Vision Inspection & Reject Machine (SPM): How It Works and Where to Use It

A vision inspection and reject machine uses a camera to check every part and automatically separates the ones that fail. It replaces the tired eye at the end of a line with a check that is repeated the same way on every piece. It is often built as an SPM, combining the camera, lighting, a PLC and a reject mechanism around the shape of your part.

How a Vision Inspection SPM Works

• Trigger: a sensor detects the part in position, or an encoder signals it on a moving conveyor, and tells the camera to take a picture.
• Lighting: controlled lighting makes the feature to be checked stand out. Lighting is usually more important than the camera.
• Image processing: the vision software compares the image with the taught good part and measures what it was set to check.
• Result: the software sends OK or NOT OK to the PLC.
• Reject: the PLC operates the reject pusher or gate at the correct moment, so the failed part leaves the line.
• Record: counts, and optionally images of rejected parts, are stored for review.

What Can Be Inspected

What Makes Vision Inspection Succeed or Fail

• Consistent presentation: the part should arrive in nearly the same position every time, or the fixture should locate it.
• Correct lighting: shiny, dark or textured parts need the right light angle and often shielding from factory light.
• Realistic limits: tight limits on natural variation cause false rejects. Set limits with good and bad sample parts.
• Sample parts: proper good and defective samples are needed to set up and prove the system.
• Reject timing: on a moving line the reject must be triggered at the right instant so it removes only the bad part.

Where It Is Used

Vision inspection is used in automotive component assembly, electronic and electrical assemblies, plastic moulded parts, FMCG and packaging lines, and general engineering. It is often combined with other operations in one machine, for example press-fit followed by a presence check, or a leak test followed by marking of the passed part.

Vision Inspection Machines from ASE

Automation Solution Engineering builds SPM machines that combine assembly or pressing with vision based inspection and automatic rejection, controlled by PLC and HMI. We start from your part, your defects and your target output, then propose a design. Read more on our SPM machines page.

Frequently Asked Questions

What does a vision inspection machine check?

Typical checks are presence or absence of a component, correct orientation, missing or wrong parts, surface defects, simple dimension checks, and reading a printed code or barcode. What can be checked depends on the camera, lens, lighting and the part itself.

How are rejected parts removed?

After the inspection result, the PLC operates a reject mechanism such as a pneumatic pusher, a diverter gate or a drop-out flap, so the bad part goes into a separate bin. The machine can also stop and show an alarm if several parts are rejected in a row.

Can vision inspection be added to a machine I already have?

Often yes. A camera and lighting station with a reject unit can be added at the end of an existing line or machine if there is space and a reliable trigger signal. Send photos and a sample part for a proper review.