From the Forums: Build report of 3DP Testbench, Including Adafruit TFT & Printer


Build report of 3DP Testbench, Including Adafruit TFT & Printer, shared in the Adafruit Forums!

The test bench uses the stepper motor to turn a “throttle shaft” approx 90°, stopping every 0.75° to take an ADC measurement of the Throttle Position Sensor being tested. Usually, 120 or more values are measured and then put in an array and analyzed for standard deviation and also some strict bounding to make sure the plot doesn’t wave around too much. The bench decides if it’s good or bad. If it’s good, the response plot is printed out on the Thermal Printer with a summary of the analysis.

My company sells aftermarket parts for Ducati motorcycles and I started supplying TPSs. Two of the 4 models we sell I had custom made for us; they’re not currently available via retail channels. During my normal OCD understanding of how and why things work, I came to learn that the manufacturing industry considers a 4 point test to be the standard QC. And it doesn’t matter what continent the parts are coming from, that’s normal. After having a customer receive a TPS that had wonky output, I built a crude v1 test bench. Using a Mega and a crappy salvage store stepper, this bench was good enough to help us eliminate TPSs that slipped through the normal 4 point QC. I used my 3D printer to make the 54T gear and input to the TPS. This setup with the 1:3 gearing and crappy stepper was able to measure 33 to 35 points in each TPS. I basically checked that the change between steps’ measurements was within some range of bounds.

But to SEE the plot of the TPS, I had to use the serial monitor, copy the values as measured, paste them into a spreadsheet, then create a graph; in other words too much work! Then I discovered the 1.8″ TFT Shield with Joystick glowy thing. Upon the completion of this other crazy project, I knew it would be great to see the plot. Then when I saw the serial thermal printer I needed to make V2 of the TPS bench happen — I could print this part’s plot and include with it! No one gives 3 cares about quality, let alone like this. A little bit of effort on my part ensures no customer or shop will have to go through the painstaking process of replacing a TPS I sold them because it was built poorly! (well, never again after that first guy)

to be continued… gotta get to the pub. Still to come: explanation of the choices of equipment, pics of the guts, and some gotcha’s I learned along the way….

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