose the best Lead Screws for velocity but respecting the torque of the stepper motor and rotary... In other words, If we use a "fine" / "slow" Lead Screws, we will take more time to cut with same quality as if we use a "fast" Lead Screws...

Let me know If I explained better now.

I post other topic that explain the values is "Which Lead Screw use?"

Thank you!
Frank

[Boort]

Frank,

That makes more sense to me now. Your die grinder should have more power than a Dremel or Rotozip type tool, and your motors carry a much larger oz/in rating than mine. I think that a set of fairly coarse screws should work well for cutting out wooden parts with your 25Kg/cm motors (~347oz/in) should move plenty fast. I can reliably get about 40-45IPM with my machine but I almost never cut that fast. Doing so causes the finish on my wood parts to look very bad and adds extra sanding and finishing time to the project.
The big thing that I would worry about choosing a die grinder over a router to be a CNC spindle, would be that it would have higher runout on the bit. Runout is a measure of the out of roundness at the tip of a bit that causes a vibration which cannot be balanced. This would cause your parts or carvings to not be as exact as they could be. Weather or not this is a problem would depend on what you are planning to do with the CNC router. For example: if you are carving decorative rustic statues this would be no problem. But if you are cutting parts for model airplanes or traces on a circuit board it would be unsuitable.

Regards,
BoorT

[old man emu]

Frank,

The power of the cutting tool you use has nothing whatsoever to do with the power of the stepper motors.

Think of it this way:

If you can hold your cutting tool in your hands and don't move it, you can make it cut a hole. Now, if you want to cut a line, you have to move the cutting tool by moving your arms. If your cutting tool is very light, this movement is easy to do, but if it is very heavy, the movement will be hard to do.

Now think of your cutting tool fitted to your CNC machine. If you set the cutter to a particular spindle speed, but only have the Z-axis steppers move it up and down, it will cut a hole. The stepper motor only has to lift the weight of the cutting tool.

Then, if you have the X-axis stepper move the cutting tool, and the Z-axis assembly across the surface, the stepper has to move the combined weight, which is a bigger effort. If you haven't changed the spindle speed of the cutter, it will be doing no more work than it did in the above case.

You are not interested in the spindle speed of your cutter when you are deciding on the size of the stepper motors you need. You are interested in moving a weight over a distance as quickly as you can.

Old Man Emu