2.5D tube lasercutting ; how to draw?

[Koemi]

Hi,

I want to create an angled slot in a hollow tube. To make it worse: An opposite angled slot is also necessary... The blue pin needs to travel thought the slot on both sides of the tube...

I would like to draw it exactly if the cutout has been done using a tube lasercutting machine, with the laser always pointed straight down and the tube is rotated and slided back and forth (like 2.5D lasercutting).

At 1st I thought this is do-able, but... No. For me it is not...

Searched the place for some kind of Workbench, but I can't find any.

How to do this? I used sweep in the part WB, but still; this is no walk-in-the-park...



OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.6712 (Git)
Build type: Release
Branch: releases/FreeCAD-0-16
Hash: da2d364457257a7a8c6fb2137cea12c45becd71a
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17

[chrisb]

I have two questions:
Is there a good reason why you still use FreeCAD 0.16? There are so many enhancements and bugfixes that I strongly recommend to upgrade.
I'm not familiar with lasercutters, but if you talk about rotating the tube, isn't that beyond 2.5D, where you move essentially in the XY plane?

[Koemi]

I have two questions:
Is there a good reason why you still use FreeCAD 0.16? There are so many enhancements and bugfixes that I strongly recommend to upgrade.
I'm not familiar with lasercutters, but if you talk about rotating the tube, isn't that beyond 2.5D, where you move essentially in the XY plane?

I have two answers
1. I still use V0.16 because of the use of older drawings and the problems I got when I switched over to V0.17 (but that is not important right now)
2. The laser points down and can only make movements in Z-axis direction, the tube can only move in X-axis direction and rotate around the X-axis (typical tube laser functionality). If I search the internet it is often described as 2.5D.... If that is ok, I do not know

[meme2704]

Hi
At first, I create a path by cutting a perpendicular shape of a tube
Then I create the laser beam, aiming towards the center of the tube
using the edge of the first cut, I make the final cut oriented towards the center in the direction of the laser (cut001)

[Koemi]

meme2704; thanks for your approach! I like the way you did this. It leads the way to solvation. But have the feeling your approach is not 100% correct... I could be wrong. but I am not sure... It is hard to explain...

You have created a cutout piece with a curve on a flat plane, but the real plane is curved (it's a tube). In reality the curve contains a double radius

See pic below;
- This is the shape which needs to be cut but shown in 2D;
- The problem is that is has to be projected on a tube shape. For straight lines this is no problem.
- The difficulty starts at the curved parts of the shape
- ...and to create a slot in this case I count not 1, but 4 curves with a double radius
- The final slot width in the tube needs to be at least 5.5mm wide, so this would be the case on the inside of the tube, because on the outside it will be wider.

How to create a curve with a double (or 3D) radius? Or how to project a 2D drawing on a bended shape?



100% correct shape would be:
- Take a flat metal plate and make a 2D cutout as pic above, but the laser must cut under a certain angle;
- Bend the plate to a tube;

[meme2704]

Your first sight suggested that you just wanted a cut line
For your new precision, I propose to place spheres in each curve tangent with the generatrices of the cylinder (the line of contact of a sphere and a cylinder is always a circle), you each spheres by tangent cubes,
you add up everything,
you materialize the laser beam oriented towards the center of the tube, in each point of tangency of the straight lines and the curves
you do a sweep between all the sketches representing the laser beam, following the common aretes (spheres, lines, cylinder) as a path

[meme2704]

- Take a flat metal plate and make a 2D cutout as pic above, but the laser must cut under a certain angle;
- Bend the plate to a tube;

I reread your questions
with Fc, is not possible to make the form "flat"
With Sheetmetal Wb no longer because the cut is in the rolled part, it causes a crash when we want to use the Unbend function

[Koemi]

I reread your questions
with Fc, is not possible to make the form "flat"
With Sheetmetal Wb no longer because the cut is in the rolled part, it causes a crash when we want to use the Unbend function

Yeah. I noticed already... Thanks

[Koemi]

I have thought it over

With help of your tips, meme2704, I tried something with actually works as in reality.

Using a cone upside down and tilted under an angle (if you look from the side, one of the sides of the cone will be vertical). But getting the right angle is undoable.

Then I tried to make a rotated part (in the end this leads to a cone). This I can position well, actually. But then the cutout... It fails.

Definately I can use somekind of a tube laser workbench.... And something to get rid of my headdache...

[gntech]

Perhaps you already know this but I want to write it just in case it will help you:

As a workaround to your problem I can inform that there are tube laser cutters nowadays that have tilting laser beam so you do not have to make the cut perpendicular to the surface of the pipe to be able to manufacture it.