Re: Offsets in configuration (again) 8-)

Quote
wretan
My goal is making the (heated) build plate approx 300mm in diameter and total height of 700-800mm (haven´t really decided yet).

The bigger the horizontal size of a printed part the bigger problem with warping especialy with ABS.

Quote
wretan
I have looked a little bit on the Marlin firmware and what difference does the Delta_smooth_rod_offset and the Delta_carriage_offset do? Especially when I make a new linear bearing design... Isn´t the three other offsets (Delta_diagonal_rod, Delta_effector_offset and Delta_radius) relative the centerline the only important measures?

At the end, the only important thing is delta_radius and it is computed like this:

#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)

If you would define delta_radius manually to a number then you can ignore the offsets used for its computation.
They are measured from center of ball links, rods, platform. See e.g. this: [trains.socha.com]

Quote
wretan
And the last configuration about "Effective X/Y positions of the three vertical towers"? What should I use here? As I will CAD my frame I could of course use the theoretical distance/angle. But on the Marlins original setting the first row says: #define SIN_60 0.8660254037844386. What is this, and other values of positions, calculated from?

Effective tower positions are only for math model to compute delta coordinates from cartesian ones. Tower positions are calculated from DELTA_RADIUS.
I hope you are joking with the question about SIN_60 meaning? Of course it represents value for sin(60). If you do now know what sin() means, maybe you should find somebody who will do the firmware setup for you.

Quote
wretan
I have attached a picture and Isn´t the position of the red line there relative to the centerline of the machine the most interesting?

It is. But at least in the original rostock it is harder to measure so it gets more complicated with carriage_offset and platform_offset and smooth_rod_offset.

Quote
wretan
Does the distance between the ball heads between two rods (yellow line in attached picture) make any difference? I suppose that it doesnt as long as they are the same both on the carriage and printer head :)

The distance does not really matter (though it must be the same on carriages and platform (pritner head)) but the bigger it is the less the printer is sensitive to precision of the diagonal rod length. So you want it as big as it is confortable (i.e. does not colide with anything else) and to not too ugly visually.

Quote
wretan
I have checked the kossel frame calculator to get a rough length of the diagonal rods for my build but why should the rod lenght always x 0.8 of the horisontal openbeam? I suppose that longer rods also will work for example 0.9 or 1?

The rod length does not really matter. You can use whatever value you like if it is bigger than delta_radius and smaller than the height of your towers. A god default for diagonal rod length is just two times the DELTA_RADIUS.