CO2 laser - the learning curve

[Simond]

Laser, water pump and flowswitch arrived, but mum’s birthday takes precedence.

 

And next weekend dad’s taxi co will be doing the return trip to Nottingham to bring young MasterD home from university. But with a bit of luck, I’ll have a chance to make it all work in the next few days. Fingers crossed...

 

Best

Simon

[Simond]

Well, curious.

 

The bits & pieces arrived Friday, but I was away over the weekend, up on the Wirral, where I managed to grab a visit the Wirral 0 Gauge group’s open day for an hour - very pleasant, and a warm welcome.

 

Yesterday after work, I fitted the water switch and pump, and topped up the water tank, and proved to my delight that the water switch worked on the flow the pump generates.

 

This evening, I made the connections for the switch in the safety loop, and checked it switched the laser off. Odd, I thought, well, the old laser tube still works! I suspect it may not be generating as much power as it might have but it is definitely cutting. I have now readjusted the y-scaling and it’s pretty much spot on (less than two tenths on a mm in 100mm) so tomorrow, I’ll try to cut a panel for the loco shed. Dependent on how many cuts it needs, I’ll ponder swapping the tubes, but if this one’s working ok, the other can stay wrapped up!

 

Might have just got away with it

 

Should anyone else feel the need, this is the flow switch I bought

https://www.amazon.co.uk/gp/product/B075QFNZC7/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1

 

There’s lots of submerged pumps on line. I turned up the adaptors to suit the silicone rubber pipe from the laser, and glued them into the adaptor supplied with the pump. I turned up an adaptor for the switch, and fitted it with a compression fitting nut. Anyone wants pix, please ask.

 

There are some suggestions regarding temperature sensors too. Will probably get one eventually to be on the safe side.

 

Best

Simon

[monkeysarefun]

The water pump thing was what put me off CO2 lasers and onto the Emblaser, I kept seeing peoples setups of Chinese lasers  posted online with precariously balanced  buckets of water and aquarium pumps - good to know that there are more professional solutions avaliable!

 

Until recently I had never heard of a Wirral - except that Half Man Half Biscuit had an album named after it. Now that you've been there  I know two things about it.

[Simond]

I can give you a few more facts!

 

I grew up there, my mum, who still lives in the family house was 92 yesterday.

The founder of the Birkenhead School was one F E Smith, who was a particularly acerbic lawyer and well worth a google.

Half Man Half Biscuit were from Birkenhead, and were regulars on John Peel’s radio programs.

There was another band called “Marseille” who had a brief hit with “do it the French way”.

And our bands, Convent Girl, and The Alkies, who didn’t.

The Summers iron ore trains were the heaviest non-continuous-braked trains in the uk for a while, running from Bidston Dock to Shotton steel works, typically behind a 9F.

Woodside was the GWR terminus.

Cammell Laird shipbuilders, Ark Royal and many other famous ships.

Central Park in NY is reputedly modelled on Birkenhead.

At one time you could get a through coach from Margate, which must have taken days - it took me five hours to get home on Sunday, and most of 1 hour was at 140mph, and a great deal of 2h40 was at 125mph!

The glory days of Birkenhead and Liverpool were based on trade links that have moved on - of course at least some of the wealth was based on cotton and thus slavery - but the town seems to no longer be the prosperous place it was even 50 years back.

 

Best

Simon

[Simond]

As planned, I etched and cut a wall panel for my loco shed. Each panel comprises an middle layer with window frames, an outer layer, and inner layer both etched with bricks. These take up a little less than 3/4 of an A4 sheet of 2mm MDF. It took around 25 minutes to cut the window apertures, etch the brickwork, and then cut the exterior. Well pleased

 

I have achieved:

 

1 scaling. Minor adjustments (99.6 up to 100 in X, 102.8 down to 100 in Y) successful.

 

2 registration. This was the turbo bug-bear of the original NewlyDraw system which caused me to start the modification in the first place. Completely sorted using the Smoothie and microswitch zero-stops. Very pleased.

