Defect rate
The percentage of the production quantity of parts that are defective. These parts can be discarded or recycled.
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Glossary
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Density
The ratio of a material's mass to its volume at a given temperature and pressure, typically measured in kg/m^3, g/cm^3, or lb/in^3. Water is 1.0 g/cm³ at 25°C and 1 atmosphere of pressure.
Die casting machine type
Die casting machines can be classified as one of two types – a hot chamber or a cold chamber machine. Hot chamber machines are used for alloys with low melting temperatures, such as zinc. Cold chamber machines are required for alloys with high melting temperatures, such as aluminum, and have longer cycle times and higher hourly rates.
Die life
The number of cycles performed during the casting process before the wear on the die is too much for it to be used anymore. If the die life is shorter than the number of cycles needed to produce the production quantity of parts, additional dies will be needed. However, a die can be repaired to slightly extend its lifetime. The die life is affected by both the material of the die and the material being injected.
Dielectric Constant
Also called the permittivity and denoted DK, or Er. The ratio of the capacitance of an insulator to the capacitance of a vacuum or dry air (the dielectric constant of a vacuum is 1.00000, dry air is 1.00054). Capacitors release charge when a circuit is broken. Capacitance is the ratio of charge absorbed to the potential (voltage applied). A dielectric constant of 3 means an insulator will absorb 3 times more electrical charge than a vacuum.
Dielectric Strength
The maximum voltage an insulating material can withstand before breakdown occurs. Imperial units are in volts per Mil and Metric units are in kilovolts per mm.
Draft
The offset of the walls of a part by a slight angle, referred to as the draft angle. A draft angle is often required on the surfaces of a part that are parallel to the tooling direction in order to facilitate removal from a mold. However, some processes do not require a part to have any draft.
Draft angle |
Drilling
An operation in which a drill enters the workpiece axially and cuts a hole with a diameter equal to that of the tool. On a milling machine, an end milling operation is required to produce a hole with a tool smaller than the hole diameter. A drilling operation typically produces a blind hole, which extends to some depth inside the workpiece, measured to the point made by the tool or to the end of the full diameter portion. On a milling machine, a hole that extends completely through the workpiece (through hole) can also be drilled.
Drilling (Milling machine) |
Drilling (Turning machine) |
Blind hole |
Through hole |
Dry cycle time
The cycle time of a process that results from no material or workpiece being used. The dry cycle time is typically a measure of machine performance that indicates the time for the machine to perform the actions necessary to manufacture a part, without the part actually being produced. This time will always be less than the actual cycle time.