Prevention of self welding of heating element.

You could schedule periodic disassembly and cleaning. That's what I do with my soldering equipment, that suffers from similar problems. S.M.

I wish I could do that. If I put the heating element into a cavity that is not really tight the out side of the element bursts and I have to replace it on a monthly basis. That is even more expensive than having the tooling drilled, reamed and have a new element put in it. I could do what you suggest if it didn't weld itself together.

A whopping $100.00 a year maintenance cost sounds cheap to me. Particularly for drilling out something welded to beryllium. I suspect that a typo here or a cost underestimation. Do you use any anti-seize compound when you install a new heater?

I sounds cheep to me too, except when you add it to all the other costs in a business that has a low profit to sales ratio. No typo.

1. So have you tried any of that high priced $37 a bottle anti-seize compound?
2. What does the blade manufacturer recommend?
3. Did you know that I've gotten very intolerant of people that don't answer my 20 questions?
4. How hot do things actually get?
5. Do you think that a $10 consultancy fee is too much to charge?
6. So when did employee safety become an unacceptable expense?
7. How much of the $100 is the cost of the heater?
8. Have you tried the more affordable $25 a bottle anti-seize compound?
9. You do realize that I'm not going to ask more than 20 questions, don't you?
10. Did you read the section in the "Tips for posting on CR4" that starts with "Provide as much information as possible"?
11. Is this an actual elemental Beryllium metal or Beryllium Copper?
12. Did you read the information on the hazards on machining Beryllium? Did you know this before I provided the link? (Wow, two for one. What a bargain!)
13. So if $100 a year is too much of a maintenance expense, do many things break at your facility?
14. Did you know that there are lubricants designed to prevent things from seizing before getting here?
15. Did you know that CR4 provides a spell checker for postings?
16. Did you know or care that David Letterman has been on late night TV now for 30 years?
17. Who built this machine?
18. Did you know that there are many stainless steel alloys?
19. Did you know that Beryllium has a thermal expansion coefficient of 6.4 in SAE units while stainless steel has a thermal expansion of 8.0 to 9.6 depending on the grade?
20. Will you answer any of these questions and did you use an anti-seize compound?

Good Bye

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Ok, I hope you didn't mind my little bit of fun there.

As you can project from my little display of absurdity (temper tantrum). I've seen many annoying posters here lately where there has been next to no information and even less comprehension. I thank you for allowing me to blow off a little steam.

Now I believe I can help after I discuss some ideas with some mechanical designers at work. At work we use Beryllium for vacuum isolating windows to allow X-Ray synchrotron light into an experimental beam line.

I suspect that the original manufacturer did not provide for sufficient expansion of the stainless encased heater. My initial concept is that a new stainless heater case should be machined down ever so slightly so that the thermal coefficient difference does not create a metal on metal seizing at the high temperature. I suspect that the original manufacturer recognized the PIA it is to machine brittle Beryllium. Because of this the dimensions of the interface where this heating element goes were never precisely specified because each one would be a little different.

Now the solution to your problem could just be as simple as people using Belleville washers instead of flat washers at critical locations.

As for the warpage issue of stainless steel versus Beryllium, Beryllium does move. (My electronics measures the microns of motion that every metal goes through in a large temperature change regardless of it being a bake out to 80°C or a superconducting magnet at 80K.) In the case of Beryllium the thermal coefficient and low density means a much faster heat dispersion so both sides of the metal are at similar temperatures at all times. So along with the added room temperature gap between heater and Beryllium you will still need a metal based compound to fill this void. Not just for anti-seize goals but to maintain contact between heater and heatsink. This is another item I must research at work but to do this properly I need to ask a clarifying question. The 1000 degree temperature you mentioned, what are the units?

Since you prefer to be brief in your answers, it would probably help to post or contact through the CR4 mailbox with some pictures. This is a case where a picture is worth 1000 words.

I did not mind your attempt at humor at all. I actually enjoy lightening things up a little. I have an expansion space now but since I am so inept at figuring all this metal to metal stuff, I surrounded the heating element with a piece of brass tubing. This application kept the heating element from self destructing because of the air gap. I thought maybe I could replace the brass tubing with titanium. The titanium would obviate the welding problem. The question, before I invest in a titanium insert to surround the heating element, is will I still end up having to drill out the heating element or will I be able to press it out with a hydraulic press. After all, titanium is slippery by nature at least when it is cold. I would really like to end up with something that, when the element goes belly up, I can just pull it out of the hot knife by its' wires. The expense of doing this right is not a worry to me. All I want is to reduce down time to a minimum. In one extreme case it took 6 business days to get the machine work done. If you have any suggestions for a better metal to use that the beryllium that I am using for the knife, please suggest away.

Well you could reverse the coefficient of expansion scenario and try cooling the heater with a can of cool spray. Remember the steel will take more time to heat up and cool than the Beryllium. The machinists use liquid nitrogen all the time at work but as you may have guessed, we have some neat toys.

Hey guys, don't shoot me down too hard but here a suggestion from an electrical guy...

Could he make a small cut (~0.5mm wide) along the cartridge side from one end to the other to give some expansion room for the steel ad let it move. It might prevent the seizing.

This sounds like a good application for a thermally conductive grease AKA heat sink compound.

Is that 1000 degrees C or F?

At 1000C your proposed brass shims will melt and you'll have to contend with an element that is brazed in nicely.

I'm guessing that this is a really interesting assembly. I'm just relying on my vivid imagination to picture it. What's the chance of having some photos of The Knife here?

What are you cutting with it?