sintering oven problems

[shane williams]

So here's the deal, I've got two MihmVogt ovens, the HT-Speed's. Lately we've been noticing issues with the Zr. Color not looking right, trans is crappy. So I contacted my Zubler rep, and they got me a program that captures the oven cycle and the actual temperature of the oven. Then you just plug it into an excel spreadsheet and it will show you how the oven acted during the cycle. So when I'm doing my "fast" program(mainly because I can check it in a few hours) the oven usually takes around 5-6 minutes to get the ramp rate to the same as the program, but by this time it's already 150-200 degrees difference. It'll stay at that rate till around 1,000 degrees then fall off again to 40-50 degrees until it reaches the hold temp(which according to the data is about 10-15 behind the program). So I'm loosing 10-15 minutes of hold time for my zr, no biggie I just increase the hold time to fix the problem, right? But why are my ovens doing this is my question? First I thought it might be a power issue. The building we just moved out of was terrible, we had to turn off suction units to turn on a microwave, and breakers blew all the time. But now we are in the new building with more power than we need and it's still acting this way. Would the elements themselves be doing it? I mean the oven does get to temp, but takes longer than I want. Any help would be great.

 

[Sda36]

So here's the deal, I've got two MihmVogt ovens, the HT-Speed's. Lately we've been noticing issues with the Zr. Color not looking right, trans is crappy. So I contacted my Zubler rep, and they got me a program that captures the oven cycle and the actual temperature of the oven. Then you just plug it into an excel spreadsheet and it will show you how the oven acted during the cycle. So when I'm doing my "fast" program(mainly because I can check it in a few hours) the oven usually takes around 5-6 minutes to get the ramp rate to the same as the program, but by this time it's already 150-200 degrees difference. It'll stay at that rate till around 1,000 degrees then fall off again to 40-50 degrees until it reaches the hold temp(which according to the data is about 10-15 behind the program). So I'm loosing 10-15 minutes of hold time for my zr, no biggie I just increase the hold time to fix the problem, right? But why are my ovens doing this is my question? First I thought it might be a power issue. The building we just moved out of was terrible, we had to turn off suction units to turn on a microwave, and breakers blew all the time. But now we are in the new building with more power than we need and it's still acting this way. Would the elements themselves be doing it? I mean the oven does get to temp, but takes longer than I want. Any help would be great.

Would be a good idea to have an electricain check your actual voltage at your new place, makes a big difference.

Sent from my LG-H873 using Tapatalk

 

[user name]

Double check the connections between the elements...? Just give them each a slight twist.

Don't forget to disconnect the power first!!!

 

[JMN]

Element age or fatigue is a possibility. They may not have liked the move and may have micro-fractures.

Source power issues - if you have a meter, you can check this yourself. Just DONT TOUCH the metal probes, ever ever ever, when you are testing anything or you become part of the circuit. It hurts, if you live through it. If you are not comfortable with this, stop. Go with @Sda36 's suggestion of an electrician.

Transferred power issues:
Some rust/tarnish on the plug into the outlet?

Very old power cord?

Did you choose the correct cord after moving? - they look very similar, but some are designed to handle power levels others cannot by using larger wire inside - see if it feels warm. If it does replace it immediately with a properly rated cord. If it feels warm, this is actually a fire hazard.

WIth the oven unplugged, as @user name suggested (he would know ),check to see if they are fully seated/connected. Again if you have a meter, you can check this on the Ohms setting. Should be near a perfect 0.

Sheesh. Just look here:
http://dentallabnetwork.com/forums/threads/sinter-temps.24437/

 

[user name]

That @Ralph32 is a disagreeable little bitch, isn't he.

 

[JMN]

Just figured either he is tryin' t' be funny or simply disagrees with the laws of physics.

 

[rkm rdt]

 

[Patrick Coon]

That @Ralph32 is a disagreeable little bitch, isn't he.

He's agreed with a few of my posts, so I'm not sure if I should be honored or afraid.

 

[JMN]

@Ralph32 come out and play, let your hair down, or put it in a manbun, we don't care. There's already an inactive Marine selling skin care products on here, you can't be get weirder than we already are. I promise you won't shoot your eye out.

 

[rkm rdt]

Scotty can't help himself.

 

[user name]

@Ralph32 come out and play, let your hair down, or put it in a manbun, we don't care. There's already an inactive Marine selling skin care products on here, you can't be get weirder than we already are. I promise you won't shoot your eye out.

 

[JMN]

you can't be get weirder than we already are

Yep. :O)

 

[BobCDT]

I'm not sure if the heating elements are wired in series or parallel in your oven. If they are wired in series it's possible one element is gone and you are sintering with one (or more) defective elements. If wired in Parallel and one is broken you will get NO heat. I would check to make sure there are no broken elements.

 

[shane williams]

So an update, when I did an overnight program the ramp rate and temp hold was spot on. Still though I'm not sure why the fast cycle would do this. I'll check the power and the oven and make sure everything is working. Thanks for all the responses.

 

[JMN]

So an update, when I did an overnight program the ramp rate and temp hold was spot on. Still though I'm not sure why the fast cycle would do this. I'll check the power and the oven and make sure everything is working. Thanks for all the responses.

it's remotely possible that if you are in a daytime-heavy-use area that gets less use in the evening you are experiencing localized mini-brownouts. Daylight heavy industry zone? Older grid portion?

Another oddball option, are you using forced air heating and A/C with a unit pointing in a path of which the furnace is directly included? It would be less active at night as well.

Just some thoughts. Who knows.

@Ralph32 Hit me. Come on, you know you want to.

 

[JMN]

Et tu 2the'?

 

[Patrick Coon]

So an update, when I did an overnight program the ramp rate and temp hold was spot on. Still though I'm not sure why the fast cycle would do this. I'll check the power and the oven and make sure everything is working. Thanks for all the responses.

Shane, is that furnace on it's very own dedicated circuit? no other outlets attached to that circuit in the breakerbox? If not, it could be that something else is drawing power and not allowing it to heat properly during the day on the short cycle, but is not turned on at night and drawing power. (a press furnace or drying/toaster oven perhaps)

If not, I think it's a question for you furnace manufacturer.

 

[tehnik]

So I reuse this thread with my problem. Having Nabertherm oven and after using dental direkt cleaning powder at 1650 degrees I am getting this weird problem that occlusal parts, that are in contact with sintering beads, are sintered ok but higher parts are opaque. I am sintering Katana at 1550. The overall color is also not correct - it is lighter. Any ideas?

 

[user name]

What do the elements look like? Are they an even graphite color, or do they have crystally whitish spots?
Ive run Katana up to 1650 just to test, so I can say it probably isnt from over sintering.
Im guessing contamination. Run a purge/regeneration cycle every week.

 

[tehnik]

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