TangerineTiger15 Is Ordinary Engraving another disappoinment

Ordinary engraving is one of the areas where the almost instant switching capability of this technology should excel. In this session we explore the superficial properties of this high speed engraving capability. However, with only 20 watts of burning power , just how fast will that allow us to go. We know this machine is currently capable of at least 1400mm/s but does that mean faster cycle times? Caution...... there may be two limiting factors that will prevent this speed being usable. First is POWER, Just how thinly can I spread 20 watts and get acceptable results? Second is ACCELERATION.,The faster the linear speed, the longer it takes to accelerate and decelerate. We have already seen how this second factor can have a HUGE effect on cycle time . Hence, the headline speed capability of a machine maybe impressive but without sufficient watts and motor power that number may be meaningless

[markpinther]

Excellent video. I had not heard of RF for lasers before so this was news to me.

[klasmalman]

Hi again Russ....
Nice to see that you finally found some upside of the RF-machine.
But i feel troubled when you talk about the PWM-issue. I think that you misunderstanding some of the principles of it despite the discussions.. :)

You will get a true (somewhat) linear modulation of the output power when running the pwm at frequency’s above the system response time.. the beam energy will not pulse from full to zero power, due to the response time the energy level will get averaged out... there might be some small ripple in the power but it will appear continuous analogue.
Lets say we use the 25kHz pwm frequency setting. The specs of the tube says rise and fall times better (shorter) than 100us. So for this discussion lets say they really are 100us long. That means that if we command the tube to turn on, it will take 100us to reach 90% of full power (as of the normal definition of rise/fall time) if we then commands it to turn off the beam, it will take another 100us for the beam to drop to 10% power level on its way to turn completely off.
If we interrupt the previous command by changing the desired target to fully on again, and doing this quicker than the response time of the tube, the output level will not have time to drop to zero, and then start to increase again... but before reaching full power it then gets turned off again.... resulting in a power level in between zero and full power.. at 50% duty cycle the output level will be about 50% of full power, at 75% duty cycle the output level will follow to about 75% power. This is the benefit of pwm signalling if driven at a frequency above the response time of the tube. The higher frequency, the smoother the output level will be, because the system will not be able to change the power of the beam that fast. It will change, but if driven well above the response time it will average out to a nearly smooth level.
If we were about to run the system at 5kHz and 50% duty cycle we might be able to see the switching on and off in the engraved line (if mowing the head quick enough). 100us on, 100us off, total 200us time ie 5kHz. If we were able to measure it we would see a power level linearly climbing from 10% to 90% before dropping back to 10% again. If we would run at a higher pwm frequency, we would not see such a wide power level spread.. the engraving would just turn gray as the frequency increased., as the output power would be more and more compressed to the 50% power level.
These response times allows a minimum pixel width of 100us (which in reality will be gray’ish if it’s dropping from full power down to 10% during that time)

So I urge you to try to engrave something with 25kHz pwm frequency, and to feed the laser with a true grey scale image instead of the dithered version.... and then tune the scanning speed to get the contrast you want out of the or in any other way test the true potential of grey scale engraving by letting rd-works control the pwm duty cycle.

:)

Best regards

/Klas

[nicojk]

At last some good news! Nice one, Russ! Thanks for sharing

[Matucks]

Reminds me of what an Epilog can do. Your making great progress when can I fly you to America to upgrade my machine? Cutting is great with these machines especially if you want to piece something together theres very little no gap and the cuts is straight without barely any sign of a curve. RF LAser is the way to go

[johnrevill]

Hi Russ. I will be very interested to hear your findings on the banding you are seeing with the RF laser. I have the same problem. My theory had to do with the metal casing temperature. My thinking was that as the temperature is rising, the output is fluctuation. Once the temperature stabilises, the fluctuations reduce. Hence why we see the banding more at the start of the job and less towards the end of the job. I have tried running a 5-minute solid engraving at 100% power to try and warm the metal tube up before starting a photo job, but have had limited success. And as you may remember, my machine is a Galvo CO2, so no belts or gantrys to worry about and a very different lens system. I have tried Horizintal and vertical scanning and the banding is always in the same direction as the scanning. So that eliminates mirrors and lenses.

Below is a share to a folder with lots of pictures of my banding issue.

[simonwood]

Russ, I need some help here, I have a 40watt RF tube, and almost the same China blue & white laser machine with your earlier video. I was using the AWC708 controller, everything is fine, engraving, cutting. Now I bought a Ruida rdc6442s controller, it had a problem . It didn't fire laser beam when I draw a line width 0.1mm vector vertical line on scanning mode, I've tried many different line width till the line width is 0.8mm, my setting is :scan interval 0.05mm, speed 500mm/s, power 70%. Newest version of RDworks & lightburn, the rdc6442s(ec
）firmware version is 8.01.57 . What happened with my machine, my 1.5" lens can deal with 0.09mm dot, but the 6442s will not fire laser beam at a such small dot untill dot size is over 0.8mm.

[xenon]

Hi Russ!
Can you explain what a compoud lens is? what are the benefits and where to get?

[WcWGoldbergWcW]

Good evening mate, I’m looking to purchase a decent High quality laser engraver to start my own side business, could you recommend any at all? I know decent ones won’t be cheap but I want to buy something that does the job! Engraving quality portraits on wood etc

Thanks

Glen

p.s

I’m only 80 miles from London, so looking to buy something local if you know any places?

[patprop]

Is it possible the tannic within the woods is reacting differently to the wavelength of the laser beam?

[WillBassler]

The problem is not with your machine the patterns that you are seeing there are moiré patterns they come about from re-screening things that have already been converted to halftone that is specific.patterns the effect can also be enhanced by the material that has patterns in it such as woodgrain I have 25+ years in the printing industry and the only way to avoid having moiré patterns in halftones is to shoot them from a continuous tone photograph there are ways to lessen the moiré pattern by rotating the screen angle and selecting the correct dot size when rescreening. It must be noted that all electronic photographs are not continuous tones.

[redherring]

In digital printing we call that "banding" would guess its y axis stepping