start stop mark cutting a circle

[Toby Hope]

Hi there, could someone point me to a setting which may help eliminate or minimise a start stop mark when cutting a circle, I'm wondering if there's a small overlap I can set which tells the laser to do 1.01 times cut so it carries on slightly to smooth out the start stop.

OR is this just something that is unavoidable , thanks in advance!

pic attached showing the line formed at start and stop position

start_stop.JPG

[Gene Uselman]

If you are familiar with CNC machining- there is something similar to lead in and lead out in Lightburn which should solve that problem- I don't use RDw anymore and don't remember where it is in that program. Normally the laser beam will dwell a few milliseconds [micro?] to punch thru the material and I think that is what you are seeing.

[Toby Hope]

If you are familiar with CNC machining- there is something similar to lead in and lead out in Lightburn which should solve that problem- I don't use RDw anymore and don't remember where it is in that program. Normally the laser beam will dwell a few milliseconds [micro?] to punch thru the material and I think that is what you are seeing.

Thanks Gene, I've heard of lead in and out, but presumed it was something I had to manually cad in?

[Toby Hope]

excellent! I've found the cut in cut out option with help from the user manual, I can't hjowver seem to get it to have a cut in line from the centre of the washer shape I'm cutting, so the central hole to be cut first is insisting on having the cut in from the washer side which is not what's needed, it needs to be from the centre so I'm left with an untouched washer of acrylic. no matter what settings I choose I can't get it to flip around... maybe it's a limitation of the software?

EDIT: I needed to take off the auto options and start again with 90 degrees rather than 45 and it's doing it from within the shape, great stuff!

[Jeffrey Aley]

I'd take a whole different approach to this problem. I'd adjust the min power setting. The laser head has to accelerate from zero to whatever your cutting speed is. If the min power = max power, then you're effectively cutting at the max power, but much more slowly during that acceleration.

On the other hand, if you have min power < max power, then the controller will automatically (and proportionally) reduce the power while the laser head is accelerating.

A few hints, for those who have never messed with min power before:
1) Probably you already know that your laser won't even fire at 1% power. So don't bother with a min power that is lower than the power supply's threshold. I think on mine it's like 5 or 6%.
2) One might think, "fine, I'll set the min to 6% (or whatever that minimum threshold is) and that's it." The issue is that the controller will interpolate speed vs power in a linear fashion (mathematically speaking). But the cutting ability of the beam is not linear with power * speed, and is dependent upon the material and other factors. So it makes sense to play with other (higher) values of min power if you're still having issues.

[Toby Hope]

I'd take a whole different approach to this problem. I'd adjust the min power setting. The laser head has to accelerate from zero to whatever your cutting speed is. If the min power = max power, then you're effectively cutting at the max power, but much more slowly during that acceleration.

On the other hand, if you have min power < max power, then the controller will automatically (and proportionally) reduce the power while the laser head is accelerating.

A few hints, for those who have never messed with min power before:
1) Probably you already know that your laser won't even fire at 1% power. So don't bother with a min power that is lower than the power supply's threshold. I think on mine it's like 5 or 6%.
2) One might think, "fine, I'll set the min to 6% (or whatever that minimum threshold is) and that's it." The issue is that the controller will interpolate speed vs power in a linear fashion (mathematically speaking). But the cutting ability of the beam is not linear with power * speed, and is dependent upon the material and other factors. So it makes sense to play with other (higher) values of min power if you're still having issues.

thanks for that i will try some different min power settings , i can’t recal if i actually tried that or not