The Shop > CNC
K40 Laser
Joules:
I was offered the loan of a brand new K40 laser, if I would troubleshoot and re-engineer where needed. Well, not going to turn down an offer like that. I have had it about a year now, and most of that time it has been sat on a B&D Workmate. I figured it's time to give it a better location. When the machine arrived I junked most of the accessories and laser cut and printed a better fume extraction adapter than that supplied. It was a straight out assembly, now the laser was going on a desk up against a wall the adapter needed to be a right angled part.
I pulled up the old CAD model (red) and developed a new right angle part for printing. Same foot print and morph from ellipse to round, the part needs breaking into two prints so the part would be easier to print and have maximum strength at both connections. The two parts are welded together after printing, both inside and out creating a rigid and air tight joint. Final image is the adapter installed and sealed with duct tape.
The laser has proved very useful over the last year, mostly doing jobs for my wife, who does craft classes for special needs. It's been interesting to compare against the Silhouette Cameo 3, craft cutter. Each still has a niche where they excel, but very much compliment each other. You can't cut vinyl mask with the laser, and anything over 1mm thick is beyond the Cameo 3. Combined with the 3D printing as well, it makes for a very flexible tool set combining flat sheet and 3D printed parts.
russ57:
I'm quite interested in this.
My wife has her eye on a trotec, but @aud20k that's not likely to happen.
She wants to cut paper, but also etch rubber stamps.
I know that needs good fume management, but not sure of the power requirements
And of course I'd like to use it as well...
So, how do the k40s stack up? What are the essential upgrades to make it usable?
Russ
Joules:
Hi Russ, I can't really comment on rubber stamps, though that was what these machines were intended for. The only rubber I got was a sample of the professional stuff and it wasn't pleasant working. My friend has a 120w laser cutter and uses that for occasional stamps, this stuff chars quickly and produces loads of white soot. I think with softer rubber you might get good results, I add a sample of the cut I could produce without going so slow as to char the rubber. The etch isn't very deep (or reversed for stamping)
I would say the number one upgrade is probably the air assist, this is the difference between clean cuts and possible fire inside the laser cabinet. The air blows the smoke and flame away, it also keeps spatter and soot off the focusing lens. On larger machines the air assist uses quite a high volume of air, but here we can get away with a small nozzle and low volume air supply. I use an aquarium air pump, very low power but sufficient for this machine. Next up I would say the water cooling, this is important, you don't want the cooling to fail or start growing into some primordial soup. I use a 30ltr barrel, with 20ltr of distilled water and a litre of RV coolant, this acts as antifreeze and anti fungal. The water should be good for a couple of years or so, before needing replacement. To monitor the cooling I added a flow gauge and temperature sensor on the output of the laser tube. The laser starts to tail off in power as you go over 22-25℃
Another addition is a honeycomb bed, chuck out the suppled sheet metal affair designed for stamp making :palm: It just gets in the way for everything else. I messed about finding the optimum hight for the bed, and then laser cut some side frames, stuck them on with double sided tape. During this I found the internal fume extraction duct protruded too far into the cavity and would foul the bed, so I pulled it out, cut it shorter.
When/if you buy one of these, strip down the optical mounts and clean everything. The supplied mirrors were a bit dirty when it arrived, but that was nothing to what happened later as I cleaned the mirrors. All the cutting fluid was still on the mirror mounts and the IPA I used fogged the mirror with cutting fluid. I didn't notice and it gradually baked on and robbed the laser of power. Fortunately new mirrors are pretty cheap and I replaced them. Other minor mods included adding internal LED strip light as visibility can be bad especially if the cabinet gets smoky. For control you don't need much in the way of a PC, I use an old Asus Netbook and run K40 Whisperer, which is free software. Basic, but does the job, you can use Inkscape to generate the vector files, be that SVG or DXF.
One issue we did note, some months after the machine was in use laser power suddenly started to drop. I had kept a record of my materials, power settings and feed rates. These all changed, not sure if it was just the power supply or tube settling down, but things have remained constant now, so it's a good idea to keep a notebook of settings. Early on I added the power settings on the control knob with a Sharpie. 12ma is my do not exceed point, it's the trade off for a longer tube life.
Joules:
Russ, I forgot to give you details on power requirements. These include all the accessories pumps and extractor running, but a static test on the machine. It will use a bit extra when the stepper motors are in motion, maybe 10w extra.
15ma - 230w
12ma - 200w
5ma - 122w
A couple of examples of work that can be done other than paper and card craft. I made a couple of Perspex spiders for the lathe chuck, these are quick to make once you have the pattern drawn. I laser engraved them both with the minimum diameter they can hold.
The other example is recycling old IKEA magazine boxes, a paper template was cut first to check fit. I am making a hanging shelf for a loom to put spare bobbins on. The brackets were designed in about 10 mins, with about the same amount of time needed to cut them as they are 4mm ply and needed a few passes to cut through. The lathe spiders were cut in one pass, engraving done at lower power and higher feed rate.
russ57:
Thanks joules, this is very helpful.
Its good to understand what is involved in getting a useful tool.
Russ
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