[SOLVED] servo motor pulse time calculation doubt

[raman00084]

i am moving a lathe x and z bed using servo motor. my servo motor drive accepts step and direction pulses

i need a formula to calculate my pulse time according to the feed rate

assume for 1mm bed movement i am giving 300 pulses to servo drive ( square pulses )

case1:


my feed rate is 1 mm per second (that is in 1 second it must cover 1 mm movement) so the pulse time will be 3.33 ms ( (1/300)*100)

case2:

my feed rate is 2 mm per second ( that is 1 second it must cover 2 mm movement) so the pulse time will be decrease to 1.665 ms

case3:

my feed rate is .5mm per second ( that is 1 second it must cover .5mm movement) so the pulse time will increase 6.66ms

and so on the value of feed rate will change according to the job

i need a formula to calculate the pulse time corresponding to my feed rate setting

kindly help


regards
kalyan

 

[BradtheRad]

From the figures you give:

Pulse time = .00333 / feed rate

(Feed rate is in mm/sec.)

 

[raman00084]

can you tell me how you got .00333 value

 

[doraemon]

Hello!

can you tell me how you got .00333 value

This is pure elementary school math.

300 pulses move your bed (or anything else) by 1 mm.

I suppose you agree that the feed rate will be proportional to the pulse rate, right?

If you want 1mm/s, then enter a square pulse at 300 Hz.
If you want 2mm/s then double the frequency of the pulses (therefore half the period).

Therefore, if you want a feed rate of F (mm/s), then you should enter a frequency of
300 * F.

I suppose you can finish the calculation.

Dora.

 

[BradtheRad]

You observed that pulse time goes up, as feed rate goes down.

This means you can't use a simple multiplication factor. Instead you divide something into something.

I had a suspicion it had something to do with your 3.33 mSec being related to 1 unit (namely mm).
I moved values above and below each other. I rearranged them to the left or right of an equals sign.

I checked whether it resulted in the correct answers for case 1, 2, and 3.

Finally the correct equation emerged.

 

[doraemon]

Hello!

You observed that pulse time goes up, as feed rate goes down.

Yes, that's why I wrote that the feed RATE is proportional to the pulse RATE.

Dora.