Sinter temps?

[user name]

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 more...heat? Time? The tech sheet on XT says 1530-1540, and I set it at 1540, 2 hour soak. s please.

Im also curious about running a calibration. I don't see anything in the manual about it.

lastly, in the display upper right it says STNBY (standby). In the manual theres a pic of the display showing READY. Have I goofed something?

 

[RileyS]

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 more...heat? Time? The tech sheet on XT says 1530-1540, and I set it at 1540, 2 hour soak. s please.

Im also curious about running a calibration. I don't see anything in the manual about it.

lastly, in the display upper right it says STNBY (standby). In the manual theres a pic of the display showing READY. Have I goofed something?

I'm at 1560 with Jensen XT

 

[user name]

I'm at 1560 with Jensen XT

Huge thanks for the post Riley. Ive run 3 cycles so far. 1st was just an unshaded single unit of XT, just to make sure the oven worked and see if I was in the ball park. It came out I guess as expected...Im not an expert on what unshaded looks like, but it looked sintered. 2nd run things looked a bit more under done in my estimation, and then the 3rd looked worse. Im wondering if theres a break-in period for the elements? I wasn't sure if I should raise the temp, hold time? Ive put my question out everywhere I can, and got back a variety of thoughts. Ive heard someone sintering XT as low as 1500, but most of the thought is I should raise the temp. I think that's where Ill go with it. What would happen to Zr if its over heated?

 

[JMN]

Something to keep in mind. Ovens are only able to tell the temp of where the thermocouple is placed. Which is usually nearer the elements. It is not the temp at stage level. Also most thermocouples are allowed a percentage of variance, or tollerance. At these temps a 1% tolerance would be 15ish degrees.

 

[Getoothachopper]

You might want to try a lid on your sintering crucible (if you don't already). Friends of mine were having a similar problem with the same make of furnace . That sorted the problem out for them. Just an idea

 

[JMN]

You might want to try a lid on your sintering crucible (if you don't already). Friends of mine were having a similar problem with the same make of furnace . That sorted the problem out for them. Just an idea

That adds a level of thought to the processing time calculation since it creates a second atmosphere that is influemced by the first but not directly knowable. Right?

Am I overrhinking?

 

[zero_zero]

I recently replaced my sintering elements and it took three firings to get it right...the third was OK already. I never cover the crucible BTW...

 

[Getoothachopper]

They purchased the large Mihmvogt furnace and spent weeks tweaking everything . All the crowns were looking slightly under fired with low trans . They were told to try covering the crucible and it solved the problem . It's not something I do , heck I don't even have covers for my AG zolid crucibles .

 

[user name]

This is what we need...

There are differences in voltage and other variables that mean not all new (or used) ovens will fire at the exact same temp. Even when, after trial and error...expensive, time consuming and unnerving, you get it dialed in...things will change. Day and night electrical demands, seasonal changes, worn elements with changing efficiency. Its not going to be a set it and forget it thing. Ok, maybe we do set it and forget it...until its obvious somethings just a little off and then we wonder; "are my eyes getting old? Do I need to change my lights? Should I shop for a different brand of Zr? I used to think things looked better, but lately my crowns just don't impress me like they used to."

We shouldn't be guessing, and I don't think we need to. Anyone remember sintering Dicor? We had those funky little clay skinny pyramids leaning to one side. When you test fired one, it would slump over; either too little or too much, but it was an accurate way of keeping it dialed in. We didn't have the luxury of a 10 degree margin of error...or more.

There must be a way to assemble a kit...maybe a combination on different Zrs, clay like with Dicor or some other materials that could all be sintered together, and be used as a visual indicator to verify what temp your oven is actually at.

Fire it once, observe which material slumped, which looked under or over fired, and calculate the offset from your desired temp. Make an adjustment and your done. No guessing.

 

[user name]

How frustrating. After running a couple cycles at the recommended temp, things just didn't look that great. I ran one last night and bumped the temp up 20 and they looked worse; very opaque and the margin areas were kind of turning white. UGH! I just re-milled a couple and dropped the temp down to the low end of the recommended temps (1530-1540),so this one is the lowest temp Ive tried...1530. We'll see in a few hours. One things for sure...it will either be better or worse.


Ive heard one guy using the same that's all the way down to 1500, so we'll see. Im re-milling a bunch and will have them colored and dried ready for another short cycle, so they can still (theoretically) make it out in the morning.

 

[zero_zero]

Might want to calibrate your oven. Give these guys a call: https://www.ortonceramic.com/en/PTCR Ring/ ,they are very knowledgeable about sintering. There's no need to buy their micrometer, there are tons on ebay for cheap.

 

[user name]

Might want to calibrate your oven. Give these guys a call: https://www.ortonceramic.com/en/PTCR Ring/ ,they are very knowledgeable about sintering. There's no need to buy their micrometer, there are tons on ebay for cheap.

Im on top of the PTCR, just haven't done it yet. That will get cooked tonight and sent in for measurement. I have some from Jensen, so they will be doing the measureing.

