Hi’yall

As rookie, I have s small problem with a script when creating a cube with some cut outs.

I have the following code:

I’m having a problem with the 2nd ‘translate’.

It supposed to cut out the opening for the switch in the housing.

What am I doing wrong here?

Any help is much appreciate.

TIA

Version: OpenSCAD version 2024.08.18.ai20248 (git a16ca2a67)

on Linux Mint v22.3

Your cylinder is only 0.001 below the top surface. It should be slightly
less than wt below. Try this:
difference () {

cube([w, w, h], false);

translate ( [wt, wt, -0.001] ) cube([w-wt2, w-wt2, h-wt + 0.001], false);

translate ( [w/2, w/2, h-wt-0.002]) cylinder ($fn=200,h=wt*2, d = hd);

};

On Wed, 20 Nov 2024 at 15:25, fpa512--- via Discuss <
discuss@lists.openscad.org> wrote:

You can use the modifier character # with objects being differenced away to
visualize them and confirm they are aligned as expected.  You also want to
slightly oversize objects for differences and unions to ensure they fully
cut through or fully overlap.

On Wed, Nov 20, 2024 at 9:26 AM fpa512--- via Discuss <
discuss@lists.openscad.org> wrote:

For differences, it can help to use # in f5 rendering,to see where the
'holes' are. A simple technique, is to multiply the height by three and
move down by 1, as the second line  shown below. It can avoid errors by
'pushing the holes through much further than necessary', so to speak.

 //# translate ( [w/2, w/2, 0]) cylinder ($fn=200,h=h2, d = hd);
  # translate([w/2,w/2,h-wt]) cylinder ($fn=200,h=wt3,d=hd);

On 20/11/2024 15:34, nop head via Discuss wrote:

The cut out cylinder is positioned on top of the cube, so it is not cutting anything.  Change the last statement to:

translate ( [w/2, w/2, h-wt-0.001]) cylinder ($fn=200,h=wt*2, d = hd);

Note that it is lowering the translation by the wall thickness so the bottom of the cylinder is at the bottom of the top wall.

Mark

That works beautifully. Thanks to all.

Fred

On 2024-11-20 12:10, Mark Erbaugh via Discuss wrote:

There's a further trick you can use:

take the following code as an example.

            translate([0,0,0])
            {
                difference()
                {
                    union()
                    {
                        color ("purple") cube([25.4, 15.88, 1],center =
true);
color("white")translate([0,-6,.5])rotate([0,0,0])linear_extrude(0.2)text("MPU9250",size=2,halign
= "center",valign = "center");
translate([11.3,4.2,0])rotate([0,0,90])index_mark();
                    }
                    union()
                    {
                        translate([10,-6,-3]) cylinder(d = 3, h = 10);
                        translate([-10,-6,-3]) cylinder(d = 3, h = 10);
                    }
                }
            }

The translate part simply allows you to offset the entire object.  Since
this is a difference, the unions make it clear (to you) what is being
subtracted from what.

The trick is that with difference on a separate line, commenting it out
simply renders the negative objects as positive, and allows you to see
exactly where the holes will be (easiest when the base object is
transparent).

Easy change to and from.

Harvey

On 11/20/2024 2:30 PM, FPA via Discuss wrote:

FPA wrote:

Another useful feature is center=true. It anchors objects in their centre, which simplifies things in most, but not all cases. I use it about 80% of the time. Regrettably, it’s not the default.

On Wed, Nov 20, 2024 at 02:30:59PM -0500, FPA via Discuss wrote:

Note that this has happend once or twice in the past that someone
tries do "difference" something and unexpectedly "nothing happens".

Openscad has a trick: Prefix the thing that's not working with # and
it will show up as a see-through pink object. Often you'll see what's
wrong immediately.

Roger. 

--
** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110 **
**    Delftechpark 11 2628 XJ  Delft, The Netherlands.  KVK: 27239233    **
f equals m times a. When your f is steady, and your m is going down
your a** is going up.  -- Chris Hadfield about flying up the space shuttle.
**  'a' for accelleration.

On Wed, Nov 20, 2024 at 11:47:28PM +0000, Caddiy via Discuss wrote:

Create a module that does it for you:

module ccube (size) cube (size, center=true);

Put it with the other "stuff I always use" in an include.
(I have stuff in there like dup2() : Duplicates an object by rotating
it around the origin, along with dup3(), dup4() and dupn(n) ).

Roger. 

--
** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110 **
**    Delftechpark 11 2628 XJ  Delft, The Netherlands.  KVK: 27239233    **
f equals m times a. When your f is steady, and your m is going down
your a** is going up.  -- Chris Hadfield about flying up the space shuttle.
**  'a' for accelleration.