Need Help! How do I calculate max rapid speed and acceleration for my G0704 mill conversion?

# Thread: How do I calculate max rapid speed and acceleration for my G0704 mill conversion?

1. ## How do I calculate max rapid speed and acceleration for my G0704 mill conversion?

Hello,

Short story: How do I calculate and/or test out how fast a stepper can RELIABLY rapid my machine? Is there an online calculator that is trustworthy to do the calculations?

Long story: After 8 years I'm getting ready to update my CNC converted G0704. I'm going to move from Mach3 with a Ethernet SmoothStepper to Centroid Acorn. At the same time I'm thinking about swapping the steppers to get a little more speed and acceleration. I've been running all three axis at 240ipm and 10in/sec2 acceleration. The machine is very reliable milling at 80in/min but on the rare occasion it will miss steps when it tries to rapid.

I'm running KL-5056D drivers, KL-23H2100-50-4b steppers (570 in/oz) and 48V power supply. The ball screws are 16mm with a 5mm pitch. According to the test report from Automation Technologies (attached) the steppers have 2.5N of torque at 400rpm, but fall rapidly down to about .4N at 1200rpm where I'm running them during rapids.

After reading a bunch of posts on the subject I purchased a D57CM31 stepper from Leadshine. It has basically the same torque at 400rpm but it has 3x the torque at 1200rpm and more than 2x at 1800rpm compared to the KL stepper. I plan to test it out and if it provides a benefit I'll upgrade all three motors.

I've calculated that the head and table both weigh between 90-100lbs. That includes a 2hp 56 frame motor on the head and a 4" Kurt vice and workpiece on the table.

My goal is to run 360IPM on X/Y and at least 240IPM on Z.

Here are the specs for the KL steppers:
Phase: 2
Step Angle: 1.8°
Holding Torque: (570 oz-in)
Phase Current: 5 A/Phase
Voltage: 3.0 V
Resistance: 0.6 ?
Inductance: 2.5 mH
Rotor Inertia: Not listed

Here are the specs for the Leadshine steppers:
Phase: 2
Step Angle: 1.8°
Holding Torque: 3.1N.m (439 oz-in)
Phase Current: 5 A/Phase
Voltage: 2.0 V
Resistance: 0.4 ?
Inductance: 1.8 mH
Rotor Inertia: 0.84 kg-cm2 (0.01189 oz-in-sec2 )

2. ## Re: How do I calculate max rapid speed and acceleration for my G0704 mill conversion?

I found this calculator on Oriental Motor's website:
https://www.orientalmotor.com/motor-...ml#QuickReport

I used the following inputs for the Z axis:
Weight 100 lbs
Friction Coefficient .2
Screw Diameter .625"
Length 28" (this is closer to the X axis length)
Pitch .2"
Efficiency .9
Material Steel
Breakaway torque 1lb/in (Not sure that I'm in the ballpark here)
External Force 10 lbs
I skipped the gearing section since I'm running direct drive.
Mechanism Angle 90 degrees
Positioning operation
Distance 10"
Positioning time 2 seconds (300ipm)
Stopping time 0 seconds
Accel time .31 seconds (2G)
Stopping Accuracy .0005"
Safety Factor 1.5

According to this calculator I need 137.6oz/in of torque at 300ipm. That lines up with the Leadshine's torque curve so I think I should be in good shape. I'll start slow and work my way up to these numbers.

I have a couple projects to finish up on the mill before I can start playing with the steppers, but I'll report back when I do.

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