mtaylor Posted January 3, 2016 Share #1 Posted January 3, 2016 Background: Well, not all K40's are created equal. So I'll put this up with caveats and the "gotchas" that I found. I hope that this will be of value to someone. At this point in the market, the prices are dropping and quality is getting better. Do some shopping, read the reviews. Ebay has great prices but... and it's a big "but".. there's hidden costs such as duty, import broker fees, and getting it shipped from the port entry to your door. There's also "service" which seems from reviews to be non-existent. I'd suggest looking for a dealer in the country you are located. The MM Laserknife, is basically an upgraded K40 with a better power supply, a safety switch to kill the beam if the lid is opened, and better quality control than the run of the mill Chinese K40. As is, it worked pretty good for what I've been doing with it but I wasn't exactly pleased trying to cut thicker woods. For example, 3/16" boxwood was very problematical, but 3/16" cherry was pretty good. Hindsight being what it is, I would have bought a totally different unit for around the same price and gained cutting size and power out. But... <shrugs shoulders>... see the first paragraph for caveats. So.. off I went into "UpgradeLand"... Previously, I upgraded the lens from the small 12mm lens to a better grade 18mm lens with the same focal length. This produced a finer beam at the wood but I did loose the ability to re-focus by moving the lens. I worked around that by setting p the z-table so I could move it up and down to compensate. So far, so good... but still, I wasn't happy with cutting the thicker bits and harder species of wood. I realized it was either buy another machine or upgrade this one... upgrade is/was the lower cost alternative. Doing the homework: I researched tubes and couldn't find a 50W that was up to snuff with a good price. I did, however locate a 45W that had a good price and the company does provide good service. The tube in the machine is called a 40W. Reality... it's about a 35W at steady-state. The 45W I selected pumps out 45W steady-state. It is however longer (730mm vs. 1000mm) and bigger diameter (50mm vs 55mm). There is a 60W available that longer than the 40W (naturally) but also has a higher power requirement so it's out. I saw some 50W tubes but I'm questioning if this isn't more marketing hype like labeling the K40 as a 40W machine. The power requirements and tube size were smaller than those for the 45W I bought. Puzzling to say the least. First thing to check was power supply... the old tube needed 15kV at about 12mV. The new one needs 15kV at ~18mA max. MM uses a 220 VAC input (using a transformer) which outputs 20kV at 20mA. This was good as PSU's are pretty pricey. The next was water pump... The new tube needs 10L/minute flow. The MM pump is rated at 50L/minute. Then there's the mounting... a hole will need to be cut in the case and an extender installed. The mounts themselves would require modification to accept the bigger size. I ordered the new tube, extender, and about 12 feet of 6mm silicone tubing. I bought 100% silicone caulking/sealer from Lowe's. The tube I received was tested the day it shipped at 45W output using 15mA of power and metered at 18" from the tube end. Yippee.... stated wattage is actual wattage. In the K40 world, this is pretty iffy. The Upgrade I took several photos of the unit before removing anything. I also marked the place where the output of the tube was located for reference. I removed the wiring, cooling hoses, and then the tube. I also removed the rubber mount pad from the tube mounts. Note that different K40's can have different mounts depending on manufacturer. Mine were metal and looked like an old style hose clamp in some ways. But they did/do give me the wiggle room for upgrading. The actual upgrade then started. First steps were to cut the hole and mount the extension. I cut the hole, put the new tube in place and checked everything. I then removed the tube and mounted the extension. There was a problem with the mounting holes for the screws. The hardware didn't match the drawings but I was aware of this from reading on the support forum where I bought the parts. I had to make my own template. One note... do make sure to completely remove any metal chips from cutting and drilling. If one gets into the wrong place, you can have sparks, fire, etc. and end up needing a new power supply at a minimum. I shimmed the mounts using foam carpet tape and several pieces of thin cardboard to get the tube close to where it needed to be. I went back during alignment and re-seated and adjusted these mounts. The tube was installed and the wiring connected by wrapping the bare copper around the post. These can't be soldered as the seal for the post to glass tube will melt. I stuck on a piece of 6mm silicone tubing and filled the tube with silicone compound. This made for a good connection and also insulation as one doesn't want 20kV sparking about. I replaced the old cooling hoses with new at this point. The unit was then "tested" by first firing up the water pump, rotating the tube to remove any air bubbles (due to the way they're made, they really only work well in position for this). I also began the alignment procedure as this is critical. The cutter now looks like this from the front The first step was shimming the tube to be level from end to end and then using thermo paper (cash register receipt) and very low power, getting the beam dead center on the first mirror. I locked down the tube and re-checked. Then I did mirrors 2 and 3. A bit fussy with checking at the near points and far points of travel but it must be done. I then locked everything down and re-did the alignment tests. Post upgrade evaluation: I've not cut anything worthwhile yet, but I have done a bunch of testing. The first after alignment was to check the focus. I'm still spot on without having to change my table shims except when I change wood thickness. The kerf is thinner and on 3/16" boxwood the "V"ing of the kerf is much, much less. This is with a bit less power (amperage) and faster speed. Misson accomplished. Next will be when I get some time is to thickness a 1/4" boxwood plank and see what happens. My total cost at this point is around $2500 including original machine, new lens and lens mount, new tube and the extension. This doesn't include a GFI protector, the cooling water and bucket, or the hole saw for the drill. I'm not an expert but I've learned a lot with this. hexnut, druxey, Dubz and 21 others 24 Quote Link to comment Share on other sites More sharing options...
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