Motion Control Resources
The SMAC Optical Encoder Story
SMAC Moving Coil Actuators, Inc. Posted 12/16/2020
SMAC has designed and built Motion Controllers, Linear and Rotary Motors and Linear Actuators for over 25 years. The most critical component inside the actuator is the optical encoder. SMAC decided to design and build their own diffractive optical encoder over 10 years ago.
SMAC relied on the standard product models of several encoder manufacturers to fill their needs but needed to be more cost effective, more adaptable to size and shape, provide faster lead times and be more responsible for the quality and reliability of the optical encoder used in SMAC products.
SMAC setup their own Encoder manufacturing group SMAC-EMC, to design, build and test their own line of optical encoders. Their engineering and manufacturing staff have over 25 years experience designing and building optical encoders at SMAC and at a other major optical encoder companies. This staff has designed large volume, optical encoder products for Markem, Brooks Automation, Varian Corp, HP, Universal Instruments, Delphi and other manufacturers from coast to coast.
SMAC Product offerings:
SMAC has developed several standard model linear and rotary optical encoder products that will be available to our customers. SMAC recognizes that custom sizes and shapes are a big factor and integration of an encoder into a customers motion control system is important, so with this in mind, SMAC will offer custom PCB encoder assemblies to their customers with the size and shape of the PCB specified by the customer along with some standard packaged products.
SMAC will make any of their Encoder PCB assemblies they use available as Encoder PCB assemblies or package them in plastic or aluminum housing to best fit the user's needs..
SMAC has many Chrome on glass linear scales, flexible metal scales or Mylar scales available up to 300 MM of travel available for these applications.
Rotary Encoder glass, Mylar or polycarbonate encoder discs along with standard and custom hubs with the disc bonded and centered to the shaft I.D. are also be available.
Rotary encoder PCB diameters down to 6 MM provide 4096 counts per rev or a "Keyhole" shaped 6 MM diameter x 12 MM long can produce 12,800 counts per rev.
A 12 MM PCB diameter design offers resolutions up to 96,000 counts per rev. All of these design are 5 Vdc with differential RS422 line-driver output.
Linear encoders PCB assembles with 20 Micron and 80 Micron pitch scales will be offered with up to 50 Nanometer resolution. These are also packaged in sizes as small as 6 MM wide. All of these interpolated Encoder assemblies are calibrated and setup at the factory per the user's specification and can be user re-programmed on site with a I²C connection to a PC and GUI downloaded from SMAC.
Some new interpolators versions of our linear encoders will offer "1 button" calibration for gain, balance and phase correction after the encoder scale and Encoder PCB assembly is mounted in the motion control system to optimize signal conditioning.
Advantages of SMAC designed Encoders:
Many SMAC encoders are made using optical components provided by large volume manufacturers of printers, cameras, cell phones and independent manufacturers of standard mixed signal ASIC semiconductor products used in optical encoders around the world.
SMAC uses these high reliability optical components that are made in the millions per year to take advantage of the latest manufacturing technologies used in these fields and latest design features patented by these suppliers.
These included using Interlaced Photo Detector Arrays to better balance the light viewed across the photo sensor array and average imperfections in the code pattern of the scale, LED light intensity auto gain to compensate for LED aging and temperature changes and GUI control of the many features selected in the interpolator and signal conditioning ASIC.
Because SMAC developed and designed their own reflective and diffractive optical encoder in-house, it has given them the knowledge and understanding of all the attributes that go into choosing superior encoder optical component for their designs.
SMAC still make 1000's of their own "reticle" based designs per year that use discrete LED's and photo-detectors because of they best fit that particular application and have a long history of quality and reliability.
Because SMAC has used over 100,000 of their own designed encoders in their own products, they have been able to discover many of the "User Issues" first hand, that would not be normally seen by a manufacturer of encoders and correct these issue in their products quickly.
Also SMAC's customer base for their Linear Actuator that use these encoders is diverse and international and "High Quality" demands and expectations from large customers such as Ford, Apple, Philips and Samsung that use SMAC products in their processing equipment is paramount.
Custom Encoder application story:
A manufacturer of PCB assembly equipment came to us to replace a discontinued 17 MM diameter, flex mount, hollow shaft, 48,000 count Rotary encoder. They wanted a form, fit and function equivalent for a drop in replacement.
They wanted high accuracy and low torque in the mechanical bearing system as they were using the motor encoder assembly in a positioning and force application. Not only did we have to come up with a way to design an optical encoder to meet the specifications for this application but also had to design a preloaded hollow shaft, ball bearing system for the 4 MM diameter bearings and 2 MM ID hollow shaft. Along with this, we had to provide the means to test for accuracy and torque variation using the "Soft Land" feature of the SMAC controller.
We were able to make accepted prototype in 8 weeks and have produced over 400 encoder in the past few years.