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Tension, backlash, and drive force on carriage

Dial indicator for backlash
Digital Scale for force
Tension of belt using torque wrench

Drywall screws

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Wiring First

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Belt Tension

The less tension, the easier it is to move the carriage, but, you will have more backlash. The more tension, the more resistance there is due to mechanical friction on motor bearings, idler bearings. We want to find ideal tension which minimized backlash while not producing a lot of friction.

Use tensiometer or use digital scale
Move carriage all way to side
Measure force required to deflect belt by one inch at the mid point of exposed belt

Pull on the upper belt
Pull at mid point between motor and carriage

Carriage on one side

Cable Tensiometer

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Backlash Measurement

The tighter the belt, the less backlash. But, the tighter the belt, the more mechanical friction. Find a balance between minimum friction and minimum backlash.

Backlash

Friction

Declare a cutoff point for tension

Point where second derivative of slope is zero?

Use dial indicator
Place it against carriage
Move 0.1 mm in one direction
Record reading
Move 0.1 mm in opposite direction
Record reading
Do same for 1 mm motion

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Drive Force Measurement

Determine theoretical value of drive force, and operate at ½ of that, while ensuring that backlash is acceptable.

*340 oz in = 21 lb in
*0.752 pitch diameter pulley 9 mm HTD 3 mm pitch
0.376 radius
55 lb theoretical pull
Guess: 25 lb max friction
Backlash requirement 1/32” at max or 800 microns

For 3D printer - want about 100 micron backlash at the high end

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New Carriage Design

New Belt Tensioner

Moving Belt

Belt Tension 1

Belt Tension 2

Concept - turn belt with a screw after capturing belt in slit of screw

Bushing holder