Understanding The Different Types Of Contact And Non-Contact Inspection Systems

Contact And Non-Contact Inspection Systems

Today there is a growing trend towards miniaturization especially in the electronics, medical device and computer industries. If you are involved in one of these industries, you need to ask yourself which inspection system best meets your requirements. Between the contact and noncontact inspection systems, which type should you choose? The resurgence of match-fitting and selective assembly practices which depend on more precise measurement data, makes the question as timely as ever.

Due to their small nature, small parts are often more prone to contamination, deformation or damage by even slight contact with a probe. The noncontact inspection systems which involve laser, video and optical usually solves this problem.

Choosing The Right Inspection System

Depending on your particular operation, factors to consider when choosing contact and noncontact inspection systems include part quality, operational simplification, process control and traceability, cost, accuracy, repeatability, measurement throughput and ease of documentation.

Quality assurance departments dealing with manufacturers require that measurement ambiguity to be calculated separately from the measuring process as well as from the manufacturing process itself. To reduce the uncertainty, one needs to get instruments with excellent statistical software, precision, and speed.  Such instruments facilitate reliability (gage R&R) and tight, accurate gage reproducibility studies.

The most common inspection methods for parts today include contact and noncontact instruments such as machine vision systems, microscopes and coordinate measuring machines. Noncontact inspection systems include laser micrometers, vision measuring machines, profile projectors and microscopes. All these instruments allow measuring small work pieces without touching them. Let’s look at these instruments separately to get a better understanding of how they work.

Laser-Scan Micrometers

Laser-scan micrometers use laser energy to pick up work pieces from the edges. They play an important role in inspecting single dimensions such as linearity, widths, heights, roundness, intervals and diameters.

Economy-size Vision Systems

These are small vision systems that are programmable and work by video imaging. They can only handle smaller workloads and smaller parts. They are very powerful in terms of repeatability and accuracy.

Microscopes And Profile Projectors

These optical instruments are used to magnify surface features of a work piece to enable the user to measure dimensions on a linear scale. These tools are inexpensive and simple but slow. They are always operated manually and rely on human vision and judgement. Profile projectors are limited to the X-Y axes inspection.

Standard 3-D Vision Systems

These systems offer users all measurement capabilities and automation features. The standard 3-D vision systems generate images using microscope optics in combination with high-resolution video to discern line straightness and edges more precisely.  These vision systems do the job faster than profile projectors and microscopes.

Contact vs. Noncontact

As you can see, noncontact systems are much faster than mechanical systems. They are particularly used for high sampling rates especially if you are dealing with multiple axes, features laid out in patterns or dozens of features. Contact mechanical devices on the other hand traverse the part point-to-point which slows things down. Noncontact inspection systems are ideal for sensitive work pieces especially when handling surgical instrument and hazardous materials.

Now that you know about contact and noncontact inspection systems, why not get your desired inspection system from Willrich? We have both types of inspection systems that can cater to a wide range of industrial needs.

by George Chitos