So....this happened

[FabMan63 (Dave Everhart)]

A week ago yesterday, I went out to the workshop, to fire up the laser. Haven’t done that in several months, because of other priorities, and weather.

Almost immediately, I heard water gushing out from somewhere. Unplugged machine, spun it around, opened the door to find water starting to pour all over everything electrical and electronic, in the side. Fortunately, I got to the power before anything seeped in, so that’s all good.

But…look at that tube. Holy h**l.

(…yeah, that little circle on the right, in the second pic, is the glass end… popped off like a soda bottle cap…)

So, now I’ve got a dilemma: funds vs. an opportunity. I’d been thinking about upgrading, anyway, from a 40w to a 50 or maybe even 60w. To simply get a replacement 40w tube seems rather counterproductive, but the alternative is to spring for a new power supply as well, which ups the cost obviously.

Then there’s the issue of tube length. Current one is 32”/800mm. Between the end of the tube and the body, there’s another 3” safely available (with clearance to body); that would bring me to 35”/890mm. Assuming I can find what I need in the 890 length, would it be safe to upgrade to a longer tube in this case, or is there a minimum amount of distance needed between the end of the tube, and the body?

Also, recommendations on brand/resellers? It’s pretty hard to tell when, for example, two different vendors have the same picture of a power supply, but two different customer ratings. As well, I would assume most of these tubes all roll out of one or two factories, with the (likely) difference being quality control.

Being as underfunded as I currently am, I cannot spring for the most expensive, but I am also uninterested in the cheapest, because you get what you pay for. So, somewhere in the middle. And I can’t move on this right away, so this is going to have to stew for a while until the funds become available.

Thanks.

[mcdanlj (Michael K Johnson)]

I haven’t checked whether the extension box here is still $35 but no particular reason it would be terribly expensive…

50W tube into K40

Welcome to Maker Forums! That tube won’t fit in a K40 case without an extension. A metal extension that is electrically connected to the case is important for safety. There have been plenty of folks here who have at least talked about doing the upgrade. Search results for '50w k40 ' - Maker Forums definitely covers more than this case, but I think there are plenty of relevant results in there worth glancing through. Whether it’s worth it or not depends on the work you are doing, I suppose. …

[jkwilborn (Jack)]

I got my last tube from Light Object in the Pacific NW in the USA. Tube is Chinese, but it comes with all the paperwork and a printout of Light Objects test.

I have an OMTech China Blue 50W.. actually it had an 880mm tube that produced about 43W out measured with a Mahoney meter.

I found this table useful.

It’s likely your machine produces around 40W out.
—

This is my original machine, but with a true 50W tube (1000mm) in it. I printed the extension on my 3d printer.

It can be tough to put a larger tube in if the mounts are for a difference physical size tube.

Have fun.

[FabMan63 (Dave Everhart)]

I have found some tubes, on Amazon, that clock in at 800 and 850mm, producing 50w.
What I’m really avoiding is having to put an extension on, as there’s really not any space to accommodate that, in the immediate shop area.

[FabMan63 (Dave Everhart)]

@jkwilborn

It’s likely your machine produces around 40W out.

(ahem) produced… past tense.

I suspect, too, that you and I have noticeably different definitions of ‘fun’.

[jkwilborn (Jack)]

@FabMan63

avoiding is having to put an extension on

I totally understand, but, more power comes with a larger tube. It’s really gas volume, so physical size is the limiting factor.

The extension, I couldn’t find any anywhere, that’s why I resorted to the 3d printer.

[mcdanlj (Michael K Johnson)]

@FabMan63

What I’m really avoiding is having to put an extension on

Ah, sorry then. So it’s really a question of how much space you need between tube and case to avoid arcing to the case when a 20kV potential is present?

[FabMan63 (Dave Everhart)]

yes, exactly.

[mcdanlj (Michael K Johnson)]

The dielectric strength of air is quoted at about 3kV/mm so 1cm separation should give 30kV, which will be sufficient for a 20kV supply, I would expect. Anyone here with more knowledge than me know something to the contrary?

[FabMan63 (Dave Everhart)]

Is this affected by humidity? It’s quite dry up here.

[mcdanlj (Michael K Johnson)]

Apparently not a lot. More by atmospheric pressure and electrode shape; sharp tips reduce the effective dielectric strength. Lower atmospheric pressure reduces dielectric strength; I’ve seen to derate by 2%/1000ft above seal level.

