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    Dialing in pressing oven.

    Discussion in 'All Porcelain-Press' started by John C, Nov 29, 2016.

    1. John C

      John C Member Full Member

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      I'm trying to dial in a new to me pressing oven. This short press was done with a high of 925 celsius, 60 degree climb rate with a 15 minute hold and 5 minute 30 second press time. I either need to raise temp or go with a longer press time. What would you suggest trying first. Ingot is a used emax MO1...just using for getting oven set up.
       

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    2. ztech

      ztech Active Member Full Member

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      Although a closer photo would help, it looks like the ingot has a fair amount of reaction layer. I think your melt temp may be close. I would increase the burnout temp in increments of 5 C until you get consistent complete presses.
       
    3. Sda36

      Sda36 Active Member Full Member

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      Also maybe try a phantom sprue which I believe is recommended for single unit presses. Balances out the pressure read back or something like that ...

      Sent from my LG-H812 using Tapatalk
       
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    4. John C

      John C Member Full Member

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      Thanks for the reply. Actually the reaction layer looks to be very minimal. Sorry about the poor picture. Best I could get with my phone.
       
    5. ps2thtec
      Question

      ps2thtec Well-Known Member Donator Full Member

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      What size ring ? Have you heard of the 10mm rule? If that pressed in a 100gm ivo ring the wax up
      should be positioned more in the center of the former.
       
    6. John C

      John C Member Full Member

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      100gram ring. Maybe should have sprued at less of an angle?
       
    7. zero_zero
      Drunk

      zero_zero Well-Known Member Full Member

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      What kind of furnace you got ? Not enough pressure maybe ?
       
    8. JMN
      Curious

      JMN Christian Member Donator Full Member

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      Th' wha?
       
    9. John C

      John C Member Full Member

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      Jeneric Pentron Autopress plus . . pressed at 4 bars
       
    10. ps2thtec
      Question

      ps2thtec Well-Known Member Donator Full Member

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      Wax up should be inside of 10mm from the ring wall.
       
    11. ztech

      ztech Active Member Full Member

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      I have to disagree with the 10mm rule. That is part of the discussion only to prevent cracking of the investment. Since in a pressing operation, your melting energy is supplied from the pressing oven the closer to that heat you are with the thin sections the better they will press. The limit to this is so close that the ring fractures.
       
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    12. JMN
      Curious

      JMN Christian Member Donator Full Member

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      Thanks!
       
    13. ps2thtec
      Question

      ps2thtec Well-Known Member Donator Full Member

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      "If all else fails, read the instructions!"
      This was a update sent out by ivo several years ago. An inside tech there once told me they never use
      the 100 gm ring. Sure, he's not paying the bills, but also center of the plunger is not the ideal position.
      Their diagram of the molar is still wrong though. Should be more like picture attached. Upside down so
      you can see a visual that the material needs to flow down and out. You don't want the flow to go back toward s the center of the ring. I'm also using the Super ring that acts as a 200 gm ring, but that's a whole nother thread.
      I also attached an old note of parameters when I had used an oven that the amount of pressing minutes
      needed to be programmed by user. Good luck.
      image.jpeg image.jpeg image.jpeg image.jpeg
       
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    14. John C

      John C Member Full Member

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      I used your exact parameters that I read in another thread. The only difference is I pressed an MO ingot where your parameters are for LT ingot. If I recall the MO ingots need a higher pressing temp. Is that correct? That could be my issue.
       
    15. ps2thtec
      Question

      ps2thtec Well-Known Member Donator Full Member

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      No. This is from the emax book
      image.jpeg
       
    16. Sda36

      Sda36 Active Member Full Member

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      Hi John, the phantom sprue I mentioned is in figure 3, above post. Makes a difference when pressing singles for the machine to read the pressure feedback properly. Just another suggestion

      Sent from my LG-H812 using Tapatalk
       
    17. Patrick Coon
      Happy

      Patrick Coon Well-Known Member Sponsors Full Member

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      Couple thoughts:

      1. Check burnout oven calibration and that it is at 850C/1562F and that the ring is in the furnace a full 45-60 minutes after it recovers (single 100gr ring). Also your burnout and press furnaces should be close together, so it doesn't take you more than 30 seconds to get the ring from burnout oven to pushing start on the pressing oven.

      2. Raise your pressing pressure to 5-6 bar (75-90 psi)

      3. Since reaction layer was "minimal" raise your high temp 5C. Older furnace may not be very well calibrated.

      4. 5.5 minutes press time should be long enough to press just about anything.

      5. Phantom or Blind sprue is used when you have either a very thin restoration (0.3mm - 0.4mm) or a very light pattern (0.2gr - 0.3gr) and the material will be flowing very slowly. But this is only really needed when you have a furnace that has a speed sensor for plunger travel (Ivoclar ovens), as they go by a set plunger speed to determine when the pattern is full and not a set press time.
       
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    18. John C

      John C Member Full Member

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      Finally had a successful press. I had to bump up the temp to 938 celcius. Time to calibrate.
       
    19. John C

      John C Member Full Member

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      So I have a couple complete presses now. My post above says successful but that is kind of an exaggeration. The margins were complete, the first one came out ok. The second one had some pitting, was missing a corner from the incisal edge and what I would call a crater( way bigger than a pit and shaped like a bomb crater). There really didn't look like much reaction layer but I'm wondering if I went too hot. I went from 930 celcius with incomplete presses up to 938 celcius, which seemed to help. I'm using the E-liminator investment which works good to minimize reaction layer. Should I try 935 celcius and see how it goes?
       
    20. labtek

      labtek Member Full Member

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      P Coon,
      Will Ivoclar ever try to make a 98mm blue block puck? With manufacturers offering alloy pucks in chrome cobalt to gold alloy, I would think it is possible. I assume Ivoclar is more eager to sell the blocks with a higher profit margin and not manufacture a 98 mm puck? If you have already discussed this previously, please provide a link.
      Thanks
       
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