Some input on K40 Laser

[Marc M]

I have been kicking around with buying one for a while now. And I was just wanting some feedback on buying one from people with experience.

Thank You

Marc

[Andrea S]

I've got a K40. I usually use it to cut acrylic and a certain type of 1/8 in MDF and occasionally engrave odds and ends. It's an okay little machine for the price. The K40 I got worked okay right out of the box, however I recommend this machine only if you're prepared to take it apart entirely and put it back together again. It can be pretty hands-on for any adjustments. I wanted to have something that was a functional baseline to use for modifying and learning enough to do a scratch build eventually and this has been great for that.

If you're getting a K40 as a tool it's not the best. Use the laser at the OMG space or DoSpace which are already calibrated and ready to go. They'll be way more consistent out of the gate. If you're getting the K40 to have a mostly assembled project where the end result might be a tool then this is the right choice.

If you want to go ahead with the k40 some recommendations:

• Scorchworks K40 whisperer, the stock software is awful
• Your first upgrade should be the ventilation, you'll spend way too much time cleaning the innards if you don't. Also depending upon your projects it can get very stinky.
• Have an extra set of mirrors/lenses on hand. I've cracked/scratched a few when calibrating/focusing/changing parts. It stinks to lose time waiting on parts and a replacement set of mirrors is inexpensive.
• When making upgrades, take the time to replace the screws. All the screws on this machine strip extremely easily. If you have the patience to replace the stock screws with better quality ones it will save you a lot of time and trouble with maintenance long term. I use green enamel paint to indicate the screws I've replaced this way so I don't replace the same screws several times.
• Don't let the laser freeze with water in it. I keep mine in the garage and use a bird bath heater and keep the pump running in the winter to keep it usable. Alternatively you could drain the machine and blow it out.
• Pay attention to the focal distance. There is no variable Z, but taking the time to make sure your project is in focus will make a huge difference in the quality of the output. There's a multitude of ways to solve this problem and a quick google will show a bunch so I won't go into great detail.
• Look for resources online. It's a huge rabbit hole and there's tons of different things you can do with it

[Ben Hutcheson]

Sorry, I totally forgot I intended to reply to this until I saw Andrea’s response.

 

OMG’s first laser was a K40. We got a ton of use out of it over the course of several years, and it was overall a positive experience. You should treat it as sort of a laser kit, though, not a 100% ready-to-run machine. It will require frequent maintenance and probably some upgrades before it performs the way you’d really hope, but if you’ve got some time to fiddle it’ll do that for far less money than a machine that’s better out of the box. Basically, the mechanics (the gantry, belts, motors, and optical holders) are totally decent, the laser tube is just fine, and everything else is more or less garbage.

 

I’d agree with everything Andrea said, but I’d also add that you should make certain to buy a version with air assist (or air assist should be your second upgrade, after making sure your machine has a lid interlock). Even a really wimpy draft of air around the nozzle will give you better cutting performance as it clears smoke out of the kerf. It’ll also help keep your lenses clean, which makes them last much longer.

 

A few other thoughts which are less urgent:

1. The lens is flat on one side and ever so slightly convex on the other (you can tell which is which by looking at your reflection at arm’s length, or by using paper as a non-scratch straight edge). The flat side of the lens goes towards the work. It’ll still work tolerably well in the wrong orientation, so it’s good to double-check that it’s correct.
2. From the factory, they generally have a gold-colored Zinc Selenide lens. If you know you’re not going to take care of it perfectly, you may want to switch to a black Gallium Arsenide lens. It’s marginally less efficient but much more robust. Ours needed 12mm diameter and 50.8mm focal length; no idea if that’s standard. They’re all over Ebay. If your replacement lens shows up and it’s not flat on one side, the convex (or more convex, depending) surface still goes up, away from the work.
3. If yours comes with the weird clampy work-holding bed, swap it out for some perforated steel plate on adjustable threaded rods. It’ll be easier to work with and will allow some degree of focus adjustment.
4. The older machines came with a dumb power supply that limited current with a chunky wirewound resistor that wasn’t rated for anything remotely like the operating voltage. When it fails, it murders the power supply and sometimes the tube. If your machine has that resistor, plan on installing a better PWM power supply at some point. It’s a pain to wire and you’ll still need to find 24v for the steppers from somewhere; I think we retained the stock power supply for that, but you could also install a separate 24v supply.

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[Marc M]

Thank you Andrea!

When the 3d printer things came around I jumped in and bought 2 Anet a8's so I am used to adjusting and changing out stuff..lol
I seem to never have time to make it when someone is there at the space so I might just pull the trigger and go from there

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[James Harr]

Buying advice aside, if we're taking about upgrades I appreciate...

100% agree on the ventilation upgrade. OMGs has a home made booster down the line made up of a ridiculous fan array. I'm pretty sure with the k40 that the booster was doing 90% of the work. If you have the fan, it's worth putting a booster at the end of the line to create a negative pressure all the way to output is. It has really helped keep all the fumes out of the shop.

Wasn't one of the upgrades we made to OMG's k40 the safety interlock? IE, So the laser wouldn't fire when the lid was open.

If that was the k40, I'd recommend that upgrade ;)

I also remember us adding LED strips to the inside of the lid to illuminate the work. That was a really nice upgrade.

One thing I really appreciate about the lasers OMG and DoSpace have is that they have a visible red laser to show the user where the laser is pointed prior to cutting. For cuts that didn't have a lot of waste material on the side, I've done a dry run with the lid open (interlock preventing the laser from firing) to make sure the laser didn't run off the edge of the material. A quick Google search says that those kits aren't terribly expensive.

Anyway, good luck and don't forget to share your experience.

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[Eric J. Kaplan]

The interlock and LED strips were the very first things we did, almost before we cut any actual projects. Definitely well worth it from a safety and usability stand. 

Sent from Eric's iPhone

On Sep 22, 2020, at 6:21 AM, James Harr <james...@gmail.com> wrote:



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