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Laser Current Drop in Y Axis

I just noticed something weird with the power of my K40 laser.

I am cutting a 30mm square with rounded corners on six sheets of paper card stuck together. I am cutting reasonably fast at 60mm/s, 24% power and doing 20 passes to try and get a cleanish edge. What is weird is that while cutting on the X axis the ammeter is showing around 7mA, but when the laser is cutting along the Y axis the current drops to just under 5mA? Is this normal?

Hi Nathan,

that's interesting!

Don't worry, there is nothing crazy in the design of the Mini Gerbil or its firmware that would do this.

A standard gantry mechanism has the gantry head moving along the X axis, which is in turn moving along the Y axis. So there is more load on the Y axis, because it has to move the X axis weight.

But typically the ammeter is connected in the HV laser return path, so should be independent of load on the motors.

So what is the connection? The K40 power supply is not powerful. It's possible that the extra load of the Y axis is reducing the power available for the laser. This is not ideal. The question is whether it's normal, or whether your power supply is starting to underperform. My understanding is that K40 power supplies can start to underperform before they fail... how old is your power supply? How much do you use it?

Alse consider what else you have connected to your power supply. If you have LEDs, fans, etc etc, try noting laser current with/without and if you notice much difference, then at least you can consider what's higher priority. Remember that LED's, fans etc could be run from a cheap external supply to minimise load on your K40 power supply.

Does anyone else notice the effect Nathan is experiencing?

A final consideration is whether you notice the current difference manifesting as problems with your image. Although the ammeter reads as a single value, of course any combinations of motors and speeds will result in different underlying waveforms of electricity reaching the laser.  It may or not be important or visible... if it's not impacting your cutting or engraving, then it's just an interesting observation.



Hi Dan,

Thanks for the very detailed reply.  I have worked out what was going on.

The problem was that, via Lightburn, I had set the Y axis maximum speed to be less than 60mm/s to try and solve a different problem of multiple layers being offset from one and other.

I'm not sure whether it is Lightburn or the firmware, but it seems that the laser power is being lowered to compensate for the decrease in head movement when travelling in the Y axis.  It makes sense in hindsight why that would be the case.



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