High Caliber Engineering On A Low Torque PCB Servo Motor

Building a 3D motor printed motor is one thing, but creating a completely custom servo motor with encoder requires some significant engineering. In the video after the break [365 Robots] takes us through the build process of a closed-loop motor with a custom optical encoder.

The motor, an axial flux design, uses a stack of 0.2mm PCBs with wedge shaped coils clamped in a 3D printed body. It’s similar to some of the other PCB motors we’ve featured, but what really sets this build apart is its custom optical encoder, which was a project in its own right. The 4-bit absolute position encoder uses IR LEDs to shine through an PCB disc with concentric gray code copper encoder rings onto IR receivers. This works because FR4, the composite material used in PCBs doesn’t block IR light.

The motor’s body was printed from ABS to withstand the heat during operation. [365 Robots] didn’t skimp on the testing either, creating a 3D printed closed-loop test stand with load cell and Arduino. Like other PCB motors it produces very little torque, roughly 2% of a typical NEMA17 stepper motor. Even so, the engineering behind this project remains impressive.

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The modified servo being calibrated on the left half of the screen, with some graphs of its operation being shown on the right half.

Servo Surgery Teaches Us DIY Encoder Implants

Today, we shall talk about how [Adam Bäckström] took a DS3225 servo and rebuilt it to improve its accuracy, then built a high-precision robot arm with those modified servos to show just how much of an improvement he’s got – up to 36 times better positional accuracy. If this brings a déjà vu feeling, that’s because we’ve covered his servo modifications before, but now, there’s more. In a year’s time since the last video came out, [Adam] has taken it to the next level, showing us how the modification is made, and how we ourselves can do it, in a newly released video embedded below.

After ordering replacement controller PCBs designed by [Adam] (assembled by your PCBA service of choice), you disassemble the servo, carefully setting the gearbox aside for now. Gutting the stock control board is the obvious next step, but from there, you don’t just drop the new PCB in – there’s more to getting a perfect servo than this, you have to add extra sensing, too. First, you have to print a spacer and a cover for the control board, as well as a new base for the motor. You also have to print (or perhaps, laser-cut) two flat encoder disks, one black and one white, the white one being eccentric. It only escalates from here!

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CES2017: Really Fast 3D Printing For Large Builds

About a year ago, Autodesk showed off one of the most innovative filament printers in recent memory. Project Escher is your basic Cartesian filament printer, but with a twist: it has five heads. These print heads work together to build large objects very quickly.

Autodesk open sourced the design of the Escher, and now it’s made it into commercial production thanks to Titan Robotics. The Cronus, which uses the same software as Project Escher, is big! Each of these gantries is driven by closed-loop servo motors and fancy ball screws, producing a total build volume of 77″x30″x20″. This open air version is printing in PLA. If you want to use it with materials where ambient temperature is an issue there is an option for an enclosed build environment.

This printer will be available for purchase starting February but no word yet on cost. They advertise the build volume as customizable so we expect the same of the price.