Micromotors driving 3D measurement systems
MEASUREMENT & MONITORING MEASURING IN THREE DIMENSIONS
EMS LIMITED
Micromotors driving 3D measurement systems
Quality means doing it right when no-one is looking ,” said industrialist and Ford Motor founder Henry Ford . Quality assurance and verification are important steps in any production process , but how can we carry out these inspections ? 3D measurement technologies are one such approach to getting a closer look at individual products as Stewart Goulding , Managing Director at DC motor supplier EMS explains .
In any manufacturing process , it ’ s crucial to ensure that the final product has been produced to its specification and to the desired quality . Any discrepancies in shape or surface metrology may negatively affect the way the product functions , as well as its efficiency and fit .
Visual inspections performed by a human or a camera robot may be sufficient for some manufacturing processes . But there are certain applications where inspections must be more comprehensive . One such example is the automotive sector . Gears , crankshafts and engine blocks must be tested thoroughly to ensure component integrity and that pieces will fit as desired with the rest of the car ’ s components .
Achieving this detailed view and examination is possible using 3D measurement technologies . A variety of techniques are available , which can be loosely split into two types — contact and non-contact .
NON-CONTACT Optical 3D scanning methods are a popular method of non-contact measurement . These offer protection for fragile surfaces that may otherwise be easily damaged by contact methods .
Typically performed using laser scanner or fringe projection systems , optical scans can measure thousands of points per second for a quick , complete scan of the finished product . The digital nature of optical method scanning combined with its speed makes it ideal for integration within highly automated manufacturing processes .
But not all products are best suited to optical methods . Items made from materials with reflective or translucent properties , like glass or synthetic resin , can be difficult to measure using light-based methods . While coating sprays are available to allow optical-based measurements , applying and removing this layer can create unwanted additional steps in the manufacturing process .
CONTACT An alternative option is to use a coordinate measuring machine ( CMM ). Generally regarded as the most accurate form of 3D measurement , these machines can take readings with a tolerance of just one micron , making them ideal for applications where high precision is of utmost priority .
CMMs rely on a probe or stylus with a ballshaped measuring tip that is positioned onto mapped reference points on the test object . A controller detects this contact to determine the precise shape of the object . It ’ s possible to manipulate the arm of the probe not only around the object , but also within it for access to cavities that would be difficult to access via an alternative method .
However , there are some disadvantages when it comes to using CMMs . This includes the long measurement time caused by the need to physically move the probe across and around the product . There is also the problem of reference points . CMMs typically measure on several pre-set reference points or along a single line , highlighting specific areas of interest rather than the whole product .
In any manufacturing process , it ’ s crucial to ensure that the final product has been produced to its specification and to the desired quality .
COMBINATION METHODS So , how can we maintain the high quality of CMM data , while achieving the speed of an optical-based method ? This is where combination or multisensor methods come into play . By using a traditional CMM machine alongside an optical technique like laser scanning , manufacturers can make the best of both approaches .
Whichever method is used for imaging , it ’ s clear that they all rely on one thing — the accurate positioning of the sensor elements . Whether it ’ s rotating the arm of the CMM or directing a fine laser , all this positioning can be done using a drive system .
When selecting a drive system for such applications , it ’ s crucial that the precision of these small DC motors is on par with what the final measurement technology is expected to deliver . This includes the use of encoders , which can generate position signals based on the motor shaft rotation or linear movement . Crucial to allowing achieving precise positioning , these also allow for closed loop control of the motor .
Manufacturers face constant pressure to always maintain high product quality . And while it ’ s sometimes possible to verify product standard by eye , making use of 3D technologies offers a far more detailed and in-depth view of every inch of product , ensuring that every single product that leaves the factory is as good as the last .
For further information , please visit www . ems-limited . co . uk
100 PECM Issue 64