Creating spirals

[jcdammeyer]

CNC G-Code can create arcs using either radius or I and J to represent the origin. The CAM program I use can create a circular pocket using a spiral path which turns out to be a series of short lines. I started thinking about how I'd draw a spiral in Alibre and stumbled a bit. The ideal is the end point of each arc becomes the starting point of the next with the arc progressing in steps every quadrant. But drawing this is very tedious although the idea was to try and recreate the g-code from a program. However it turns out the program also has a bug and start and end of the arc have a different radius so that didn't work.


Anyway, is there a way to draw a spiral in Alibre? It doesn't have to be a logarithmic spiral. In fact probably archimedes type.

Spiral | Definition, Examples, & Facts

Spiral, plane curve that, in general, winds around a point while moving ever farther from the point. Many kinds of spirals are known, the first dating from the days of ancient Greece. The curves are observed in nature, and human beings have used them in machines and in ornament, notably

www.britannica.com

 

[HaroldL]

Use the Spiral option in the Helix tool.

 

[jcdammeyer]

Use the Spiral option in the Helix tool.

View attachment 39189

Thanks
Although I've created threads it never occurred to me to use the helical option to do this. I should then be able to mark a point at each intersection with the axis and measure distances.
I'm not even sure the IJ method is valid. Problem is the radius changes too. So instead of short straight segments I suspect it will be quadrant based arcs where the origin moves around in order to have the start and end points at the same radius.
Just exploring. It's nothing serious or pressing. Exercising my brain so to speak.

 

[HaroldL]

For a logarithmic spiral use Tangent Arcs to connect the ends of the arcs. I started the first arc on the Origin then created and dimensioned the remaining ones, one at a time. I also added the vertical and horizontal constraints to the arc end point so they are all on a quadrant of arc.

Use the Spiral option of the Helix tool for the Archimedes type.

I suppose someone could write a script to create this, if they haven't already. There are a couple that may be a good starting point, Spiral_Sweep_dbc and Spring_Sweep_forum. You'll need to do a search to find them or look in the Resources section.

 

[jcdammeyer]

For a logarithmic spiral use Tangent Arcs to connect the ends of the arcs. I started the first arc on the Origin then created and dimensioned the remaining ones, one at a time. I also added the vertical and horizontal constraints to the arc end point so they are all on a quadrant of arc.

Use the Spiral option of the Helix tool for the Archimedes type.

I suppose someone could write a script to create this, if they haven't already. There are a couple that may be a good starting point, Spiral_Sweep_dbc and Spring_Sweep_forum. You'll need to do a search to find them or look in the Resources section.

View attachment 39190

Thanks. You make it look so easy. Of course at the time I thought the C program that generated the G-Code actually worked. Turns out it didn't. I couldn't figure out how the author managed to keep the XY of the origin incrementing in the way it did. Of course that's where the error was. It's figuring out where the IJ which specify the origin.
G03 X0.0000 Y0.0312 I-0.0625 in this example the I parameter was incorrect. J was the same as the current Y axis.
In reality for each line I and J need to be specified. And of course it's not just the curve but curve is the center line of the depth of cut of the tool. So a 0.5" tool with a 0.125" cut depth needs to traverse a profile that is 0.125" larger than the center line of the actual tool.
Like I said this is a good exercise for the brain.

 

[HaroldL]

I should then be able to mark a point at each intersection with the axis and measure distances.

That distance is set with the Pitch of the spiral.