Technical Tips

Ceramic Shell

  • Autoclaving
    Under certain operating conditions, autoclaves can often be the cause of shell cracking problems. R&R recommends adhering to the following autoclave operating procedures to prevent or minimize shell cracking in your foundry.
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  • Binder Remixing
    In certain cases, it may be necessary to remix a binder prior to using (e.g., binder is old or requires remixing). Remixing a drum or Intermediate Bulk Container (IBC) is typically thought to be a cumbersome task. However, there is a simple and inexpensive way to do it.
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  • FlashFire Dewax Method
    The FlashFire dewax method is used to dewax and burnout the ceramic shell. When completed properly, this process puts less stress on the ceramic shell than the autoclave dewax process and allows the recovery of a significant portion of spent wax. A brief review of general process recommendations, using Pacific Kiln FlashFire Dewax equipment, follows.
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  • Shell Building
    Ransom & Randolph recommends adhering to the following technical tips for building a consistent shell in your foundry.
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  • Shell Inclusions
    A shell inclusion is normally considered to be a defect that results in ceramic breaking free from the shell and ending up in the casting. This defect leaves a void in the casting that will need to be welded or the part may be scrapped. There are a variety of causes for shell inclusions. The most common are as follows.
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  • Slurry Additives
    Understanding what slurry additives do, when to use them and how to use them properly is imperative to appropriately maintain slurry life and performance.
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  • Slurry Control
    Conducting regular testing is essential to best understand the properties of your slurry. To control the slurry in your foundry, Ransom & Randolph recommends conducting the following tests. For your convenience, automated Slurry Control Worksheets (Microsoft® Excel®) are available for download at www.ransom-randolph.com under resources.
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  • Slurry pH
    The pH of a slurry is a property that requires monitoring and maintenance. Slurry pH needs to be monitored with a pH meter. Using pH papers does not give accurate results.
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  • Spalling of Primary Shell Coats
    Spalling is not always caused by the primary coat, as often believed. A variety of factors can cause spalling. Six of the most common causes and potential solutions include the following.
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  • SuspendaSlurry® Materials FAQs
    Is SUSPENDASLURRY material compatible with super alloys and stainless steel? SUSPENDASLURRY ZR material should be used for super alloys and stainless steel.
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  • Viscosity Control for Primary Slurries
    For primary slurries, the key slurry test parameters are binder solids and viscosity. Other slurry tests, such as density and pH are important and provide a more complete representation of a slurry's composition. However, basic slurry control can be accomplished with viscosity and binder solids.
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  • Wax Pattern Defect Troubleshooting
    R&R recommends utilizing the following potential causes and corrective actions for troubleshooting wax pattern related defects in your foundry.
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Jewelry

  • Potential Causes of Casting Defects
    Porosity; Fins or Flash on Castings; Inclusion (Foreign Particles) in Castings; Rough Castings; Bubbles or Nodules on Casting; Spalling (An Area of the Mold Wall Flakes into the Cavity); Non-Fill or Incomplete Castings; Growth-Like Rough Casting That Resists Removal in Pickling Solution; and Shiny Castings.
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