Thank you though for your help. Lord knows I don't have all the answers. Just read my tag line at the bottom...

 

[user name]

Well...I noticed something.

Ive ran a few cycles now and have been playing with the temps because things haven't looked right. When I ran the first 2, I was impressed with the ovens insulation...even the long program at the high temp, the outside of the muffle was barely warm to the touch. Im currently in the middle of a short cycle and have dropped the high temp down quite a bit to check results, and surprisingly, the muffle, esp. on the right side is so warm its uncomfortable to lay hands on; the left side is warm, but not nearly so. When this cycle is done Im going to power off and wiggle the electrical connections on the elements and insure there is good contact.

 

[zero_zero]

When this cycle is done Im going to power off and wiggle the electrical connections on the elements and insure there is good contact.

Careful with the wiggling...the elements are metal coated where the braided wire contacts them, if you damage that coating you ruin the element. Measure the resistance across each element instead, it should read the same.

 

[user name]

Careful with the wiggling...the elements are metal coated where the braided wire contacts them, if you damage that coating you ruin the element. Measure the resistance across each element instead, it should read the same.

Thanks! If I had to make an assumption, Id think you were one of those smart guys, like an engineer or something.
Am I to check resistance on each element or between elements? or open it up and check volts while its running?

You don't know how close I was to getting out some steel wool and giving the part the straps slide on a little rub down...just to ensure good contact.

 

[JMN]

Thanks! If I had to make an assumption, Id think you were one of those smart guys, like an engineer or something.
Am I to check resistance on each element or between elements? or open it up and check volts while its running?

You don't know how close I was to getting out some steel wool and giving the part the straps slide on a little rub down...just to ensure good contact.

DO NOT MEASURE WHILE RUNNING! Unless you have nothing left to do in this world!

Set your meter to Ohms resistance, the highest range it will go to. (some meters are auto-sensing/auto-ranging now and it will say so on the meter)
Put your probes on the point where the element connects to the wiring. Measuring the resistance of the element itself.
If you get no reading or an insignificant reading, then adjust range on the meter till you do. Always start higher than you think you need when reading.

Repeat with each element.
checking the resistance between elements..

You are looking to put your probes where the ...wire enters/connects to the n element's legs or as close as you can without contacting the working portion of the element.

If they are in series like this ...n...n...n...n...
none of them will work without all of them working at least somewhat.

If they are in parallel like this
.
.
.
|..n..|
|..n..|
|..n..|
|..n..|...

Then the reading may be meaningless without a schematic to see how they are driven. Note *may be* meaningless. There should only be a big variance on the first and last in the parallel loop because they are going to the driving circuit instead of the next element.

Please never check something with the power on, unless you know exactly what you are doing and know what safety measures to use. Your daughter needs you. And if you have your meter on the wrong setting when doing it you could get flash-blinded by it exploding in your hands. I lost a nice meter that way when I thought I knew something I didn't.

 

[user name]

Great. I thought all I had to be concerned about was clean underwear and not getting a pencil stuck in my eye.

So when I check this, all Im looking for is continuity? It doesn't take much connection to establish that, does it?

 

[JMN]

Great. I thought all I had to be concerned about was clean underwear and not getting a pencil stuck in my eye.

So when I check this, all Im looking for is continuity? It doesn't take much connection to establish that, does it?

You're looking for the resistance reading to be the same for the elements. A 0 ohm reading between them, if they are in series the wire between them should test as if you are touching the probes together.

The larger and stronger physically the connection is the larger the current which can pass.Oh, the meter's probe contacts will have plenty of connection to test properly. Under load the elements are passing dozens of amps.

Simply put continuity just means there is a circuit, not how much resistance is in the path between the points under test.

 

[zero_zero]

Am I to check resistance on each element or between elements? or open it up and check volts while its running?

Just like JMN said it should be unplugged, it shouldn't be running unless you really know what you're doing. Assuming your elements are connected in series your setup should look like the sketch bellow:

For more elements the idea is the same. You need to measure across the elements as shown, probing on the braided wire. The readings should be within 5%, 10 at most...excessive resistance means bad connection or faulty element. Depending on controller type the resistance measured could be a tiny bit less what really is, but that shouldn't be a concern.

 

[user name]

Just like JMN said it should be unplugged, it shouldn't be running unless you really know what you're doing. Assuming your elements are connected in series your setup should look like the sketch bellow:
View attachment 23134
For more elements the idea is the same. You need to measure across the elements as shown, probing on the braided wire. The readings should be within 5%, 10 at most...excessive resistance means bad connection or faulty element. Depending on controller type the resistance measured could be a tiny bit less what really is, but that shouldn't be a concern.

Wouldn't it be better to measure from the terminals that the straps are connecting? otherwise it seems Id be checking the straps resistance; should be checking the connection theyre making with the posts..?

Also, I need to run and grab a new multi meter. Analog or digital?