High- and low-tech ways to ensure parts are correctly placed.

A core element of Lean manufacturing philosophy is the requirement to understand where inefficiencies and waste exist, in order to eliminate them. Even in a factory that thoroughly embraces Lean manufacturing and trains its personnel on all aspects of their jobs, there will be inefficiencies and waste related to operator error, supplier quality issues and process variation. SigmaTron International’s facility in Suzhou, China uses a two-part strategy to address this. At a systems level, it developed a proprietary Manufacturing Execution System (MES) system known as Tango to enhance shop floor control. At a granular level, the team evaluates production operations for areas where tooling or fixtures can minimize process variability and the potential for operator error. This month, we look at some of the common areas where this defect mitigation strategy can be most effective.

SigmaTron’s IT department takes a distributed approach to continuous improvement in its systems by letting teams at individual manufacturing facilities identify specific gaps in shared systems and develop appropriate software tools. These solutions are then tested at the facility that identified the need and later transferred across all facilities. Following development and testing in Suzhou, Tango was deployed to other facilities beginning in 2014.

Consolidation is the enemy of innovation. Don’t believe me? Look at how, ahem, fast AT&T rolled out changes during its early heydays.

Ma Bell – the colloquial name for the telecom monopoly – took three years of testing (!) before it rolled out touchtone phones (aided by the invention of low-cost transistors, which Bell also patented). That was 1963. And the rotary dial was still the norm when I grew up in the 1970s. It wasn’t until the early ’80s that we made the shift, and even then AT&T was still offering rotary for wall-mounted units.

In 1982, the US government forced the breakup of Ma Bell. Cordless phones were starting to take hold about that time. The breakup unleashed a slew of digital features that to date had been wasting away in research labs. Call waiting was a revelation. Conceived by Western Electric in the 1970s, it was offered an option and hardly commonplace until the mid to late ’90s. Voicemail was invented in 1979.
It was picked up first by businesses and made its way to consumer accounts only as cellphones began their relentless penetration.

Predictions on material transfer get a wrinkle.

When you’re pushing the limits of area ratio rules and trying to realize an acceptable result out of a shrinking window, even the slightest dimensional alterations can make a big difference. That was the topic of my last column, as we looked into the impact of challenging area ratios of 0.4 (the accepted standard is 0.66), as well as the aspect ratio influence as the geometric shape of the aperture moved from a square to a rectangle. The work revealed that at an aspect ratio range of 1.6 to 1.8, the Cp values were noticeably higher than for those apertures with a 1.2 or 2.0 aspect ratio (each end of the square to rectangle spectrum). Intrigued by these results, our team pushed on with the miniaturized aperture (0.4 area ratio) shape analysis, this time to understand the effect of moving from a square to a circle.

I should note a few years back, our company also evaluated the printing performance of pure squares versus pure circles when using activated squeegee technology. Ultimately, the square apertures produced better transfer efficiency rates, which improved dramatically with the use of an activated squeegee versus a standard squeegee. However, what this previous study didn’t assess, and what our team set out to investigate this time, were gradual changes in aperture shape when moving from a square to a circle. For example, taking the Y dimension and slowly changing the radius by slight percentage increases to round the square edges and eventually move to full circle (FIGURE 1).

If parts are turning up where they shouldn’t be, check the feeder and paste.

Chip components sometimes appear on the surface of a board completely out of position. On some occasions they may be under other components or, as in FIGURE 1, even shorting under parts. If it’s a random chip component, then there is little chance of finding the cause. If all the parts are the same resistor or capacitor, it may be a feeder problem where the parts are being dropped after pickup, or are jumping out of the tape due to static, which can occur on small parts (below 0201).