 

3 water flow detection & interlock. Working.

 

4 computer control of laser power. Not sorted, but possibly on track.

 

5 software. LightBurn is great. Will buy a licence.

 

6 control of speed & power to get a consistent cut through. Not sorted. More work required. Multiple passes seem to char the MDF, and it’s strangely not consistent. At 3mm/s and 20mA it was pretty much cutting through, but not right through everywhere. I etched at 25mm/s and 10mA, quite good relief, happy with that, then made a mistake on the second set of panels - set it off to cut at 3mm/s, but forgot to turn the power back up - so it cut at 3mm/s and 10mA. Strangely this gave similar results to the higher power, in that most of the cuts went through, but not all of them - and it doesn’t seem to be related to anything. The problem is that if it does not cut right through, delicate bits like the window frames get broken. A repeat cut just charred the edges horribly and didn’t actually cut through any better.

 

I need to find the lowest power that will cut through in one go, and the speed that goes with it. Being able to etch / engrave at 25mm/s does make the brickwork much quicker .

 

I do wonder if the MDF varies in fibre/resin mix across the sheet - if it does, it might explain the variability I’m seeing, but I’d have thought that MDF manufacture would be a predictable and consistent industrial process, so I don’t expect it to be the case.

 

Herewith the fruits of this evening’s efforts, having had a waft of rattle can whilst I was failing to make a second set!

 

 

Best

Simon

Edited June 13, 2018 by Simond

[monkeysarefun]

As planned, I etched and cut a wall panel for my loco shed. Each panel comprises an middle layer with window frames, an outer layer, and inner layer both etched with bricks. These take up a little less than 3/4 of an A4 sheet of 2mm MDF. It took around 25 minutes to cut the window apertures, etch the brickwork, and then cut the exterior. Well pleased

 

I have achieved:

 

1 scaling. Minor adjustments (99.6 up to 100 in X, 102.8 down to 100 in Y) successful.

 

2 registration. This was the turbo bug-bear of the original NewlyDraw system which caused me to start the modification in the first place. Completely sorted using the Smoothie and microswitch zero-stops. Very pleased.

 

3 water flow detection & interlock. Working.

 

4 computer control of laser power. Not sorted, but possibly on track.

 

5 software. LightBurn is great. Will buy a licence.

 

6 control of speed & power to get a consistent cut through. Not sorted. More work required. Multiple passes seem to char the MDF, and it’s strangely not consistent. At 3mm/s and 20mA it was pretty much cutting through, but not right through everywhere. I etched at 25mm/s and 10mA, quite good relief, happy with that, then made a mistake on the second set of panels - set it off to cut at 3mm/s, but forgot to turn the power back up - so it cut at 3mm/s and 10mA. Strangely this gave similar results to the higher power, in that most of the cuts went through, but not all of them - and it doesn’t seem to be related to anything. The problem is that if it does not cut right through, delicate bits like the window frames get broken. A repeat cut just charred the edges horribly and didn’t actually cut through any better.

 

I need to find the lowest power that will cut through in one go, and the speed that goes with it. Being able to etch / engrave at 25mm/s does make the brickwork much quicker .

 

I do wonder if the MDF varies in fibre/resin mix across the sheet - if it does, it might explain the variability I’m seeing, but I’d have thought that MDF manufacture would be a predictable and consistent industrial process, so I don’t expect it to be the case.

 

Herewith the fruits of this evening’s efforts, having had a waft of rattle can whilst I was failing to make a second set!

 

5FEBFD5B-23E3-4041-A22A-5669BD35CFAD.jpeg

 

Best

Simon

 

 

On the darklylabs forum users of the Emblaser 2 -  which has an enclosed cabinet  - are continually reporting issues with  loss of performance when cutting MDF due to it coating the laser lens with soot.

 

This apparently  affects cutting in a very short time and the lens often needs a thorough clean after each job. Might be something to look into if you are getting inconsistent results or the laser appears to get less effective over a short time.

