Rather than a case study, this article is a step-by step guide describing a simple yet effective assembly tool — the “cart” — and how it can turn a plant into a Lean Manufacturing machine.

Bliss Industries has developed an entire family of carts for electronics assembly. These carts have been proven over many years. An assembly operation can become significantly more efficient when using this cart-based process.

Typically, PC board assembly lines run smoothly and generate profit for the respective company. In fact, most meet or exceed target volumes, yields and cost structures. In today’s market, a company must run a lean operation to compete. When managers see these products as “just carts,” they miss the real benefit toward Lean Manufacturing. This article educates readers on the importance of carts.

Measure the current process
Use existing metrics to determine how many PC boards per hour come off the line that require no rework to ship. Figure total cost per hour to run the lines, including labor, maintenance, finance charges for the machinery, electricity, overhead, etc. and then factor in the profit margin. These calculations tell how many PC boards per hour or per shift, and the cost per PC board to produce them.

The next phase of this measurement test is to walk down the assembly line, starting at the finished end of the line. Watch to see if a PC board is in motion on the conveyor at all times. Continue this walk until you reach the beginning of the line.

Identify bottlenecks
Most find that component placement is the largest bottleneck. Examine the top three bottlenecks carefully and, using structured problem solving methods, identify the root cause for each one. Are any of them related to handling, for example components, work-in-process or feeders? Carefully observe the next feeder     exhaust     or     assembly     line

changeover. How long is the line down for a feeder exhaust or assembly line changeover? Make note of all the tasks that occurred while the line was down.

Finally, calculate how many PC boards should be produced per shift at 85% utilization. At the end of the shift, determine how many PC boards were actually produced. What is the variance between theoretical result and the actual result?

Make departments Lean
Receiving
Components are received in many formats including bags, tubes, plastic trays, tape-and-reel, and matrix trays. To save space, remove components from the shipping container and store them on a cart that is specifically designed for the job. The cart can be used to transport the components directly to the stockroom location.

Stockroom
Reduce handling, labor and inventory while increasing inventory turns, which means improved cash flow by using Bliss stockroom units in single depth, dual depth or on wheels. Bliss Subdividers separate and organize individual part numbers. Determine the total quantity of part numbers that come on tape-and-reel, then install that number of subdividers into the stockroom units. Position each subdivider to allow enough space to accommodate the maximum standard reel quantity of that part. Reels can be stored in any order, regardless of width or diameter. Based on Bliss Industries’ experience, it is recommended to store by part number. To ensure FIFO (first-in-first-out), take reels from the left of the bin and insert new ones on the right. To monitor consumption place a dated “post it” note on the right side of each reel and note what date the last reel is consumed. Use Bliss magnetic label holders to clearly identify part numbers on all shelves.

If you use a large quantity of DIP tubes use Bliss “dual depth” stockroom unit with flat shelves to store the box and the

tubes, remove the end of the box for easy access. To store large quantities of matrix trays, or loose components in bins or boxes, use a Bliss “single depth” stockroom unit with flat shelves to store the trays. Use magnetic label holders to clearly identify each part number.

During SMT assembly, each hour of downtime will cost 8 to 12% of shift capacity wasted. More PC boards per shift means lower costs and greater profits, resulting in Lean Success.

Screen printer stencil storage and staging
Store large quantities of stencils offline in our stencil storage carts. As they are

needed for production, move those selected stencils to a 22" stencil staging station. Roll this cart over to the printer.  It

features a small footprint and protects the stencils. Having the stencils staged near the printer during changeover reduces downtime. When stencils are mishandled or stored improperly, such as leaning them against the printer, they are vulnerable and easily damaged, which can affect print quality.

SMT feeder storage and staging
Bliss Feeder storage carts eliminate damage caused by improper feeder storage and protect the feeder investment by surrounding the feeder in a   steel  frame  cart designed  specifically

for this purpose. Our open-style carts with feeder storage shelves can accommodate all feeder types and sizes.

Using Bliss feeder staging stations can pre-stage all of the feeders in advance in the exact sequence they are needed for the next changeover. Pre-stage ”Job B” offline while “Job A” is running. Set up each feeder needed for “Job B” using our feeder set up rack mounted