I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Clamp a torque wrench into a vice and turn?
Thanks for any possible practical insight...
Chet

In article ,
"Chet" wrote:

I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?

Lots of ways. First of all, units of torque are the product of a
tangential force and the length of the lever arm, so it is not "in/oz",
it's inches times ounces "in*oz", usually written "in-oz".

The units of torque are the same as some units of mechanical energy.
There is a rule where the order the units are given (oz-in versus in-oz)
in tells which it is, but nobody remembers or consistently uses the
rule, so one must always determine which is meant by context.

So, 131 inch-ounces of torque is 131/12= 10.92 foot-ounces, or 10.92/16=
0.68 foot-pounds of torque.

http://en.wikipedia.org/wiki/Torque


Clamp a torque wrench into a vice and turn?

That works, if you have a torque wrench that goes that low. Or, hang a
weight from a radial rod with a knob on the axle, and hold the knob to
feel the torque.


Joe Gwinn

Joseph Gwinn fired this volley in
:

So, 131 inch-ounces of torque is 131/12= 10.92 foot-ounces, or
10.92/16=
0.68 foot-pounds of torque.

http://en.wikipedia.org/wiki/Torque


Clamp a torque wrench into a vice and turn?

That works, if you have a torque wrench that goes that low. Or,
hang a
weight from a radial rod with a knob on the axle, and hold the knob
to
feel the torque.


You'll quickly notice it's relative merit in your situation, if you'll
just "hand feel" the pressure on the end of your X crank that it takes
to move the table.

For instance; because my old Cincy has a little 'belly' in the table
ways, I've got the gibs snugged up a bit more than normal. In the
belly, it's free -- the handle weight alone is enough to move the
table under a little vibration. But out near the ends, it takes maybe
two pounds on the end of the handle (about 10" long) to move.

That's roughly twice the torque a 131 in-oz feed motor would produce.

LLoyd

....
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?

For steppers, anything less than 600 oz/in is a joke. I used 2000
oz/in units on my knee mill and missed steps with big cuts and/or high
feeds.(direct drive to ball screw) I geared down 2:1 and went to 1/2
hp. servos; now i can remove some metal.

Karl

Chet wrote:

I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Clamp a torque wrench into a vice and turn?
Thanks for any possible practical insight...
Chet

It's far more complicated than that.

If you're talking about steppers, the rated torque is holding torque,
and it decreases with increasing RPM. If you're talking about servos
it's the continuous rated torque and the available torque can exceed the
rated value for short durations.

This FAQ has some good info:

http://www.geckodrive.com/faq.aspx?n=680054

Karl Townsend wrote:

For steppers, anything less than 600 oz/in is a joke.

Entirely dependent on the type and size of machine you're talking about.
For a machining center with conventional ways and heavy cutting loads
you need a very large axis drive motor, but for something like a plasma
cutter with ball bearing ways and no cutting force much smaller axis
drive motors are appropriate.

On 2009-01-28, Chet wrote:
I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Clamp a torque wrench into a vice and turn?
Thanks for any possible practical insight...

Yes, clamp a torque wrench into a vise and turn to see 131 oz/inches.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Karl Townsend wrote:
...
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?

For steppers, anything less than 600 oz/in is a joke. I used 2000
oz/in units on my knee mill and missed steps with big cuts and/or high
feeds.(direct drive to ball screw) I geared down 2:1 and went to 1/2
hp. servos; now i can remove some metal.

Karl

You have a rather large mill....
131 oz-in will move something like a Sherline or Taig
table at 10-15 inches/minute during rapids, using a microstepping
drive running at 24VDC. A 1/2 HP servo motor weighs perhaps more
than the table in this case - slight overkill, I'd say.

On Wed, 28 Jan 2009 10:12:05 -0500, "Chet"
wrote:

I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Clamp a torque wrench into a vice and turn?
Thanks for any possible practical insight...
Chet

What you ususally care about is axis thrust, and that depends on the
ballscrew pitch and any pulley ratios between the motor and ballscrew.

Axis thrust = motor torque*2*pi/(distance traveled per motor rev)

Of course, efficiency and friction will reduce this, but it will get
you in the balpark.

HTH,
STeveA

On Wed, 28 Jan 2009 15:22:09 -0500, SteveA
wrote:

On Wed, 28 Jan 2009 10:12:05 -0500, "Chet"
wrote:

I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Clamp a torque wrench into a vice and turn?
Thanks for any possible practical insight...
Chet

What you ususally care about is axis thrust, and that depends on the
ballscrew pitch and any pulley ratios between the motor and ballscrew.

Axis thrust = motor torque*2*pi/(distance traveled per motor rev)

Of course, efficiency and friction will reduce this, but it will get
you in the balpark.

HTH,
STeveA

Steppers have problems with large inertial loads that are rigidly
coupled.

Right on Pete.

I looked for data on my Servos on my 3 axis CNC plasma.

data is not easily had - copy cats ... but he servos are
physically smaller than a small coffee can and weighs 4 pounds.
They move my gantry at 1000 ips in two axis at once. I
run it around 400 ips and cut from 10 to 300 ips.

Martin

Pete C. wrote:
Karl Townsend wrote:
For steppers, anything less than 600 oz/in is a joke.

Entirely dependent on the type and size of machine you're talking about.
For a machining center with conventional ways and heavy cutting loads
you need a very large axis drive motor, but for something like a plasma
cutter with ball bearing ways and no cutting force much smaller axis
drive motors are appropriate.

Martin H. Eastburn wrote:
snip
They move my gantry at 1000 ips in two axis at once. ...

