investment for emax

rkm rdt

rkm rdt

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I disagree with everyone except Affinity so he must be right.
I use Bellavest sh as well.
 
Zubler USA

Zubler USA

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A good consistent investment is crucial, We QC ours twice prior to packaging. However reaction layer is controllable. Time & temperature are key...you can use special investments if you can't control your time & temperature well. The decision is yours, however they tend to be expensive and totally unnecessary.

99% time I find that no one realizes how significantly out of calibration their burnout ovens are and how much affect they have on their pressing results. If you would all switch labs for one day and use each others equipment, you would find out how different your results are using identical materials.

It amazes me when I walk into a laboratory that complains of inconsistencies and I measure their burnout ovens, how far off they are. I don't mean 5 or 10 degrees F, I am seeing fluctuations between 50-150F! You have no idea how many times I have seen this. Even laboratories with a calibration protocol have a lack of real understanding the ovens and their effects.

Everyone is looking at the investment or adding something to the investment, or this or that or...the list goes on. The funny thing is... it's as simple as time & temperature. Usually it has to do mostly with your burnout!

1. Burnout temperature (too high - more reaction layer & even surface issues) / (Too Low - mis-presses)
2. Different investments have different thermal masses, one investment will work better for you than another because of the way you are set up. Hot ovens or cold, plunger type used (Alox or disposable),practice consistencies..

Most burnout ovens are cheap, the parts are cheap, but the problems are expensive.

1. Thermocouples in burnout ovens are exposed to a lot of contamination and therefore should be closely monitored.
2. Heating elements in burnout ovens usually gather toward the bottom of the oven or fall over with detached insulation linings, they should be replaced.
3. People overload their ovens often...buy another oven or slow down.
4. Place your rings so that they see the elements on all/both sides of the rings evenly, this will help control overloading and make sure rings are not under heated.
5. Keep them at least 1 inch from the elements and back of the oven and at least 1.5" to 2" from the front of the oven.
6. Make sure your burnout oven is at the FINAL hold temperature for speed cycles before you put a ring in the oven or start the timer for the ring.

All of these points are important, not to say there are not other factors, but I promise you, if you really scrutinize your burnout...you will see a difference quickly.
 
Affinity

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I hope this time I didnt misqoute you chris!!
 
JohnWilson

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Reaction layer is a direct result of heat and time, NOT necessarily investment.

Also a ton of other variables as well, the best thing we did was eliminate any surfactants which essentially soften the investment in that area.

We used Ivoclar's speed for a LONG time with great results and then we started having issues. Calibrated everything and I just chalked it up to a bad batch. I bought one more box and it same issues continued. I of course blamed the techs and then I took a case from start to finish SPECIFICALLY by the instructions and still had an issue with reaction layer and a micro crack to the ring.

I then tried a bunch of others investments with some great results but more inconsistency. Finally found the JP Vest and this too I had a problem with initially and then reread the instructions, set up specific programs on the vac mixer and our dosing machine to measure out and dispense specific weight/ratio. (never trust premeasured packages) The ratios and the materials instructions have been tweaked since we started and we see the new instructions to be giving us great results

We are sold on it.
 
Affinity

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The big mystery here, to me, as Chris mentioned, is calibrating your burnout... Anyone have a kit or a tool they use for this? I have probably one of the most expensive burnouts out there, the renfert magma, yet theres not calibration kit for it that Ive ever seen.
 
Car 54

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I was wondering the same thing. Do I just use silver strips (calibration strips) for my Jelenko and Ney burn out ovens? It sounds like the days of, "it looks hot enough in there, and it's all casting and pressing", could be improved upon, to say the least.
 
ps2thtec

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The big mystery here, to me, as Chris mentioned, is calibrating your burnout... Anyone have a kit or a tool they use for this? I have probably one of the most expensive burnouts out there, the renfert magma, yet theres not calibration kit for it that Ive ever seen.

I remember some blue tablets for calibrating that came with my Jelrus oven
 
Affinity

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Im too cheap to buy a nice infrared thermometer gun.. the ones that go that high are pricey I think.
 
vurban210

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I don't have a link or a pic right now but you would want to use a long probe and go from the top down into the chamber.

The issue then becomes how to correct the furnace. I'm not familiar with every furnace on the market but I don't think many allow for the user to offset the temp. So you would have to do that manually.

Having tested probably close to 200 burnout furnaces over the years in different labs I can say most are off by at least 50 F and up to 250 F or more.
 
Zubler USA

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It's a CATCH 22 - I could tell you where to get one of the tools I use...I could tell you what to do. The problem is, are you really willing to go through the trouble and use it correctly? Like any oven, you cannot calibrate or offset the temperature of a P.O.S. that has seen better days and needs to be replaced. Get a new oven! However, if you have a good burnout oven and keep it in good condition then there is a way to just use a thermocouple to correct the temperature. It is not a practice to take lightly. The problem is that this is treacherous territory. You could get confused really fast.

On the other hand:

The expensive guns do not work. Silver is not an appropriate test for a burnout oven. The calibration pellets get you close, andif you want to really know, you have to get your own thermocouple and test your oven with a consistent protocol.

Tough....
 
Car 54

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Why Chris...won't it give a good enough reading, in my case compared to my, "it looks hot enough" calibration, wouldn't it be a step in a better direction? What do or should we use other than our own "thermocouple and test with consistent protocol" o_O
 
2thm8kr

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Why Chris...won't it give a good enough reading, in my case compared to my, "it looks hot enough" calibration, wouldn't it be a step in a better direction? What do or should we use?
spit test, like with an iron skillet.
 
Car 54

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That's about where I'm at.
 
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