sintering oven problems

[user name]

Well the problem started after the cleaning program. It was perfect before that.

What cycle parameters did you use for regeneration? How often do you run it?

 

[tehnik]

The program in the instruction for nabertherm. I have use it before with no problems.

 

[user name]

So what do the elements look like?

 

[user name]

If you havent been maintaining them and cant correct with a regeneration cycle, its time to replace.

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[tehnik]

I have been using cleaning cycles before and there have been no problems but now it is different. After the cleaning cycle I checked the heating elements and there were no contamination on them. I also made test sintering with broken etc crowns and all was good. But the next sintering was bad. Now I used oxidation cycle, that came with the oven, and there are some white crystals on some elements (area on the picture, nowhere else). So I am running the cleaning cycle again. As I said there were no problems with sintering prior the last cleaning cycle and I am doing them regularly.

 

[tehnik]

So the white spots are gone but there are now dark patches on the rods....

 

[user name]

They should look like pencil lead. Im guessing your black spots are the burned formerly white stuff. Maybe wipe them off? Id try removing them and a very gentle wipe with a cloth; if that doesnt work, maybe a dish scrubber, then reinstall and run another regeneration cycle. Best bet is replacement. It is a consumable item. Expected life when treated well is 4 years. Neglected, much shorter.

 

[tehnik]

I think it is time to replace the rods... after cleaning cycle the test patch of 2-3 crowns are good, but after that, there are problems again. 2 of 4 rods have black spots and patches and it looks like they are increasing by every firing.

 

[tehnik]

Is it recommended to change all of them or only the ones with spots? I did another test firing and the crowns are totally opaque and one of the rods is covered again with white and black spots. Also I think the problem could be avoided by not firing with the maximum allowed temperature. It is 100 degrees more than the highest temp I am using with the oven. As I said there were no problems at all before the cleaning firing.

 

[JMN]

Is it recommended to change all of them or only the ones with spots? I did another test firing and the crowns are totally opaque and one of the rods is covered again with white and black spots. Also I think the problem could be avoided by not firing with the maximum allowed temperature. It is 100 degrees more than the highest temp I am using with the oven. As I said there were no problems at all before the cleaning firing.

If they are in seriies, all must be changed at once. If in parallel, they can be changed out individually.

If you don't know what that means:

Series:
.........n......n.....n.....n......

Parallel

..........
l l l l
.........

 

[JMN]

You may find this thread helpful.

Sinter temps?

Im trying to dial in a program on Mihmvogt HT Speed. Im just replicating the factory recommended numbers for Jensen XT, and I was getting beautiful results in another oven, but my first 2 cycles (long program) came out slightly opaque, and a tad whiter than usual. Im guessing it need...

dentallabnetwork.com

 

[tehnik]

They are parallel. Nabertherm (oven company) suggested to change all the elements as they are over 2,5 years old and are used on daily bases.