Splitting Moulds

JeffT

JeffT

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Hi All,
Having a few hassles with molds splitting during the burn out process. Sometimes the split goes right through and ruins the press.
I am using Pro art Cad Wax ATM, but have used other milling waxes with the same result. It doesn't seem to happen with Renfert wax "hand wax".
If I start temp low and bring up, then this helps....
Are there resins in the CAD waxes that are causing expansion during burn out and splitting the molds?
Are any others on the forum seen/ing this?
Any help appreciated....cheers

Using EP 3000, burn out at 800c
Anaxvest PM investment

Thanks ....
 
JMN

JMN

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Hi All,
Having a few hassles with molds splitting during the burn out process. Sometimes the split goes right through and ruins the press.
I am using Pro art Cad Wax ATM, but have used other milling waxes with the same result. It doesn't seem to happen with Renfert wax "hand wax".
If I start temp low and bring up, then this helps....
Are there resins in the CAD waxes that are causing expansion during burn out and splitting the molds?
Are any others on the forum seen/ing this?
Any help appreciated....cheers

Using EP 3000, burn out at 800c
Anaxvest PM investment

Thanks ....
Pro art Cad Wax isn't really wax. It's a polyurethane blend. It will burn out somewhat differently for that reason alone. A staged burnout, and cold oven entry may be required so the 'wax' softens before it expands.
I'm sure someone has more information.
 
Contraluz

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Are there resins in the CAD waxes that are causing expansion during burn out and splitting the molds?
Could very well be. However, I see you burn out at 800c. Most investment, I have used, burn out ~ 850c, could that be your issue (I am not familiar with Anaxdent's investment)?

I use the 'wax' Harvest Dental sells. Mills nicely and burns out well. Handling after milling is good, too, and I use JP vest, as investment. No issues with that combination.

That said, I had issues with printed patterns and cracked rings.
 
Affinity

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I run my moulds up to 900c (or put them in at 900c),then back down to 840c. I think at the suggestion of Chris @ zubler. Dont have any issues with cracking unless the mould is in for 3+ hours. I use GC lisi pressvest for ceramic and Bego bellavest for gold.I also wipe the patterns with alcohol and put the ring in a pressure pot to cure. But every investment is different.
 
JeffT

JeffT

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Thanks for your suggestions guys...I have just purchased some Harvest press wax actually (coincidence) and will give that a go..
Will also look at burnout end temps and ramping furnace..
I can only guess that the resin is added for better milling properties?

Cheers
 
JMN

JMN

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Thanks for your suggestions guys...I have just purchased some Harvest press wax actually (coincidence) and will give that a go..
Will also look at burnout end temps and ramping furnace..
I can only guess that the resin is added for better milling properties?

Cheers
You hit it right on with the resin purpose.

Change one varible at a time and keep records. In 3 weeks you won't remember.

Let us know what you find, please.

Oh, have you checked the burnout for calibration?
 
Affinity

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I use cheap wax from ebay, mills and burns out fine. Also the speed of your vacuum mixer matters depending on the investment.
 
JeffT

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You hit it right on with the resin purpose.

Change one varible at a time and keep records. In 3 weeks you won't remember.

Let us know what you find, please.

Oh, have you checked the burnout for calibration?
No....not lately but will over the holidays
 

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