Tolerances

Definition: A tolerance is a permissible limit of variation .

The casting industry's method for quoting tolerances is to state a general variation from nominal.

Trilore’s stated tolerances are as follows:

+/-.010 to 8”.

+/-.001 for each additional inch.

+.010/-.005 across parting lines.

These stated tolerances offer a general idea of what variation to expect from nominal when casting a part. For a better understanding of tolerances the following explains what actually occurs at Trilore. The first step in the tolerance chain is the tooling. Trilore starts with patterns that are built to +/-.002 from nominal and assures that all of the steps following the construction of the pattern to create the rubber tooling are completed to specification so that we start the casting process with the most accurate tooling possible. A short cut to this process would result in a degradation to the achievable tolerance. Once the tooling is completed, the gating and process variables come into play which have the greatest impact on the final outcome. Once the first part is poured and measured, changes are incorporated as necessary to assure that the first off casting is as close to nominal as possible. Once this is done, Trilore’s repeatability tolerances take hold. Trilore’s repeatability tolerances are as follows:

ME Process                                                      RPM Process

+/-.007 to 8”                                                      +/-.010 to 8"

+/-.0005 per inch for each additional inch     +/-.001 per inch for each additional inch

+.010-.005 across the parting line.                +/-.015 across the parting line

Example:

If Trilore was to produce a casting with an overall length of 20 inches the stated tolerances would be +/-.022 which would result in variations of 19.978 to 20.022. In this example the first off casting measures 20.008, or +.008 from nominal. Using the repeatability tolerances the customer can then expect to see parts from 19.995 to 20.021 or +/-.013 from the 20.008 first off casting. Resulting tolerance from nominal +.021/-.005.

Properties of Trilore's ME Process 356-T6 compared to other processes:

                        ME            Investment    RPM           Sand          Permanent Mold

Yield               37,000      32,000          24,000       24,000       26,000

Tensile           41,000      38,000          34,000       34,000       37,000

Elongation     4                3                    3.5              3                 5

Brinnel            85-115     70-95            70-95         70-105       70-105