Case Study: New Products, New Challenges

Newly engineered products bring with them loads of design challenges. As companies strive to evolve their product lines, new problems are bound to arise. Even old fixturing methods quickly find themselves out of date. A structured approach and fresh outlook can make all the difference getting – and keeping – things on track.

A client of Mackenzie Design had a new product and when it came time to develop an End of Line (EOL) test for the assembly line they found themselves developing something entirely new and unfamiliar. The highly manual and complex testing that was required was bottlenecking the assembly line in a big way.

A Fixturing Problem

The EOL testing process required operators to bolt the Device Under Test (DUT) to an aluminum fixture and form a liquid tight seal. Routine threading of hard steel bolts into the soft aluminum quickly became a safety hazard. Crossed and stripped threads were frequent and greatly reduced the holding power of the joint. Were a bolt to fail the operator could be sprayed with high-pressure test fluid. A patient operator and a lot of maintenance were required. Additionally, the manual threading process was very time consuming and an ergonomic nightmare.

Once the DUT was secured in the fixture the operator would sequence a number of valves by hand to fully purge the air from the device. Any mistakes in the sequence or any residual air would cause the EOL test to fail. Upon completion of the test the operator would have to cycle the same valves in a different sequence to remove the excess liquid.

Finally, the operator would unbolt and remove the DUT. Breaking the seal was difficult and often resulted in a “pop” that would splash fluid around the work area. Once removed, the operator would dump remaining fluid into a reservoir and place the DUT in a drip-drying rack. This was all very messy and required the operator to don multiple types of Personal Protective Equipment (PPE) and waste time cleaning the work area.

The Structured Approach

To address these problems Mackenzie Design worked heavily with their client’s engineering department. By applying a structured brainstorming process and some in depth analysis, dozens of fresh ideas were created and some old ones were reevaluated. With a little work, self-centering jaws were designed to withstand hundreds of thousands of cycles. Also, the movement of the jaws was adapted to positively break the seal upon test completion and aid the operator in part removal. The final design was robust with a minimum part count and a high degree of reliability.

An experimental clear test fixture was also developed to examine and better manage fluid flow. Various orientations and valve sequences were tested to determine which best purged air prior to the test and which flushed the remaining fluid from the system upon completion. A specific orientation of the DUT was chosen that eliminated the need for external purge and flush equipment, significantly improved cycle time and eliminated the need for operators to wear special PPE.

Results

Upon completion, the new fixturing device:

  • Eliminated the use of threaded fasteners with a fail-safe clamping mechanism. A huge safety improvement!
  • Liquid spillage was drastically reduced eliminating the need for special PPE and greatly reducing slip hazards!
  • Takt time was improved from just over ten minutes to ~52 seconds per test – over 11 times faster!
  • The device has been maintenance free for over 2 years and 150,000 cycles! (As of date of this publication.)
  • The design is aesthetically pleasing and a point of pride during customer visits.

The new fixture in action!

A video of the fixture in action