Drawing a spiral/snail cam

[Marcus_Wakefield]

Thanks very much!

[Marcus_Wakefield]

@Marcus_Wakefield

SVG uses pixels as its unit and the application that’s importing it has its own way of determining the DPI. The most common standards are 72 & 96 DPI.

Ok, for those that are interested, I’ve learned a bit more about SVG since then.

By default SVG uses pixels as it’s unit. However, you can specify units such as ‘mm’, ‘cm’, ‘in’ etc. Unfortunately most of the applications I’ve tested it on don’t seem to support them. I’ve tested LightBurn 1.4.05, CorelDraw 2018, Inkscape, LibreOffice Draw, Fusion 360 and Affinity Designer. All fail in one way or another except for Affinity Designer. Now, either I’m doing something wrong and Affinity is clever enough to correct my mistake or all the other apps are getting confused by the units.

Here’s a screenshot of the latest version with units:

Luckily (for those of us who use LB in mm) selecting ‘none’ works just fine, if you use LB in inches you’ll just need to scale accordingly.

[StevenM (Steven Marston)]

This is excellent!

I’m sure I’m missing it but I’m not seeing a means download it to give it a “swirl” (pun intended).

[berainlb (PY)]

There’s a link in an earlier post:

Drawing a spiral/snail cam

For the past couple of days I’ve been (re-)familiarising myself with B4J as well as learning a bit about SVG files. I’ve been working on an application that will generate a spiral in SVG format. I usually develop my apps in Lazarus but wanted this to be cross-platform because there are LB users running on Windows, MacOS, and Linux. Lazarus will create cross-platform apps but I don’t think it is very straightforward hence I’ve written this in B4J. I haven’t managed to work out the cross-platform …

[stixstudios (Steve K)]

Well time to show how this “snail/spiral” cam has been used in the “real world”. The cam has allowed me to position within 0.2mm (or better).

It is used for cutting/routing out wood for a picture frame insert - a rebate/rabbet. The cam is used as a device to “knock up” to the fence of my router table at a known distance. Amazingly accurate.

After the frame has been made, a piece of glass-artwork has been inserted. The artwork mask was cut using my co2 laser and Lightburn.

Wonderful result IMO In this instance, LB has been used in two ways. Excellent!! Cheers.

Oh yeah, I should have rotated the numbers 180deg, but no big deal to me because I can read upside-down mirror reversed - a skill I learned from the printing industry. But yeah, the numbers could have been rotated. Oh well.

[StevenM (Steven Marston)]

Could you look at this file?
I’m using identical parameters as shown but I’m getting different results depending on if I save as SVG or DXF.
Also, should I get the rays/lines extending from the center? With Text?

Marcus’s Spiral Generator Output.lbrn2 (34.1 KB)

[StevenM (Steven Marston)]

Phi-Spiral.ods.txt (1.6 MB)
I use LibreCalc so the usual renaming of the attachment should work.
It’s not my original work but I have made some changes to the graphing portion and some of the numbers used.
Anyway, you can copy and paste the chart from the ODS into LibreDraw, then export that to an SVG from there. Clunky, but it does work and I’m not generating multitudes of spirals anyway. Fun to play around with. Been trying to get something usable for months off and on. That’s why I was/am intrigued by the standalone app.

[Marcus_Wakefield]

@StevenM

I’m using identical parameters as shown but I’m getting different results depending on if I save as SVG or DXF.

The result you’re seeing with the SVG is probably due to selecting a unit other than “none” when generating the spiral. Take a look at my post above that explains units in SVG.

@Marcus_Wakefield

By default SVG uses pixels as it’s unit. However, you can specify units such as ‘mm’, ‘cm’, ‘in’ etc. Unfortunately most of the applications I’ve tested it on don’t seem to support them. I’ve tested LightBurn 1.4.05, CorelDraw 2018, Inkscape, LibreOffice Draw, Fusion 360 and Affinity Designer. All fail in one way or another except for Affinity Designer. Now, either I’m doing something wrong and Affinity is clever enough to correct my mistake or all the other apps are getting confused by the units.

@StevenM

Also, should I get the rays/lines extending from the center? With Text?

No, it’s just a spiral generator with optionally some construction geometry to assist with positioning etc. If you’re using it to create a cam similar to the OP you’ll need to add your own lines and text.