Dan and Gary,
To answer both of your inquiries, I think I will need to explain the design
intent a bit and why/how I came to the layout of the machine as it is:
• The machine will be mainly used for cutting aluminum
• I definitely wanted to go with servos. That brings the rpm range to about 3000 to 4000 rpms
• I wanted the linear drive as compact as possible and didn't want protruding motors
• The 1204 screw size seemed to offer the highest resolution with a 4mm lead
• Per Teknic's engineers, a 48" long 1204 screw is limited to about 800 rpm
• A speed of about 500 ipm seemed sufficient for the size of machine
• A 1204 sized rotating ball nut requires a 40 tooth pulley, fitting within the width of a Nema 23 motor
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So, the 1204 sized PowerBallNut with a 40 tooth pulley was designed:
Attachment 419054
The servo motor also has a 40 tooth pulley, fitting within its width:
Attachment 419056
Result is a narrow mounting plate which fits between the brace and the end of gantry beam:
The selection of the servo was based on max rpm, available torque at 1000 rpm for cutting, size and cost: