Assistive Technology: Power Drill Handle [Fall 2021]

Course: Engineering Design I

Task: To design an external component that modifies the use of the power drill so that it is easier for members of unique populations (who might not have initially been accounted for) to use the tool. We chose to redesign for people with Cerebral Palsy (CP), and account for some of the challenges they tend to encounter (as confirmed by our user survey) during usage of a drill. These included involuntary muscle movements and subsequent imbalance, as well as difficulty in gripping the drill and trigger button for long periods of time.

Challenge/constraints:

  • Weight

  • Cost

  • Complexity (should not make the drill more complicated/drastically increase the number of steps required)

Tools: SolidWorks (CAD and FEA), 3D printer

Material: PLA Filament, McMaster set screws

 

Process

After brainstorming, a final design of a two-handle gripper for the drill was proposed, with three main components. The adjustable trigger collar, an internal spring-damper system, and the two ergonomic handles. For the purpose of the in-class project, we were to only prototype and test one component, so the entire design process was completed for the trigger collar initially.

1)

Initial sketches

2)

Hand calculations:

  • Performed simple stress analysis to assess most likely failure modes (compression/buckling, axial stress, bending, etc.)

  • Used a Factor of Safety (FoS) of 3 to solve for minimum width dimensions of interfacing tabs (connected by set screw). A high FoS was used since the product was designed to be attached to a power tool, so safety was a priority.

3)

Created CAD model to dimension in SolidWorks

4)

Performed complex stress analysis using FEA to find the points and values of highest stress, maximum displacement, and FoS to compare with hand calculations.

5)

Prototyped using 3D printer, used McMaster set screw to be able to press drill trigger with hands free. The screw could also be adjusted to vary speeds.

The final product was one component of a proposed two handle design, which would increase overall stability. I plan to finish prototyping all parts of the design, which would include the central collar which was tested and prototyped successfully , as well as two polymer handles with a central spring-damper system.