Smart Screwdrivers combine control and monitoring functions

Consumer goods are typically assembled with small screws inserted by hand, but this close hand-eye work is prone to error. SMAC Moving Coil Actuators has devised an alternative that removes human error, replacing fallible pneumatic screwdrivers with Smart Screwdrivers.

Using a pneumatic handheld auto-feed screwdriver to install screws is dramatically more productive than manually picking up a screw, inserting it into a part and driving it home, but simple pneumatic screwdrivers are not ideal either. Workers using pneumatic tools with compressed air and dials to estimate the amount of torque for the screw can strip or misalign the threads if an incorrect torque or angle is used. For some manufacturers, a misaligned critical screw could result in stopping an assembly line.

Furthermore, there is little or no feedback on the work until the assembled product reaches the quality assurance (QA) department. If QA misses the critical screw, it could lead to faulty products, angry customers and the one word no manufacturer wants to hear - particularly in the automotive and aerospace industries - recalls. When you add this all up, a small screw could cost big money.

A common problem with screws and lug nuts is cross-threading. To avoid cross-threading, many assemblers will start screws or lug nuts by hand, turning the screw the wrong way until a bump is felt and a sound heard; this is the screw threads falling into position. The assembler would then turn the screw several rotations before using a wrench or screwdriver to 'snug' it into place. Up until now, this process has been difficult to automate, performed by human operators only.

However, this is exactly how the Smart Screwdriver automates the process. First, it performs a fast approach, then finds the surface using patented Soft-Land capability. Then it turns counter-clockwise and the screw moves up and drops as the first thread is found. This is, in effect, 'thread matching' and prevents cross-threading. The linear rotary actuator then starts rotating clockwise. A 'snug' torque can be applied, which is useful when there are a number of screws holding a part on the clamping surface and they need to be snugged evenly before a final torque is applied. Throughout this entire process, the Smart Screwdriver is monitoring the torque and pitch verification. Good, shallow, cross/no-threads, and the precision of the thread are detected through feedback of position and torque from the two axes.

The SMAC Smart Screwdriver performs the same work as a pneumatic auto-feed tool but electronically. There is no compressed air, no mechanical parts, and no need for oil or recalibration. On top of being maintenance-free, the Smart Screwdriver also has a high degree of programmability so that users know the screw has been inserted correctly, when linear height, degrees of rotation and the desired torque have been reached. The Smart Screwdriver monitors the linear position and force, rotary torque and degree of rotation while simultaneously driving the screw. These parameters are all completely programmable with the capability to have feedback sent to a PLC or database in real time. This ability to perform work and verify, all in one move, eliminates the need for downstream quality checks that are costly and time-consuming.

SMAC's Smart Screwdriver is intended for a wide range of screw sizes, including but not limited to 1.4mm or less, like those found in watches, eyeglasses, cameras, consumer electronics, cell phones, power tools and similar consumer products. SMAC Moving Coil Actuators tend to be small but the Smart Screwdriver is so small that it could be attached to a larger robotic arm for special applications, providing 100 per cent quality every time.

Of course, the reverse could also be done. The Smart Screwdriver could be used to automatically disassemble devices, quickly, efficiently and carefully.

Follow the links to find out more about SMAC linear/rotary actuators and to watch a short video presentation of the Smart Screwdriver.