Monthly Archives: April 2021

Why You MUST Add A Water Flow Sensor Switch To A K40 Laser

My K40 (and various other CO2 lasers) does not have a water flow sensor switch on it.   There are folks who put a water flow meter on the outside of their lasers which gives you a visual representation that the water is indeed flowing.  That’s great.  Until you turn your back and the pump fails causing water to stop flowing and your laser tube and power supply go “POOF”.

You would have to watch that flow meter 100% of the time to be safe.

With a water flow sensor switch it kills power to the laser firing circuit if no water flow is detected thus saving your precious CO2 laser tube and power supply.

The switch in the flow sensor is in the normally open position.  That means the circuit is BROKEN until water flows through the sensor and then the switch closes which ENERGIZES the laser firing circuit.

In fact laser power supplies have a protection circuit ready to roll.


Bypassing the Water Protection Circuit On A CO2 Laser

Yikes.  The jumper, if it could talk would say……”there is a protection circuit here, and it is working just fine”.  But if your pump fails it would also say…….”there is a protection circuit here, and it is working just fine”.  NO PROTECTION.  THIS IS UNSAFE!

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More Laser Discussion For New Users

Beating a dead Horse by PotatoeHuman on DeviantArtI hate to beat the proverbial dead horse but I digress.

First I have got to say that anyone ABSOLUTELY HAS THE RIGHT TO BUY A CO2 Laser for their business or hobby or whatever.  I am not opposed to that at all.  More power to ya.  Seems since this COVID pandemic the “work from home” DIY business model has exploded and CO2 lasers are at the forefront of this.  Heck, it is hard to buy a laser right now.

Also let me throw in that while this blog is largely about a lack of technical prowess just know that I am jealous AF of the artistic and creative ability of a lot of you.  I can fix some stuff……but art……..I failed art and I didn’t even take it, and still failed it.  I can’t draw a circle with a compass and a can of beans.

What bothers me when I peruse the forums Facebook groups for CO2 lasers there are a rash of new users with no experience whatsoever on the technical aspects of a CO2 laser.  And let me add…….THAT INCLUDED ME AT ONE TIME.   Again, if you want a laser and can afford one………get one.

Here’s what worries me.  I will frequently see discussions where the new user buys a giant laser and says “What do I do now?”

I’m not knocking you if you are asking that question or any other.  That’s what forums are for.  You are most assuredly doing the right thing.   Just know that I’m scared for you.

The answer I can best provide is “Don’t Kill Yourself”.  First and foremost, know that your CO2 laser uses a High Voltage Flyback transformer that pulses anywhere from 1000 volts DC to about 20,000 volts DC.   Allow me to translate:  That will stop your heart in an ……errrr…….heartbeat.   We’ve all been shocked by household current.  You get tingled, a moment of OUCH and then a giggle.   If you take a 1000vdc shot to your body you will likely die and you better hope you are standing next to someone who knows CPR.  I wish I was joking.  I’m not joking.

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Replacing Crap Water Flow Sensor – Shutoff Switch in Chinese Laser

CO2 lasers are water cooled.  If the cool water stops flowing the laser tube will die.  That’s all there is to it.   To prevent the laser from firing when there is no water flowing most lasers incorporate some kind of switch that chops power to the laser circuit when no water flow is detected.

My new 50 watt laser has such a switch but forums are FULL of reports of failures and especially the fact that the switch will begin leaking.

Crap Water Flow Sensor

While this may not be the exact switch, it is darn similar. There is no outlet port on these things.  The switch is hooked to a Y valve.  One side is inlet, the other is inlet flow and the top opening goes to the switch.

In my mind that doesn’t really measure “Flow”, rather the fact there is water pressure present on the switch.

Let’s say you had a fancy water chiller and the chiller was setting up higher than the laser.   Gravity and shit, would put head pressure on the switch allowing it to fire EVEN WHEN THERE WAS NO FLOW.  I’ve seen several reports of this already.  That renders this switch USELESS.  And again, even if it is working right I’ve also read MANY reports of “this failed after a month” or “this started leaking right away”.

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Spares, spares, and more spares for Lasers

There seems to be an epidemic in LaserLand™ where people buy really expensive, and large CO2 lasers for their home business and experience component failures and become frustrated with the re-seller for selling crap.  I’m sorry to keep harping on this but it’s like watching a car crash, paint dry, and grass grow all at the same time.

