The K40 laser cutter/engraver - My journey into the laser world.

[Brumby]

Well, I finally succumbed to getting my feet wet with primary credit to Bean the enabler, Mnem in a supporting role and the rest of the EEVblog membership in the cheer squad.

This is a second hand unit that (according to the seller) has only been used for making two signs.  It has had the milliampmeter mod - which is something I regard as essential - and came with a box of all the pieces that were associated with it.

So here is what I bought:
1. The K40 unit

with a photo of the laser tube label:

Date of manufacture looks like 2019-12-02, so not too old.

2. Box of extra bits which includes fan, filter and ducting as well as water reservoir (lidded bucket), pumps and other pieces.
  and this 

All this for $300 .... and a 2 hour drive each way to pick it up.  (This wasn't all that bad as I had borrowed SWMBO's wagon to transport it and with her along for the ride, we stopped in on some old friends we hadn't seen for ages who lived up that way.  That made the trip an easy sell.)

[beanflying]

So have you made your S/O's 500 piece Purchase Peace Jigsaw yet 

Unless you are doing any serious production runs then 3-5L of water storage will be fine for a container too. Given mine lives in more or less a Tin Shed anything over 30C ambient I avoid using it and I have never seen a rise in water temp on mine that is of any concern for my 'normal' use.

Also worth lifting the Electronics side lid and double checking it is well earthed and connected. Some of the K40's simply were not 

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While I was there, the seller and I started chatting about a few things and he informed me he was moving and was shedding a lot of things.  He offered me a filtration system which could produce all the pure water I could want for the cooling system of the laser.  When I asked how much he said $50, so I thought - why not.

This is what I got for my $50....
   
While I don't know much about such systems, I think I got more than my $50 worth.

[Brumby]

So have you made your S/O's 500 piece Purchase Peace Jigsaw yet 

Funny b****r .... No - but Mnem has thrown me a couple of links (in another thread) to aid in that.  (You enablers are such a giving bunch!)

Unless you are doing any serious production runs then 3-5L of water storage will be fine for a container too. Given mine lives in more or less a Tin Shed anything over 30C ambient I avoid using it and I have never seen a rise in water temp on mine that is of any concern for my 'normal' use.

I will be keeping an eye on temperatures.  Heat is an enemy.

Also worth lifting the Electronics side lid and double checking it is well earthed and connected. Some of the K40's simply were not 

There will be a review of the entire unit's wiring - mains, low voltage and EHT - with the prevention of "unfortunate incidents" in mind.  I'll be looking at this as a creature that will be trying to kill me .... and I plan to entirely thwart its efforts.

[Jackster]

Check out https://www.scorchworks.com/K40whisperer/k40whisperer.html
Great bit of free software that takes the k40 potato into an actually usable machine.

[Brumby]

Ah yes .... you are the third (or fourth?) person to recommend that software - the seller and a couple of other members here.

That is definitely the direction I will be going.

[beanflying]

Workflow sort of runs like this with K40/M2 based Lasers.

Cad file from weapon of choice into a DXF (preferable with a kerf allowance pre done). Fusion 360 and Mapboards does that and there is a few other options too.

Inkscape works well and is free for the next bit and K40 Whisperer needs it anyway. Import your DXF or vector graphic file and or convert your raster for engraving which is another whole art of DPI, Grayscale etc. Next you need to apply one of three Colours Red (vector cutting/outlines), Blue (vector engraving) or Black (Raster engraving). There is a fill and stroke menu in Inkscape. Save out as an SVG with the colours applied. Vector Engrave I don't use much but it is useful for workflow as you can do things like letters and scribe lines first.

For some strange reason Inkscape saves slightly differently depending on how you save and they have lifted the default DPI setting in recent versions some files are ambiguous when you load them into Whisperer. Assuming to have the current version always select the higher DPI.

Power and speed settings vary from Laser to Laser so copying directly won't work. So you will need to test a batch of materials to build up your own library. Below is some ballpark numbers based on % of full power rather than indicated for my 40W Laser

100% for most cut operations
3-4mm/s 6mm Acrylic
5-6mm/sec for 4.5mm Acrylic
8-10 for 3mm Acrylic

For Ply typically you can push 30% faster Balsa much faster again but I tend to drop the power too.

