Typical values needed to calculate cnc drive train mechanics

[rogerjames]

Please help,

-- I'm reposting this here. I think I posted it to a dead thread earlier --

I need some guidance regarding realistic feed rates, accelerations, cutting forces etc. for stepper motor sizing calculations.

I'm also hoping someone can give me a reality check on the results of my initial calculations.

** Seeking typical values for the following **
-What is a realistic rapid rate
-Typical cutting rate for router in ¾ mdf
-Typical cutting rates for 60watt & 100watt lasers cutting cotton fabric (bed sheet weight)
-Typical cutting rate for plasma torch cutting 16 gage steel.
-What are realistic accelerations for the weights indicated below?

** The machine **
The machine will be a multi-purpose XYZ table. Initially, it will direct the beam from a 60-100 watt CO2 laser for cutting cotton fabric. Down the road, it will also do plasma cutting and light router work.

** Controls being used **
Gecko G203V stepper drivers
PDMX-122 breakout board
Mach 3 software

** General parameters **
Gantry weight: 70 lbs
Cross slide weight 30lbs
Table size: 4’x 8’
Motor resolution 1.8 degrees per full step
Motor resolution .18 degrees per microstep
Desired linear resolution of .001”
The X & & will be driven by belt. The Z will be ball screw.

** my attempt at the drive calculations **
Assuming 1.194 pitch diameter final linear drive pulleys for both axis, the necessary ratio between the motor and final drive shafts should be 1.875 to 1 to get the desired linear motion per micro step

I calculate that, at this ratio, the driver will need to receive 16,666.7 pulses per second to run at the rapid rate of 1000ipm while the motor will be turning at 500rpm.

Both the X and Y axis are linear belt driven with reduction between motor and final drive. I have not gotten to the z – axis calculations yet.

The x axis which will move the gantry has the following specs:
Mass to move: 70lbs
Motor pulley: 1.194” Pitch Diameter
Intermediate pulley: 2.387 Pitch Diameter
Final linear drive pulley: 1.194” Pitch Diameter
This axis needs 432 oz – in of torque to accelerate at 2 G’s

The Y axis which will move the cross slide has the following specs:
Mass to move: 30lbs
Motor pulley: .637” Pitch Diameter
Intermediate pulley: 1.273” Pitch Diameter
Final linear drive pulley: 1.194” Pitch Diameter
This axis needs 198 oz – in of torque to accelerate at 2 G’s

How close am I?

Thanks in advance!

Roger