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What’s Happening Today at Panasonic

Inheriting Tradition - Iron Series Residential Rain Gutters

Dec 18, 2015

Rain gutters are an essential part of any home. Here we take a look at efforts being made at Panasonic's Ritto Factory, which has worked for decades to hone its core manufacturing technologies and support innovation in the rain gutter industry.

The Iron series: Rain gutters with high market share and unique structure

The Eco Solutions (ES) Company (formerly Matsushita Electric Works) has always maintained a "dig deep" spirit. If you dig a well deeply enough, you will eventually strike an underground aquifer and your well will never go dry. Business is the same. If you are tenacious in pursuit of your goal, you are certain to succeed.

Panasonic began marketing residential rain gutters in 1958, and since then, the company's Ritto Factory has been tenaciously improving its manufacturing processes.

Rain gutters protect the walls and foundations of homes from water damage by channeling rainwater away from the structure. The gutters are exposed to the elements for years, including extremes of cold and heat, storms, snow and frost, and the effects of UV from sunlight on clear days. As products intended for extended use under severe conditions, the ES Company's rain gutters are outstanding among Panasonic Group products.

In 1982, the ES Company launched its Iron series of horizontal eave gutters, which featured an industry-first metal core surrounded by layers of rigid polyvinyl chloride (PVC). Today, rain gutters with this innovative structure are available only from the ES Company. In terms of resistance to shock as well as deformation due to temperature fluctuations, Iron series rain gutters are markedly superior to PVC-only products. An external coating of highly weather-proof PVC prevents discoloration and bleaching from UV and other environmental factors, and contributes to maintaining the appearance of the residence for many years.

"Although Iron series rain gutters offer superior customer value, they are comparable in price to PVC-only products, which has helped drive their popularity since they first appeared on the market," says Kunihiro Takeda of the Ritto Factory Plant. "The product is also highly trusted by sales representatives, construction contractors, and housing manufacturers." Today, all of the ES Company's eave gutters are Iron series products, and they have maintained a consistently large market share.

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    Kunihiro Takeda
    In the past, we developed our personnel on the assumption that it took 10 years for an employee to fully master his or her job. However, standardization is now critical. We are using our own in-house certification system, supervisory promotions, and other measures to ensure that the needed techniques are propagated internally.

  • img_201512_amatoi_00_03.jpg

    Cross section of Iron series rain gutter.
    Iron series gutters for installation along the eaves of residences feature a three-layer structure that includes a zinc-plated steel core, a layer of rigid PVC, and an outer layer of highly weather-proof, UV-resistant PVC.

  • img_201512_amatoi_00_04.jpg

    These gutters have been exposed to the elements for around nine years. The PVC gutters (two gray gutters, top) have suffered significant deformation from expansion and shrinkage. The Iron gutter (black gutter, middle) shows virtually zero deformation.

  • img_201512_amatoi_00_05.jpg

    The Ritto Factory outdoor UV exposure test area. Products from 1982 can also be seen.

  • img_201512_amatoi_00_06.jpg

    The ES Company Ritto Factory began operation in 1970. The factory specializes in rain gutters and produces around 5,000 individual products.

Rain gutters: History and sales network

The earliest mention of rain gutters in Japan is found in sources dating to the Heian era. The oldest rain gutters still in existence are found on the eaves of Todaiji Temple's Lotus Hall. In the Edo era, tiled roofs were promoted as a fire-prevention measure in a highly urbanized environment, and rain gutters fashioned from wood or bamboo were widespread.

In the Meiji era, the introduction of Western culture brought imports of bricks and oil in tin containers. Metal workers began using the discarded containers to produce rain gutters, and the techniques improved and spread.

After World War II, plastics technology, originally developed in secret for military applications, became available for civilian use, leading to the development of plastic rain gutters. Sheet metal distributors who had previously handled metal rain gutters adopted and popularized the new product, which did not require special processing and could be joined using adhesives.

In 1958, Matsushita Electric Works began marketing plastic gutters featuring a patented dual-layer joint system, but the company struggled initially to establish a sales network. Its principal distributors were in the construction materials and electric equipment industries, and these companies did not handle rain gutters. To develop its network, the company finally turned to metal products sales representatives who formerly dealt with metal rain gutters. The National Rain Gutter Construction Material Association, an association for sales representatives and distributors, was established in 1963 and continues to serve as the foundation for the ES Company's sales network.


(Top) Rain gutter, Lotus Hall, Todaiji Temple, Nara.
(Bottom) The first rain gutter from Matsushita Electric Works with patented dual joint system (1958).

