Major Appliance Teardowns:

Transcription

1 Since 1947 Major Appliance Teardowns: A Review of Electrical Best Paper 2005 International Appliance Technical Conference Interconnection Results By Brian J. Stumm, Director of Engineering Old Values, New Ideas W W W. E T C O. C O M

2 Old Values, New Ideas ABSTRACT As a manufacturer of connectors, the use of product teardowns is useful in reviewing one s own product as well as the industry into which it fits. It is important in keeping appraised of the changes in industry and the trends in technology that directly affect one s business. These teardowns, when performed for proactive reasons, are primarily used to check the performance of a given product or its component parts. When the results of these teardowns are recorded and reviewed together, however, they can also reveal a trend that may be worthy of attention. This paper will discuss a series of teardowns and what they revealed. It will further discuss the potential of teardowns as a valuable tool in the pursuit of quality. W W W. E T C O. C O M

3 BACKGROUND The major appliances that are found in most homes today have a common design aspect; they utilize, to varying extents, discreet components that are connected together by standard electrical connectors terminated onto wiring. The wiring used ranges from individual connections to complex wire harnesses (including modern RAST-style harness designs). These harnesses are a key and vital component to the reliability and function of the major appliance in which they are installed; they can also be a source for potential problems, as evidenced in the results of past product teardowns. In a complete product teardown all aspects of the unit are observed, documented, and analyzed from a quality and engineering perspective. The process used in the implementation of a product teardown is a matter of personal preference, as long as the methods used are well documented and consistent. The data collected must be collected in sufficient detail, and care must be taken to insure the integrity of any remaining items to be studied. The process that is selected for a given teardown is typically dictated by the objective of that teardown. Different types of manufacturers will focus their efforts differently in order to benefit their own business. They will use the teardown process to observe their product in the end-state, as well as to gain information with regard to the impact that their product/process has (both up and down stream) on that product. A connector manufacturer, for example, would see how their connectors were terminated and where their product was used throughout the appliance. They would also observe how the wire harness was constructed, installed, and mated to the components within the appliance. These observations could then be used by the connector manufacturer to determine possible areas for improvement in the design and/or manufacture of their own product; in addition, the teardown may show possible opportunity for improvement in areas beyond what they supply. The way in which the connector manufacturer s product is being used within the appliance, for example, may not be optimal. Such information can then be shared and discussed with the appliance manufacturer to improve the overall product design, function, quality, and reliability. Product teardowns can be a powerful tool that brings different perspectives to the review of a given product, and provides a springboard for discussion between manufacturer and supplier that can head off potential problems, or create innovation that will improve a product. 3

4 Figure 1: Teardown Preparation Figure 2: 1st Layer Removed Figure 3: Terminal Numbering PROCEDURE This paper will discuss several examples taken from actual teardowns that were performed on major appliances. First, a brief description of the process used in the teardowns should be given. Each step of the teardown was fully documented in order to preserve the exact condition of the given appliance and its components for future reference and verification. Documentation took the form of digital photography and detailed written notes. Figure 1 shows a typical appliance before a teardown is started, exactly as it would look prior to final installation at a consumer s home. The teardown is started with the removal of the outer sheet metal and door(s). As with each step of a teardown, anything unusual is recorded as it is observed. Once the wiring is exposed, each of the individual electrical connections are identified and marked. Starting in one location each electrical connector, regardless of whether it is connected to a switch, heating element, or sensor is carefully photographed to capture its mated, undisturbed state. Once photographed, each side of the connection is numbered and recorded. Figures 2 and 3 show how each layer is documented before being disturbed for numbering and identification. Each recorded electrical connection is identified by its number on the wire and mating component. The recorded information includes the connector type (ring, spade, disconnect, etc ) the size of the connector (.187,.250, #8, etc ) its material composition and plating, the wire size to which it is terminated, an information on the termination itself (height, width, and general condition, etc ). Once all of the visible electrical connections have been identified and recorded they are then disconnected and carefully moved to allow for further disassembly of the appliance. Once the teardown is complete the documented data is organized for further study. 4

