EMAX Question

[Toto]

Perhaps Patrick could answer this - I pressed 3 single crowns for a friend yesterday and they came up short of the margins . 3 single crowns in a 200g ring(thats how it was sent to me) but only one LT Ingot as the weight was just below .75 . I used the 200g cycle in my Ivoclar EP 3000 furnace.
Should I have used the 100 g setting? May be a sprueing technique failure?
Up until now I have had no mis presses -only one where I did not weigh and came up short of material.

 

[ps2thtec]

Do you have a sprue guide like this pic. Only thing I can think of is maybe wax ups were outside the ideal
area for pressing.

 

[Gru]

Describe "short" margins. Jagged, rounded, etc. Also, were the patterns wax or resin?

 

[[email protected]]

Sounds like either a sprue angle blooper or could also be an investment material issue, I tried bego investment as it is cheaper than pressvest speed and started getting short margins, changed back to pressvest speed and problem disappeared.
Pressvest speed costs a bomb but it works.

 

[[email protected]]

Isn't the max wax weight to be pressed with one ingot 0.7 gr, your wax weight was just under 0.75, this could also be the cause.

 

[Kaypan]

What kind of wax? Milling wax for example might have different density from regular wax. I have set a limit at 0,6 with our milling wax,had a few failed pressings going above that. You should see on the button if this is the problem,even though there will always be a small button.
Shape/thickness of the restorations can also highly influence the flow ability of the press material. In many cases spruing technique is essential, in others not as important. Pictures would help alot!

 

[pjd cdt]

The ratio of one pellet for 7 grams of wax assumes a specific gravity of 1.


Sent from my iPad using Tapatalk

 

[Toto]

Thanks for the answers - no photo avail - pressed again and all ok - think it was a sprue angle blooper. On the failed press the sprue was at 45 degrees but crowns were at a slight angle to the sprue -too upright?

 

[Toto]

Photo of the mis press(found it) - what do you think ? Cervical half of all 3 crowns was not there

 

[[email protected]]

Looks like there is enough ceramic so is probably another reason, is the investment material pressvest ?

 

[Toto]

Hi Keith - investment was Adenta Vest CB which has been working fine - usually use pressvest tho

 

[Patrick Coon]

Hi Toto,

Sorry I just saw this. Been out of the office for the last couple days.

Looks to me like the patterns are angled too much towards the center of the ring (coldest area). Then what happens is that some of the material will press into that area and start acting like a heat sink pulling all of the heat energy out of the ingot and it fails to press fully. See if you can get one of the sprue guides that ps2thtec shows. They are great for making sure you have everything in the proper heat zone for pressing. they are available for the 100 gr, 200gr, 300gr, and the 200gr Multi rings/bases.

As for the wax weight. The recommended wax weights are as follows: small ingots press upto .75grs and the large ingots press upto 1.7 grs. Depending on your scale we will sometimes recommend not going over .7 grs if your scale only shows to tenth (0.7). If it goes to the hundredth (0.75) and you trust it, .75 should be no problems. Of course this is factored for a normal density sculpting wax. Some milled waxes and printed pattern wax/resin have a different density and could affect these numbers so ymmv.

 

[shiggy]

Hi Toto,

Sorry I just saw this. Been out of the office for the last couple days.

Looks to me like the patterns are angled too much towards the center of the ring (coldest area). Then what happens is that some of the material will press into that area and start acting like a heat sink pulling all of the heat energy out of the ingot and it fails to press fully. See if you can get one of the sprue guides that ps2thtec shows. They are great for making sure you have everything in the proper heat zone for pressing. they are available for the 100 gr, 200gr, 300gr, and the 200gr Multi rings/bases.

As for the wax weight. The recommended wax weights are as follows: small ingots press upto .75grs and the large ingots press upto 1.7 grs. Depending on your scale we will sometimes recommend not going over .7 grs if your scale only shows to tenth (0.7). If it goes to the hundredth (0.75) and you trust it, .75 should be no problems. Of course this is factored for a normal density sculpting wax. Some milled waxes and printed pattern wax/resin have a different density and could affect these numbers so ymmv.

 

[shiggy]

Make sure you let the 200 g ring bench set for the allotted time before you separate the former and throw it in the oven. Had a friend using a different investment and only allowing a 15 min set time before pulling the ring former. What happened was the plunger hole was still expanding inwards creating a smaller hole. He finally used disposable plungers which are smaller in diameter and solved the problem that way. After the 5th time they came out and that's why I always follow the direction.

 

[Toto]

As always plenty of help from you all - much appreciated .

 

[Doug4DAL]

That's what I would guess , sprew angle . Your margins were in the cold spot of the ring , they need to be angled away from the center button .The plunger will draw heat away .

 

[Doug4DAL]

Pressing is opposite of centrifugal casting . Margins fill last.