[Simond]

Thanks, I do have air assist, which keeps the smoke out of the lens cavity, but an occasional lens clean & polish definitely improves matters. The other mirrors need cleaning too.

 

I don’t think that’s the issue as it seems to vary in the same sheet, rather than being a slow degradation over a few hours cutting.

 

More experiments after work today

 

Best

Simon

[Simond]

Ok, precarious water buckets and stuff...

 

 

The corner of my garage; top left, wall mounted mini air compressor, drives the air blast that moves the smoke away from the lens and work. Below that, the white trunk that feeds the smoke out through the wall via one of those flappy things they sell for bathroom and tumble dryer vents.

 

The pink & cream thing is the laser. It’s labelled HPC Laser Ltd, and the phone number. It’s called an LS3020, aka a cheapo K40 with some added bits: there’s a magnetic door interlock switch just to the left of the ammeter. I suspect the emergency stop label was added too.

 

On the back there are three multi-plug type sockets, which accept a UK 3-pin, a continental 2-pin or 3-pin, or a US flat 2-pin, one for the water pump, one for the fan and one for the air pump.

 

On the right is a tv arm with a shelf on top for the laptop. The clamps are holding a batten to the back of the shelf whilst the glue dries. It’s there to stop the laptop power supply falling on the floor.

 

Under the shelf is the material store, and the water tank, which is simply one of those plastic boxes you can get in the discount stores. Inside it...

 

 

Is an aquarium pump, and the flow switch as previously described. It’s screwed to the back of the box, using a cut down 15mm pipe clip - it’s the white things visible around the lower end of the switch.

 

And here it is, cutting MDF!

 

 

It’s taking about 21 minutes to cut the three panels that make a section of wall. It seems that the MDF that I was using was much tougher than the packet I’ve started on now.

 

Cutting at 4mm/s and 15mA, etching at 25mm/s and 8mA

 

Best

Simon

[Simond]

A bit of light-hearted malarkey

 

It’s pleasing what you can do with a Corn Flakes packet!

 

 

A few little adjustments here & there will make the corners neater, and it can then be lasered at different sizes.

 

Best

Simon

[BrushType4]

Simon,

 

Just picking up on your comments about MDF, it certainly isn't all the same. It has taken me some time to find the best boards, but I now use a very hard MDF. It sucks up moisture the least so is a very consistent thickness and the laser cuts the same every time. I have found that the cheaper MDF and particularly the DIY MDF is very fibrous and will absorb moisture, and consequently a variable thickness and laserability.  

 

Love the packing crate too.

[Simond]

Phil,

 

Thanks for the comments. The last batch of 2mm came from a framers’ suppliers In Ashford, in a pack of 25 sheets. I need to buy some more in the next day or two & it seems challenging to find a good on-line supplier, so if you have any hints... the thickness seems variable too, finding thinner sheets is also a challenge!

 

The packing crate was an attempt to make a one-page fold-up, but being cereal packet, it’s printed one side, so the fold-up didn’t work. I think I might do it again so there are two folding patterns, which nest. Trouble is, if you fold, there’s always a visible non-continuity on the outside. Doesn’t matter for the planked box, but the bracing pieces look better cut individually, and can be made to fit snugly that way. I was hoping to have a pattern that I could just scale, but the thickness of the bracing won’t scale, so it’ll have to be adjusted for different sizes of crate.

 

The wall panels are on my PD thread if you want to have a look.

 

Best

Simon

[Simond]

So, the PWM works,sort of. By chance I discovered that, in a small window, it does exactly what it is supposed to. Rather annoyingly, I had missed it when I’d tried earlier, by setting a series of squares to burn at different power settings. As I’d done this in steps of 12.5% and presumably wasn’t listening carefully, I missed the couple of steps in which it did work. I’m not sure why I tried it again, but serendipity must have played a part.

 

When LightBurn is set to less than 7%, nothing happens; above 35%, it runs at full power, thus the only settings at which I might have noticed would have been 12.5 and 25%. If you’re listening, when the PWMis working, there is a distinctive, but quiet “hiss”.

