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Help with selecting pulley gear ratios for belt driven turntable


eb19db15d9d72ca1321e962048df7741?s=80&d=mm&r=g
(@charles-ross)
Member Customer
Joined: 2 years ago
Posts: 14
Topic starter  

I would like to upgrade my original slider and use more off the shelf metal components instead of printing moving parts, replacing the two 8 mm polished rods and linear bearings with extrusion and a gantry plate with rollers to carry a new rotation assembly. I plan to go with a GT2 loop belt between metal gears/pulleys.The original printed gearing has a ratio of 10:1 (100 tooth printed platter and 10 tooth stepper motor pinion.) 

Problem: I have yet to source a metal 10 tooth pinion in GT2 6 mm with a 5 mm bore. So I might have to play with ratios. I don’t usually tinker with firmware but if I’m told it’s possible to adjust the ratios in the program to keep the object tracking accurate with a change of mechanical ratios, I will do it.

Any experience with this is required and most welcome.


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350a26dd49eb55d3494500240423a207?s=80&d=mm&r=g
(@robotn1)
Member Admin
Joined: 5 years ago
Posts: 735
 

Modify the Arduino code here (configuration.h file):

// This depends on the pulley teeth and microstepping. For 20 teeth GT2 and 1/16 => 80 200*16 = 3200/(20*2mm) = 80
#define X_AXIS_STEPS_PER_UNIT 40
//Convert steps to degrees: 200 steps *16 (microstepping) * (motor reduction) / 360 degrees = 8.888
#define Y_MOTOR_REDUCTION 4 // 72/18
#define Y_AXIS_STEPS_PER_UNIT (8.88888888888*Y_MOTOR_REDUCTION) //Convert steps to degrees

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eb19db15d9d72ca1321e962048df7741?s=80&d=mm&r=g
(@charles-ross)
Member Customer
Joined: 2 years ago
Posts: 14
Topic starter  

That’s a bit too advanced for me to parse. I can’t even start to identify which numbers in the formulae are referring to the number of teeth. 
I’m not a coder but usually for the last 25 years of delving into software I can spot that sort of thing and make educated guesses on what to change for my circumstances. Not in this case.

The original model slider had the gears printed as 100:10 on the turntable. The belt (Y axis?) has a metal 20 tooth pulley. I don’t know what the current version’s components are. There are a lot of choices in metal pulleys available online. 


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