Why Have a Sensor Location Strategy?
Knowing where to put your in-mold sensor to get the most useful information is imperative. Control sensors do not guarantee quality everywhere in the cavity, but here are some basics steps to consider:
- Define the problem you are trying to solve
- Place the appropriate cavity pressure or temperature sensor near the location where the problem is so that it can “see” the changes that cause the defect
- Place sensors in the “area of influence”—sensors can be used for V->P transfer control (switchover) to improve consistency, so it is important that they are located in a place where the machine can still drive plastic during the switchover.
In order to choose the right cavity pressure sensor, there are several questions that must be answered:
Will the sensor be installed behind an ejector pin, blade, or core pin?
This application will require a button style sensor. You’ll also need to answer:
1. What is the diameter of the pin or width of the blade?
Strain Gage sensors are rated in pounds of force and can be overpressured and damaged if too large a pin is used with a low force rated sensor.
2. What is the expected plastic pressure at the intended sensor location?
Strain Gage sensors can be overpressured and damaged if too much plastic pressure is applied and the resolution can be poor if too low a pressure is applied.
3. What is the expected mold temperature?
Strain Gage and Piezo sensors have two components: electronics and the sensor element. The electronics for both must be kept below 140 °F. The sensor element for strain gage comes in standard (250 °F) and high temp (425 °F) models. The piezo comes in one standard temp (425 °F).
4. Is there enough non-interfered space behind the pin for a .505” inch sensor?
Only one pin can contact the sensor. Our most common model of sensors require .505” of space behind the ejector pin. We have a 6mm sensor (9211) for tighter fits and we have some alternate installation methods available.
5. How many sensors will be in the mold?
Single channel sensors work well for one- and two-cavity or sensor applications. Above two, we recommend our multi-channel line of products that reduce the connections and real estate on the mold.
This application will require a flush mount style sensor. You’ll also need to answer:
1. What is the expected mold temperature?
2. Is there room for a 2.5mm or 4mm sensor?
The chart below is only a guide. In order to assure correct sensor selection for your application, we recommend contacting us directly.
Select the Proper Sensor from the Table
- Locate the pin size that will be used and match it to the location on the part (Near the End of Fill or Near the Gate).
- The intersection of the row and column is the sensor to use (Lynx Strain Gage or Piezo based on the mold application).
Normal Pressure, (e.g. Typical Molds, End of Cavity)
5000 PSI / 350 Bar / 35 MPa
High Pressure (e.g. Thin Wall, Post Gate)
10,000 PSI / 700 Bar / 70 MPa