Continuing the discussion from Taper Warp tool for rotary engraving:
@JohnJohn - Did you ever determine if the length in the taper tool is the height of the glass or the hypotenuse (length) of the sidewall?
Not John, but I am pretty sure it is the height of the glass.
I drew a lot of things.
Length represents the height of the tapered object proportionate to the change in the diameters. Because the diameters are known, the height can be known and can inform the correction for the amount of taper needed.
Changing ‘Length’ does not change the size of the art, it only forces more correction or less correction when warp is applied to the art.
After the job is completed, the initial height and width of the art are preserved, assuming the step width on the rotary is correct. With the art Locked (so both axes adjust equally) you can re-scale the art to change the size without changing the amount of correction applied.
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Appendix:
I might have to do this in a few edits. I was exploring when I figured this out.
I used a 3-4-5 right angle triangle to confirm that the height ratio is preserved. I wanted numbers that would be easy to get a feel for.
The statement in the above image is incorrect. The Art was 100mm tall and the cup was 100mm tall. The height of the art didn’t change when Length was changed below.
The 3-4-5 triangle comes back as a (x25) instead of the expected (x20). (Figure with blue numbers on the left).
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@JohnJohn - Thanks for the info and your approach got me thinking. I’m not sure what to make of the data so I wanted to bounce it off a few other minds.
My laser is a simple setup and the rotary is one of the roller setups where I put just the top edge of the glass on the roller and setup a bearing to hold the glass level with the laser.
Something like:
The further down the glass you go, the more rotary motion you need to move to make the same linear motion. Assume a glass with a top circumference of 360 mm and a bottom circumference of 180 mm for example. To draw a line 90 mm long at the top of the glass, the roller will move 90 mm which equates to 90 degrees of rotary motion (or 1/4 rotation). At the bottom of the glass that 90 degrees of rotation will only result in a line 45 mm long (180 mm / 4).
If we want the bottom of the image to be aligned with the top of the image the width needs to be double.
Now taking that into Lightburn to experiment.
Circumference 360 = Diameter 114.59
Circumference 180 = Diameter 57.29
Draw two lines, both 90 mm long and put them 100mm vertically apart
Now taper warp the image for a glass that is 100 mm tall
Correction is 200 (This is probably a percentage, 200% which is what was calculated above)
The bottom line is now 180 mm long, the top line is still 90.
The X axis of my setup is parallel to the hypotenuse. So the 100 mm height in the experiment above is actually along the hypotenuse, not the height of the glass. So I think the tool is asking for the length of the side of the glass, not the height of the glass.
Thoughts?
You’re right. With the axis of travel parallel to the side of the glass, it becomes the hypotenuse of the triangle. The path of travel (top-to-bottom of the art) becomes longer for the laser and the path of the laser wouldn’t cross the measured diameters.
You measure the side of the glass, so the art is produced along the side of the glass as you have defined it.
If I’m reading this correctly, you’re driving the top edge of the glass and you’re allowing the glass to move freely. With the centerline of the glass ‘tipped away’ from the laser, the centerline of the glass is effectively shorter along the X-Axis. I’m starting to think that any error introduced by the tilted axis will mostly cancel out.
Are you up for some testing?