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### Author Topic: Mach3 Sherline Rotary Magic Number  (Read 7857 times)

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#### Keith

• 187
##### Mach3 Sherline Rotary Magic Number
« on: June 21, 2014, 04:04:53 PM »
I haven't used my Sherline Rotary Table in some time and since did a lot of re-installed. And I know this topic has been covered before but from what I read and apply, I can't get my rotary table to move in degrees properly.
I understand that the worm gear is a 72 turns to get 360 degrees of movement on the table top.
I believe it's doing half stepping, so 400 steps per stepper revolution (.9 degree per half step).
I don't think the velocity and acceleration numbers effect the ability to input degrees and get the table to move to the inputted degree.
I'm just forgetting the magic number in 'steps per' in motor tuning that I had and that worked before.
I'm coming up with the number 28800 but that doesn't work correctly.
So if anybody has that number that allows to put in a G01 A5 and the table goes to 5 degrees from zero, I'd appreciate it very much.
Thanks, Keith

#### Fleck

• 31
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #1 on: June 21, 2014, 04:21:53 PM »
I may be wrong but I believe steps per for angular is. Steps*microsteps*Gear Ratio/360
this is my router, there are many like it but this one is mine

#### RICH

• 7,427
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #2 on: June 22, 2014, 07:47:07 AM »
Keith,
Sample rotary table calc for 1.8 degree stepper:

- 72 handle turns per one table revolution x 200 stepper pulses per stepper rotation = 14400 pulses  per one table revolution ie; 360 degrees

- 14400 pulses x 1/360 degrees = 40 pulses per degree

If you are micro stepping say 10x.....then  10 x 40 = 400 pulses

With a .9 degree stepper------- 72 x 400 (1/360) = 80 pulses per degree, then adjust for based on your drive step setting

- Note that you should set your max velocity and accel from trial and error so it doesn't skip.

BTW, there is a calculator in Members Docs.

RICH

#### RICH

• 7,427
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #3 on: June 22, 2014, 08:10:53 AM »
Keith,
Just some more info for what it's worth as this pertains to resolution.

RESOLUTION

Resolution is just an indication of how fine the A axis system will turn the spindle per step.
Typical stepper is 1.8 degree ( 200 pulses for 1 rev ), most folks micro step ( say  a value of 10 ),
and then it is a matter of how much gear reduction takes place ( lets use 72:1 ).

Steps in one revolution= 200 motor pulses X 10 micro steps X  72 = 144000 steps per revolution
Steps in one degree = 144000steps per rev / 360 degrees per rev = 400 steps per degree
Theoretically with just a single pulse sent to the motor you would have the following:
Resolution = 1 / 400 = .0025 degrees   ( which is equal to .15 minutes = 9 seconds )
Practically speaking, due to backlash, variances in the gears / belts / motor or whatever, you will not get that kind of movement in one pulse / step.

The following is an example of different combinations:
+ -  RESOLUTION
# MOTOR   MICRO STEPS  GEAR RED  STEPS / DEGREE  DEG  =      MIN   =   SEC
1 200                -NA-                     NONE      .5555                       1.8
2 200                10                         NONE       5.555                      0.18         10.8
3 200                10                         72               400                        0.0025      0.15         9
4 200                10                         135             750                        0.00133    0.08         4.8
5 200                10                         200             1111.1                   0.0009      0.054       3.24

Here are some angular to linear relationships:

ANGLE     PER INCH      PER 3"       PER FOOT
1 SEC       .000005"        .000014"       .00006"
30 SEC     .00014"          .00044"         .0017"
1 MIN       .00029           .00087"         .0035"

Here is just one aspect of resolution to linear positioning and can be envisioned by the following example.

Lets assume that you are going to index the spindle and drill some holes out 3” from the center of the plate.
So if you were to drill a hole out from the center 3", then index 3 min, and drill another hole,
the distance you have between the holes would be approx 0.006” for no gear reduction.

RICH

#### Keith

• 187
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #4 on: June 22, 2014, 08:49:32 AM »
Thanks so much Rich. It looks like (since I'm half stepping) that my steps per=28800 is correct from what you wrote.
And so if I entered G01 A80, I should get 1 degree movement.
However, many years ago I set this up so that if I typed G01 A90, it would go to 90 degrees (from 0 degrees) and don't recall why it worked.
I do have the box checked in Mach for angular on the A-Axis I'm using.
Let me ask you, do you know do I have to do anything special with my Smoothstepper configuration that might have changed things since back when, I was using the parallel port to get the above results.
Thanks again, Keith

#### RICH

• 7,427
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #5 on: June 22, 2014, 09:06:08 AM »
Keith,
G01 A80 and you should get the table to turn 80 degrees.

----------------------------------------
There are some general config settings in Mach that you should select.

Rot 360 rollover – if checked the A axis DRO will display from 0 to 360 degrees and then start over at 0. If not checked the A axis DRO will be additive such that 2 revolutions will display as 720 degrees.

Ang Short Rot on G0 – The axis will move in the shortest possible move to a new position. So if at 0 degrees and you jogged  to 359 deg then it would just rotate  -1 degree.

Rotational Soft Limits – if checked will apply software limit switches to the rotary axis.

-----------------------------------------

I have not used my SS in a few years so don't remember if you had to do anything speacial for a rotary.

RICH

#### Keith

• 187
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #6 on: June 22, 2014, 09:34:26 AM »
Okay and thanks Rich. Well here's an example of what I get which is of course way off but if I type in G01 A.05 (that's point zero five) the table moves a bit more than 5 degrees.
Does this hint to where I've gone wrong? Again, I have the steps per at 28800 (half stepping mode, also box checked in ports and pins for Sherline half pulse mode)
-Keith

#### Keith

• 187
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #7 on: June 22, 2014, 11:25:34 AM »
So now with a little fiddling, at 28,800 steps per, G01 A.5 goes to 90 degrees, A1 goes to 180, A1.5 goes to 270, and A2 brings me to 360. Weird.
And A0 brings me back exactly to 0. How strange.-Keith

#### RICH

• 7,427
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #8 on: June 22, 2014, 05:51:16 PM »
Keith,
Your rotary table based on info you posted as follows:

Rotary table calc for .9 degree stepper:

- 72 handle turns per one table revolution x 400 stepper pulses per stepper rotation = 28800 pulses  per one table revolution ie; 360 degrees

- 28800 pulses x 1/360 degrees = 80 pulses per degree

Since you are 1/2 stepping .....  2 x 80 = 160 pulses

So your steps per unit should be 160 for the A axis.

----------------------------------------------------------------------------------

http://www.machsupport.com/forum/index.php/topic,16315.0.html
See attached pic.

---------------------------------------------------------------------------------------

Now if you wanted to, you could always use the axis calibration in Mach > Settings (ALT-6 ) tab to set the steps per unit for the A axis.
Click on Set steps per unit  button ( it's just above the Reset button) it will ask you to select the axis and how much you want it to move.
Then based on the actual DRO value displayed, you would put that number in and Mach would calculate what the steps should be. So if you accept the steps per unit will be changed.

RICH

#### Keith

• 187
##### Re: Mach3 Sherline Rotary Magic Number
« Reply #9 on: June 22, 2014, 06:02:52 PM »
Thanks Rich. I'll try that tomorrow.
However, that axis calibration intrigues me. So when the program asks: "how much to move", what unit are they asking for (in other words, knowing what you do about my setup, what part of the equation are they referring to?
Thanks for all your help. I'll get there.
160 does seem to be a very familiar number I used in the past.
-Keith