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Cheap Chinese Laser Cutter

experiences with a Chinese laser cutter

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FlyinFlynn13/12/2019 16:37:03
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Posted by Andy Joyce on 12/12/2019 19:21:51:

Can someone please advise how the carriage limit switches should be set/wired. Have set $20 & $21 to 1 with the switches wired to NO but cant seem to get then function as expected.

That sounds right...but if you have a new cncshield have you seen this -

End Stop Configuration

By default GRBL is configured to trigger an alert if an end-stop goes low(Gets grounded). On the forums this has been much debated and some people requested to have active High end-stops. The jumpers in the picture provides the option to do both. (To run with default setting on GRBL the jumper need to be connected like the left shield in the image below)(This Jumper was only introduced in Version 3.02)
End-stop Configuration Active LOWorHIGH

When triggered it should stop the motors and bring up the alarm which will require a reset to clear. what are you getting?

FlyinFlynn13/12/2019 16:49:31
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116 forum posts
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Posted by alex nicol on 12/12/2019 19:52:27:

I've just taken the plunge and ordered an Alphawise C30 DIY kit and have absolutely no experience in cad or what software to use or even what works with what etc. Very steep learning curve ahead methinks

Is there an idiots guide somewhere that outlines the basics of how it all works

Thanks in advance

Alex

It can be a steep learning curve Alex, What are you wanting to achieve with the laser? Benbox software comes with that kit, that will allow you to import image files and engrave onto wood and other 'soft' materials. If you are wanting to cut balsa then you are going to want better software, I would suggest LibreCAD for your CAD and DeskProto for your CAM with LaserGRBL for a sender...but that is just me...if you ask 10 people you will get 12 different answers. some users on here use LightBurn, which has all 3 functions, but that is a paid for app. I am not aware of an all encompassing tutorial, but YouTube is full of 'how to' videos.

I am sure you will be aware but take care when the laser is operating, it will not any prisoners.

Get the kit built and start playing!

alex nicol13/12/2019 17:47:47
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334 forum posts
15 photos

Thanks for the info.

I'm looking to cut balsa, lite ply and birch ply up to a max thickness of 3mm.

It'll be light hobby use, ideally I'd like to be able to cut formers and wing ribs for plan and od builds.

I can foresee many evenings of gnashing of teeth and hair tearing ahead

Andy Joyce13/12/2019 19:37:36
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127 forum posts
26 photos
Posted by FlyinFlynn on 13/12/2019 16:37:03:
Posted by Andy Joyce on 12/12/2019 19:21:51:

Can someone please advise how the carriage limit switches should be set/wired. Have set $20 & $21 to 1 with the switches wired to NO but cant seem to get then function as expected.

That sounds right...but if you have a new cncshield have you seen this -

End Stop Configuration

By default GRBL is configured to trigger an alert if an end-stop goes low(Gets grounded). On the forums this has been much debated and some people requested to have active High end-stops. The jumpers in the picture provides the option to do both. (To run with default setting on GRBL the jumper need to be connected like the left shield in the image below)(This Jumper was only introduced in Version 3.02)
End-stop Configuration Active LOWorHIGH

When triggered it should stop the motors and bring up the alarm which will require a reset to clear. what are you getting?

Yes I had seen these posts Alex which did confuse me as don't have the end stop jumper on my shield PCB.

After a bit of searching on the topic discovered it was likely noise on the limit switch wiring. So added a few pf's across the two switches on the Y axis which were causing the issue and now have a working system.

Traced out last night the ribs for a Bird of Time using Inkscape just for a bit of fun. Found the bezier tool is so easy to use that I had the task done in minutes. The only issue I have is there must be a control key to draw only a horizontal/vertical lines when selecting the next node but darned if I can find it.

Andy

FlyinFlynn14/12/2019 19:53:06
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116 forum posts
82 photos
Posted by alex nicol on 13/12/2019 17:47:47:

Thanks for the info.

I'm looking to cut balsa, lite ply and birch ply up to a max thickness of 3mm.

It'll be light hobby use, ideally I'd like to be able to cut formers and wing ribs for plan and od builds.

I can foresee many evenings of gnashing of teeth and hair tearing ahead

 

Indeed...if you get stuck help is at hand!

 

Andy.. Those mods will only be on the genuine cnc shield from Protoneer.. i don't think the Chinese have ripped off his latest design, it just sounded like it might have been your problem but I am glad you have sorted it. The internal pull-ups on the Nano are a bit on the weak side so a bit of noise filtering can do the trick.

