When using a linear rail, there's no (that I know of) graceful way to
control the slide position.  The carriage can be positioned off the
rail at either end.  There's also no model for a dual carriage rail.

using the function limit, the following functions can be built. Note
that these functions take into account the carriage type.

A single carriage rail needs limit1:

function limit1(len, slide_position, carriage = MGN12H_carriage) =
limit(len - limit(slide_position,0,len-1*carriage[1]), 0,
len)-len/2-carriage[1]/2 ;

where len is the slide length.

The carriage cannot be positioned beyond the ends, and the carriage
length is taken into account.

If the position is less than zero, then zero is used.  If position is
greater than the slide length, then the slide is positioned to the end.

a dual carriage needs to take into account both slides and the
distance between them.

function limit2(len, slide_position, carriage = MGN12H_carriage,
separation = 1) =
limit(len -
limit(slide_position,0,len-2*carriage[1]-separation/2), 0,
len)-len/2-carriage[1]/2 ;

len is the slide length, the separation is the distance between the
two slides.

// ************************* single carriage calling example

// single carriage

// ypos is processed here.  xpos is passed to a cross slide (dual
carriage)

module left_top_rail(ypos = 0, length = 550, slide = 500, xpos = 0)
{

 // allow reassignment, slide is total permissible travel of

carriage (ex: 500 mm slide, real travel is less)

 y1pos = limit1(slide, ypos);


 difference()
 {
     union()
     {
         color("DeepSkyBlue") translate([0.0 *

extrusion_width(E2040),0 *
extrusion_width(E2040),0*extrusion_width(E2040)])
rotate([0,0,0])Erail(E2040,length);

      // standard implementation of slide, where slide is as

above, y1pos is processed value

         translate([slide/2 + (length-slide)/2

,0,1*extrusion_width(E2040)])rotate([0,0,180])
rail_assembly(MGN12H_carriage,slide, y1pos);

     // these are fixed to slide and move with carriage position
         translate([25 +slide/2 - y1pos,0,35])
         {
             belt_clamp_assembly(1);
             translate([0,0,11.9]) cross_clamp();
             translate([-0,-107,14.0]) rotate([0,0,90]) x_rail(xpos);
         }
     }
     union()
     {
     }
 }

}

// ************************* dual carriage calling example

module x_rail(xpos = 0, length = 700, slide = 500)
{
x1pos = limit2 (slide, xpos, MGN12H_carriage, 20);

   translate([slide/2 + (length-slide)/2 +40

,0,1*extrusion_width(E2020)])rotate([0,0,180])
// carriage, length, position, separation
rail_assembly2(MGN12H_carriage,slide, x1pos, 10);
}

// ************************* code to add

// copied from nopSCADlib
function limit(x, min, max) = max(min(x, max), min);

// single slide limit
// given a linear slide of len, and a slide position from 0 to len
(maximum extent)
// keep slide from going below 0, and beyond end of rail. Compensate
for carriage length.

function limit1(len, slide_position, carriage = MGN12H_carriage,
separation = 0) =
limit(len - limit(slide_position,0,len-1*carriage[1]), 0,
len)-len/2-carriage[1]/2 ;

// dual slide limit
// given a linear slide of len, and a slide position from 0 to len
(maximum extent)
// keep slide pair from going below 0, and beyond end of rail.
Compensate for carriage length and
// space between carriages.

function limit2(len, slide_position, carriage = MGN12H_carriage,
separation = 1) =
limit(len -
limit(slide_position,0,len-2*carriage[1]-separation/2), 0,
len)-len/2-carriage[1]/2 ;

// does dual carriage linear rail
// same as rail_assembly, but
// parameters are carriage, length, position (as standard) but also
add separation (default = 1)
// change limit parameters to add carriage and separation

module rail_assembly2(carriage, length, pos = 0, separation = 1,
carriage_end_colour = grey(20), carriage_wiper_colour = grey(20))
{
//! Rail and carriage assembly
rail(carriage_rail(carriage), length);

 translate([(pos - (carriage[1] + separation)), 0])
     carriage(carriage, carriage_end_colour, carriage_wiper_colour);

 translate([pos, 0])
     carriage(carriage, carriage_end_colour, carriage_wiper_colour);

}

Hope this proves useful:  I'd like to see it added to the rails.scad
library.