These lasers are so capable, and so fun and provide the ability to make the owner some money.  But they are not without issues.

Let’s be clear about these CO2 lasers.   They come from CHINA.  That is about all one really needs to know as it relates to product reliability.

The blue power supplies in these lasers = Crap that will fail

The Water Flow Sensors = Crap that will leak

The Air Assist pump is in a special category of crap = Crap that crap calls crap.

Look.  I dig laser etching and cutting.  It’s fun and its a great way to make continuous $20 bills.

But I spent a career in the US Navy and as a Gov’t Employee fixing equipment that costs a lot of money.  I’m an Electronics Tech Rep for DOD that supports the Navy and Marine Corps.   I know how to fix broken things and I can smell a crap component a 100 yards away with the wind blowing away from me.

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Random Musings About Lasers

I’m not sure what is going on in the world of Home/Small Business Lasers.  Just a couple of months ago they were relatively easy to get, and now suddenly they are nearly unobtanium.  Kind of like last year when Coronavirus hit and you couldn’t buy a bicycle to save your life.  Everyone all at once decided to buy bicycles.  So it goes with the larger CO2 lasers right now.  I think a lot of folks have decided to do the side hustle thing and laser engraving from home is a viable and sometimes profitable endeavor.  I refer to my lasers as “$20 bill vacuums”.

I belong to several forums regarding lasers, and software and they are filled with first time users who have no idea at all what they are doing.  And, let’s be clear……..there is nothing wrong with that.  That’s what forums are for………helping each other and learning.  When I bought my first laser I had no idea what I was doing either.

If you buy a Chinese Laser …… YOU ARE ESSENTIALLY ON YOUR OWN.  You might get some limited support, but you better be able to be self-sufficient.

Laser engravers and cutters are pretty complex systems that require at least some technical skill.  Larger CO2 lasers consist of a few different subsystems such as:

  • High powered laser
  • Precise Optical Alignment system with mirrors
  • Water cooling system
  • Air Assist system
  • Electronics – power supply, controller, switches
  • Machine settings in firmware and software
  • G-Code – you may just have to pass some G-Code settings to your machine manually

And I’m really oversimplifying things here.    Once you ship a machine half way around the world, it may or may not have problems upon arrival.  Your choices are then:

  • Send the Machine back and wait for the reseller to fix it or provide another machine, which by the way is unobtanium at the moment.
  • Deal with the problem, whatever it is.

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First Week With A Bigger Laser

OMTech Preenex K40

I cut my teeth in the CO2 laser world the same way most other people do……..with a Chinese eBay K40 laser.  Hobbyists love them because they cost next to nothing (about $350 and up) and they are pretty powerful devices.

That being said they are Chinese, are cheaply built, with not the highest quality parts.


Much of the allure here is in the hacker installing upgrades and building it into a much more capable machine.   At the end of the day though the machine has some serious limitations.  Here are some that got my attention:

  • Very small work area – 12 x 8 at best.
  • Doesn’t interpret g-code which means you can’t use some of the better software out there for it (i.e. Lightburn).  You must upgrade the controller card.
  • Upgrading the controller card renders the control panel basically useless.  All controls are now software controlled.
  • The z axis (up and down) is fixed.  The machines are basically configured to cut or etch 3mm materials.  There are things that can be done to provide some z lift capability but I don’t think it is worth the time, effort, or money to do.
  • The machine I own isn’t really a 40 watt.  Probably more like 30.  It is a “Mini” with a shorter tube.  Essentially, the longer the tube, the more powerful it is.

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OMTech 50Watt Laser First Impressions

Laser + Poodle

Got my new OMTech 50 Watt Laser today.

I also own 2 Ortur Laser Master 2 – 20 watt diode lasers and a K40 Laser also from OMTech.

After tons of research I have decided that your best bet on buying a Chinese laser system is to buy it from OMTech.  Your mileage may vary and in fact some people’s mileage DOES vary.   That has NOT been my experience.

The K40 I bought from them and now this 50 watt machine………JUST WORKS. Right out of the box. No damage.  Not one scratch.  Not one dent.   The machines both came aligned right out of the box.

Shipping was fast,  the price was competitive albeit you could save a few dollars by buying from other dealers.  I don’t recommend it unless you are prepared to take a machine out of the box and spend time aligning it and making it right.  If you posses those skills then by all means…….save some money.  Me. I posses those skills but it isn’t worth $50 or $100 to me to do all that quality assurance and work.

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