1000 ips = 83 /feet/ a /second/???

On Jan 28, 10:12*am, "Chet" wrote:
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Chet

Lift a gallon jug with one finger.

jw

Bob Engelhardt wrote:

Martin H. Eastburn wrote:
snip
They move my gantry at 1000 ips in two axis at once. ...

1000 ips = 83 /feet/ a /second/???

IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.

I'm building a small CNC plasma (24x36), close to complete now, and so
far the ~126 oz-in steppers are doing up to 400 IPM fine without much
time spent tuning and tweaking. Presumably with a bit of tweaking of the
acceleration and possibly the reduction ratio, currently 3:1 between the
stepper and the final belt drive pulley, I might be able to push it a
bit higher. Given that it's already above the normal cutting speeds and
with the small machine positioning moves aren't significant, 400 IPM is
fine.

Pete C. wrote:
IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.
...

It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.

Bob

Bob Engelhardt wrote:

Pete C. wrote:
IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.
...

It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.

Bob

Could go metric...

Pete C. wrote:
Bob Engelhardt wrote:
Pete C. wrote:
IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.
...
It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.

Bob

Could go metric...

Cubits per fortnight

On Thu, 29 Jan 2009 10:21:48 -0800, Winston
wrote:
Pete C. wrote:
Bob Engelhardt wrote:
Pete C. wrote:

IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.

It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.

Could go metric...

Cubits per fortnight

No, Furlongs per Fortnight. Gotta keep the alliteration going!!

-- Bruce --

Bruce L. Bergman wrote:
On Thu, 29 Jan 2009 10:21:48 -0800, Winston
wrote:
Pete C. wrote:
Bob Engelhardt wrote:
Pete C. wrote:

IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.

It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.

Could go metric...

Cubits per fortnight

No, Furlongs per Fortnight. Gotta keep the alliteration going!!

-- Bruce --

1,799,884,800,000 = the speed of light in furlongs per fortnight.

Bruce L. Bergman wrote:
On Thu, 29 Jan 2009 10:21:48 -0800, Winston
wrote:
Pete C. wrote:
Bob Engelhardt wrote:
Pete C. wrote:

IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.
It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.
Could go metric...
Cubits per fortnight

No, Furlongs per Fortnight. Gotta keep the alliteration going!!

-- Bruce --

Fantastic! Fortunate! I feel a foul fool.

--Winston

Yep that baby moves fast with 4 pound servos driving each axis.
Now consider my table is 4' side to side and end to end. 1.4* that
on the corner to corner move.

So it slams to the zero x and zero y micro switches before anything
can be done.

Martin

Bob Engelhardt wrote:
Martin H. Eastburn wrote:
snip
They move my gantry at 1000 ips in two axis at once. ...

1000 ips = 83 /feet/ a /second/???

Being a man of physics I used seconds.
It is minutes - 1000 in/minute. Max slew rate on my 4'x4' plasma table.
I cut 1/2" armor plate AR400F or AR500 at 10in/min and
21 ga. 7075 at 300in/min.
I could run faster on the 21 ga - but I test fate so it seems :-)

Martin

Bob Engelhardt wrote:
Pete C. wrote:
IPM, divide by 60

10-300 IPM is typical plasma cutting speeds.
...

It's funny that they would use IPM as the unit rather than IPS. IPS is
much easier to grasp intuitively. E.g., 5 IPS vs 300 IPM. 5 inches per
second I can "visualize" the velocity: think "one thousand one" &
imagine a 5" distance. 300 inches per minute I can't.

Bob

I think one method to get a measurement of a feedscrew or shaft, would be to
put a 2" diameter pulley (the 2" dimension being a surface that tough string
or small cable can be secured to and wrapped onto without overlapping), then
pulling the cable with a tension gage or pull scale, ideally something
fairly accurate (not a cheap spring pull scale).

If a lot of friction would be introduced from pulling a sideways load on the
shaft or leadscrew, the measurement will likely be higher than the actual
motor torque required if directly coupled to the motor shaft.

I wouldn't suggest this method for moving an axis while actual cutting
forces are taking place, as it might go wonky and cause injury and/or
damage.

The result would be a measurement from the 1" radius (inch) and the
measurement of the gage while pulling (ounce).

Foot-pounds would be a similar setup with a 12" lever or pulley radius and
the amount of pull in pounds.

FWIW, different sized pulleys can be used as long as a conversion for the
size takes place in the calculation.

On this list, see Measure Torque
http://www.baumhydraulics.com/pages.php?pageid=5


--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Chet" wrote in message
...
I've been toying with the idea of experimenting with some basic CNC...
The motors that are offered are rated according to oz/inches of power.
How do you develop a sense for the size you would need?
For example, just how much is 131 in/ozs of torque????
Is there a way to translate that number into some demonstrable amount?
Clamp a torque wrench into a vice and turn?
Thanks for any possible practical insight...
Chet

"Martin H. Eastburn" wrote:

Yep that baby moves fast with 4 pound servos driving each axis.
Now consider my table is 4' side to side and end to end. 1.4* that
on the corner to corner move.

So it slams to the zero x and zero y micro switches before anything
can be done.

Big machines have decel switches an inch or two out from the home
switches, so it can rapid in and then decel to safely find home even if
the axis isn't referenced.

Opinions appear to have tapered off, and I'd like to thank everyone who
offered their insights!

Chet

Chet, you can return the favors so-to-speak by keeping us informed of your
progress with your projects.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Chet" wrote in message
et...
Opinions appear to have tapered off, and I'd like to thank everyone who
offered their insights!

Chet