Cheap Chinese Laser Cutter

[Gervaise Vernon Retail manager StarLoc]

I dont use this type of laser ours is a co2 one but , Are you joining the lines together to form one line in the cad pack you are using, the line type can cause problems spline or non spline curves, one doesn't cut it cuts in stages, depending on the speed it can power up you can with some led lasers get gaps.

The burning, unless you cut at very low power a few times you will burn the wood, cut at high power as the power goes up if you hit softer parts of the wood it will suddenly flame up and set the piece on fire,

The cure is `air assist` to run a tube to point at the cutting dot and blow air down it we have 50psi from a big oilless compressor , we disabled the fancy air assist nozzle that our co2 lasers have as ithey are not as good, we blow down a piece of 2mm id nylon tube and get no flames,

The air also removes dust from in the cut allowing you to cut faster and deeper in one pass as you remove the dust that otherwise blocks the laser as you cut.

[Rob Ashley]

Posted by adrian garnham on 19/02/2020 20:38:45:

Hi all

I have finished building a 5W laser cutter which is a hybrid between the FlyinFlynn and Geoff Gardiner machines (thanks to you both for your input as I don't think I would have been able to complete it without your help)

I am more than happy with the results for cutting balsa but not so impressed with ply so I have almost finished making a CNC router with a 500W spindle motor.

What type of cutter should I use for cutting up to 6 mm birch plywood ?

Adrian,

I have found that 1mm end mills, as shown by Geoff Gardiner, are perfect for cutting balsa and ply (you can also use larger). I found its is best in ply to cut no more than 3.2 mm each pass so 2 passes for 6mm ply. Balsa can be cut in 1 pass. Your total depth limit is the length of the cutter - so a 3mm bit with a 3mm shank can cut 20mm thick material.The main thing is not to stress the cutter and clearing the swarf is essential to reduce heat. I often use 0.8mm mills for balsa and even 0.3mm engraving bits for extra fine work.

Feed rate is also important so for ply I find 250 mm/min works well and 300-350m/min works great for balsa. You can go faster but I like to reduce the stress on the cutter - they last longer and you get a much better cut.

For aluminium and mild steel use decent end mills and I find 1,2 & 3mm proxxon bits are awesome.

Others may have their own methods/ideas that work - the info I have I found from personal experience and there is always something to learn. It is quite a fascinating part of the hobby for me and I have been CNC machining/routing for over 10 yrs now making everything from single parts to kits to engine parts. I hope you have fun with it as it can be quite absorbing.

Rob

[FlyinFlynn]

Martyn - Your description of the machine pausing at the end of every arc is precisely what laser mode was designed to overcome. In a router the x and y axis must pause at the start and end of each linear movement to allow changes on spindle speed to take effect, when using a laser, spindle speed changes happen all the time to change the laser intensity. Are you sure you have laser mode set to ON in your GRBL settings? ($32 = 1)

[Former Member]

[This posting has been removed]

[Stephen Smith 14]

Barrie thats a really nice head on your K40 what make is it and where did you get it from would like one on mine.

[Former Member]

[This posting has been removed]

[Martyn K]

Thanks for the advice.

The settings on the controller are:

$30=1000

$31=0

$32=1

which I think is correct.

I also fail to understand why the laser only appears to be running at about half power

I have also grouped the object so all the arcs should now be contiguous.

Any thoughts?

Martyn

[Martyn K]

I have tried setting $32=0 - that gave me back my power but the cut path still stuttered in the same places. So now its back to $32=1 and reduced power again. The main wheel circle - which is definitely one object also stutters.

I still think this is a controller issue struggling to process commands in a timely manner.

So, starting from scratch, using the little drawing package in Lightburn, I drew a random shape of a square overlapped by a circle with a few random lines (scribble) intersecting the square and circle.

It worked perfectly, I had full power back (or it appears to be), no stuttering and nice clean cuts. The only gaps were at the corners where the power reduced as it slowed down.

So, is the problem the way that the program is interpreting the DXF file and generating GCODE?

I will get to the bottom of this...

Martyn

[Former Member]

[This posting has been removed]

[Stephen Smith 14]

Thanks Barrie will see if I can get there head once the world returns to some normallity but they don't list any parts on there Web site.

I see they supply the same poor exhaust fan, I found one on thingyverse which uses the same motor with a different housing printed in several parts, seals much better on the back of the machine and the difference in performance is night and day.

[Martyn K]

Hi Barrie

Good question. I am absolutely sure, but I will double check in the morning. The wheel outer stutters and that is definitely a circle.

