I’m trying to cut a 2.000" square, with radius corners out of a 4 inch block of cross-linked foam. What I want is a smooth cut left in the foam on all 4 sides and corners.
NOVA 63\100 by ThunderLaser. LightBurn 1.5.00
I tried changing the start point to one of the sides and not the corner. I tried using a lead in and lead out of 15 degrees and 0.750" length.
Three of the sides are smooth, these are the sides where the laser has been moving and the laser power is up to 100%.
My problem is where the point the laser starts and stops, It appears I’m getting a melting of the foam and it’s leaving a mark.
I’m attempting this at 2.5 mm\sec and 100% power and just 1 pass. Attempting multiple passes doesn’t give me smooth sides.
While not an answer to your issue, I question if adding a small tag at the beginning of the cut that is not on the perimeter of the 2x2 square would allow the power to stabilize before the critical edge is cut. Are you cutting the 2x2x4 block or are you cutting a 2x2x4 hole in surrounding foam? If the stand alone 2x2x4 block, start the cut on a small tag at the origin corner on the outside of the block.
If the 2x2x4 block is removed from the critical cutout, start the tag on the inside of the shape. It makes sense in my head.
I am thinking that lead in adjusts power along the path the laser is moving. My idea to to start the laser path in the scrap area and have it trail off into the scrap area at the end of the cut.
You stated the middle actions are good, but the start/stop are where the problem is. Ipso facto, remove the start/stop from your critical cut areas.
If you need to run 100% power, you bought the wrong machine. This is much akin to running your car at red line and slowing down to 95% of red line to go around a corner.
If it’s a glass tube, it’s analog and you shouldn’t need to run it at 100% and if you do it should only be used here for a limited amount of time.
Ah, that’s your problem. By setting min power like that, you almost entirely disabled power scaling. Of course it’s going to overburn start/stop and corners
With the tube’s current set for the mfg rated long-life current, you should always be cutting at 100%. You won’t get more by setting it lower- actually you can end up reducing tube life by doing that
You find the mfg’s rating for the tube. Like a W6 is 26mA.
If your high voltage power supply has an adjustment pot, set it so 100% power makes 26mA. On some like the MYJG you can buy an external pot box to do this, and it’s a really good idea.
That’s not a “red line”. It’s the intended drive current. The mfg power ratings are taken at a much higher current, only fired very briefly to get this reading, and basically fictional. The system should not be set to ever allow that current. In reality, 70% of the tube’s output power rating is reasonable to get from the correct drive current and can be run for a long time like that.
If you just let the power supply drive whatever current it does and don’t have a current meter or a way to adjust the current, who knows what % power will actually produce the correct current. But let’s say we do have a current meter and find “68% power” produces 26mA. OK, you could set the PWM to 68% max, but IMHO that’s a messy way to do it for a lot of reasons. Just analog adjust the supply so it drives the long-life current and use the PWM to reduce it when you need less power.
Also, the HVDC excited tube actually doesn’t need a Min Power set when correctly configured. It’s worth mentioning I have never seen one configured correctly.
Interesting info share, but gents, a tad off-topic.
@MisterTFM, Where on the square did you place the lead-in / lead-out? Have you tried extending the lead to allow more room (thus time) for the system to get “up to speed” to avoid this result? I might suggest further testing of that using scrap material. Additionally,
With DSP controllers as you have in your laser, the speed and power ramp together in an attempt to avoid depositing too much power or overburning as the laser head speeds up or slows for direction change. I might also recommend testing the different behavior and results on that material by spreading out the power more. Maybe test lowering the min setting, testing several times, comparing the results of the finish.
