SigmaTron Source 2Q, 2017

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Suzhou China Facility Expands Facility, Launches Box Build Project

SigmaTron International’s Suzhou, PRC has expanded into a new 15,000 sq. ft. environ-mentally-controlled production facility that uses HEPA filtration in addition to air conditioning to control temperature and air quality. The production facility will be focused on SMT and box build assembly. A new line featuring a DEK screen printer and Panasonic NPM machines has been purchased and went into production in May. An inline KOH YOUNG 3D solder paste inspection (SPI) station and TRI Automatic Optical Inspection (AOI) will be added in the SMT line early in Q3. The facility will be adding a Universal Multiple Function Machine dedicated to placing electromagnetic interference (EMI) shielding.

“The number of projects requiring shielding has grown. Centralizing placement of this part to a machine optimized to place right after the AOI station improves quality, line capacity and throughput,” said Hom-Ming Chang, Vice President China Operations.
The strategy also minimizes misaligned or missing components and insufficient solder, as these issues can be difficult to check after shielding placement.

The Suzhou operations’ business growth includes a box build assembly for an industrial product display. The project is shipped to the customer’s China facility for final system test.

To support it, the Suzhou engineering team created an innovative two-tier assembly line workstation configuration to improve efficiency and ergonomics. The conveyor line moves product under assembly on the top tier and operators can access parts and tools from the lower tier.

“The project includes large parts and because it is medium volume we are limited in terms of automation options. The goal was to configure each assembly station in a way that kept parts orderly and easily reachable, while improving production throughput, said Hom-Ming.

The team also worked with the customer’s team and their third-party test system design firm to develop an automated test solution that fit well into an industrial test environment.

“We provided test reporting data format and test interface recommendations to our custom-er for developing test program output which can be integrated into our shop control system, Tango, plus generate the test report data our team needs to monitor yields and analyze trends,” Hom-Ming added.

Suzhou’s manufacturing engineering team also focuses on some low tech solutions to identified manufacturing challenges by developing fixturing that minimizes operator error and process variation in manual or semi-automated assembly operations.

For example, a recent industrial prod-uct box build required production operators to mate a connector on the printed circuit board assembly (PCBA) with a power cable. Because the connection involved powering a unit, a misaligned connection could create a safety hazard. While in theory, operators could be thoroughly trained to assemble the part correctly; in reality, even diligent operators working at speed tend to make errors occasionally. A poka-yoke exercise was done on that assembly step and a low-cost gauge was developed to make surethe power connector is plugged properly without misaligning the pins.

In another situation, a poka-yoke fixture was created for an assembly operation that involved use of a large number of small screws. Operators could drop screws into the fixture and they would fall into small holes giving the operator easy access to the exact number of screws needed to assemble the unit. This sped up that stage of the assembly process and eliminated the attrition that was occurring when operators attempted to count out the correct number of screws on the work-bench.

“While we focus on optimizing processes as we set them up; we also recognize that there are opportunities for improvement as we observe actual production activi-ties. In situations such as the first example assembly consistency directly impacts product quality and safety. In cases such as the second example, an improvement reduces material attrition, foreign object damage (FOD) from stray parts and as-sembly time. We recognize that attention to detail is a key factor driving our growth,” said Hom-Ming.

Tackling the Internet of Things Challenges

The Internet of Things (IoT) has become as transformative today as the personal computer (PC) was in the 1970s. The applications are endless and most devices are plug-and-play after the appropriate app is downloaded. However, the engineering behind IoT can be much more challenging.

SigmaTron International’s Spitfire Controls division offers a joint development model for companies needing product development sup-port aligned with Spitfire’s design competencies. The Spitfire Control’s team core competences in software-driven controls, near field communications (NFC) and smart grid data streams enable them to help clients integrate IoT applications into appliances and industrial equipment.

“When you are designing an IoT device, you need to think holistically. What else is in the box? Where will it be used? Understanding the enemies of signal integrity can be very important,” said Jay Ramsey, Spitfire Controls’ Founder.
Helping customers identify potential signal integrity issues early in the design cycle is something the team at Spitfire Controls does well. Here are four examples of issues to avoid:

Unit Structural Considerations
Most IoT devices are a single board transceiver with antennas. However, when that board is mounted in a metal chassis for appliance or industrial equipment applications, the metal can cause the antennas to become directional or create attenuation, causing a weaker signal.

