Multi-purpose inkjet production test system
The Brief
A global provider of industrial inkjet drop-on-demand printers needed a production test solution that could support multiple legacy and future products through the various stages of their production process: part assembly module test; end-of-line; and rework station.
The product being tested required flexibility and had high voltage levels, therefore, the solution needed to have two types of logins: one for the engineering team and another for the test operatives. The engineering team would be able to configure the test system for different stations while the test operatives would use a simplified semi-automated interface for safe and high-throughput testing during production shifts.
The testing requirements included continuity testing, functional testing of electrical and pneumatic systems, and high voltage testing. The test results would be stored in a server database linked with a barcode that would be scanned at each stage of the production process.
The Solution
We began this work by developing the test specifications in cooperation with client production engineers. Knowledge of the products’ test requirements and legacy test equipment rested with a number of the client’s engineers. Once this consolidation process was complete, the next challenge was to specify and design a production tester that could be dynamically re-purposed, to meet all product test requirements, at all stages of the production process. Care was taken to follow the look and feel of legacy test solutions so as not to alienate production line workers. A series of interviews and workshops helped in this process.
We designed and manufactured a test unit that used a combination of off-the-shelf DAC & configurable IO modules, and bespoke analogue interface PCBs. An FMEA analysis was undertaken as part of the process, resulting in several safety & poke-yoke features. In addition, a number of easily replaceable sacrificial elements were added to the design, to maximise the tester lifetime on the production line, with minimal maintenance effort.
We created a Windows application to exchange control commands and data with the embedded test hardware over a USB port. The application’s admin mode allowed the definition and scripting of command & control test sequences, including pass/fail thresholds and user instructions. The admin user could then set the test UI into any one of its user modes appropriate to the installed test station.
In the chosen test user mode, the test operative would be guided through a predetermined sequence, resulting in a clear pass/fail indication and appropriate error codes, with all test results stored in a network database against a pre-scanned barcode ID.
After completing design verification testing, our engineers delivered and installed a number of test stations on the client’s production line. This included initial handover training and longer-term support for maintenance and feature enhancement.
A number of key features had to be integral to the design.
– Ease of maintenance
– User safety protection
– Tester adaptation for multiple product lines & multiple test station functions.
– A user experience familiar to production line operators
Central to the hardware design was striking the right balance between the use of appropriate off-the-shelf solutions and bespoke electronic PCB design. Configurability, cost, ease of maintenance and performance were central to this choice.
Careful connector choice and sacrificial board design helped guarantee a long-term solution that was easy to use and maintain.
By selecting an appropriate DAC solution with built-in API, it was possible to make significant engineering savings by avoiding the need for embedded software design.
Software effort was focussed on a highly configurable, easy-to-use PC interface, developed on a fast turn-around feature-rich UI development environment.