Brookfield Engineering

Ceramic Slurries

Process Viscometer Application Data Sheet

Application

Brookfield's model TT220 immersion-probe viscometers are ideal for measuring and controlling viscosity of ceramic slurries. The industries that are best suited for this requirement are investment casting, “Lost Foam”, and refractory coatings. Most precision cast product demand that the encapsulating stage, where the ceramic slurry is applied, is precisely controlled.

Problem Description

Within the industries noted, the companies require that the ceramic slurries remain consistent while they perform the essential encapsulation of their precision mold. This stage is crucial to the efficiency of their production of the end product. Not only does this slurry require the correct composition, percent solids, the viscosity should be maintained so that consistent product is produced. The mold may be first coated with higher viscosity, higher solids, coating to obtain crucial coverage of all exposed surfaces of the mold. Subsequent dipping of the mold into secondary and tertiary stages of the coating process still remains as crucial as the initial stage, however. If the predetermined amount of slurry is not applied, the firing of the ceramic may not hold up and the ceramic cast will fail when fired or filled with molten metal. Typically, this industry can waste a lot of material and produce low yields of fired castings due to improper viscosity control. The weaknesses of this coating may be realized as late in the process as molten metal insertion into the fired ceramic cast, after approximately 85% of the process was complete.

Solution

Manufacturers in this industry have already linked the % solids control with off-line viscosity measurements. However, the manual viscosity measurement method and the ever-changing process conditions within the dipping tanks hamper proper control of this critical stage. The condition of the off-line viscosity measurement is often a non-agitated sample that may not give a true representation of the coatings resistance to flow, viscosity. A more accurate method is to measure and eventually control the viscosity (% solids) of the ceramic slurry with the use of an immersion probe viscometer, model TT220.

Qualifying Your Application

  • Is viscosity measurement a key parameter in your coating application?
  • Are there currently large fluctuations in the bench-top viscosity measurement, or efflux cup viscosity measurement?
  • Can the yield value of ceramic castings be improved?
  • Are there more complex casting designs that are not easily controlled by your current test methods?
  • Can the viscosity measurement be automated to eliminate manual procedural measurements?

Benefits

  • Automates viscosity control, which directly relates to % solids and coating thickness of final cast.
  • Optimizes coating thickness.
  • Maintains desired composition (% solids).
  • Increases the final cast yield.
  • Quick payback due to increased productivity and less product waste.

Return on Investment

The use of Brookfield's model TT220 viscometer typically provides a payback of instrument cost and installation within 6 months to one year.