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Rostock delta robot firmware

Posted by fma 
fma
Rostock delta robot firmware
June 19, 2012 01:13AM
Hi,

I started to build the very nice Rostock Delta robot 3D printer:

[forums.reprap.org]
[www.thingiverse.com]

and I'm now having a look at the firmware.

Johann, could you explain a little bit what are the main modifications you made in the Marlin firmware?

I would like to use the repetier firmware, as is has very nice features, and the author is ok to add such modifications in the original firmware if we can get something working.

Thanks,


Frédéric
Re: Rostock delta robot firmware
June 29, 2012 01:07AM
My modifications to the Marlin firmware are here:
[github.com]

First I improved the G28 (home all axes) command:
1. Move all three carriages up until each hits the top endstop microswitch.
2. Now we know that the end effector is exactly centered at the top.
3. Move the end effector down and touch each of the three bottom endstops.
4. Use each bottom endstop to calibrate the zero position of that motor.
5. All top and bottom endstops are adjustable with M3 screws on the moving parts.

Then I changed the G1 prepare_move() function in Marlin.pde to do the following:
1. Estimate how many linear steps should be done for this line.
2. Divide the line into many very small linear segments (less than 1 mm each).
3. Calculate delta coordinates and speed for each segment.
4. Add each segment to the path planning buffer.
5. If the path planning buffer is full, wait until the next segment has been executed.
Re: Rostock delta robot firmware
July 24, 2012 03:24PM
Hi,

I'm pretty new, so excuse me for my noob question..

1. we just upload one of the 3 modified marlin pde's into the mega right? Which one is best to use?
2. is this the correct process?: stl file gets converted to g codes then fed through ramps and the arduino uses marlin to translate the gcodes to physical movement of the printer?
3. do i still need motor driver hardware with ramps 1.4?

I was afraid to build my own 3d printer just because of the daunting number of parts from the mendel. but this setup seems easy to build.

Edited 1 time(s). Last edit at 07/24/2012 03:38PM by heyarn.
Johann,
I want to build a larger Rostock, and am having trouble finding information about how to size the different components--ie. the arm length vs the vertical height, the ratio of the arm length to the radius of the vertical rods to center, etc.

How do you size the parts for different size builds?

I saw that the arm lengths can be set in the firmware, but how do you calculate them for a given size work area initially?
I'm looking at a 20-1/4" dia circle instead of the original approx 9" dia circle, just to give you an idea.

Many dimensions may work--if so, are there rules of thumb to get the scaling right?

If you just double the length of arms and add to the height and double the radius from support arms to center, then do you have to double the size of the center platform? that would not seem to be desirable in all cases.

Another question, some commercial designs use 4 arms instead of three (Quattro for example).
If cost is not an object, what do you gain by adding the 4th arm?
Stability?
Flatness of build?
more accurate positioning?
less vibration?

Carrying that further, what if you make it 5 or 6 arms? what would you gain?
I'm sure it could be carried to extremes and generate more complexity with reducing gains.

smitchel@bnin.net

Do you know of any technical papers that might answer the questions I am asking?
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