Exploring core technologies for manufacturing resin-clad metal products at the Ritto Factory

The rain gutter manufacturing process consists of forming and extrusion. Unlike plastic gutters, Iron series rain gutters feature a clad steel core which is first formed into a gutter shape. PVC resin is then extruded onto the metal core and molded into its final form. Takeda notes, "The extrusion process is a core technology of the Ritto Factory. Forming, mold design, and resin coating are also core technologies." Since the plant started manufacturing Iron series rain gutters in 1982, the process has been continuously improved through an ongoing cycle of incremental innovation, evaluation, and further innovation.


(Left) During the forming process, the core is passed through a series of metal frames and gradually assumes the required gutter shape. The final shape and the handoff process from machine to machine is based on expertise accumulated over many years.
(Center) Heated resin is mixed with additives, including coloring agents, and sent for application to the metal core. As shown here, the formed core passes through a heated mold and white resin is applied with the required shape. After cooling, the gutter is cut into standard construction lengths of under four meters and sent to the packing stage. The length of the production line, from forming through extrusion, cooling, and cutting, is very compact at around 20 meters.
(Right) Mold maintenance. The resin flow varies depending on the properties of the plating, requiring measures to maintain consistent quality. For Iron series gutters, the shape of the mold ensures consistent resin application; this is yet another benefit of incremental innovation and improvement.

  • img_201512_amatoi_00_10.jpg

    Manabu Mizutani
    We have developed a proprietary resin formula that behaves as required in the molten state and gives superior performance when fully cured. Furthermore, we continue to tweak the formula in a continuous search for even better performance.

  • img_201512_amatoi_00_11.jpg

    Tatsuhiko Kondo
    Resin flows continuously during the extrusion process. Consequently, if the process is not properly controlled, the resin does not adhere consistently. Through long experience, we have developed proprietary expertise to monitor the process in real time and make any required adjustments.

  • img_201512_amatoi_00_12.jpg

    Kazunori Fujii
    Today, when technological breakthroughs in manufacturing have everyone's attention, the Ritto Factory is, in a sense, preserving an established technology. Our focus is on continuous incremental improvements that add up to something quite significant over time.

Using requests from customers to bolster the factory

Nonstandard roofs, such as those with curvilinear or discontinuous eaves, also require rain gutters. These and many other special requirements cannot be met with standard materials. The Ritto Factory also strives to meet demand for special-order gutters configured to unusual roof shapes. Building contractors take note of this capability at product exhibitions, where special-order rain gutters attract intense interest. Uncompromising manufacturing has a powerful attraction.

A wide range of customers visit the Ritto Factory. Rain gutter installation professionals suggest ways of making installation easier. Such suggestions are invaluable, especially since small adjustments are frequently all that is needed to make installation considerably easier and more reliable.

Housing manufacturers also provide their own unique perspective. For example, they prefer attachment components that are invisible from the outside, to harmonize with modern residential designs and convey the feeling that the gutter is an integral part of the roof. The Ritto Factory's technology is strengthened and enhanced through close contact with diverse customers.


(Left) Standard gutters must be cut at the proper angle to match the slope of the roof. Specialized expertise is required to cut the material precisely as specified in the blueprints.
(Right) Components are welded together using bar resin. Yasuhiro Tateishi notes, "We are working to make the techniques visible and thereby easier to transmit. This will ensure a smooth transition when experienced personnel retire."

Never stop moving
Our strength lies in our continuous cycle of innovation and feedback

Ikuo Takamatsu
Director, Exterior Products & Systems Business Unit, Housing Systems Business Division


The ES Company's Iron rain gutters offer the advantage of a unique steel and PVC structure. The product's uniqueness was reflected in the challenging development process. We had no precedent to go on, and of course we had to create nearly everything from scratch, including new production facilities, new material formulations, mold designs, and evaluation and testing procedures. Our continuous cycle of incremental improvement, evaluation and feedback, and further improvement, and the accumulated benefits we derive from this cycle, are the principal strength of the Ritto Factory.

Naturally we also incorporate external technical innovations, but we believe it is important to maintain and strive to enhance our core technologies. Every day, we use our senses during the manufacturing process, including sight, touch, and smell, to make the continuous small adjustments required. The process is that subtle. The factory staff and I do not think of the manufacturing process as perfected; we aim for continuous improvement. We also have building contractors who actually install the product visit the factory frequently. This gives us an opportunity to receive their input, have them check the quality of the product, and ensure that they are satisfied. Their expectations are often tough to meet, but by doing so, we bolster their trust in the product. We believe this trust is the basis for our leading market position.

At the same time, the Exterior Products & Systems BU will seek growth by applying its core technologies to new businesses, including technologies developed at our Ritto as well as Maibara Factories, with the goal of propagating our strengths and applying our extrusion manufacturing technologies, including technologies for manufacturing resin-clad metal products, to the manufacture of such products as LED guide lights, or, applying our metal-forming technologies to the manufacture of functional roofing systems.

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