Start points (again)

[krosstoph]

Hello,
although i read all the topics about start points and tried the different approaches, it just does not work for me. Whatever specific point I define, the start point always is either in the left corner or the right corner, but i want it in the middel of a rectangular part. And maybe that is just the problem. I assume that the algorithm for defining the start point is only allowing it to be at the beginning or end of a "line", am I correct? Or is there something I am missing. Would be great if there was a way.
Thanks in advance!
Best regards,
krosstoph

[CompoundCarl]

Just set your start point mode so that it's "closest to a specific location", and then input the XY value that you want it to be close to. I like to use the cross section tool to double-check the XY values I want, then enter those in the process settings.

If you're still having trouble, it would probably help if you posted a factory file and a screenshot of what you're trying to achieve

[wirlybird]

I have been wondering on this also. If I have a 20X20X20 cube centered on the build plate and pic specific start point it defaults to 0, 300 which seem to make it the right rear corner as I face the printer.
This point doesn't seem to be either the 0 on the X or on the Y. so let's say I wanted the start point to be at the left front corner of the cube would I figure out those coordinates and punch them in based on the center of the platform being 0,0?
Haven't had a chance to experiment yet but any guidance would be great!!

[krosstoph]

Thank you for your answers.
I just tried again with a simple cuboid having the following coordinates for start point (x = 200 is the mid of the cuboid) :
1st try: x = 200 (mid of cuboid), y = -9999 --> Start points in right corner, viewing from x-axis
2nd try: x = 200 (mid of cuboid), y = 0 --> Start points in right corner, viewing from x-axis
3rd try: x = 190 (left of mid of cuboid), y = -9999 --> Start points in left corner, viewing from x-axis
4th try: x = 190 (left of mid of cuboid), y = 0 --> Start points in right corner, viewing from x-axis
If I try y = 9999, it just flips the start point to the other side, but again just in the corners.
So no matter what I try, the start point always ends up in a corner.
Here are some pictures and the factory file:

x = 200, y = -9999

x = 190, y = -9999

Quboid.factory

Factory file

(2.87 KiB) Downloaded 303 times

I think I really have been looking at this so hard, I can't find the right solution...

[krosstoph]

What I want is the start point to be in the middle of the Cuboid:

Here :)

[CompoundCarl]

You can't put the start point there, because the printer never stops there. It prints that entire side as a straight line. Same with the 3 other sides. So if you are printing something like a simple cube, then the only possible places to start or end are in the corners.

[krosstoph]

Thanks for your answer.
That's too bad, because I have many mechanical parts where I would prefer the weld points on the flat sides instead of in the corners to optimize stability. The weld points are essentially starting points for crack growth. An if the applied force is in direction of the corner, I will have to make the mechanical feature thicker because of this.
The only workaround I figured out just now is not ideal, but for anyone interested I will post it:

If you put a small nose where you want to have your seam, this allows for the travel paths to start there. The nose thickness has to be in the dimension of your extruded line width. For a 0.4 nozzle with 0.46 line width you have to extrude the nose around 0.4 mm (one time extruded line width) outwards from your part with a width of 0.8 mm (two times extruded line width) or it will just be ignored by the slicer.

[wirlybird]

Carl, that explains some stuff for me then.
Would I be correct in assuming then that if I have a 20X20X20 cube centered on the build plate and a start point of the default (FFCP printer) I think it is x-0, y-300 that it is going to find the closest corner to that coordinate?
So if I wanted it to start on a different corner then I just need to rough in that corners coordinates and it should work?

Now, on a cylinder, I again assume it would set a start point that is closest to the coordinate entered?

[wirlybird]

Thanks for your answer.
That's too bad, because I have many mechanical parts where I would prefer the weld points on the flat sides instead of in the corners to optimize stability. The weld points are essentially starting points for crack growth. An if the applied force is in direction of the corner, I will have to make the mechanical feature thicker because of this.
The only workaround I figured out just now is not ideal, but for anyone interested I will post it:

cuboid_nose.png

If you put a small nose where you want to have your seam, this allows for the travel paths to start there. The nose thickness has to be in the dimension of your extruded line width. For a 0.4 nozzle with 0.46 line width you have to extrude the nose around 0.4 mm (one time extruded line width) outwards from your part with a width of 0.8 mm (two times extruded line width) or it will just be ignored by the slicer.

Interesting. Thanks.