Lots counting errors at using the DDCSV with MPG

enjoy_cnc

DAMIGO Posted at 2018-2-27 19:30
Hi ytliu,

thank you very much for your detailed explainations.  I appreciate you effort to solve  ...

Hello DAMIGO!

I am one of the DDCSV controller technical support engineers and I am happy to respond to your questions.

You said the handwheel problem I did not reproduce here;

Can you upload the parameter picture?
I follow the parameters you set to test under.

Please upload the following parameters to me via photo or text:

[Motor Parameters]
34 X axis pulse equivalency =?
35 Y axis pulse equivalency =?
36 Z axis pulse equivalency =?
38 A axis pulse equivalency =?

[MPG parameters]
428 =?
429 =?
430 =?
431 =?
432 =?
434 =?
448 =?

Thank you!

enjoy_cnc

Lukasz Posted at 2018-2-28 03:23
Hello CNC fans,

Today I have conneced MPG to my DDCSV2.1 and I noticed a simillar behaviour as desc ...

Dear DAMIGO  , Dear LuKasz,

The following controller parameters are used as analysis conditions:

[Motor Parameters]
34 X axis pulse equivalency = 640,00
35 Y axis pulse equivalency = 640,00
36 Z axis pulse equivalency = 640,00
38 A axis pulse equivalency = 640,00

[MPG parameters]
428 = Enable
429 = Low
430 = Standard
431 = 0.010
432 = Low
434 = Low
448 = Open

Hand-held box
Axis Select the X axis
Magnification x1



  A: ___ | ----- | ___
   B: _____ | ----- | ____

1tick = 4 unit

1 unit = 0.01 / 4 = 0.0025 mm = 640 * 0.0025 mm = 1.6 pulses

1tick = 1.6 * 4 = 6.4 pulses

1tick can not issue 6.4 pulses, can only send 6 or 7;




                         init             1tick            1tick               1tick                 1tick           .......
    
REL unit              0                4                  4                    4                     4              .......

ABS unit             0                4                   8                   12                    16           .......

ABS Pulse out     0            4 * 1.6≈6       8 * 1.6≈13      12 * 1.6≈19      16 * 1.6≈26        ........
   
ABS pos show   0.000      0.009 (6/640)   0.020 (6/640)   0.029 (19/640)   0.040 (26/640)   ........

REL pos             0.00        0.009                0.011              0.009                 0.011             ........


   

As can be seen from the table above, the maximum deviation after shaking the handwheel will not exceed (1p = 0.0015625mm), which is determined by the drive and screw precision;

Coordinate display is the real-time display of the current actual location, if 0.009 mandatory display 0.010, this is not appropriate;

Due to the limitation of the shaking speed of the handwheel within the software, when the handwheel is shaken at the limit and the handwheel is lost,

Suggest the following:

When you are far from the target position, you can choose x10 or x100 gear, and the manual speed parameters increase, even the normal speed of the hand wheel can also allow the machine to achieve rapid movement effect;
When close to the target position, you can choose x1 gear to slow precise positioning;


Do not recommend the following:

Hand wheel in the x1 file, and fast speed handwheel used to achieve rapid movement effect This is an unconventional approach;



The following G code and the above hand wheel analysis principle is the same;

G90 G54

G01 X0
G01 X0.01 (show 0.009)
G01 X0.02 (show 0.020)
G01 X0.03 (show 0.029)
G01 X0.04 ​​(show 0.040)

M30


When the pulse equivalent is 80 or other values, it can also be analyzed according to the above table.

I hope my answer will make everyone satisfied!

Kind regards

enjoy_cnc

DAMIGO Posted at 2018-3-1 03:43
Dear all,

thank you for the analysing and trying to sort out the problem, we come to the

Dear DAMIGO,

Thank you for your DDCSV product support.


According to your machine XYZ pulse equivalent X: 80 Y: 80 Z: 200 can be obtained
The accuracy of control commands for each axis is:

X: 0.0125 mm / p
Y: 0.0125 mm / p
Z: 0.005 mm / p


Hand wheel control software design principles as analyzed above 14 # as,

Each tick of the handwheel will be incremented and decremented by 0.8 (0.01 * 80) pulses,
Since 0.8 is not an integer, each pulse issued after the rounding operation will have errors;
But the overall error will not exceed 0.0125mm after the handwheel finally stops;


The minimum accuracy is 0.0125mm, then the precise control of each step 0.01mm is impossible to achieve!


There is a minimum precision of 4 decimal places, the display accuracy is 3 decimal places,
So the third decimal point display in the floating-point to string casting accuracy loss, resulting in the phenomenon of 0.013 or 0.012, is a normal phenomenon;

The purpose of the software is such that the MPG can shake 100 or 500 ticks continuously, then the machine movement distance will be 100 * 0.01 mm, 500 * 0.01 mm; to achieve precise control;

It can also be designed such that the MPG accuracy unit is pulse, for example, 1 puse. This design accurately increments or decrements the MPG by 0.0125 mm for each shake; and the forward and reverse displays are very accurate.


If you want to precisely control and unify the control accuracy of all axes, you can follow the following method.


A known:
Z 0.005 mm
XY 0.0125 mm

It is recommended that the MPG accuracy be set to 0.025 (2 pulse) 0.05 (4 pulse). . . .

Z axis:
   0.025 / 0.005 = 5 step

    0.05 / 0.005 = 10 steps

The MPG can also be set to 0.0125, but the number of steps in the Z axis is 0.0125 / 0.005 = 2.5 steps. It is not an integer;


Accuracy of the above handwheel (0.0125 * n) can be accurately displayed under the handwheel operation, and the increment and decrement of each tick are the same;

Because the movement of 0.0125 * n (n> 1) corresponding to the XYZ issued pulse is an integer;


Kind regards!