Is it a Mechanical Problem or an Electrical Problem

In electromechanical systems with servo motors, chain drives, and other physical moving parts, it’s not as easy to tell a mechanical problem apart from an electrical problem as you might think. There are a lot of gray areas and symptoms that may look like one or the other. Also, it may be a combination of both. Here are a few situations where there can easily be confusion between mechanical issues and electrical issues.

Dirty Photocells

Photocells are often used in different parts of a machine to keep counts and ensure that a machine is working. If a machine processes paper, if there is a lot of oil or grease, or if there are other sources of dust and particulate matter in the environment, it is easy for photocells to get dirty over time. Occasionally, photocells may become defective, but generally speaking, they’re pretty rugged. When a photocell gets dirty, it goes into a “blocked” state all of the time. Depending on the position and role of the photocell in machine operation, it can create confusion as to whether mechanical subsystems are working correctly or not.

Low Quality Parts

Unfortunately, there are some components that fail easily and often simply because they were built poorly to begin with. For example, low quality switches can cause a host of problems that appear to be either electrical or mechanical because their contacts will intermittently close for a fraction of a second when they should be open (or open when they should be closed). Poorly made parts are also especially sensitive to dust and contaminants because they are not properly sealed. Low quality motor encoders can result in drive errors, overcurrent, overheating, and can even ruin motors. If you are in a situation where you constantly replace certain parts on your equipment, it may be worth re-evaluating which type of part to use.

Dislocated Proxes and Sensors

Magnetic proximity sensors are commonly used to time and synchronize machine cycles, as well as auto-calibrate home positions. If the positioning of a prox is out of whack, it can knock machine timing out of sync. Depending on the type of drive being used, a dislocated prox might sometimes cause an error condition that will stop the machine, but not always. If a prox or sensor is just a little bit too far away from its position, it can cause the sensor to be tripped some of the times but not others.

Jams

If a drive chain or drive belt is obstructed, this will cause a spike in motor current since the motor has to work harder. If the motor is controlled by a drive, the drive should register an error condition if this occurs. If the motor is not connected to a drive, a jam might cause a breaker to trip or a fuse to blow. This is one case where a mechanical problem will manifest as an electrical symptom.

Most of these problems can be avoided by proper preventative maintenance and cleaning. Also, training technicians adequately is essential so that they know how to recognize commonly-appearing symptoms.

This entry was posted on October 16th, 2013 and is filed under Electrical, General, Technology. Both comments and pings are currently closed.