Upgrading a Laser Cutter from China (Part Two)…

by Stephen Hobley on April 25, 2011

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More information on the (ongoing) saga of my recent purchase…

Using a multimeter it was easy to work out the wires coming from each motor. They are bipolar and so two pairs of the four wires will register a resistance, these are the A and B coils. They require 24V and 0.5 Amps. They stay cool during a run and I haven’t had any issues yet. Within Mach3 Motor Tuning I set them to 1016 steps per inch, 120 i.p.m. and an acceleration of 4. This seems to work OK.

After getting the gantry under control, all that remained was turning the laser on and off. Luckily Andy Slater had already solved this problem, by identifying an external control line on the laser power board.

I hooked up the two extra wires describe in Andy’s article, and connected them to Gnd and Pin 8 on my parallel breakout board. Inside Mach3 I was able to configure output #1 to use pin 8 and therefore get the spindle commands M11P1 (On) and M5 (Off) to control the beam. Important note – by default the pin is High when the computer starts, only being pulled low when Mach3 starts up, therefore it’s important to disable the laser until you are ready to start cutting, either by opening the lid of the machine, or using the “Laser Enable” switch.

So now on to create some laser-ready G-Code. All my existing work had been milling with a spindle – here the spindle was just turned on and off by hand and the Z depth denoted how much cutting was applied to the billet. I decided to create the G-Code for a standard milling operation and then replace the Z plunge/retract movements with the laser on/off commands.

Laser Cut Seal of Rassilon

I set the tool to be 1mm wide, with a max depth of 2mm. The safe Z was set at +10mm. I then set the plunge depth at 1mm (ensuring only a single pass would be generated) and create the G-Code file. In a text editor it was simple matter to replace all the calls to set the Z depth to -1mm with M11P1, and all calls of Z 10mm to M5. This strategy worked rather well.

BTW : Here is a neat online G-Code commenter – plug in some G-Code on the left, and get an explanation on the right.

Shiny things made with the laser cutter

This video shows one of my first few cuts – I forgot to remove the initial M6 from the file, hence the laser starting up even before moving into position.

Acrylic cuts really well, however I think it would benefit from an “air assist” upgrade – I think I’ll try adding that next. It’s my goal to be able to cut quarter inch acrylic cleanly – then I can make *stuff*.

Laser Cut Seal of Rassilon

I seriously doubt that I would be able to make the above figure using my CNC mill.

The vendor has offered a free replacement controller board (or a refund on just the board) – I was tempted to go for the refund, but I’m thinking now that I should give him a chance to replace it, and see how I get on with the “NewlyDraw” package that came with the cutter.

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{ 9 comments… read them below or add one }

B April 28, 2011 at 6:53 am

Looking good, be interesting to see how the “newly draw” goes

Jelle May 1, 2011 at 2:19 pm

you don’t need much air assist with acrylic: you need the cut surface to stay/get hot so it melts into a smoother surface. You do need air for cutting paper cardboard and plywood though.
The newly draw will make you tear your hair out, but going cad/cam for a simple laser might too.

Hammer Mill machine July 31, 2011 at 3:10 am

A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines. Unlike a drill press, which holds the workpiece stationary as the drill moves axially to penetrate the material, milling machines also move the workpiece radially against the rotating milling cutter, which cuts on its sides as well as its tip. rical control (CNC).

EK August 1, 2011 at 4:25 pm

Your machine exterior looks exactly like the machine I just bought from a US board maker – http://www.fslaser.com

They make their own processor board that works in conjunction with Mach 3 and have already added air assist and other mods to the “deluxe” units which run $2350 and works out of the box.
The processor board/software combo treats the laser as a printer for Windows (no NewlyDraw!). You may want to take a look, could save you some trouble. Unless you enjoy the tinkering part 🙂

Stephen Hobley August 1, 2011 at 4:40 pm

Thanks for the info – I’m so far down the G-Code path that I’ll probably stay with that. (Yes I enjoy the tinkering 🙂 )

Doug April 20, 2012 at 4:14 pm

Hi there,
Great tutorial. My understanding is that the cheaper Chinese Laser Cutters do not do Vector Graphics. Is this something intrinsic to the boards used? I asked an eBAY vendor if changing the software would address this limitation and he said “no”.

Any thoughts?
Thanks
Doug

Stephen Hobley April 20, 2012 at 4:27 pm

Difficult to say, I replaced the controller so it hooked into Mach3 directly.

The Chinese software is certainly proprietary, and treats the cutter like a printer (rather than a plotter).

Doug April 20, 2012 at 5:49 pm

Thanks for the reply.
Are there DIY boards that can be setup like a printer and so work with any graphics software? On the other hand, is Mach3 able to deal with Vector/Raster Graphics directly or only through G-Code interpreteurs?
Doug

Nicki March 15, 2014 at 4:50 am

Hi
Please can you help bought the Chinese 40w laser engraver and can’t work out how I do the writing part on the wood….?.
Would be really grateful for your help

Nicki

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