ASTM D957 Standard Practice for Determining Surface Temperature of Molds for Plastics

Get Certified ASTM D957 Testing for Reliable Mold Surface Temperature Data

Mold temperature can influence the properties of the molded part. This makes it easier for the processor to produce quality parts. The controlling medium temperature may not match the cavity surface temperature. By measuring surface temperature, you can see the actual temperature the plastic reaches. ASTM D957 provides a standardized method for molders and processors to understand this. This helps set up the process, identify issues, and produce consistent-quality parts.

The scope of ASTM D957 includes:

• Material type: Plastic molds, including their cavity and base surfaces.
• Purpose: Determination of the surface temperature of a mold.
• Properties evaluated: The temperature at one or more specified points on the cavity and base surfaces.
• Testing method: Technicians use a calibrated surface pyrometer or a non-contact radiation (infrared) thermometer to measure the mold surface temperature.
• Results: Surface temperature values at the measured points, which together describe the temperature condition of the mold.
• Test limitations: The measured surface temperature can differ across the mold and thermocouple interface and at the leads, so technicians take precautions to minimize these differences.
• Use conditions: The surface temperature can differ from the temperature of the control medium of the mold. SI units are standard.
• Applications: Mold setup, process control, and troubleshooting in plastics molding.

What are the Uses of ASTM D957 Testing?

ASTM D957 testing tells molders and processors the actual surface temperature of a mold. They use the data to set up molds and to explain differences in molded parts. This practice:

• Determines the temperature at specified points on a mold surface.
• Covers cavity and base surfaces.
• Shows the difference between mold surface temperature and control medium temperature.
• Gives an overall picture of the temperature condition of the mold.
• Supports process setup and consistent part production.

Which Materials Can Be Tested Under ASTM D957?

ASTM D957 applies to molds for plastics. Technicians measure the temperature at points on the cavity and base surfaces of the mold. The practice does not test a plastic material itself. It measures the mold that shapes the plastic, so it suits any plastic molding process that depends on mold temperature.

Why is ASTM D957 Important?

Mold temperature can impact the properties of the molded components and how easy it is for the processor to create good-quality parts. The temperature of the controlling media may differ from the surface temperature. ASTM D957 provides a standardized method of determining the real surface temperature. It also highlights potential issues with mold temperature variation and thermocouple interface issues. With this practice, processors can adjust a process from measured values and not from assumed ones.

ASTM D957 Testing Process and Data Collection

Technicians place the measuring instrument on the cavity and base surfaces of the mold. The placement is determined by the mold’s size, shape, and configuration. A surface pyrometer and infrared thermometer are used to gather data. If the test requires contact, the technicians will ensure that there is good contact between the pyrometer thermocouple and the mold surface. This should be done until the temperature reaches equilibrium. Analysts then take note of the recorded temperatures and where they were taken on the surface. This can then be used to give the engineers an overview of the overall surface temperature and how it compares to the temperature of the control medium.

Common Challenges and Troubleshooting

To get accurate ASTM D957 results, the equipment must be calibrated correctly, samples must be measured in the right place, and the chosen pyrometer must be used correctly. If the sensor is not properly fitted or the lead is not controlled, it can affect results. Technicians then take several readings to ensure the sample is being measured in enough places. The surface temperature may not be the same as the control media temperature, so analysts report both and do not assume they match.

• The laboratory reports the surface temperature at each point in °C or K, together with the location of the point on the cavity or base surface. The set of readings gives the overall picture of the temperature condition of the mold.
• Analysts report the control medium temperature next to the measured surface temperature. Engineers use the difference between the two to see how far the actual surface temperature departs from the control setting.
• Technicians document the mold, the points selected, the type of thermocouple, and the way they placed it on the surface. Laboratory records the precautions taken at the mold and thermocouple interface and at the leads.
• Analysts record the operating condition of the mold at the time of each reading, including the control medium and any deviations that could influence the results. Technicians note the number of points measured, because enough points are needed to describe the surface.
• Engineers compare surface temperature results while considering the location of each point, the operating condition, and the interface and lead effects. Analysts avoid comparing readings taken under materially different conditions without accounting for those differences.

Link to ASTM D957