How do you use calibration rings in your sintering furnaces?

[tuyere]

I don't mean, literally, how do you use them, I mean- what sort of systems you have, when you choose to use them, what you're looking for, what brand/type you use, etc?

We use Ferro PTCR rings, but I recently realized they don't work how we thought they did, i.e. the number you get from the diameter table is not indicating temperature, but rather a unitless heat-applied-over-time thermal-work number with no direct temperature correlation. So I'm re-evaluating how we use them, or if we should be buying a different product if it's temperature we actually want to check.
A suggested PTCR firing program is +120C an hour, 1 hour hold, at 1500 degrees. But the manufacturer's literature doesn't make clear that that will approximate a real temperature measurement. I think it sort of implies it, but the wording is unclear. They're clear that, in general, the 'heat number' you get is not a temperature measurement, so... i dunno. Orton Ceramics sells a couple other products that are explicitly for temperature verification vs. heat work quantification, maybe we could go with those for occasional temp calibrations, and keep using PTCR rings to compare our furnaces and make sure their performance isn't fluctuating.

 

[Car 54]

I know I'm probably paying too much for Ivoclar's version for my S1s, but they come in a 10-pack with the chart and have a program for it, so I'm good with that.

 

[tuyere]

Yeah, the Ivoclar setup kind of takes care of itself. We have a couple Zircoms that are poorly-documented and the manufacturer guide for calibration is sloppy and badly-translated to the point of incoherence, they interchangeably talk about using 2 or 3 different brand of calibration ring, provide a calibration cycle that's incomplete ("2:30 at 1500" without including soak time or ramp-up),include tables that could apply to two different ring types, etc. And they clearly wrote the calibration document after the fact, because they didn't tell people how to calibrate in the actual instruction booklet! Zircom's furnaces are good but their documentation is always so god-awful and lazy.
Also you can order identical rings from a ceramics supply house for far cheaper, it's the same product without the mark-up. we were ordering them in sets of 4 at like $5 a pop from Argen but I think I'm gonna get 'em to just order a case of 600 for $720 from Orton Ceramic, it'll take us a few years to chew through that stockpile but they don't have an expiration date and it's an easy way to save a couple thousand in the longer run.

 

[zero_zero]

I haven't use them for a very long time, but IIRC it was pretty straight forward to calculate the temperature from shrinking. There's a specialized micrometer they sell to center the rings perfectly.

 

[Car 54]

Older thread, but just in case.

Checking Sinter Oven temps

Ive been using Orton Ceramics Temptabs, both a 650 and a 700. Fire, measure and average the two. My Mihm Vogt is showing a substantial amount of error. I just reached out to Ferro to inquire about their PTCR rings. Is anyone using any of these? Are they consistent with the Orton products?

dentallabnetwork.com

 

[tuyere]

I haven't use them for a very long time, but IIRC it was pretty straight forward to calculate the temperature from shrinking. There's a specialized micrometer they sell to center the rings perfectly.

One would think so, but from Ferro's product info package:

For ease and for comparison this shrinkage ‐ and therefore the total absorbed heat quantity ‐ is translated into a single, fictitious conversion parameter, the so‐called „ring temperature“ (RT). Basically, this is not a „temperature“ but a parameter that depends on time and temperature. The RT for example does not reflect the maximum temperature of the firing process and does not correspond to the real kiln temperature because the PTCR accumulates the absorbed heat quantity over time.

we're getting readings that are 40C higher than nominal from our Zircoms, but when we calibrate comp the temp lower than 5 degree's we're immediately under-sintering. I've asked the manufacturer for a compensation table or more info on using it to check temperatures but they haven't replied.

 

[tuyere]

Older thread, but just in case.

Checking Sinter Oven temps

Ive been using Orton Ceramics Temptabs, both a 650 and a 700. Fire, measure and average the two. My Mihm Vogt is showing a substantial amount of error. I just reached out to Ferro to inquire about their PTCR rings. Is anyone using any of these? Are they consistent with the Orton products?

dentallabnetwork.com

This is useful, thanks. This in particular:

This is the response from Orton:

The TempTAB product is better for several reasons.

1. The heating rate used to establish the temperature data is 5°C/hr for TempTAB, where the PTCR rate is 2°C/hr. Dental ovens fire between 5-10°C/hr on heating. The TempTAB match that rate better.
2. TempTAB has several data columns for whatever hold time you use from 10 minutes up to 4 hours. The PTCR charts are only good for a 1 hour hold. We typically see Zirconia held for 2 hours.
3. The TempTAB are made from high purity Alumina Oxide, 99.8% Al2O3. The Alumina used in PTCR contain some silica which can vaporize and deposit on the Molybdenum Disilicide Heating elements.
4. The TempTAB 700 work best for 1550°C. The maximum temperature for the TempTAB 650 is 1520°C.

Ill continue to study. First is to try a new batch of Tabs.

The PTCR rings aren't a good fit for dental applications in some ways, it's true- their specified heating rate in particular is glacial to arrive at 1500 and results in a 10+ hour cycle to check anything by the book, and we'll always be using a soak that's longer than 1 hour. They claim the PTCR rings are accurate to +/- 3 C, but if we're not running them 'correctly', is that any better than Orton's own TempTABs at +/- 5 run correctly? I dunno, but I'm inclined to give both a try and see for myself.