Technical Article Continued from pg 11
than the polymer plus fiber slurry. The deviations for the Zahn Signature 5 and EZ Zahn 5 cups with the polymer plus fiber slurry are roughly double that of the polymer slurry, meaning that the viscosity range measured by the operators was twice as large. The ISO Mini 6 cup, however, only showed an increase of about 50%. Meaning the ISO Mini 6 cup measurements showed greater accuracy over the other two cups, regardless of slurry type. Table 2 summarizes the above statements into a succinct table. For both slurries, there was
much more difficulty determining the endpoint when the viscosity was higher. In general, there is a positive correlation between viscosity and deviations where the higher the viscosity, the higher the deviations and vice versa. As an example of this, Table 3 shows the deviations for the three cups over five loadings of the polymer plus fiber slurry. The range of deviations from the Zahn Signature 5 and EZ Zahn 5 cups across the loadings is more pronounced than with the ISO Mini 6 cup. Due to this, it will be more difficult to be accurate with the Zahn Signature 5 and EZ Zahn 5 cups at higher viscosities. On the other hand, the ISO Mini 6 cup is more consistent across a broad range, with the only exception being at the lower viscosities tested.
Conclusion and Best Practices With the amount of variation that is inherent within the viscosity measuring process, the above data can be used to create a set of best practices in order to reduce variation between readings in a foundry, regardless of the number of operators. These best practices can be adapted to suit the available equipment in each facility as well, so it is not a “one size fits all” situation.
First, any time a slurry is made, it is highly recommended that homogeneity of viscosity throughout the tank is
34 ❘ April 2020 ® Best
Better Good
Table 2 SIG Bottom
L1 L2 L3 L4 L5
Table 3
checked before any dipping takes place. This would ensure that all parts on the tree encounter the same slurry once in the tank. For any other viscosity measurements, readings should be taken behind the plow in a rotating tank, so the slurry is the best mixed, or next to the shaft with a prop mixer. In a foundry setting where multiple
operators are taking viscosities on slurries, the ISO Mini 6 cup is the best option. It consistently had the lowest deviations amongst operators when compared to other cups, and it also maintains a low deviation across the tested viscosity range. The low deviation allows the foundry to hold tighter viscosity because the deviation occupies less of the recommended slurry viscosity range than the other cups, resulting in both consistent and accurate measurements. An ISO Mini 6 cup is roughly 2-3 times more costly than a Zahn Signature 5 or EZ Zahn 5 cup. Most foundries use a Zahn Signature or EZ Zahn cup though, so they can reduce variation by employing the through the hole method.
About Ransom & Randolph
Ransom & Randolph is an international manufacturer/supplier
of ceramic
shell and industrial mold materials. Dedicated to advancing the investment casting industry, we developed the first high performance binder (Primcote® binder); the first coat reducing binder (Deluxcote® concentrate) and comprehensive solutions (Matrixcote® system). By coupling our revolutionary product developments with our experienced staff, manufacturing and warehousing facilities, we successfully help you become a casting industry leader. We are committed to partnering directly with you to identify your process hurdles and casting goals; consulting with you to customize a precise solution tailored specifically to fit your foundry’s needs.
1.061 0.457 0.493 0.307 0.214
EZ Bottom
1.220 0.596 0.615 0.390 0.189
ISO Bottom
0.373 0.239 0.381 0.332 0.397
Endpoint TTH
Bottom 1 inch
Cup
ISO SIG EZ
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