support for grbl laser cutters

[dvc94ch]

would at least require supplying a custom tool to the state to override gcode_e.

[fullcontrol-xyz]

Hey, good plan. Aside from getting rid of the E term at the end of G1 commands, is there anything else required?

[dvc94ch]

Don't know yet, still working with the plotter to get the geometry right. To vary the Energy/Area to produce a gradient I guess the speed can be varied instead of laser power. In addition turning the laser on/off before/after a G1 block might be necessary using M3/M5. Don't recall if G1 moves do that automatically.

[fullcontrol-xyz]

These are all easy enough to do 👍 if you write your exact GCode requirements and any additional design requirements (e.g. to change laser power) and associated GCode for them, I'll implement a custom laser cutting FullControl

[dvc94ch]

1. Set laser power with M3 Sx where x is between 0-1000 (M4 can also be used which will scale S while accelerating/decelerating to prevent over burn)
2. Disable laser with M5 at the end
3. Make sure no Z or E is emitted
4. Have a spot size config for the plotter to extrude the geometry on G1/G2/G3 moves
5. Make sure G91 and G21 are specified (relative/mm)

Doesn't seem like producing a gradient is possible as you can't specify an acceleration or an increment like with E in marlin.

Is this sufficient information?

Computing the Energy per Area would be a bonus:

E/A = max_power * (S/1000) / F * spot_size

Where max_power is in W, F in mm/s, spot_size in mm seems to work out (units are J/mm2).

[fullcontrol-xyz]

Mostly looks easy but is G91 required. Can it work with G90. FullControl already works with G90 but would need revising to make it work with G91. For G21, that's fine and can appear at the start of the program.

Also for point 4, do you mean so that the fullcontrol preview fc.transform(steps, 'plot') shows the correct line width?

[dvc94ch]

G90 is also fine. Well the existing extruder geometry works fine. But if you disable the extruder you only emit G0 moves. But a 2d circular geometry might be more accurate, if the beam profile can be ignored since the laser is strongest at the center and gets weaker as it spreads outwards.

[fullcontrol-xyz]

What do you mean by "But if you disable the extruder you only emit G0 moves" - are G0 moves not good for you?

And also, what do you mean by 2d circular geometry? Ignoring the beam profile, won't the path look almost exactly like the currently preview if it's viewed top-down, aside from minor issues at corners?

[dvc94ch]

What do you mean by "But if you disable the extruder you only emit G0 moves" - are G0 moves not good for you?

grbl disables the laser on G0 moves. right now I use fc.Extruder(on=True/False) to switch from G0/G1 and this gives the correct plots. but this emits E gcode.

And also, what do you mean by 2d circular geometry? Ignoring the beam profile, won't the path look almost exactly like the currently preview if it's viewed top-down, aside from minor issues at corners?

yes that's right

[dvc94ch]

Think this would be really cool. These features would also let people produce gcode for CNC, although you'd need to add a subtractive mode to the plotter if you wanted to do that.

Currently working on a 2d slicer (left-right fill and outline fill) using the opencascade kernel (via the build123d python package). Think extending it to 3d wouldn't be too hard, just intersect the model with a z-plane would be sufficient to support stereolithography, and adding support for partial fill layers and overhang supports would support FDM.

[fullcontrol-xyz]

Ah I understand what you meant with G0/G1. Yep I'll also make it so G1 has no E value. With regards to the plot, would it make most sense for the designer to specify laser width or laser power - e.g. designer directly writes fc.Laser(spotsize=XX) or with fc.Laser(power=XX)

It would be nice if the designer didn't need to write the same information twice (once to control the line width in the plot and once to control the gcode M3 commands. Is the relationship between spotsize and power always known (even for basic users)? If so, we can have the user design with either spotsize or power, as they prefer, and fullcontrol will update the other parameter as necessary.

With regards to filling strategies, I need to get this stuff all together. I'm in touch with a few different people, who have all developed different strategies, and need to get everyone working cohesively. I intend to create some 'Projects' within this github library in the next week or two. One will be for filling. I'll try to remember to tag you or this issue when the project is live. But keep an eye out. There are so many things that can be reused across machining, robotics, 3D printing, laser cutting, etc.

FYI I'm already doing extrusion and machining at my university as research. So am also keen for a nice viewer to simulate the additive+subtractive toolpath. Ideally, build directly into FullControl python rather than needing to export to a CAD/CAM package (although that would be useful to support too! But their additive previews are nowhere near the standard/value of their subtractive ones). Anyway, it's in the pipeline!

Let me know about fc.Laser(spotsize=XX) or fc.Laser(power=XX) or something else

[dvc94ch]

you need to specify the spot size and the power. the spot size is the diameter at which the beam intensity drops below 1/e2, while the power determines the pulse width. so at 100% power the laser is always on, at 1% power the laser is only on 1% of the time.

[dvc94ch]

already made progress on the slicing:

here is a resistor and capacitor sliced using outline fill, for patterning a layer of graphene on polyimide film. there are still a few issues with it as you can see, but it's getting there

[fullcontrol-xyz]

Ah, very cool! Note that there is an offline path function in fclab.offset_path().

Can spot size be changed during the process, or is it something that is typically set once and left? Not just for your cutter, but for laser cutters in general? This will affect whether it is best as a design object or an initialization parameter.

Laser cutting is quite nice compared to extrusion 3D printing cos it doesn't matter if you go over the same area twice or overlap your lines too much, am I right? Since if the laser goes over hole, it doesn't matter? With extrusion 3D printing, you'd end up with too much material being deposited, so you need to be careful to get just the right overlap (too little = bad porous structure; too much = messy over-deposition).

[dvc94ch]

Spot size is a property of the laser. You could do a tool change during the job, but I think it's fine as an initialization parameter.

Yes, gave the builtin offset a go, but since I'm already using build123d to define the geometry to export for cad etc. seems like doing something custom is fine. Also easier to handle curves, the builtin only handles polygons.