Gasketed lid
- The sensor can be opened for calibration or repair
- Needs a flat gasket land, screw points, and room for the seal
- Leaves air inside, so condensation needs a plan
Molded part guide: sensor housings
Injection Molded Sensor Housings
A sensor housing is not just a box. Light, sound, pressure, or a magnetic field has to reach the sensing element through or around it, so the housing becomes part of the measurement.
The job
Protect the element without getting in its way
Every sensor housing trades protection against signal. Where that trade lands depends on what the sensor measures.
An enclosure for a controller can be as closed as the heat allows. A sensor housing cannot. The optical sensor needs a window, the pressure sensor needs a port, the ultrasonic transducer needs a face that passes sound, and the proximity sensor needs nothing conductive between it and the target. The molded part has to leave that path open while still keeping out water, dust, and handling damage.
The housing also aims the sensor. Mounting faces, locating pins, and the seat for the sensing element are datums. If they move with warp or shrink, the reading moves with them, which is why these features deserve a place on the drawing with their own callouts rather than being inherited from the general tolerance block.
By sensing type
What the housing has to do for each kind of sensor
General design behavior. Your sensor supplier's mechanical notes take priority where they exist.
| Sensor type | What the housing must allow | Common molded solution |
|---|---|---|
| Infrared receiver or proximity | A window that passes infrared while hiding the inside | An IR-transmitting resin that looks black to the eye, kept thin enough over the sensor to limit signal loss |
| Camera or visible light | An optically clear, scratch-resistant window | A separate clear lens seated in the housing, so the lens resin can be chosen, or the lens replaced, without changing the housing |
| Ultrasonic transducer | A face that passes sound, and isolation so the housing does not ring | A controlled front face in front of the element, with a softer overmold or potting behind it to damp vibration |
| Pressure or flow | A port to the medium, sealed from the electronics | A molded port with an O-ring gland, or a membrane seat, with the parting line kept off the sealing surface |
| Hall effect or inductive | Nothing conductive or magnetic between the sensor and the target | A plain plastic sensing face, with metal inserts and fasteners kept away from it |
Potting
If the sensor is potted, design the housing as the pot
Potting seals and supports the electronics, but only if the compound bonds to the housing and fills without trapping air.
Low surface energy resins such as polypropylene and polyethylene are hard for potting compounds to grip. Housings that will be potted are often molded in resins that bond more readily, and the inner walls can be given a texture or small grooves so the compound locks in mechanically rather than relying on adhesion alone.
Give the compound a way in and the air a way out. A fill opening at one end, a vent at the high point, and no blind pockets under the board let the potting fill in one pour. Mold release left on the part also weakens the bond, so say on the quote that the part will be potted.
Sealing
Gasketed lid or potted body
Both keep water out. They differ in what happens when something goes wrong.
Potted body
- No internal air space, and the electronics are supported against vibration
- Smaller housing, with no lid or fasteners
- Permanent, so a faulty unit is replaced rather than repaired
Cable exit
Most field failures start where the cable leaves the housing
The cable is pulled, bent, and flexed for the life of the sensor. The housing has to take that load instead of the solder joints.
A molded strain relief boot, a cable gland threaded into a molded boss, or an overmold that bonds to the cable jacket all move the bending load away from the board. Overmolding also seals the exit in the same step, which is why it is common on sensors that live outdoors or on machinery.
If the sensor uses a connector instead of a pigtail, the connector cavity is part of the housing. Terminals can be insert molded so the pins are located and sealed by the plastic itself, which removes a separate seal and an assembly step.
Drawing
What to send with a sensor housing
Most of these come from the sensor datasheet or the mechanical notes from its supplier.
The sensing element part number and its mechanical notes, including any window or port guidance
Which faces are datums for aiming the sensor, and how they are toleranced
Whether the housing is potted, gasketed, or overmolded, and with what compound
Cable jacket material and diameter, or the connector and terminals
The environment: outdoor exposure, washdown, chemicals, and temperature range
Any inserts, and how far they must stay from the sensing face
Keep reading
Related guides
Processes that sensor housings rely on, and the sibling housing pages.
Overmolding
Seal the cable exit and add a soft damping layer in the same part.
OvermoldingInsert molding
Terminals and threaded inserts located and sealed by the plastic.
Insert moldingSensor bracket case study
An insert molded mount for a sensor assembly.
Insert molding sensor bracketConnector housings
When the sensor plugs in instead of using a pigtail.
Connector housingsElectronic enclosures
Board mounting, shielding, and heat inside a molded shell.
Electronic enclosuresGD&T for molded parts
Calling out the datums that aim the sensor.
GD&T for molded partsPolycarbonate vs acrylic
Choosing a clear resin for a window or lens.
Polycarbonate vs acrylicWarpage
Why mounting faces move after molding, and how to stop it.
WarpageMolded parts hub
Every part-type guide, grouped by family.
Molded parts hubFAQ
Questions about molded sensor housings
Can the IR window be molded as part of the housing?
It can, if the whole housing is molded in an IR-transmitting resin. More often the window is a separate part in an IR-transmitting grade, or a second shot, so the housing itself can use a stronger or cheaper resin.
Why do our potted sensors let water in after thermal cycling?
The usual cause is the compound pulling away from the housing wall as both expand and contract at different rates. A resin that bonds better, a textured or grooved inner wall, and clean parts without mold release on the bonding surface all help.
Can you mold the housing around the cable?
Yes. Overmolding bonds a second material over the cable jacket and the housing, forming the strain relief and the seal in one step. Share the cable jacket material, since adhesion depends on it.
Do you publish IP ratings for sensor housings?
No. An ingress rating belongs to the finished, assembled product and is proven by your testing. The molded housing gives the seal the surfaces it needs to pass.
Next step
Quote the housing with the sensor in mind
Upload the housing CAD and attach the sensor datasheet or mechanical notes. DFM feedback covers the window, port, and cable exit before tooling is released. NetProto manufacturing is ISO 9001 certified.