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Cheap Chinese Laser Cutter

experiences with a Chinese laser cutter

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Andy Joyce15/12/2019 20:25:07
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Turning for max smoke does not help me as when I type S0 the laser stays on and even M5 will not turn it off

Andy Joyce15/12/2019 20:31:00
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150 forum posts
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To get it to correctly modulate the diode I have to ramp down the power significantly. Also do currently have a 10k pull down on the spindle control, so could reduce that to say a 4k7 but I dont think it is going to help as even tying down the TTL A to logic 0 does not turn off the laser output unless I ramp down the output power.

Andy Joyce15/12/2019 20:41:57
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Posted by Geoff Gardiner on 15/12/2019 18:38:20:

I have installed an extension into Inkscape called - J Tech Photonics laser tool (free download).

This produces the G-Code to send to the laser via CNCjs.

Thanks Geoff that tool gives me far better results for the GCode

FlyinFlynn16/12/2019 14:33:45
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Posted by Andy Joyce on 15/12/2019 20:25:07:

Turning for max smoke does not help me as when I type S0 the laser stays on and even M5 will not turn it off

10K is too high.. even 4k7 is bit too much, I use a 1K but a 2k2 would do the job I guess.

Well that is a crappy regulator. It is not even a hard thing to do ...all it needs is a variable voltage regulator to limit the maximum voltage applied to the laser and a MosFET switch to handle the PWM. Those two modules from aliexpress would set you back under £4.

I guess this is why you see so many people having problems controlling their laser modules.

If you ground the PWM pin and the laser stays on you would need to look at the waveform coming out of the regulator to see what is going on....

Andy Joyce16/12/2019 18:05:52
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Well almost given up on the laser and have raised a case on flea bay to return it as defective.

Possible I could still use it though by not fully turning off the laser and ensuring the carriage travel to each new outline does not run over the previous object but cant seem to find in Inkscape how the start points for each object are defined. Currently in a stack of three ribs it selects the middle object first then goes to the top rib before descending to the lowest. Unfortunately in the travel from one rib to the next it travels over the middle rib which then produces a burn mark in an area within the rib so need to understand how I can modify the path.

FlyinFlynn16/12/2019 18:47:04
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122 forum posts
85 photos

I don't use Inkscape so can't really help, I have my doubts that it will have that sort of functionality though...it is primarily a drawing program, perhaps the simplest way around your described problem might be to cut each rib separately.

I personally would remove the suspect regulator board and fit a step down volts regulator module and a mosfet switch providing I could see the 2 wires going to the laser diode from the onboard regulator... either that or send it back and buy a laser without the pot on top like this one or this one, the adjustable power pot is really only of use if you are engraving and don't want to burn the target and are too lazy to experiment with the correct PWM setting!

Bon courage!

Andy Joyce16/12/2019 19:15:56
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150 forum posts
27 photos

Alex did look on flea bay and found several drivers for example this one. Can see the laser and fan connections so an external drive is an option.

FlyinFlynn17/12/2019 13:06:49
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122 forum posts
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The biggest problem with using a third party regulator is knowing the maximum rating of your laser diode. Unless the model number is stamped on the diode and you can find the diode spec sheet, the only thing you can do is measure the voltage that the existing regulator pushes out and set any new regulator to that or just a smidge under that.

The one you linked would do the job once you have deciphered the connector designations, but it is a big lump and I personally would go for one of these for the regulator

lm2596.jpg

12V in and regulated voltage out, a single pot to set the required voltage, a decent inductor for spike suppression as laser diodes do not like transient spikes. The output pads are wired to the input connectors of this

mosfet.jpg

Which provides PWM control. The laser diode is connected to the output block, the input signal and GND from your arduino goes to the J1 pads. You would also need to provide the 12V to the fan on the laser (check it is a 12v fan first).

In the picture of the regulator you linked there is some form of processor in the middle, I can only guess as to its function. Perhaps, as the specs specify 150kHz frequency it modulates the laser power at 150kHz for the duration of the incoming PWM pulse from your arduino question....anybody know? I do know that the laser diode works well using just these two modules as I had one working with a nichia NUBM08.

Andy Joyce17/12/2019 19:25:29
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150 forum posts
27 photos

Alex,

Could I not just to use the existing regulator PCB and route the laser diode output through the dual MOSFET switch that you suggested and divert the TTL/A signal to that board?