5 Figure 4: Sheet Metal Connection Figure 5: Partially Installed Terminal & Tight Wire Figure 6: Crushed Motor Wire TEARDOWN RESULTS Reviewing all of the results from the various teardowns that have been completed, we can summarize the problems into four general categories: Assembly, Design, Manufacturing and Termination. We will present examples from each of these categories and will discuss the termination issues in greater detail. Assembly The assembly problems that were observed during teardown appear to have been created during the final stages of assembly of the appliance. The following are examples of the various problems observed that could be attributed to assembly. On one teardown when we opened the control panel we came across a disconnect lying against the metal frame. After some investigation it was determined that the disconnect was supposed to be connected to a tab that was made out of sheet metal. Figure 4 shows the disconnect as it was originally installed. During another teardown a disconnect was found partially installed onto the tab of a cooking element; Figure 5 is the image of the disconnect as it was originally discovered. The last example for assembly attributed problems is a motor wire connection that was crushed during final assembly; Figure 6 shows that wire. Figure 7: Non-Standard Tab 5

6 Figure 8: Double Wire Crimp Figure 9: Double Wire Crimps Figure 10: Insulation Strands in Crimp Design It is more difficult to definitively determine the cause of problems related to design issues. This is primarily due to the fact that the original design intents and the product prints are typically not available to us at the time of the teardown. The sheet metal tab, shown in Figure 4, could be assigned to either assembly or design categories. Based on the fact that the sheet metal tab was not made to the disconnect standard, it is most likely a design issue. Two possible options to correct this problem would have been to design the sheet metal tab to the disconnect standard or a different terminal could have been chosen that would be a more appropriate connector for a sheet metal edge. Another potential design issue was a connector that had its attached wire length made too short; Figure 5 shows this straight connector with the short length of wire between the terminals, resulting in the red wire being bent at a 90º angle to the mating end (In addition to connector selection and harness design, component connections are another design related issue.) Figure 7 shows a component that has nonstandard integrated tabs. The tabs are non-standard in that they are required to have a constant width down to their end, or to an optional shoulder, but do not. Manufacturing Manufacturing issues can be found in many aspects of the appliance, but the majority found during these teardowns can be attributed to the process of creating the harnesses; one reason for this is that appliances, in addition to individual components, have a large number of harnesses. In Figures 8 & 9 a double wire termination for several flag-style connectors is shown. This configuration is common to many wire harnesses; in these figures we can see how the wire insulation was stripped back to two different lengths. This is of serious concern because terminals are not typically designed to accommodate unprotected wire strands within the insulation crimp of a double wire termination. The benefits of having an insula- 6

7 Figure 11: Cross Sectional View Figure 12: Close Up View of Tear tion crimp is lost when this phenomena occurs. In Figure 5 we saw a tight wire situation that we attributed to a design problem; it could also have been a manufacturing related issue. Termination For the purposes of this work, termination issues will be considered as those that are a group of problems associated with the wire and insulation crimping; as well as the tooling used to create the crimps. Terminations must be inspected in order to identify problems, and to ensure that they pass the associated manufacturer s requirements and any UL requirements. Some of the problems can easily be seen with a casual visual inspection; other termination problems require cross sections and more detailed reviews. Problems with the wire terminations can potentially lead to abnormal heating of the wire crimp and potential failure of the terminal & appliance. In Figure 10 we can see a wire termination with the high temperature glass insulation braid caught in the wire crimp; aesthetic considerations aside, this situation can also be indicative of a wire stripper problem. A more detailed review of this same termination identified more serious problems; in Figures 11 & 12 we can see a cross section and a closeup view of the termination. In the close-up view we can see a tear in the terminal caused during the termination process. The open gap in the cross section of the crimp shown is not preferred, and is indicative of an applicator problem with either the setting or the tooling itself. The variations in the crimp, and what is preferred, will be discussed in the next section. Figure 13 shows ring terminals that have two issues; the first issue is the bellmouth feature on the wrong end of the terminal and the second issue is an improperly adjusted cut-off of the terminal. The bellmouth feature is typically created toward the wire end to alleviate potential strand cutting. An improperly adjusted cut-off can damage the terminals. 7

