Fiber System Testing
The Fiber system with my accelerometers mounted onboard the tool head and coupling mechanism
As a part of my Desktop Metal co-op, I designed a durability test for measuring when the tool-changing mechanism of Desktop Metal’s Fiber system fails while it loads and unloads a tool. My approach to this test was to have two Inertial Measurement Units (IMUs) and compare their respective linear and rotational accelerations. In the ideal case if the tool head is perfectly mounted to the coupler mechanism, then both IMUs would experience identical accelerations if they hit a bumper. However, if the tool is loosely attached, it will experience a change in acceleration before the coupler does.
Let’s Get Some IMUs in Here!
Close up of the accelerometer mount onboard the coupler.
Close up of the accelerometer mount onboard the tool head.
I used an LSM6DSOX Inertial Measurement Unit (IMU) and an STM32F405 Featherboard from Adafruit as the microcontroller. I wrote and ran code onboard the microcontroller to read and log data from both sensors onto a micro SD card. I mounted the Featherboard on the top of the printer chassis and routed extended wires to the IMUs. I used a laser cutter to cut acrylic plates to mount and vibrationally isolate the IMUs. I designed the plates such that they mounted to existing hardware onboard the coupler and tool head so as to not interfere with tool changing or sensor readings.
Now Let’s Have Them Bump Into Stuff!
My G-Code script I ran to automate testing.
Close up of the bumpers mounted onto the Fiber system’s frame.
Close up of another set of bumpers with stiffer springs.
To test if the tool was properly mounted to the mechanism, I designed a bumper assembly. I mounted two springs to check whether the tool was loose in one direction or another. I used brass press-fit inserts inside a thick acrylic plate to house the 3D-printed spring mounts. To run the test automatically, I accessed the machine’s Duet board to program a G-Code script where the printer would repeatedly couple with a tool, touch two bumpers, and uncouple. The video shows the Fiber printer running my G-Code and the IMUs streaming its output through the Arduino serial monitor. You can see every time the tool coupling mechanism bumps, there is a spike in acceleration in the serial monitor.
Video of the Fiber system performing a coupling durability test.
