I have seen faster processing time for files and the disappearance of a ‘Shadow line’ around the edges of engraves that really bothered me, as well as random deeper scores across engraves in this pre-release unit.
The power control is great. All of a sudden, it’s a lot more fun!
Never owned a tool that continued to improve. Looking forward to that evolution - Nice work 
team. 
lol
Happy to be of service. I’d love a good laugh too, wanna share?
That would be most of mine. Seems the more I use them the better my results 
I think we have a different definition of overburn. It still applies two much energy in the corners due to slowing down and that will make the score go deeper in the corners. So I consider the title of this post to be untrue.
What has changed is that with the low power settings you can make much shallower scores, so when it goes too deep it doesn’t go all the way through. So it has fixed the pinprick holes in the corner when scoring thicker materials but it still overburns in corners.
I thought that Dan meant it was fixed by “no momentary hot or cold spots” but when I asked he said “We haven’t addressed corner power yet - things will continue to get better for a long time to come.”
Being able to reach very lower powers should allow them to ramp down the power during deceleration. If power level 1 is low enough that might be all that they need to do. If not they need to decelerate to the speed commensurate with the minimum power and then turn off the laser, overshoot the corner and orbit around to start the next line at minimum power and then ramp up while accelerating.
I got the idea the overburn in the corners is not fixed, but harder to notice because of the lower power settings available. If you look at the last picture in @jamesdhatch 's power settings test, it seems the corners are still getting more power than the rest of the square, but that if your material is thick enough and you pick just the right settings you can have the corners not burn all the way through. In his example on baltic birch plywood, 100% power even at the highest speed still shows corner burn-through.
Yes at full power the corner burn will be as before. When cutting through it doesn’t matter much apart from more splash back.
When doing shallow scores in opaque materials it also doesn’t matter much if they are thick enough. The score is so narrow it would be hard to see that goes deeper in the corners but perhaps the kerf gets a bit wider as well.
In acrylic it will be very obvious when viewed at angle.
So yes the low power mode is great for mitigating the effects of over burn but doesn’t affect the cause, which is slowing down at corners without reducing power.
I imagine the calculation is pretty complex, given if the curve is a perfect circular arc that’s at least constant, and right angles seem better to overrun (shut off on the right moment), but a complex spline curve seem a very complicated power/speed calculation. Since you seem more up specifically on this algorithm, how does one calculate that around crazy curves?
I imagine a CNC mill has similar issues (adjust feeds and speeds when curving) so what do those CAM packages do (I’ve got an X-carve so have used Easel a bit, but not sure it does anything special on curves)
3D printers don’t slow down for smooth curves they try to run at constant speed. Of course a “curve” is made from line segments and they meet at corners. Typically with 3D printers they take shallow corners at full speed if the instantaneous change in speed of each motor is less than the maximum “jerk” setting. They only slow down as they approach a sharp corner to keep within jerk limit.
CNC mills (which are generally heavier) can be instructed to slightly round off corners to avoid instantaneous speed changes.
It isn’t the CAM stage that does this. It produces G code with the desired speed setting. It is the motion controller that works out the acceleration and cornering speeds, etc.
Motion planning for standard trapezoidal acceleration is not particularly difficult. You have to do two passes, one forwards and the other backwards because the speed you can run on any particular segment depends potentially on all the previous segments since you last stopped and all the following segments until you next stop.
I am playing with a laser diode at the moment and the spot is more than twice as long as it is wide. Motion planning for that will be fun as for constant power density it will need to run at a speed depending on the angle.
So the jerk limit is essentially how fast you can transition from a given speed to another, which I assume is a non-linear function?
Jerk is how fast acceleration changes.
Jerk in applied maths is rate of change of acceleration but in the 3D printer world it is the maximum instantaneous change in speed. So when it starts from stationary it will instantly jump to the jerk speed and then accelerate to the target speed linearly. When it takes a slight corner where the speed of each motor changes by less than the jerk limit it won’t slow down.
Obviously the head obeys the laws of physics so doesn’t change speed instantaneously.
It is expressed as a single constant. It might depend on speed but that is ignored.
So interesting in a device such as a laser cutter that’s going to be a constant, but clearly in a CNC mill it changes with the weight of the end-mill (a 1/64" ball mill vs. a giant 4" flat cutter clearly have huge differences in mass) so is that taken into account? (especially in a unit with a tool changer)
I assume on something like my Taz6 where I can swap heads (dual extruder, single, flex, dual flex) does one have to change the jerk settings (off some manual list I presume)
I think there is enough margin in the normal jerk setting that people set them and forget them.
In my own firmware I don’t have a jerk setting other than with a stepper motor the time between the first step and the second step defines the instantaneous start speed. I.e. you can’t ramp up from zero with a discrete step.
I’m far from an expert, but I do have an X-Carve and have spent a fair amount of time making things with it. In my experience, the weight of the mill isn’t a meaningful factor in the general case. I’m sure there are outlying cases where there are unusually heavy tools, but typically the mill is a very tiny component when you’re looking at the overall mass of the Y axis.
For instance, the Y axis on the X-Carve looks something like this (off the top of my head):
The aggregate mass of the Y gantry plus the cutting resistance (driven by type of material, depth of cut, speed, mill size/shape, etc) is more of a factor, I’d expect.
Oh yeah, didn’t mean the X-carve (I have one too, but yeah, the tools are all pretty much the same), I meant a real mill like a big tormach or something with a rotary tool changer. Some of those big flat cutter bits weigh many pounds…
Ah, gotcha. Yeah the constraints there are different. I wonder if the relative increase in rigidity and mass of the machine still makes it moot. Good question, now I’m curious too!
My guess is that the machines with the big honking cutters aren’t moving all that fast with them. And when you have a really big cutter you usually have a really heavy motor/etc to move it.
But if I might break in for a moment with a related question: has anyone else noticed cutting speeds being size-dependent? I made a bunch of tiny little rectangles to see how my cheapjack baltic birch would cut (about 1cm on a side), and got a through cut at about 100/80. But when I tried to make something bigger (a circle 6 cm diameter and a rectangle about 7x10, I had to drop down to 100/60 to get through.
It would certainly make sense in terms of acceleration and maximum speed and so forth, but it could complicate some designs.
My guess is the acceleration limit is such it can’t actually hit 80ipm over 1cm and stop again. I.e. it would need to go 0-80 over 5mm. In that case the motion planner would have to limit the speed. In a large circle that isn’t the case, so it will run full speed.