 

Having discovered that it does do what it is supposed to, I homed in. With the laser set to 20mA, the PMW gave the following currents at each power percentage:

 

1%. 0mA

2%. 0

5%. 1 (laser did not strike)

10% 6

15% 13

20% 17

25% 19

30% 20

35% 20mA

 

Re-ran the test with new percentage settings

 

5% 0mA

8% 4mA (laser running)

11% 7

14% 12

17% 14

20% 16

23% 18

26% 19

30% 20mA

 

I’ll re-run the tests - I suspect the limits are something like 6% and 27%, and I now need to work out what needs to be changed in the configuration to get the range to be more like 1%-99%.

 

There’s quite a bit on smoothies on their website and associated links. It’s just finding the right bit...

 

http://smoothieware.org/smoothieboard

 

https://plus.google.com/+ArielYahni/posts/VkJ4pWh4uAy?cfem=1

 

http://donsthings.blogspot.com/2016/11/k40-laser-power-supply-control-take-2.html?m=1

 

This one...

 

http://donsthings.blogspot.com/2016/12/engraving-and-pwm-control.html

 

More, soon, I hope!

 

Best

Simon

Edited June 21, 2018 by Simond

[Giles]

Glad you're getting to the bottom of this.... you'll end up with a very useful machine - even though you're being forced round the houses!

 

Incidentally, I get my 2mm MDF from Hobarts, with very good service.

Edited June 21, 2018 by Giles

[Simond]

Hi all,

 

We’re making progress, in a sort-of-predictability sense. As I said on my Porth Dinllaen thread, I purchased a pack of 2mm MDF last week. It’s in 3’x4’ sheets, from which I can get 16 pieces 9”x12”, which will fit the laser. Happily we have a guillotine at work which makes short work of the chopping. This works out at around 17p per piece, which compares favourably with the 30p or so I was quoted for A4 pieces.

 

I spent quite a bit of time over the weekend, burning squares into offcuts of MDF. This was not fruitless. What I have learned is that more power does not necessarily lead to a better, or cleaner cut. Obvioulsy, one wants to cut as fast as possible, as its fairly boring standing around watching the laser do its stuff - actually, it’s mesmerising, but only for a while - the novelty wears off... but more importantly, its necessary to ensure a complete, clean cut. And you don’t want to leave it unattended. There are some horrible photos of burnt ones online...

 

What I have discovered is that this 2mm MDF cuts cleanly at 6mm/s and 13%, whereas slower and/or more power chars the MDF, and doesn’t cut through, and faster and/or less power makes great brickwork etching, but also doesn’t cut through. And, once it’s charred, even 6 or 7 passes might not cut right through, as the char seems to protect the board, and prevent effective cutting. I can etch brickwork at 25mm/s and 17%, which gives clean cuts without charring, and they’re sufficiently deep to allow for painting and dry brushing. I haven’t tried but guess I could sponge plaster over the brickwork if I wanted pointing. An experiment beckons, methinks...

 

Same is at least partially true for Perspex/acrylic, cuts sweetly at 6mm/s and 12%, but higher and lower settings are not as good. Once you learn this, and I think it is pretty counter-intuitive, then the hunt for predictable, repeatable stuff gets much easier, and one can concentrate on the design a bit more.

 

A brief moment of frivolity, and an offcut of Perspex - it’s not tall enough, due to a minor cock-up, but that can be easily fixed. Then a drop of paint!

 

 

Should look good through the workshop window, I hope.

 

(OTOH, I have a work colleague who is into 3D printing, maybe if I do the STL files, he’ll print a few machine tools for me, might be better - and, so far, I’m resisting the urge to copy what he’s doing...)

 

Best

Simon

Edited June 26, 2018 by Simond

[Giles]

Nice! Although I haven't quite worked out what make of lathe it is.....

 

Completely agree with your MDF buffing observations - they match my Emblazer experience (interesting that a little diode laser has similar cutting speed characteristics as your 40w (?) Tube type...)

[Simond]

Hi Giles,

 

If I’d cut two more layers below the tray it would be a reasonable replica of my Smallpeice!