If you want to be safer, put a layer of silicone on the inside of the case near the business end. Cured silicone has a dielectric strength of over 14kV/mm so 2mm of silicone should do great.

I’m a software developer, not an electrical engineer, so check these numbers.

[FabMan63 (Dave Everhart)]

That may be, but my level of engineering ability is such that I totally understand what you present, here, but would not have begun to think of it, in the troubleshooting/problem-solving process.

To that end, one could even theoretically cast a simple silicone pad, a few mil thick, and epoxy it to the business end.

[FabMan63 (Dave Everhart)]

Any real, significant advantage of the metal head, over glass?

[FabMan63 (Dave Everhart)]

Additionally, I’ve been seeing more options for 55mm tubes, than 50, so I looked at the machine. Looks like I can accommodate a 55 tube in there, with no real issue. The clamps are straps, not cast, so it looks like I can pretty easily get a 55 in there.

Then the question becomes one of alignment. If I sat a 55 in there, with no adjustments, the center of the tube (thus, the beam) is going to sit high, yes? As it happens, the pads in between the glass and the strap, are 5mm thick…

…do you think simply removing the one underneath, is going to keep the new tube to center, or am I going to have to devise a 2.5mm pad solution for top and bottom?
Obviously, I’m trying to avoid having to completely realign the entire path.
From the outset, it seems they designed this thing to accommodate a thicker tube, to begin with, so maybe this has all been thought out.

[dougl]

Keep in mind that the mounting implemented was designed to be capable of handling shipping. Once on-site, some of that padding might not be needed.

I’ve seen many 3D printable clamping mechanisms on Thingiverse and other websites and they often have adjustment capabilities besides scaling for different tube diameters.

[jkwilborn (Jack)]

@FabMan63

I’m trying to avoid having to completely realign the entire path

If you replace anything in the optical path, you will have to re-align it from that point on.
–

Change out a tube, you will need to completely re-align it. You might be able to get it close, but even with snug fitting mounts, it’s off a bit. Don’t know what issue you’ll have with those mounts and the correct tube. That’s a pretty sloppy system for replacing things in a properly aligned system.

You don’t want to raise the position of m1 if you can help it. You might be able to get m1 to get the beam to m2, depending on how much adjustment you have at m1.

Raising anything becomes more of a problem when you get to the head, most of these have no Z adjustment at the head. It may be very difficult to take this path.

Might be able to shim the anode of the tube up, so it strikes m1 in the middle?

@FabMan63

I’ve been seeing more options for 55mm tubes, than 50

I have not… where did you find these? Most of these machines are 50 and 80mm diameter. Some of the intermediate tubes use 55mm, but I only saw one when searching.

–

The most simple way is to put in a longer tube with the same diameter. You will likely have to open the end of your machine up for the tube to extend. The issue with this, is the extension is difficult to come by.. I couldn’t find any and had to 3d print the one on mine, in red. It’s a true 50W tube from Lightobject.com and is 50mm in diameter but 1000mm in length.

Putting a larger diameter tube in a smaller mount will cause pressure points on the glass tube..

As @dougl mentioned it might be smart to 3d print the mounts.

Good luck.

[FabMan63 (Dave Everhart)]

Due to space limitations a longer tube really isn’t much of an option.

I looked on Thingiverse. You might find this amusing…

https://www.thingiverse.com/thing:4935101

[jkwilborn (Jack)]

I understand completely when it comes to real estate…

---

I don’t worry about being shocked, so much, although I’m sure it will set off my defibrillator.

My main concern is to keep from walking into it and causing physically damage. The mason jar would do the equivalent. As long as the mason jar is deep enough..

[leakyjoe (Joe Leak)]

I don’t have access to a 3d printer, so I just used what I had to hand.

[FabMan63 (Dave Everhart)]

More questions:

Just went out to really look at the connections, at the tube, to compare with what I’m finding available on the internets. This seems kinda…lame.

The wire was just wrapped around the terminal at the tube; a short section of the water tubing was slipped over it and filled with silicone. I both can - and can’t - imagine that this was done at the factory. Seems like the connection should be more robust. Perhaps the new tube should have the wires soldered on?

Then: Does this seem wise, securing both wires with zip ties, to the tube like this?

And, third: Is there a specific or ideal distance the end of the laser should be from M1?