 

Sorry, can't help with Inkscape..don't use it.

 

 

Edited By FlyinFlynn on 14/12/2019 19:57:53

alex nicol14/12/2019 20:10:11
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334 forum posts
15 photos

Thanks FF, I have a feeling a little help or a steer in the right direction may be needed and will also be very much appreciated.

Id also add, there's been a couple of suggestions that regular laser cutting and 3D printing topics would make good and popular magazine features .......... it'd get my vote

Andy Joyce15/12/2019 10:34:56
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127 forum posts
26 photos

Currently stuck regarding the laser control.

Proven that the laser turns on with 5V applied to its TTL A pin and turns off with 0v applied.

Testing spin enable on the Arduino Shield which I thought should be used to control the laser I find it stuck at 5V. Tried sending M3, M4 & M5 commands but the logic state remains at 5V.

Have I missed something here or has the shield output been damaged, or should I be using another output to modulate TTL A?

Andy Joyce15/12/2019 11:10:56
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127 forum posts
26 photos

Think I have an old shield that has swapped Spin enable and Z+ end stop. So again tested the z + pin and found that sits at 0V even after typing M3 M4 or M5 commands.

Am I using the correct format to toggle the laser on and off as simple type M3 into the command line?

Geoff Gardiner15/12/2019 11:12:37
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444 forum posts
781 photos

Hi Andy.

Are you powering your laser with a separate power supply. If so, you need to make sure they share the same ground connection. I had similar issues with mine which I fixed by powering everything from one power supply.

Hope that helps.

Edited By Geoff Gardiner on 15/12/2019 11:14:36

Andy Joyce15/12/2019 12:03:36
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127 forum posts
26 photos

After playing around and using CNCjs now have the shield laser output pin Z plus working, but it does not fully turn off the laser. Therefore should I put a 10K pull down resistor is used for prevent the momentaneous laser powering on when Arduino resets and put the driver input control at high impedance state.

Andy Joyce15/12/2019 12:05:15
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127 forum posts
26 photos

Geoff

No using a single 12V 5a psu. Wondering if I should now link 5V GRND to 12V GRND.

Andy Joyce15/12/2019 13:53:19
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127 forum posts
26 photos

Well think I should delete some of my posts because have been led up the garden path by an intermittent PSU.

Going back to the start I do have a working Arduino Spindle start output but when using the Laser off command I still get a reduced output from the laser under the control of CNCjs after the M5 command is sent.

Thinking the issue was the Arduino or possibly the software, I then tried grounding the laser TTL A pin to 0v but again the laser stays on.

So open to any suggestions as how to fix the issue and to get the laser to turn off completely.

As previously stated I am only using a single PSU so the issue is not the 0V refs between 5V and 12v rails.

Suppose I could put a mosfet onto the Laser power rails under the control of Spindle Start.

Edited By Andy Joyce on 15/12/2019 14:06:44

Edited By Andy Joyce on 15/12/2019 14:07:57

Andy Joyce15/12/2019 18:29:11
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127 forum posts
26 photos

Well beginning to make a bit more progress as noted the gcode samples I had created from inskape did not appear to be turning the laser on and off. Nor was the spindle control changing state. So assume I have not correctly set up the conversion.

Sample of my first test code is:

(Using default header. To add your own header create file "header" in the output dir.)
M4
(Header end.)
G21 (All units in mm)

(Start cutting path id: path191)
(Change tool to Cylindrical cutter)

G00 Z5.000000
G00 X106.985560 Y23.194600

G01 Z-1.000000 F200.0(Penetrate)
G02 X106.580342 Y21.496198 Z-1.000000 I-3.761889 J0.000000 F200.000000
G02 X105.410460 Y20.081620 Z-1.000000 I-3.709958 J1.877158
G02 X103.723897 Y19.227222 Z-1.000000 I-3.039246 J3.907588
G02 X101.131660 Y18.866190 Z-1.000000 I-2.592237 J9.125711
G02 X99.606977 Y18.962763 Z-1.000000 I-0.000000 J12.084020
G02 X98.303921 Y19.225850 Z-1.000000 I1.154410 J9.076265
G02 X97.044947 Y19.645037 Z-1.000000 I4.884494 J16.770103
G02 X96.158316 Y20.032010 Z-1.000000 I3.265368 J8.690817

So tried using DFX2GCODE and whilst I found the drawing paths was not correct at each corner, the spindle control was correctly activated. So now pondering what I am doing wrong in INKSCAPE with regard to the tool selection.