Electrical Noise Within the Unit
If the product the IoT device is built into includes lines carrying motor current or high speed switching the concomitant electrical “noise” can be picked up inductively on the power supply lines of the wireless modem which causes signal-to-noise problems that reduces range drastically.

Layout Considerations
Lack of low impedance grounds or antenna placement adjacent to power supply lines can result in a poorly operating system that cannot reliably log on to a router. It may also go offline when the machine it is providing connectivity to has a load switched on and signal strength goes to nil.

Failure to Consider the Cumulative Impact of Component Tolerances
While the tolerances of individual components may be within specification, the combined tolerances of components in the total unit may generate unacceptable levels of interference. Small variances in tolerance at the component level may not be noticeable during design validation or in prototyping. However, if the cumulative values of the components are marginally acceptable, as volumes increase there is likely to be higher levels of defects in test. Individual components can have wide variations in tolerance and the more components being purchased, the more the full range of that variation is likely to occur. Sole-sourcing components on the approved vendor list (AVL) can magnify this problem if the component manufacturer selected has poor process control. Obsolescence can also create problems if replacement microprocessors or UARTs do not have identical signals.

“Our team has helped clients address all of these scenarios. Simply knowing and adhering to industry-standard design rules addresses much of this, when there is a good understanding of where common layout problems occur. We are able to use design tools such as the SPICE circuit simulator or Monte Carlo analysis to address component tolerance issues. And, we have tools at SigmaTron that help analyze component obsolescence risk,” added Jay.

The engineering team can also help with software development.
“We still have a demonstrated edge in software design and in many cases, are doing entire firmware packages. Our scalable support model enables us to handle the entire project or simply fill gaps in a customer’s team,” said Jay.

Enhancing Efficiency and Quality in Medical Box Build

One of challenges many medical device manufacturers face is that while product volumes are often far less than found in consumer industries, they are under the same pressures to continually reduce cost while meeting significantly higher quality standards. SigmaTron International’s Union City, CA facility addresses that challenge by utilizing Lean manufacturing principles to eliminate non value-added activity and reduce defect opportunities. Operational synergy is also evaluated to achieve better economies of scale.

For example, in a project involving a patient assistance device, an ergonomic work cell has been designed that handles both ongoing production, and repair and upgrade operations. That minimizes raw materials inventory requirements and capital equipment requirements, since the programming and test equipment supports both types of production activities.

The printed circuit board assembly (PCBA) has three separate models. The SMT area is treat-ed as supplier that ships to a Kanban in the stockroom. The PCBAs are pulled from the Kanban and kitted as part of the top level assembly as orders are released.
The top level assembly process uses a fixture to minimize process variation and wasted motion in fan assembly, but most other operations are simple assembly steps. The work cell frame is adjustable to facilitate ergonomics and operators can sit or stand to perform their tasks based on personal preference.

Programming, test and pack is an integrated operation to ensure serialization integrity. The serial numbers are stored in both an Excel database and SigmaTron’s proprietary Wallaby program. The product is traceable through the serial number and the customer utilizes this information for warranty verification.

The work cell also handles repair and upgrade operations. In some cases, units are returned in bulk shipments from the customer for a retest and soft-ware upgrade. In other cases, units are returned from the field for warranty repair, which involves troubleshooting and repair. Repaired or upgraded units have their existing serial number annotated in the database and a new serial number (traceable to the original) is issued.

Several operators in the work cell are cross-trained on similar projects enabling them to shift to other work cells if demand drops.
The end result is a highly organized work area that can be easily scaled to meet customer production and repair depot requirements. Fixturing has been added as needed to minimize the defect opportunities and wasted motion in the most complex assembly step. The product is tracked through all operations via bar code scans, providing full traceability in support of device history record-keeping requirements. Capital equipment intensive operations have been combined to minimize the customer’s specialized test equipment costs while maximizing equipment utilization. Co-location of program-ming, test and pack minimizes product handling and the defect opportunities related to serialization that can occur if these operations are separated.