[Jdavis733]

I have a Leadwell 3 axis mill at work, with a 21-M control, that is making rapid moves slow.

When I checked the parameters, rapid is set at 1000inch/m, however the machine will only do 394 inch / m

It's almost as if the mill is running in metric mode, in which case the parameter value of 10000 is in 0.1MM/ min.

The machine is clearly in inch mode, which makes the problem something new for me.

Anyone else have this issue with 21-M control, or know whats up?

I could just set parameters to 25400, but I would really like to know whats going on. 15 years fanuc experience and this is a new one for me

[Dan Fritz]

If your machine has metric ballscrews, then it's a metric machine, and many of the parameters will be set to metric values. Most machines have metric ballscrews, and just use inch/metric conversion in the control to run in "inch mode".

I don't have a 21i parameter manual in front of me, but read the description of that parameter closely. It may be set to 10000 mm/min because that's the maximum speed of the servos on this machine.

Of course, you could always look at the Leadwell sales brochure. That would give you the manufacturer's number for rapid traverse.

[Jdavis733]

All other parameters related to "inch machine" are valid, only max feeds seem to be defaulting to metric.

Unit of input is set to inch.

CMR is set to "2"

So if it is a metric machine, I don't see what parameter determines this?


*1002 INM set to 1 (inch system)
1004 ISA, ISC set 0,0 IS-B

[Fabio1]

Sure sounds like parameter is a metric setting.394=1000.7mm.Would think u have to up the parameter(P1420 I think) for each axis to a higher setting.Did u get a error or is the rapid just n ot goin g fast enough?

[cnc2149]

Leadwell is an Asian machine with metric screws. Par 1001.0 needs to be set = 0 for metric feedback units. If you have the Inch/Metric switching option, then you can set par 0001.2 (INI) = 1 to allow inch programming.


If par 1001 is set to inch, you should also have a positioning problem in addition to the unexpected rate.

[sinha_nsit]

A ballscrew is a ballscrew!
It can have any pitch which we design.
What exactly is a metric ballscrew?

The answer to this question may answer my another question in a different thread:
"What is the difference between least input increment and least command increment"?

[dcoupar]

A ballscrew is a ballscrew!
It can have any pitch which we design.
What exactly is a metric ballscrew?

The answer to this question may answer my another question in a different thread:
"What is the difference between least input increment and least command increment"?

And a Socket Head Cap Screw is a Socket Head Cap Screw. But you can buy inch sizes and metric sizes, just as you can with ballscrews.

Thompson makes 2" ballscrews with a 0.500 inch lead.
NSK makes 50mm ballscrews with a 10mm lead.

[dcoupar]

All other parameters related to "inch machine" are valid, only max feeds seem to be defaulting to metric.

Unit of input is set to inch.

CMR is set to "2"

So if it is a metric machine, I don't see what parameter determines this?


*1002 INM set to 1 (inch system)
1004 ISA, ISC set 0,0 IS-B

According to the 21M-B manual, parameter 1001 bit 0 is INM
0 = MM
1 = INCH

1420 is the rapid rate for each axis:

1000 is 1000 MM/min or 394 IPM

I believe 394 IPM is as fast as your machine is going to rapid.

[sinha_nsit]

Ok, Ok! Cool down! Let me understand.
"Thompson makes 2" ballscrews with a 0.500 inch lead. NSK makes 50mm ballscrews with a 10mm lead".
Are these the only standard sizes, or other sizes also used?

I now have a feeling that the control (Fanuc) assumes either 2''/.5" or 50mm/10mm depending on a parameter. Ballscrew of no other size can be used. am I correct?

Typically, how much angular movement of the ballscrew is caused by a single electrical pulse? It has to be dependent on several factors including gear ratio. I want to know typical minimum and maximum values.

I am fighting to understand what a least command increment is, and how is it different from least input increment.

[dcoupar]

Ok, Ok! Cool down! Let me understand.
"Thompson makes 2" ballscrews with a 0.500 inch lead. NSK makes 50mm ballscrews with a 10mm lead".
Are these the only standard sizes, or other sizes also used?

I now have a feeling that the control (Fanuc) assumes either 2''/.5" or 50mm/10mm depending on a parameter. Ballscrew of no other size can be used. am I correct?

Typically, how much angular movement of the ballscrew is caused by a single electrical pulse? It has to be dependent on several factors including gear ratio. I want to know typical minimum and maximum values.

I am fighting to understand what a least command increment is, and how is it different from least input increment.

No, Thompson makes ballscrews of many diameters and leads (as does NSK).

Fanuc doesn't "assume" anything; the MTB sets parameters based on ballscrew lead, motor speed, encoder pulses, etc. when the machine is assembled.

YCM, for example uses 40MM dia. x 20MM lead ballscrews on it's XV1020A X and Y axes, but 40MM dia. x 12MM lead ballscrews on the Z axis. X and Y rapids are set to 36,000MM/min, and Z rapid is 24,000MM/Minute.

Least input increment is the smallest value you can program (input). This can be set to metric input or inch input in the settings page, bit 2 of parameter 0000, or by programming a G20 or G21 at the head of the program.

Least command increment is the smallest increment the machine will move (output). This is set (on most newer Fanuc's) in parameter 1001 bit 0 (INM).

[sinha_nsit]

Ok.
But, how can these two be different?
If I command an increment of 0.001 mm, the machine has to move by 0.001 mm, whether it is inch machine or metric machine (ballscrew).
Or, am I not able to pose my question properly?

[angelw]

Ok.
But, how can these two be different?
If I command an increment of 0.001 mm, the machine has to move by 0.001 mm, whether it is inch machine or metric machine (ballscrew).
Or, am I not able to pose my question properly?

Sinha,
Bit 0 and 1 of 1004 is used to set the least input increment and least command increment in systems A, B and C.
Bit 7 when set to 1, indicates that the least input increment for each axis is set to a value 10 times as large as the least command increment specified in increment systems B and C for mm settings. Accordingly, when bit 7 is set to 1, and the least input increment is set to 0.01 mm, the least command increment will be 0.001mm.

Regards,

Bill

[sinha_nsit]

Ok.
Still there can be a difference between what you explain and what I interpret.
So, check my statements:

Based on type of leadscrew (metric/inch) and its size (pitch), the MTB designs the machine in such a manner (mechanical parts as well as required electrical signals) that the minimum slide movement would be exactly 0.001 mm or 0.0001 inch in increment system B. If we select increment system C, the control would change the electrical signals such that the minimum slide movement is 0.0001 mm or 0.00001 inch. The minimum slide movement requires a large number of electrical pulses to ensure positioning accuracy in both inch and metric modes.

G20/G21 actually changes the electrical signal such that the minimum movement is 0.001 mm or 0.0001 inch in IS-B, since 0.001 mm is not same as 0.0001 inch.

The minimum movement described above is least command increment.

We can choose to have the same value for least input increment, or ten times this value. But this is possible only on metric machine (why?). On inch machine, least input increment is always same as least command increment.

It is still not clear the significance of 1001#0 (INM). This parameter should be used and set by MTB only, and is a part of design. How can a user change it?

[sinha_nsit]

Too many questions go unanswered. So, just one question:

It is still not clear the significance of 1001#0 (INM). This parameter should be used and set by MTB only, and is a part of design. How can a user change it?

[sinha_nsit]

The answer is, the user should not change it unless he wants to spoil the machine.