Sample of the new code is:

(Generated with: DXF2GCODE, Version: Py3.6.7 PyQt5.11.3, Date: $Date: Fri Oct 25 20:45:56 2019 +0200 $)
(Created from file: C:/Users/Slick/Documents/storch1.dxf)
(Output format description: G-CODE for LinuxCNC)
(Time: Sun Dec 15 18:23:55 2019)
G21 (Units in millimeters)
G90 (Absolute programming)
G64 (Default cutting) G17 (XY plane) G40 (Cancel radius comp.) G49 (Cancel length comp.)
G0 Z 15.000

(*** LAYER: DRAFT_ENTITIES ***)
T1 M6
S6000

(* SHAPE Nr: 1 *)
G0 X 64.611 Y 20.724
M3 M8
G0 Z 3.000
F150
G1 Z -1.500
F400
G2 X 62.611 Y 20.724 I -1.000 J -0.000
F150
G1 Z -3.000
F400
G1 X 26.599 Y 20.721

Geoff Gardiner15/12/2019 18:38:20
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444 forum posts
781 photos

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.

FlyinFlynn15/12/2019 19:02:53
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116 forum posts
82 photos

Do you have the following values in GRBL -

$30=1000

$31=0

$32=1

if so then your PWM level is set by Sxxxx

first ascertain if your hardware is working correctly. in the console send

G1F2000M4

S1000 the laser should come on full

S500 the laser should dim to half power

S0 the laser should switch off

M5 disables the laser

If that is ok you are looking at a software configuration issue

Your inkscape output has no S command so i cant see the laser switching on at all.

Your DFX2Gcode output has a single S6000 command so I would expect the laser to come on at full power with the M3 command but there is nothing switching it off....

The following GRBL commands all have to be present for the laser to switch on

G1... active move command as opposed to a rapid, positioning move (which is G0...and the laser wont fire)

Fxxx sets the speed

M3 or M4 enables the laser but it wont fire until it is told the strength

Sxxx once GRBL has all 4 commands (in any order) the laser will fire

You can then shut off the laser either with an M5 or an S0

Andy Joyce15/12/2019 19:41:45
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127 forum posts
26 photos

Alex

Yes my starting condition is:

$30=1000 for the max spindle speed

$31=0 for the lowest speed

$32=1 enabling the laser

Don't see any voltage on the spindle control after typing G1F2000M4 S1000, but is does work with G1F2000M3 S1000.

FlyinFlynn15/12/2019 19:57:13
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116 forum posts
82 photos

Ah yes.....that's because you ain't moving! M4 ramps up the laser power from 0 at a standing start to whatever the S command sets when the laser carriage is moving. You would see a voltage if you added a G1X100 for example to move the X axis 100 mm

 

Got an oscilloscope?  It makes it easy to see what is going on.

Edited By FlyinFlynn on 15/12/2019 19:58:27

Andy Joyce15/12/2019 20:01:45
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127 forum posts
26 photos

Success, after lowering the power setting pot on the laser now able to turn the laser off with S0, but its certainly not operating at full power with S1000. Adjusting the power pot on the top of the laser in the other direction certainly increases the power but then does not give me zero emissions with S0.

Andy Joyce15/12/2019 20:04:08
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127 forum posts
26 photos

Afraid not re an oscilloscope, but the board is correctly modulating spindle control as S500 gives me 2.5V on the DVM.

FlyinFlynn15/12/2019 20:14:55
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116 forum posts
82 photos

Ummm.I assumed that the adjustment pot on top of the laser was to adjust the maximum power sent to the diode, but that should not affect the low end...a bit like a throttle trim in reverse!

Sending M5 should cut the laser, so you will just lose a bit of control at the bottom end and we aren't too worried about that when cutting. Set the knob to maximum volume set S1000 and turn the laser on with M3/M4 and off with M5. By the way I don't think GRBL understands the T commands in your headers.. it is for tool changing.

There is no pull down on the cncshield Z+ pin so maybe you could do with a 1k resistor between Z+ and ground...it is a mod done on the eleksmaker control board to try and prevent spurious firing during the processor boot...can't hurt to try it!

 this would do the job!

Edited By FlyinFlynn on 15/12/2019 20:16:07

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