TECHNICAL FIELD

An aspect of the present invention generally relates to (but is not limited to) a method of operating manufacturing cell, comprising: manufacturing a hot-runner component in accordance with a one-piece flow manufacturing operation.

BACKGROUND

The first man-made plastic was invented in Britain in 1 851 by Alexander PARKES. He publicly demonstrated it at the 1862 International Exhibition in London, calling the material Parkesine. Derived from cellulose, Parkesine could be heated, molded, and retain its shape when cooled. It was, however, expensive to produce, prone to cracking, and highly flammable. In 1 868, American inventor John Wesley HYATT developed a plastic material he named Celluloid, improving on PARKES' invention so that it could be processed into finished form. HYATT patented the first injection molding machine in 1872. It worked like a large hypodermic needle, using a plunger to inject plastic through a heated cylinder into a mold. The industry expanded rapidly in the 1940s because World War II created a huge demand for inexpensive, mass-produced products. In 1 946, American inventor James Watson HENDRY built the first screw injection machine. This machine also allowed material to be mixed before injection, so that colored or recycled plastic could be added to virgin material and mixed thoroughly before being injected. In the 1970s, HENDRY went on to develop the first gas-assisted injection molding process.

Injection molding machines consist of a material hopper, an injection ram or screw-type plunger, and a heating unit. They are also known as presses, they hold the molds in which the components are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than five tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The total clamp force needed is determined by the projected area of the part being molded. This projected area is multiplied by a clamp force of from two to eight tons for each square inch of the projected areas. As a rule of thumb, four or five tons per square inch can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force. With Injection Molding, granular plastic is fed by gravity from a hopper into a heated barrel. As the granules are slowly moved forward by a screw-type plunger, the plastic is forced into a heated chamber, where it is melted. As the plunger advances, the melted plastic is forced through a nozzle that rests against the mold, allowing it to enter the mold cavity through a gate and runner system. The mold remains cold so the plastic solidifies almost as soon as the mold is filled.

Mold assembly or die are terms used to describe the tooling used to produce plastic parts in molding. The mold assembly is used in mass production where thousands of parts are produced. Molds are typically constructed from hardened steel, etc. Hot-runner systems are used in molding systems, along with mold assemblies, for the manufacture of plastic articles. Usually, hot-runners systems and mold assemblies are treated as tools that may be sold and supplied separately from molding systems.

Hot runner nozzle stacks are made in two ways, such as: (A) method 1 includes machining a nozzle housing, and applying a heater in a subsequent operation, usually in a highly manual process, such as winding a heater element around the nozzle housing, attaching leads, sealing the assembly, etc., or (B) method 2 includes machining a nozzle housing, and manufacturing a separate slip-on heater element (either in parallel to the step of machining or pulled from stock), and then mating the slip-on heater element with the nozzle housing.

SUMMARY

It is understood that the scope of the present invention is limited to the scope provided by the independent claims, and it is also understood that the scope of the present invention is not limited to: (i) the dependent claims, (ii) the detailed description of the non-limiting embodiments, (iii) the summary, (iv) the abstract, and/or (v) description provided outside of this document (that is, outside of the instant application as filed, as prosecuted, and/or as granted). It is understood that "comprising" means "including but not limited to the following". According to one aspect, there is provided a method of operating a specialized manufacturing cell, comprising: introducing raw material (also called blanks) to the cell, manufacturing the nozzle housing in a one-piece flow manufacturing operation, and applying a heater element directly to the nozzle housing.

According to one aspect, there is provided a method of operating manufacturing cell, comprising: manufacturing a hot-runner component in accordance with a one-piece flow manufacturing operation.

Other aspects and features of the non-limiting embodiments will now become apparent to those skilled in the art upon review of the following detailed description of the non-limiting embodiments with the accompanying drawings. DETAILED DESCRIPTION OF THE NON-LIMITING EMBODIMENT(S)

It will be appreciated that for the purposes of this document, the phrase "includes (but is not limited to)" is equivalent to the word "comprising". The word "comprising" is a transitional phrase or word that links the preamble of a patent claim to the specific elements set forth in the claim which define what the invention itself actually is. The transitional phrase acts as a limitation on the claim, indicating whether a similar device, method, or composition infringes the patent if the accused device (etc) contains more or fewer elements than the claim in the patent. The word "comprising" is to be treated as an open transition, which is the broadest form of transition, as it does not limit the preamble to whatever elements are identified in the claim.