Still waiting to hear if I can return the laser as that is probably my best option rather then trying to make the existing PCB work that came with the device.

Edited By Andy Joyce on 17/12/2019 19:35:18

Andy Joyce18/12/2019 09:32:41
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150 forum posts
27 photos

Have purchased a MOSFET switch as illustrated so will try that first before I completely exchange the control board.

mosfet.jpg

Andy Joyce18/12/2019 16:52:12
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150 forum posts
27 photos

Well the voltage applied to the laser is not quite as I expected.

More o/p power seems to be applied by lower the voltage on the -ve rail so increasing the voltage across the diode.

Withe laser enabled and set to max power the +ve supply wrt 0v grnd is 5.93v & the -v pin is 1.55V wrt 0v grnd.

With the the laser turned off both pins go to 5.62V wrt 0v grnd.

FlyinFlynn19/12/2019 10:53:46
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I'm a bit confused Andy. Are you saying when you tune for max smoke the 0V is lowered to -1.55V making 7.48V across the diode? That is not sustainable for the diode.

Your 3rd paragraph makes more sense.. with the laser fully on ie. 100%PWM the +ve side of the laser diode should be at +5.62V and the negative side of the diode should be at 0V. If the negative side is sitting at +1.55V when measured with a digital meter then the PWM is not at 100%..more like 75%. You would need to see the wave form to be sure.

With the MosFET turned off both sides of the laser diode will be sitting at +5.62V because there is no path through the MosFET.

The most common MosFET switches are N-channel and these work by interrupting the GND going to the load(look at the tracks on the MosFET switch you linked, the +in and +out are commoned.

mosfet1.jpg

If your regulator is taking the negative output below 0V it will affect the MosFet as it conducts when a positive voltage is applied to its gate WRT its source..which is held at 0V

Edited By FlyinFlynn on 19/12/2019 10:55:10

Andy Joyce19/12/2019 11:52:58
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150 forum posts
27 photos

No, when On and set for full power the +ve supply to the diode sits at +5.93v wrt gnd and the -ve supply to the diode sits at +1.55V wrt grnd. So there is 4.38V across the diode.

For me that would suggest the MOSFET switch is not operating correctly as would have expected the -ve pin to go close to zero.

Jason Channing20/12/2019 09:09:14
105 forum posts

Having built my laser cutter are their any files I can down load from somewhere already designed to check the set up, i'm looking for wing ribs in particular the type im not too bothered by as I want to start with a known quality.

I have done quite a lot of 3D printing and am familiar with thingverse etc.

FlyinFlynn20/12/2019 10:24:00
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122 forum posts
85 photos

Here you go Jason. Not specifically designed for checking setups but they should work ok. The clarkY profile should be 200mm chord, the symmetrical one is 150mm chord and the X10 is 146mm.

Andy, the 4.38V sounds like a reasonable voltage, the 5.93v sounds a bit too high, although there are laser diodes out there that do have a higher maximum rating there are far more around the 4.5 - 4.8v range.

Andy Joyce20/12/2019 11:37:58
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150 forum posts
27 photos

Thanks Flynn, think this MOSFET switch I ordered is on a horse and cart for delivery as it is showing the end of the month despite only coming from Manchester.

Jason... if you let me know what wing profile and chord you need I can see if I can generate one in profili for you and then I will export it to Inkscape which will allow you to modify if required and generate a gcode file. Its all good practice for me, as there is a steep learning curve generating cutting files as you will quickly find out.

Jason Channing20/12/2019 12:18:50
105 forum posts


Hi Andy, anything will do about 125mm chord , its just so that I have a known. regards Jason

Andy Joyce20/12/2019 12:58:59
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150 forum posts
27 photos

Any preference as to regards the profile?

Andy Joyce20/12/2019 15:19:16
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150 forum posts
27 photos

Jason...try this file in inkscape : File This is the first time I have used google drive so hope the link works.

Edited By Andy Joyce on 20/12/2019 15:23:16

Edited By Andy Joyce on 20/12/2019 15:27:07

Andy Joyce24/12/2019 16:54:17
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150 forum posts
27 photos

Is timing belt supplied as a standard pitch? Ooznest seem to stock GT2, 2.5 & 3 belts so a little confused.

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