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Cheap Chinese Laser Cutter

experiences with a Chinese laser cutter

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FlyinFlynn26/12/2019 18:48:19
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121 forum posts
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No such thing as standard these days...they all used to be 2mm pitch and 6mm wide but now there are a few different ones in use.

Andy Joyce27/12/2019 19:55:35
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148 forum posts
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Well finally got an operating switch to modulate the laser by inserting an dual gate MOSFET pcb in line with the old laser output as pictured. However I do find it difficult to find an optimum setting for cutting 2mm balsa.

Tried moving the balsa close to the cutter and re-focusing for that distance but it seems I get far better results with the work about 10cm from the lens. So is there an optimum distance for the these types of lasers?

Currently using 2000mm/sec 100% power and 3 cuts to go through 2mm.

dsc01102 (small).jpgdsc01103 (small).jpg

Andy Joyce28/12/2019 14:08:40
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Posted by FlyinFlynn on 17/12/2019 13:06:49:

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.

Flynn, what was the source of the constant current regulator you pictured as mine seems to have now given up the ghost and only firing the laser in brief pulses?

FlyinFlynn29/12/2019 12:18:04
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121 forum posts
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There are millions of them....aliexpress has a selection, as will ebay and banggood. Most operate within the voltages you need for a laser diode, just pick one with a high enough current rating. The LM2956 based regulators have a max rating of 3 amps but will need some additional cooling if you go above 2...which you shouldn't with a 3.5Watt diode. Some of them have an integral digital voltmeter that you can switch between input and output volts.

Andy Joyce30/12/2019 10:28:42
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148 forum posts
27 photos

Well have ordered a constant current regulator but tempted just to try my lab PSU to allow simple adjustment of the laser drive voltage and max current.

FlyinFlynn31/12/2019 10:08:21
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121 forum posts
85 photos

That's what I did to test a new laser.yes

Andy Joyce31/12/2019 16:06:19
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148 forum posts
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Back in business, so can start cutting some ribs now at long last.

dsc01104 (small).jpg

FlyinFlynn01/01/2020 10:39:21
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121 forum posts
85 photos
Posted by Andy Joyce on 27/12/2019 19:55:35:

Well finally got an operating switch to modulate the laser by inserting an dual gate MOSFET pcb in line with the old laser output as pictured. However I do find it difficult to find an optimum setting for cutting 2mm balsa.

Tried moving the balsa close to the cutter and re-focusing for that distance but it seems I get far better results with the work about 10cm from the lens. So is there an optimum distance for the these types of lasers?

Currently using 2000mm/sec 100% power and 3 cuts to go through 2mm.

dsc01102 (small).jpgdsc01103 (small).jpg

Sorry I missed your post. There are different lengths of heatsink available which suggests that there are different focal length collimating lenses. some lasers state 10mm is optimal and some more like 10cm. I have a lens that needs screwing almost all the way out of the housing in order to focus the beam, I have a longer diode holder on order.

p1010223.jpg

p1010225.jpg

I guess if you have the 10mm type then the focus will be much more critical to the cut, besides it must be more difficult to see the focus at 10mm

"Currently using 2000mm/sec 100% power and 3 cuts to go through 2mm."

That is consistent with the results others have achieved with similar kit.

Edited By FlyinFlynn on 01/01/2020 10:41:58

Andy Joyce01/01/2020 17:43:45
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148 forum posts
27 photos

Does anyone have any recommendations as to the flow rate for air assist?

Edited By Andy Joyce on 01/01/2020 17:44:08

Andy Joyce04/01/2020 10:00:58
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148 forum posts
27 photos

Will do some further experiments in the cutting height as it is taking in excess of 5 cuts just to get 50%-60% through 2mm hard balsa at a speed of 2000mm/min when cutting a ~6cm rib chord.

Strangely a star shape 1cm across cuts 100% through the same balsa in 3 passes using the same speed. So unclear why this should be other than the cutting area is a lot smaller and possibly the average speed between all the cutting nodes is lower.

Do agree with your comment on focus Flynn. Is there a simple trick to establish the optimum setting?

Andy Joyce05/01/2020 10:53:35
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148 forum posts
27 photos

A possible explanation as to cutting small shapes against larger is that I am using M4 to turn the laser on against M3.

Unfortunately using M3 tends to result in burn marks close to a node. So is there any way of accelerating the laser ramp up to the max power level when using M4?

FlyinFlynn05/01/2020 12:53:01
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121 forum posts
85 photos

I think that as M4 calculates the power to be used for the speed of the carriage if you increase the acceleration value and/or maximum speed you should reach max power sooner - no?. If you lower the speed from 2000 to say 1500mm/sec it will take less passes... your laser outputs a set cutting energy level into the workpiece...it is all around finding what works for you.

As to the focus, it is easier to see the focus point if you reduce the power to 2 - 5%. All my lasers have a focal point of around 10cms, this is more than is widely recommended but it makes the acceptable focus depth a bit more than having a focal point at 2 cms where half a mm deeper makes a big difference to the spot size.

focus.jpg

Andy Joyce08/01/2020 16:17:20
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148 forum posts
27 photos

Still looking for recommendations as to the size of a pump for air-assist.

Martyn K08/01/2020 16:36:34
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5041 forum posts
3677 photos

Hi Andy

I bought a very cheap low air throughput pump from a fleabay Chinese supplier for about £4. It works ok but I need to plumb it in properly. As I use my laser to cut tissue, I don't want a big draught, just a gentle waft to remove the smoke.

I'll let you know how I get on. My laser is in bits at the moment for mods - fitting this is one of them.

Martyn

Andy Joyce08/01/2020 17:04:43
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148 forum posts
27 photos

Thanks Martyn, noticed others have purchased 38L/min units

Edited By Andy Joyce on 08/01/2020 17:10:10

Martyn K08/01/2020 20:09:46
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5041 forum posts
3677 photos

My little pump claims to be 1.5 l/min. Just a waft of air to clear the smoke. If its not enough I'll go for something a little larger.

Martyn

Andy Joyce09/01/2020 06:54:27
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148 forum posts
27 photos

Do get the odd flame when cutting balsa so think I need the extra air rate to blow out any fire and remove the smoke. However it remains unclear what air rate is best for this.

Martyn K09/01/2020 21:21:26
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5041 forum posts
3677 photos

Fitted my little pump tonight and it does keep the smoke away. Quite pleased with that.

I do have a problem though. I am trying to cut very light 1/32 balsa and it keeps burning.

I have switched on laser mode. $32=1 and then enabled laser level ramping $4=1 which is meant to reduce power at corners (think stringers slots) which is where the fires start. Now, setting $4=1 in non laser mode disables the steppers which is what is happening.

it appears as though the controller does not recognise laser mode.

Anyone got any ideas? I am wasting a lot of wood trying to get this sorted.

thanks

Martyb

FlyinFlynn10/01/2020 10:21:56
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121 forum posts
85 photos

$4 is Invert step enable pin with GRBL v1.1f.... what makes you think it has something to do with ramping laser power?

The command I use to enable dynamic laser power mode in the corners is M04 instead of M03 to switch on the laser.

See **LINK**

 

Try increasing your speed to reduce the balsa burning...you will need to increase the number of passes to compensate as well.

Edited By FlyinFlynn on 10/01/2020 10:23:31

Martyn K10/01/2020 12:52:23
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5041 forum posts
3677 photos

Thanks.

So how do I switch M4 on? I thought the $ commands were the M code instructions.

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