Sandblasting question?

[VincentCeramics]

Im just curious whats the best way to do sandblast?

I always sandblasted my metal (Wiron99) with 70 nm sand before i do my opaqer and ceramic on it, then one technician told me that the retention is better if metal was sandblasted with bigger granules. ??

I made this picture just to show you what i have after a make sandblasting with both sizes.

http://img816.imageshack.us/img816/3782/dsc02542c.jpg

How do you sandblast metals for PFM ?

After looking my metal it's kinda is logical to sandblast it with 250 nm granules, but i would like to hear how do you do it...

I stopped my work to talk to you guys, to seek help, i believe in your experience

Thx

 

[DMC]

50 uM (50 Micron average particle size) White AlO2 (ALumina Oxide)

65PSI or 4.2 BAR minimum I would think for NP alloy.

I have mine cranked up to at least that.

250 uM is like Beach-Sand, right? Too course for porc. I think?

 

[VincentCeramics]

4,2 bars sounds dangerous but i bet every oxide get out when u rock it!

so i should not use 250 um sand?

ill go with 50 on 4.2 in this case , ill be careful not to make any holes

 

[user name]

YIKES! 50 micron, 40 psi~2.7 bar. Look at your margins under a microscope! Blasting isnt for creating texture, its to clean and remove little burs that might trap impurities. Its removing metal. Shooting gravel at high pressure...OUCH!

 

[amadent]

Sand Blasting is metal specific

any alloy you puchase should come with a data sheet,
i have found that is the only way to be sure you are sandblasting your cases correctly

 

[DMC]

Whoops, I have an SternGold blaster that uses 50% of the power to make a suction in back of machine. It's not a regular measurement. Sorry.

I love the older style Sterngold blasters.

 

[VincentCeramics]

Thx for answers!!

I rocked it on 4,2 with 50nm lol but it worked out fine... opaqer is already on, and enough for today ill take a rest, watch TV and order some food with my girlfriend

 

[DMC]

65 PSI is fine IMO using 50um AlO2. It looses velocity almost right out the nozzle being so small.

My sandblaster is up to full output of my compressor, around 110PSI
but again, a portion of the pressure is sent to rear of unit to create a vacuum

 

[Mountain Goat]

Read your metal specs, each alloy have different settings...and for that matter different alloys have different metal finishing instructions.....carbides/stones, and high gold yellow ceramic alloy, be careful to follow psi/bar as instructed, you can blast those so hard you could imbed sand into alloy, this came from Ivoclar tech support when we were getting blow outs from the metal,we were blasting the yellow ceramic alloy too hard.

 

[VincentCeramics]

Im using wiron 99 and in manual instructions there is:

" Always blast the surface to be veneered (Korox® 250, 3 - 4 bar) and clean the frame thoroughly (steam clean or boil in aqua dest.). After cleaning, hold with artery clamps and refrain from touching.

" If oxide firing is carried out to check the surface, always blast the oxide again with Korox® 250 . Clean thoroughly (steam clean or boil in aqua dest.).

" Always apply basic material in two firing operations. The first coating thin (washbrand),the second coating opaque. Wash off frame under running water before application of next ceramic coating.

" Allow to cool down normally after firing.

" Remove ceramics only mechanically. Hydrofluoric acid (HF) corrodes the metal frame.

Ok, i can blast it with 250 nm on 3-4 bars, but i don't have neither steam cleaner or boiled aqua water uh!
And i never wash in running water after opaqe.
And about HF, is that use lets say if u miss the color fully...then just place your work in that acid and ceramic will fall off?

Any advice will be helpful, thx

 

[DMC]

Some may argue, but I have thrown a hot crown into water to have the porc fracture on purpose. Then I grind it off, or pick it off. Then re-clean metal and start all over again.

I try not to use acid. I use it on big bridges that I'm too lazy to grind the porc opaque off of. Never noticed any problems either way.

 

[DMC]

I've never seen 250 um called for, but if you alloy company suggest it then I guess it's the right thing to do??