New K40 Laser Heads

[NedMan (Ned Hill)]

Recently went looking for a replacement of a stock K40 laser head for the K40 at my local maker space. I was surprised to find out that there was a slightly different design being sold then I was use to seeing. Seems like these came out maybe a couple of years ago?

The most obvious difference is in how the mirror is retained. Instead of the metal clip there are 3 plastic (nylon?) screws. You do have to be careful not to cross thread them.

The really big difference is that it allows use of either a 12mm, 16mm or a 18mm lens all with the same head.

I got a really good price from the Cloudray store on Aliexpress

https://www.aliexpress.us/item/3256801332491652.html

It arrived today and I got it installed. If you get one just note that there are 2 set screws holding on the air nozzle when you first go to take it apart. You will only be able to tighten one of the set screws after you get the head mounted to the plate, which I guess is why there are 2 screws.

[dougl]

The worst part about those is how far away from your focus/cut the cone output is. The Coudray tube system is far better but it does require something like a Russ Sadler K40 head mount setup.

[NedMan (Ned Hill)]

True. My main concern was just getting something to knock down flames and help keep the lens clean.

[NedMan (Ned Hill)]

I also did run across this K40 head from Light Object that would be better for cutting.

Pro K40 Laser Head with nozzle

[dougl]

with enough air pressure those do work and for engraving or other light duty work turning down the pressure just enough to keep smoke out of the cone is also handy.

[dougl]

@NedMan

I also did run across this K40 head from Light Object that would be better for cutting.

Pro K40 Laser Head with nozzle

You would really need to have your mirror alignments dialed in for that one.

[Kinsway (Keith Taylor)]

I did get one of these as I assumed it would be better that the stock head but in reality it still took the same number of passes to cut so I sent it back. I had read somewhere that a cone can actually cause smoke to swirl around inside the cone and it was better to use a side air assist nozzle which I printed myself and simply pushes onto the stock head. It simply blows the ash and smoke away from the groove. My air assist is particularly strong and I do wonder if there are circumstances where it it ought to be held back. The nozzle also includes the housings for the red dot lasers which I find extremely helpful in knowing where the cut line is and having two perpendicular mounted means that they are always correct irrespective of height. Luckily I have a manually raised bed so changing for differing material thicknesses is also very simple.

[dougl]

@Kinsway

I had read somewhere that a cone can actually cause smoke to swirl around inside the cone

Have not heard of that. How does the smoke get inside of the nozzle to swirl around?

[NedMan (Ned Hill)]

I remember someone at some point was saying, quite definitely, that there would be a venturi effect from the air flow that would pull air down into the lens from above. Totally not a thing though. It would need to be a laminar flow for that to even be remotely possible. The air impinging from the side, into the nozzle, creates a turbulent flow that would actually cause a slight over pressure inside the nozzle. So I don’t see how any air could actually enter the nozzle and get to the lens with flowing air.

[dougl]

I’m surprised it isn’t designed to “leak” a bit of air into the area above the lens to help keep smoke out of that area too. Agreed, there should be a positive pressure so nothing should be getting in and if the mirror isn’t help in place well, more than smoke is going to be effecting your design. $0.02

[Kinsway (Keith Taylor)]

To be fair I can’t remember where I saw this. I think it is to do with the air coming in at the bottom of the cone can cause eddies at the top under the lens but it seems to me that blowing from the side with the lens in the open is a more logical way to remove debris from the groove and I find this does seem to work for me particularly when cutting.

[NedMan (Ned Hill)]

@Kinsway

I do wonder if there are circumstances where it it ought to be held back.

Absolutely, if you are doing thin / light materials (e.g. paper, wood veneer) it’s nice to be able to turn down the air flow so pieces aren’t blown around. If you are using a compressor as an air supply you can get an air flow meter to control the flow. Like this one:
https://www.amazon.com/Flowmeter-Control-2-5-25-Suitable-Measuring/dp/B07XL3T6BK

[dougl]

It most likely works well because the tube is much closer to the cut/focus point than the end of the cone and maybe your tube output hole is smaller also so it’s a faster air stream.

Until I saw Russ Sadler’s air assist nozzle which can be adjusted vertically, I didn’t get why people were using the cones. The hole had to be rather large and it was so far from the cut it did little but to blow smoke away and needing a larger air pump. The tube design allows for the tube outlet to be closer to the cut and they can be very small holes so high pressure streams of air can blow lots of debris away. But the cone keeps smoke off the lens, so I created this design because it leaks air into the cone to keep smoke out AND it get a very small hole and fast stream of air close to the cut.

Merged Air Nozzle V1 for K40 by DOugL

[NedMan (Ned Hill)]

@dougl

so I created this design

Huh, I saw that design on thingiverse and admired the dual air flow set up. Totally didn’t catch that it was your design. So, nice design.

[dougl]

Ya, that username is inspired by a famous Jeti master. “do, not try.”

[Kinsway (Keith Taylor)]

It is actually used for aerating aquariums although the description states used for air assist. It is very noisy, like one for pumping up car tyres but yes I will look into this later.

[Kinsway (Keith Taylor)]

Yes I agree and my initial preoccupation is to use the machine for cutting which I could not really do with a diode laser so I did want that focussed air stream. I did see a post whereby someone had used the Pro head but then placed masking tape over it and pricked a hole in to reduce the hole size. I took a look at your design on thingiverse and mine is also from thingiverse is clearly a remix of your design to include the red dots but without the cone so I will consider this design in the future. In practice because I have a short tube to extract smoke to the outside and I fitted two fans pulling air in from the front and across the bed, I am not having any smoke problems inside the cabinet and indeed checking both the mirror and lens I have not not seen any deposits.

[jkwilborn (Jack)]

I might be out of line here, not owning a K40, but my China Blue has been upgraded… I think the basics are the same… how much is applicable I don’t know… I also haven’t see the Sadler K40 head…

Fire is always an issue, but I don’t have the primary cause (it seem) of it being a honeycomb bed that accumulates flamable debris and then ignites… I also have a CO2 extinguisher for unexpected bbq’s.

@NedMan

knock down flames and help keep the lens clean … would be better for cutting

Part of the issue is what are you cutting… Mdf I use 60lbs. Acrylic doesn’t respond the same so I use very low air pressure, just a breath to keep lens clean.

The C series lens tube and nozzle are very configurable. Depending on what you are doing.

They can be flipped to handle different focus length lenses.

Configured for different operations.

If the air pressure in the container (nozzle) is greater than outside, I don’t know how you could get debris in the nozzle area…

My lens tube has no top, it’s open… I depend on good ventilation to get the debris out of the machines other areas so it doesn’t condense. Probably why @dougl comment on leaking air to keep the tube above the lens clean. Good ventilation helps prevents this.

I switch sizes of nozzles, so I have no idea of what volume you need… You would have to be able to measure the pressure, not the volume of the air in the nozzle to determine much of anything. My air assist hose is smaller than my large nozzle outlet… so how would volume be an indicator here without knowing the flow rate of different nozzles or doing the math…?

This is my head assembly… no led pointer or drag chain… lowers the mass immensely, allowing higher acceleration values and of course speed great than you could really use.

If debris could enter top of the tube, I think it would … ventilation keeps it close to smoke free in the cabinet…

I hope this isn’t for naught… hope it helps…