Disclosed is a method of operating a specialized manufacturing cell, including: (i) introducing raw material (also called blanks) to the cell, (ii) manufacturing the nozzle housing in a one-piece flow manufacturing operation, and (iii) applying a heater element directly to the nozzle housing.

Also disclosed is a method of operating manufacturing cell, comprising: manufacturing a hot-runner component in accordance with a one-piece flow manufacturing operation. The one-piece flow manufacturing operation is also called: one piece flow, single piece flow, continuous flow, make one - move one, and flow manufacturing. The one-piece flow manufacturing operation will sometimes be referred to as the "one-piece flow". One-piece flow is a process that allows the right parts to be made in the right quantity at the right time. In the simplest of terms, one-piece flow means that parts are moved through operations from step-to-step with no (or few) WIP (work-in-process) in between either one piece at a time or a small batch at a time. One-piece flow works best in combination with a cellular layout in which all necessary equipment is located within a cell in the sequence in which it is used. To achieve true one-piece flow, equipment must have basic stability: (i) highly-capable processes (that is, processes must be able to consistently produce good product, and if there are many quality issues, one-piece flow is not likely impossible, (ii) highly-repeatable processes (that is, the process times must be repeatable as well, and if f there is much variation, one-piece flow is not likely impossible, and (iii) equipment has a very high (near 100%) uptime (that is, equipment must always be available to run, and if equipment within a manufacturing cell is plagued with downtime, one-piece flow will not likely be impossible). One-piece flow is usually associated with low-mix, high-volume manufacturing environments. However, one-piece flow also lends itself to high-mix, low- volume environments. It is usually achieved by creating mixed model or group technology cells, in which a number of products run through a particular cell utilizing one-piece flow. One-piece flow can be achieved through proper application of the principle. One Piece Flow refers to the concept of moving one workpiece at a time between operations within a workcell. At the opposite extreme, we might process an entire batch or lot at each operation before moving it to the next operation. This idea has many benefits. It keeps WIP (work-in-process) at the lowest possible level. It encourages work balance, better quality and a host of internal improvements.

IMPLEMENTING CONTINUOUS FLOW CELLS (ONE-PIECE FLOW CELLS)

After a value stream is mapped, a continuous flow manufacturing cell (hereafter referred to as the "cell") may be set up. Most cells that have been set up in the past ten years do not have continuous flow; most changes to cells have been a layout change only. That is, machines were moved in a cellular arrangement and nothing more was changed. A change in layout alone does not create continuous flow. The following is a discussion for steps to creating continuous flow manufacturing cells. Step 1 , includes: deciding which products (such as a nozzle assembly) will be assembled in a cell, and determining the type of cell, such as product-focused or group Technology (mixed model). For product focused cells to work correctly, demand needs to be high enough for an individual product. For mixed model or group technology cells to work, changeover times must be kept short. Some common types of types of manufacturing cells are: (i) functional cells are cells consisting of like equipment. For example, a factory that does primarily machining operations might have a bank of lathes together in a "turning cell." Another example would be a cell consisting of several sets of like test equipment. These cells are called "functional cells" because they perform a specific function (as opposed to manufacturing a complete product, assembly, etc.) Though there are exceptions, in most cases functional cells do not fit into a lean manufacturing environment, (ii) group technology (or mixed model) cells in which a series of operations for several products takes place. The products are often very similar, and the operations are very similar for each product (though not usually identical). This type of cell can work very well within a lean manufacturing environment, particularly if the organization is characterized by high-mix, low volume products. In such organizations, it is rarely possible to have product-focused cells, (iii) product focused cells are cells that are product-focused typically run one type of product through a series of operations. These are often thought of as the ideal lean manufacturing cell. They are perfect for low mix, high volume environments.

Step 2, includes: calculating takt time, takt time, often mistaken for cycle time, is not dependent on productivity - it is a measure of customer demand expressed in units of time, by way of the following example:

Takt Time = Available work-time per shift / Customer demand per shift

Example: Work time/Shift = 27,600 seconds

Demand/Shift = 690 units

Takt Time = 27,600/690 = 40 sec.