 

(http://www.lathes.co.uk/cromwell/)

 

Most curious the way it doesn’t work when you might reasonably expect it would...!

 

Progress on the loco shed is rather pleasing - post on my PD thread.

 

Best

Simon

[JohnGi]

Re-ran the test with new percentage settings

 

5% 0mA

8% 4mA (laser running)

11% 7

14% 12

17% 14

20% 16

23% 18

26% 19

30% 20mA

 

I’ll re-run the tests - I suspect the limits are something like 6% and 27%, and I now need to work out what needs to be changed in the configuration to get the range to be more like 1%-99%.

 

 

 

 2mm MDF cuts cleanly at 6mm/s and 13%

 

 

Hi Simon, 

 

Did you change the configuration to be between 1 and 99%?

 

John

[Simond]

John,

 

No, not yet.

 

Working on the “it ain’t broke” principle, and given that I have 20 or 30 sheets of MDF to turn into locoshed, I thought I’d defer faffing with it until I have my parts cut out.

 

I’ll post up the optimum settings for different materials over the weekend, and maybe get a bit more cutting done. I need to make another three sections of floor, six sections of inspection pit, 13 roof trestles, plus planked roof and Perspex skylights, about 300 windowpanes, plus the entire workshop, and around four square feet of slates! So no shortage of stuff to keep me busy.

 

And I haven’t done the smokehoods & chimneys yet...

 

Best

Simon

[Simond]

This rather bizarre photo is a snap of some of my test burns.

 

The laser is now set at 20mA which is apparently outside its maximum operating level - should be 18mA but it doesn’t seem bothered, and I’m running at less than full waft anyway. I suppose it’s a bit like “chipping” your car to make it less reliable, sorry, faster...

 

 

From the bottom up, on the 2mm MDF

 

4mm/s, 30% down to 14%. Clean cuts at 16 & 14 %

6mm/s, 28 - 12%, clean at 14 & 12%

8mm/s, 26 - 10%, clean at 24 & 22%

7mm/s, 26 - 10%, clean at 22, 20 & 18%

 

Variable speed, 5 - 9 mm/s in 0.5mm/s steps, 20% power, only cut at 7mm/s

 

Upper sheet, 6mm/s 10% to 18%, clean cuts on every setting, but marginally better at 11-14%

 

White stuff is 3mm acrylic. Alternate squares at 4&6mm/s, power in mA at 7, 9, 11 & 13. Good results obtained at 4mm/s and 11 or 13mA, so choose 12mA! This translates as 15%.

 

I’ll post up a nice table when I’ve a bit more data, as I’m entering all this on an Excel spreadsheet as I go.

 

Best

Simon

[Simond]

Latest & greatest on the K40 front. The old tube died yesterday. I feared fitting the new tube that I bought when I thought I’d killed the old one might be stressful, but in fact it was marginally more hassle than changing the light in the oven.

 

Old one hot end

 

 

And lens end

 

 

I labelled the cooling pipes, and I did clean it all, whilst it was dismantled. The HT and ground wires appeared to have been welded to the pins on the tube, they’re hidden within the silicone tubes you can see sticking out. They would not solder, so I made some very thin brass tubes to fit tightly on the pins, and soldered the wires to them. I scraped the silicone sealant out of the tubes, put them over the pins, connected up and squirted some bath sealant over the joints. It’s a good 40mm from the pins to the metalwork, which would need many more volts than the supply produces, and the silicone sealant will protect against creepage.

 

Just a word on these things, the power supply voltage is very high, (20kV?) and it can drive 20mA which would certainly be lethal. Lasers can cook the lens in your eye, and if focussed, your retina too. Spoils your modelmaking, being dead, or blind.

 

I then put it back together, but forgot to photograph the new tube - suffice to say, it looks rather like the old tube but cleaner. I’ve put the old tube in the box the new one came in, but I ought to just throw it away. Why do we hoard things? (Or is it just me??)

 

I’d did photograph the test cut...