Harvey

OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

When using a linear rail, there's no (that I know of) graceful way
to control the slide position. The carriage can be positioned off
the rail at either end. There's also no model for a dual carriage rail.

using the function limit, the following functions can be built. Note
that these functions take into account the carriage type.

A single carriage rail needs limit1:

function limit1(len, slide_position, carriage = MGN12H_carriage) =
    limit(len - limit(slide_position,0,len-1*carriage[1]), 0,
len)-len/2-carriage[1]/2 ;

where len is the slide length.

The carriage cannot be positioned beyond the ends, and the carriage
length is taken into account.

If the position is less than zero, then zero is used.  If position
is greater than the slide length, then the slide is positioned to
the end.

a dual carriage needs to take into account both slides and the
distance between them.

function limit2(len, slide_position, carriage = MGN12H_carriage,
separation = 1) =
    limit(len -
limit(slide_position,0,len-2*carriage[1]-separation/2), 0,
len)-len/2-carriage[1]/2 ;

len is the slide length, the separation is the distance between the
two slides.

// ************************* single carriage calling example

// single carriage

// ypos is processed here.  xpos is passed to a cross slide (dual
carriage)

module left_top_rail(ypos = 0, length = 550, slide = 500, xpos = 0)
{

    // allow reassignment, slide is total permissible travel of
carriage (ex: 500 mm slide, real travel is less)

    y1pos = limit1(slide, ypos);

    difference()
    {
        union()
        {
            color("DeepSkyBlue") translate([0.0 *
extrusion_width(E2040),0 *
extrusion_width(E2040),0*extrusion_width(E2040)])
                    rotate([0,0,0])Erail(E2040,length);

         // standard implementation of slide, where slide is as
above, y1pos is processed value

            translate([slide/2 + (length-slide)/2
,0,1*extrusion_width(E2040)])rotate([0,0,180])
                rail_assembly(MGN12H_carriage,slide, y1pos);

        // these are fixed to slide and move with carriage position
            translate([25 +slide/2 - y1pos,0,35])
            {
                belt_clamp_assembly(1);
                translate([0,0,11.9]) cross_clamp();
                translate([-0,-107,14.0]) rotate([0,0,90])
x_rail(xpos);
            }
        }
        union()
        {
        }
    }

}

// ************************* dual carriage calling example

module x_rail(xpos = 0, length = 700, slide = 500)
{
    x1pos = limit2 (slide, xpos, MGN12H_carriage, 20);

      translate([slide/2 + (length-slide)/2 +40
,0,1*extrusion_width(E2020)])rotate([0,0,180])
      // carriage, length, position, separation
      rail_assembly2(MGN12H_carriage,slide, x1pos, 10);
}

// ************************* code to add

// copied from nopSCADlib
function limit(x, min, max) = max(min(x, max), min);

// single slide limit
// given a linear slide of len, and a slide position from 0 to len
(maximum extent)
// keep slide from going below 0, and beyond end of rail. Compensate
for carriage length.

function limit1(len, slide_position, carriage = MGN12H_carriage,
separation = 0) =
    limit(len - limit(slide_position,0,len-1*carriage[1]), 0,
len)-len/2-carriage[1]/2 ;

// dual slide limit
// given a linear slide of len, and a slide position from 0 to len
(maximum extent)
// keep slide pair from going below 0, and beyond end of rail.
Compensate for carriage length and
// space between carriages.

function limit2(len, slide_position, carriage = MGN12H_carriage,
separation = 1) =
    limit(len -
limit(slide_position,0,len-2*carriage[1]-separation/2), 0,
len)-len/2-carriage[1]/2 ;

// does dual carriage linear rail
// same as rail_assembly, but
// parameters are carriage, length, position (as standard) but also
add separation (default = 1)
// change limit parameters to add carriage and separation

module rail_assembly2(carriage, length, pos = 0, separation = 1,
carriage_end_colour = grey(20), carriage_wiper_colour = grey(20))
{
    //! Rail and carriage assembly
    rail(carriage_rail(carriage), length);

    translate([(pos - (carriage[1] + separation)), 0])
        carriage(carriage, carriage_end_colour, carriage_wiper_colour);

    translate([pos, 0])
        carriage(carriage, carriage_end_colour, carriage_wiper_colour);
}

Hope this proves useful:  I'd like to see it added to the rails.scad
library.

Harvey

OpenSCAD mailing list
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