Card drop the power to 15-25% and 15-30mm/s is common

Engraving is going to be partially a function of how fast you can push the head without losing steps but 300mm/sec on mine is fine but 400 is pushing toward giving issues. Adjustable acceleration and more current to the steppers would fix this but can't be done with the software/hardware combo.

Typically go low on power 10-30% for a fine to deep result depending on material.

[Brumby]

Looking to find a home for my K40 and it's a little challenging to slot it into the existing room layout.

I have shuffled a couple of things around and have an ideal location ... when it's just the box.  Add the exhaust air ducting and the thing has to move out from the wall far enough to be a problem.  One option is to sit it on a wheeled stand and move it out when I want to use it - but I was thinking of something else.

I was considering an alternative path for the air flow.  Instead of going out the back, cut a hole in the bottom of the case to take it out the bottom.  I could run the ducting from below fairly easily.


(Dotted line is indicative.  Actual location to be properly determined.)

It is clear on the inside...


There is the matter of that reinforcing section, but I had considered running a couple of others which are parallel to the existing one and either side of the cut-out.

Blanking off the rear hole is an obvious move ... and I was thinking a curved piece inside the corner between the top and the back, to help guide the air downwards...

Any thoughts ... good, bad or indifferent?

[beanflying]

Airflow should be as clean as possible to maximise the removal of Carbon/Creasote/smoke in the case of Timbers and Acrylic Vapours so in at the front and out at the back will be best.

I modded the front of mine if you look at my thread for extra air inlets and you will see Russ and others propping their doors open as the designers are dummy's in a lot of cases. You will find mentions throughout Russ's videos about it but no specific one on it.

For the larger Lasers something like the multiport option below is best but for a K40 sized machine the single large port works well. If you want to pull from the bottom then go as far back as possible and maybe consider a manifold of say Two or Three 65mm DWV pipes branching into the single 100 after? If you go to a single 100 then think about what you are asking the airflow to do in a short space.

The diagrams below are just one I did a while ago for a similar question elsewhere.

EDIT: Mmm so that was strange I never posted a finished photo  Modded my thread and here is the 3D Printed inlet sitting in place in the removable panel below my door.

[Brumby]

My key guiding phrase is "laminar flow".  This, together with cross-sectional area will determine all considerations for a solution.

[beanflying]

Yep and even go larger than the Fan size for the front opening and duct to reduce losses. Your fan will be better than the stock one so that is a plus 

Also not sure what the K40 cutting chamber is like for extra 'speed holes' but mine was like swiss cheese for reasons unknown so initially mine pulled air from everywhere else but the front of the bed  Duct Tape would work or magnetic sheet or because you own a Laser https://www.eevblog.com/forum/mechanical-engineering/40w-300x200mm-laser-cutter-engraver-vollerun/msg2460816/#msg2460816 Really worth sealing as much as possible.

[Brumby]

That is one thing I will be looking at in greater detail - especially after having seen Russ Sadler's journey.  Getting a solid stream across the working area is going to help clear the machine more effectively.


(I still haven't plugged it in yet.  But I have checked the fan.... it's not too shabby.)

[Brumby]

Finding time for this is frustrating - especially since I have to dig out my woodworking gear from the garage (really used as an oversize storage unit) which has had random stuff just dumped in there.  Also, Murphy will be laughing his head off as, on the first day I have clear, it is raining.  This prevents me from sorting anything unless I want it - and me - getting wet.  Also, it's cold with just enough air movement to make it really uncomfortable.

I have decided to not do any modifications to the unit at this time - just to make up a cabinet on wheels for it to sit on and be right out of the way when not in use.  Water system will live inside the cabinet, as will the blower and ducting.  I'll roll it out from the wall and deploy the blower and ducting when I want to burn something.

[Brumby]

Had a minor issue with the 3DP air duct adapter.  Layer adhesion failure at the change of contour which extended across half the layer.  Addressed with application of superglue, assisted with a dusting of sodium bicarb.

[Brumby]

Again, with all the enabling that Bean could muster, there is now a new chapter to this journey:

A new journey begins.... Omnisign 4000 1390 CO2 laser cutter