 

 

Th3 figures up the left are speed in mm/s and the power percentages read fro 6% to 22% left to right.

 

What is most noticeable here is that I’m getting good clean cuts at 20mm/s and could probably go faster. Indeed, it’s so much more effective that I had to turn down the power when etching, otherwise I was getting “pre-demolished” walls!

 

I’m now cutting 2mm MDF at 20mm/s and 18%, and engraving the mortar lines at 25mm/s and 8%

 

I’ll have to reassess card and Perspex cutting settings too, of course. I also want to get an extractor that’s worthy of the name, as the one that came with the machine is pretty wimpish.

 

Lots of pictures of the latest bits & pieces will be on the PD thread later today.

 

Best

Simon

Edited October 14, 2018 by Simond

[Giles]

Simon, you might try your hand at ecthing slate...... I did this on my Emblazer a coupe of years ago. Around 5mm/sec at 100%.

 

slate engraving by giles favell, on Flickr

[Simond]

Thanks Giles, I might indeed, that’s rather nice.

 

I need to do a couple of domestic things, I want to do a “cat’s face” coaster with a happy, smiling (fed) cat on one side and an unhappy (not yet fed) cat on the other as a means of communication for those days when MrsD & I miss each other at mealtimes. The dear little animal cannot be trusted...

 

I also need to do a new cover for the drain on the shower, for some reason something reacted with the “chrome” and it looks horrid. White Perspex will look much nicer.

 

Cheers

Simon

[monkeysarefun]

Speaking as a fickle  shallow follower of fashion I haven't touched my emblaser since I got a DLP 3D printer... this is where the  cool kids are at these days !

 

 

 

[flubrush]

Latest & greatest on the K40 front. The old tube died yesterday. I feared fitting the new tube that I bought when I thought I’d killed the old one might be stressful, but in fact it was marginally more hassle than changing the light in the oven.

 

Old one hot end

 

4E52124E-5F9B-40DF-9584-26F20412BBD7.jpeg

 

And lens end

 

CF8F7405-92A2-4489-A7D3-A8FE708DD95C.jpeg

 

I labelled the cooling pipes, and I did clean it all, whilst it was dismantled. The HT and ground wires appeared to have been welded to the pins on the tube, they’re hidden within the silicone tubes you can see sticking out. They would not solder, so I made some very thin brass tubes to fit tightly on the pins, and soldered the wires to them. I scraped the silicone sealant out of the tubes, put them over the pins, connected up and squirted some bath sealant over the joints. It’s a good 40mm from the pins to the metalwork, which would need many more volts than the supply produces, and the silicone sealant will protect against creepage.

 

Just a word on these things, the power supply voltage is very high, (20kV?) and it can drive 20mA which would certainly be lethal. Lasers can cook the lens in your eye, and if focussed, your retina too. Spoils your modelmaking, being dead, or blind.

 

I then put it back together, but forgot to photograph the new tube - suffice to say, it looks rather like the old tube but cleaner. I’ve put the old tube in the box the new one came in, but I ought to just throw it away. Why do we hoard things? (Or is it just me??)

 

I’d did photograph the test cut...

 

46311EBB-A83E-44DB-9C41-3CCB743CC824.jpeg

 

Th3 figures up the left are speed in mm/s and the power percentages read fro 6% to 22% left to right.

 

 

Simon,

 

Good news that you had a successful replacement.

 

I note from your tests for number of cuts to get a cut through that you use the same as I used to - i.e. cutting squares of (I guess) 10mm side length.   Do you find that the results from these tests are slightly under when you cut much longer perimeters.  I have found on my 4W Emblaser 1 that I usually have to increase the number of cuts by at least one if I have done the test with 10mm squares.   I wondered if it was the MDF retaining some heat with the shorter perimeter and improving the effectiveness of succeeding cuts.

 

Jim.

[flubrush]

Speaking as a fickle  shallow follower of fashion I haven't touched my emblaser since I got a DLP 3D printer... this is where the  cool kids are at these days !

 

What printer?

 

Jim.