You may, what are the specs on the tube.
old one is 600mm and no mention of power, new one is 700mm and 40w (peak)
I have one of these being printed to accommodate the longer tube.
I don’t intend on running the laser at full power so thinking it should be fine. I heard the power unit is the same but not sure how true that is
If its 40W you should be ok. Worse case you will notice you cant get to full power.
I highly recommend adding an MA meter do you can tell what the tube is doing.
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I’ll get on with getting an ma meter. Turns out the machine has a removable panel for a longer tube. I’ve got an end cover being printed as we speak. Will get it all together and tested this week!
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Just make sure that you don’t end up the shortest path to ground for the 20,000V in that high voltage wire now that it’s not entirely enclosed in a metal cabinet. 
A plastic enclosure for the anode end is not a good idea.
Its cover should be grounded. That LPS can easily pierce the plastic if a ground … like you … were to get to near it.
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I see, there’s me thinking plastic was the ideal material owing to it being an insulator. Not sure what to do now then.
Could I add an earth inside the plastic tube? Like, a metal bolt close to the cathode with a wire to the machines earth?
Im also interested in the best solution as I will be doing the same.
Perhaps bend some sheet steel inside and ensure it grounds to the case ?
What is considered safe?
Mmmmmm …
Perhaps some adhesive-backed metal tape affixed to the inside and outside of the plastic.
I was thinking that since this stuff is so thin having an inner and outer layer wouldn’t hurt.
Here is some copper tape used to shield guitars. https://amzn.to/3iO366I
You could ground the inside and outside by running a braided strap to the case(or mounting screws) and soldered to the foil.
You could use “solder wick” for the ground strap
If the tape runs under the heads of the mounting screws that could also work.
I like the ground strap in addition to the mounting.
You should also ensure that the spacing from the anode to the ground is about as it would be with a laser mounted in the cabinet.
Safe is just having a path to ground for an arch that is NOT your body :0!
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Will take a look at grounding strap options. I opted to use one of these connectors than solder, seemed like a better option. May wrap with electrical tape too
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For your extension, there is also at least in the US adhesive aluminum foil tape sometimes used in ductwork (duct tape, as opposed to duck tape which is so named because it sheds water). Not all duct tape is foil, but the product exists. It has a paper backing you have to peel off to apply. It’s what I would use there. Easy to cover the whole thing, including under all the screw heads.
Most electrical tape is basically useless for isolating 20,000V. Common electrical tape has a dielectric breakdown voltage of at least 600V and often 1000V. Tape does exist that has 10,000V dielectric breakdown voltage, and I see reference to some that is 60,000V/mm, but you’ll want to check the specifications on your own electrical tape because of the orders of magnitude difference in dielectric breakdown voltage.
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I think I remember someone making a tube extension from a metal coffee can one time.
Of course you could always go with the purpose made one from LightObject
https://www.lightobject.com/K40-Upgrade-Parts/K40-Mini-Laser-Machine-Tube-Extension-Case
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Website says access forbidden. If there was a purpose made one available in the uk that’d I’d known about I’d have bought it
Hmmm…link works for me. Any way, sorry I didn’t catch that you are in UK 
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I did come across this box on Amazon and if it was uk I’d have bought it. Hmm odd that the site doesn’t work for me ‘403 forbidden’ message comes up
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Works for me in the UK.
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Some folks geo-block europe because the GDPR penalties are too high for them to accept as a business risk, and while I know “it’s complicated” currently describes the situation WRT UK and GDPR, you probably don’t want to ship from US to UK anyway. 
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