The customer demands one unit every 40 seconds. What if the demand is unpredictable and relatively low volume? Typically, demand is unpredictable; however, aggregate demand (that is, demand of a group of products that would run through a cell) is much more predictable. Takt time should generally not be adjusted more than monthly. Furthermore, holding finished goods inventory will help in handling fluctuating demand. Step 3, includes: determining the work elements and time required for making one piece. In much detail, document all of the actual work that goes into making one unit. Time each element separately several times and use the lowest repeatable time. Do not include wasteful elements such as walking and waiting time.

Step 4, includes determining if equipment can meet takt time. Using a spreadsheet determine if each piece of equipment that will be required for the cell that is being setting up is capable of meeting takt time.

Step 5, includes: creating a lean layout. More than likely, there will be more than one person working in the cell (this depends on takt time); however, an arrangement should be made such one person can work in the cell. This will ensure that the least possible space is consumed. Less space translates to less walking, movement of parts, and waste. U- shaped cells are generally best; however, if this is impossible due to factory floor limitations, other shapes will do. For example, I have implemented S shaped cells in areas where a large U-shape is physically impossible.

Step 6, includes balancing the cell. This involves determining how many operators are needed to meet takt time. For example:

Number of Operators = Total Work content / Takt time

Example: Total work content: 49 minutes

Takt time: 1 2 minutes

Number of operators: 49/12 = 4.08 (4 operators)

If there is a remainder term, it may be necessary to kaizen the process and reduce the work content. Other possibilities include moving operations to the supplying process to balance the line. For example, one of my clients moved simple assembly operations from their assembly line to their injection molding operation to reduce work content and balance the line.

Step 7, includes determining how the work will be divided among the operators. There are several approaches. Some include: (i) splitting the work evenly between operators, (ii) having one operator perform all the elements to make a complete circuit of the cell in the direction of material flow, (iii) reversing the above, (iv) combinations of the above. After determining the above elements, much of the necessary data required will have gathered to begin drawing and laying out a continuous flow manufacturing cell.

The concept of cell-system manufacturing was developed to produce the best quality product in the most efficient possible way. The idea behind cell-system production is to provide a continuous flow of produced goods through the absence of delays in the process. It is a notion of producing one quality item at a time, and to have those items continuously moving off the production line and in route to the customer-in short, one- piece flow. Central to the idea of one-piece flow manufacturing is the concept of motion- motion of materials, motion of parts/assemblies, motion of personnel, and the motion of finished goods out of the plant. Cellular environments facilitate one-piece flow production through having everything that is needed for production within easy reach, and ensuring that each assembly step is completed before the part is moved along to the next. In one-piece flow production tasks are reduced to their simplest components so, if done correctly, errors are reduced and continuous flow of goods enhanced. By raw material, parts, and assemblies being delivered to the cell system, operators have the process components at hand and are able to quickly produce goods within the flow. Particularly suited for efficient repetitive process production, one-piece flow provides continuous output, improved quality, and enhanced bottom-line profits without the need for enlarging production capacity or staff. As well, one-piece flow production is able to adjust to customer demands and shortened lead times better than large batch production operations. In contrast to large batch production, where delays are inherent as parts move slowly through the system, one-piece flow works to reduce not only delays but also the negative impacts on the system such as inventory build-ups, damage or obsolescence, and missed on-time deliveries. Once infrastructure is developed to support the continuous maintenance of one-piece flow, cellular production systems provide that continuous flow of activity between shop floor personnel and finished goods. The key difference between large batch and one-piece flow production techniques is motion. The continuous motion of production provided by one-piece flow means that there is no wasted time from start to finish. Processes overlap in one-piece flow whereby products are constantly on the move from one part of the cell to another. And, it is here, in the lean elimination of wasted time and effort that companies have their best shot of winning on the 24-7 global manufacturing stage.

It is noted that the foregoing has outlined the non-limiting embodiments. Thus, although the description is made for particular non-limiting embodiments, the scope of the present invention is suitable and applicable to other arrangements and applications. Modifications to the non-limiting embodiments can be effected without departing from the scope the independent claims. It is understood that the non-limiting embodiments are merely illustrative.