[rfresh737]

I'm learning to gcode manually my laser machines.

I've spent the last month working with circles and arcs G02/G03.

Now I'm starting on Elllipses and Elliptical Arcs.

Is there a G02/G03 like command to make these or do I just have to step through each x,y point and keep moving the laser head?

Thanks...

[rfresh737]

From what I can find online, it looks like I can make an Ellipse and an Elliptical Arc by making individual Arcs...4 Arcs for an Ellipse and 1, 2 or 3 Arcs for an E-Arc...does that sound right?

[postwrtr]

If your application is a repetitive one, your best bet would be a macro that would handle this for you with some variables, changes in a few variables would provide any elliptical shape within the mathematical terms as found in the machinery's handbook, I wrote one for flat spiral to any diameter from center stepping out evenly every 360° until specified diameter that then stays at that diameter for full 360° then spirals equally back to center all at same z. for special flatness requirement on aerospace part I used point calculations as number of points per 360° to calculate via Sin/Cos. Ellipse could be done the same way however addressing the different in the fo-sigh focal points as seen the this shape, the circle is an ellipse however the fo-sigh are the same. using the arc function G2 G3 may present some problems at the machine though dependant on the handling of the center point of the arcs, I would think due to the math involved calculating point to point motion would be the best way and less information to pass to the control through the code you write. the ellipse is not just 4 tangent arcs it is a contantly changing arc that is tangent all the way around. point to point caluculations done with Sin/Cos would be basically the same as circle except including variables for the floating points for radial distance from the center of the coordinate system to do your trig from and applying those values to G1 X and Y statements repeating the cycle through each quadrent of the coordinate system and every 90° changing the axis sign to match until you have done all four quadrents.

If you try arc output you still need to address how many arcs you need to get the desired results on the machine, the more arcs the smoother the shape, the more arcs which become very short features of geometry could cause some problems at the machine - center point tolerance parameters and end point parameters might require adlustment - also machining accuracy will come into play as well and some exact stop at arc end points may cause you to see pause in each segment.

If you are just starting with g-code this maybe down the road and I guess I should have asked if your machine has macro function our varibles avalible to use.

[rfresh737]

Thanks for taking the time to explain this.

I'm doing this at the hobby level so I have a very basic laser machine...and its using Grbl and therefore doesn't support variables or macro's.

I created some Ellipses in LibreCAD (a 2D CAD app) and it does look to me like they force the concept of creating their Ellipses with 4 Arc objects.

I did some tests creating some manual gcode to do some x,y points to create a curve and the laser head did not move smoothly at all, like it does with a G02/G03 Arc. I guess its the moving from one point to the next.

So, at this point I'm favoring to try and create 4 arc segments from the Ellipse.

[sinha_nsit]

In manual drawing, an ellipse is drawn using four arcs. It is an approximate method, and called four-center method. It does look reasonably accurate. It actually shows how a circle looks on isoplanes in an isometric view.

[Superman]

From what I can find online, it looks like I can make an Ellipse and an Elliptical Arc by making individual Arcs...4 Arcs for an Ellipse and 1, 2 or 3 Arcs for an E-Arc...does that sound right?

Just to put an idea in your head

Some controls can scale, some can scale a particular axis at differing ratios
- have you thought about drawing ( / programming ) a circle ie 1" diameter then scale the Y axis by 50% would give you a 1.00" x 0.50" oval ?? ( not really a true ellipse )

[CNCFr]

( not really a true ellipse )

Why do you think so? Scaling an axis results in a mathematical exact ellipse.

[rfresh737]

In manual drawing, an ellipse is drawn using four arcs. It is an approximate method, and called four-center method. It does look reasonably accurate. It actually shows how a circle looks on isoplanes in an isometric view.

This is the method I chose to do. Thanks.