Martyn

[Martyn K]

I appear to have a fix after posting my problem on the Lightburn forum

I got a very good suggestion which didn’t work unfortunately, however an explanation of laser mode gave me the clue I needed. I simply dropped the cut speed down from 600mm/min to 300mm/min and it worked perfectly, with nice clean corners.
I also tried with an ai file type and join selected shapes (suggestions from the Lightburn forum) . In fact, the fix may be a combination of all 3 but there was no obvious improvement until I reduced the speed. I need to experiment a little more but the quality of cut now is very much better.

The problem was that the head could not accelerate or decelerate fast enough to keep the laser going at the desired power.

Simple really.

Martyn

[Former Member]

[This posting has been removed]

[FlyinFlynn]

Barrie - Yes Barrie, I am sure my statement was correct, but I think you misunderstood it.

**LINK** describes it better than I can......operational procedures for mechanical routing and laser cutting are vastly different.

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[FlyinFlynn]

Barrie, 100 square square what?

Did you read the explanation I linked? Your examples show only a very simple job performed on cnc router software. Predator is a full blown professional cnc router software suite which pays lip service to laser work with the provision of a laser post processor. Does Predator even have a laser mode?.. I doubt it . The PP may allow you to specify spindle speed changes to, for example, engrave the former numbers on the workpiece, but if you do that you will see the problem of burnt corners manifest itself. You are also using a 40Watt CO2 laser, probably with air assist to help limit smouldering. It is not running GRBL, which is much more suited to this application using low power laser diode heads when cutting and engraving balsa type woods. It is what this thread is about.

As to the procedures for cutting balsa by laser or router, You do not vary the spindle speed all that much on a cnc router, probably only when a tool change occurs, whereas if you are engraving with a laser the spindle speed is changing all the time, without the laser mode setting in GRBL the laser motion would pause with every spindle speed change command. I would call that vastly different operational procedures.

Engraving on a cnc spindle router is a very different process than engraving with a laser, the cnc router cuts away material at varying depths usually all at the same spindle speed whereas a laser varies its intensity to change the amount of charring of the wood all in one plane....very different processes.

[FlyinFlynn]

Posted by Jason Channing on 21/04/2020 21:21:38:

I dont know where to start.

Jason - there is no 'best' software, only personal preferences. You can think of software for producing ribs, formers and stuff as being divided into two camps, CAD and CAM. The CAM part is quite easy to come by and eleksmaker does an OK job at that but CAD is a different story. Eleksmaker is very limiting and Lightburn is more complicated but much more functional in that regard. There are others, but any CAD software worth its salt will not be free, at least I haven't found one, and it will probably be more complicated than Lightburn because Lightburn is written specifically for laser work whereas other CAD software will be more router based. Many functions for cnc routing are not required for laser work.

So if you are finding Lightburn too complicated I suggest you keep trying to understand what the options do in Lightburn until the free trial period expires and then make a decision. There is a manual for Lightburn here.

I use Vectric Aspire, 123DDesign, LibreCAD, Deskproto, LaserGRBL and yes Lightburn..... until I was required to pay for it!

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[FlyinFlynn]

Thanks Barrie but I am reasonably familiar with what a post processor does and how to make one, I have written a couple for my machines when using a predominantly cnc spindle CAD/CAM software without 'proper' laser support.

To my mind making multiple passes to vary the burn when laser engraving is only done in the Preditor suite because it uses exactly the same process for cnc spindle engraving, so you may see cnc spindle and laser processes as the same, however it is not be most elegant solution as you will need multiple passes and will possibly still get burns in the corners as the laser carriage is stationary and the laser is delivering its energy onto one spot on the workpiece.
It may be that a CO2 laser can spend less time stationary at a corner due to the lower mass on the carriage, but as we are talking low power laser modules here the problem is very pronounced.

So the long and the short of it is you are talking about a totally different animal, cnc milling for the (semi) professional where the software writers are not going to materially re-write their software for the 'maker' laser community and will just write a PP to deal with the worst problems that running a laser instead of a mill brings.

GRBL, which is specifically aimed at the 'maker' community and not at the (semi) professional community, deals with laser operations in a different way to the cnc milling environment. The CAD/CAM software I sometimes use, Vetric Aspire, was developed purely with cnc milling in mind, with only a recent nod to laser operations by the users publishing a PP for laser use - that too is a fudge to get your .nc processed.

It may not fit your workflow but I suspect LightBurn would do a 'better' job, with laser specific functions, than your milling software could achieve, and it is a lot easier to get your head around.

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[FlyinFlynn]

Can't really help with settings for harder woods Jason, but I think it will all come down to how much energy you can get focused onto the cut line. Perhaps an air pump clearing away any smoke will have tangible benefits, getting a proper focus will help too.

If 3.5Watts isn't going to do the business perhaps the best solution is just using the laser to accurately mark the wood for cutting out on a band saw ( or Stanley knife in the case of the really thin ply)