Tantillus Calculations

@ Sublime. Hey, I am new to the reprap, but i really admire your Tantillus 3D Printer, I just wanted to know how the calculations for Tantillus are done in terms of:

How is the calculation is done like how fish wire is being used with Herringbone gears, what values are we dealing with? I am not sure what values to put in!

1) Steps per millimeter X and Y

Steps = motor Steps per revolution x driver microstep ÷ belt pitch ÷ number of teeth on the pulley

The gears on X/Y are 1:1 so they are not in the equation.

They should be.

1 / ((rod_diameter*3.14159) / (motor_steps*micro_stepping)) = steps_per_mm

But that does not work out correctly when measured. My theory on this is with the cable under tension it does not stretch much around the outside so instead the cable gets compressed on the inside. This makes the actual circumference some where inside the wraps of the cable.

So if the rods are 7.92mm like mine and 0.5mm cable and you end up with 122.5 steps per mm as measured and adjusted with a set of digital calipers attached to the carriage.

We find it works out as 8.315mm drive diameter.
1/((8.315*3.14159)/3200)

And if we figure backwards:
1 / (((rod_diameter+(cable_diameter*0.79))*3.14159) / (motor_steps*micro_stepping)) = steps_per_mm

It looks like the drive diameter is rod diameter plus 40% of the cable diameter on each side of the rod:

rod_diameter+((filament_diameter*0.4)+(filament_diameter*0.4))

But even at this if your rods are not 5/16" (7.92mm) I would measure the movements and readjust the steps per mm to move the carriage exactly the requested amount.

Edited 1 time(s). Last edit at 06/10/2013 03:14PM by Sublime.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Thank you Sublime, it is all cleared now! I like your design though, its really neat!

When I use the tantillus.org calculator from here and change only these fields:

layer height: 0.25mm
nozzle: 0.4mm

The calculator gives me PLA temperature of 214C. Is that correct? Do you really print PLA that hot?

As the calculator says it is only approximate but yes some times you do need it that high. It has to do with the time the plastic stays in the hotend (dwell time) and not the actual extruded filament temperature. We also have to deal with the amount of heat the filament removes form the inside wall of the hotend as the filament goes through it. So with the medium length melt zone of a J-head we need a higher temperature setting to maintain the actual extrusion temperature of around 185c. Not all PLA is the same and if you notice it oozes a lot between parts then it may be too high. If the parts are weak then it is too low. If the melt zone was as long as the ones in a 3Dsystems commercial machine it would always be a constant temperature regardless of the volume going through the hotend.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Thanks for the info. You obviously know a lot more than I do. Really appreciate you sharing it.