8 Figure 13: Ring with Bellmouth Issues Figure 14: Insulation Crimp Issue Figure 15: Loose Insulation Crimp Another common termination problem is related to the insulation crimp; Figures 14, 15 & 16 are examples of insulation crimp problems. Improperly adjusted terminations that are too tight can allow the insulation ear ends to penetrate the insulation and damage the wire strands. In the other extreme, shown in Figure 15, a termination that is adjusted to be loose can allow the wire to move around which can damage the wire and lead to a failure of the crimp. One possible reason for these tooling problems is the use of tooling other than that specifically designed by the connector manufacturer for the given terminal and wire combination. Not using the connector manufacturer s specifically designed tooling could lead to problems with the crimp quality as well as the tooling itself. On a side note, UL Listing is granted to a terminal with the wire range and applicator tooling specified; using nonspecified applicator tooling with a UL recognized terminal nullifies the Listing. Figure 16: Damaged Insulation Crimp 8

9 Figure 17: Preferred Cross Section Figure 18: Worn Anvil Cross Section CRIMP QUALITY As discussed previously, there have been a wide variety of problems associated with the termination process of the electrical connectors onto the harness wires. Problems have been identified in both the wire and insulation crimps. A worn anvil or rolling tool can.appear to create a good termination when viewed externally, but inside the crimp the wire strands may not be properly deformed. Additionally, the ear may be fractured or damaged, allowing for potential reliability problems during the life of the product. Figure 17 shows a typical cross section of a crimped wire termination that has a proper anvil and rolling tool; the section shows minimal side extrusions, tight meeting between the edges along the top, and good deformation of the wire strands into a honeycomb pattern. All of these features should be evident in a wire termination using an open barrel design. Poor quality tooling can lead to chipping or premature wear on the tooling. If the anvil has been damaged, the cross section of the termination can look similar to Figure 18 which shows extra extrusions along the sides. If the roll tool is damaged or worn, the resulting cross sections can appear similar to Figure 19. When both tools are not properly maintained the resulting crimp will probably look visually poor and the cross section would reveal something like what is shown in Figure 20. Another popular type of crimped termination used extensively in many of the wire harnesses reviewed was a style of pre-insulated closed barrel design as shown in Figure 21. The closed barrel design differs from the open barrel design in that the ear section to be crimped is embedded within a plastic enclosure; also, the insulation and metal are crushed simultaneously to generate the crimp shown in the cross section in Figure 22. Figure 22 shows a common cross sectional result obtained from this type of termination. Figure 19: Worn Roll Toll Cross Section Figure 20: Worn Anvil & Roll Toll Cross Section Figure 21: Closed Barrel Terminal Figure 22: Closed Barrel Cross Section 9

10 CONCLUSIONS This work has highlighted a number of problems identified in a fairly small group of products. The teardowns performed were detailed and looked at every connection and termination; given the small number of products involved in the teardowns, the number of issues revealed by them is somewhat disconcerting. Perhaps more disconcerting is the fact that most of these appliances were taken apart right after being uncrated, having had no usage or movement to explain the observations. Many times the electrical connectors and wire harnesses are the last items to be designed for an appliance. The importance of choosing the proper terminal is often minimized due to the relative cost of terminals when compared to the other components; this is unfortunate since it is these components that contribute to many field problems. One possible way to minimize these problems is for the appliance, harness and electrical connector manufacturers to work together to ensure that proper design decisions are made from the beginning. Working together to eliminate potential failure modes is a key to improving quality. By combining the strengths of each manufacturer the end product can be made more reliable and have better quality. Improved quality can also have a positive impact on the bottom line. As shown in this work, the teardown process, while time consuming, is a valuable tool that can be used to generate feedback on a wide variety of items within an appliance. The feedback can help improve the overall quality and reliability of the appliance and reduce the potential for field failures. Recently, there has been a higher level of attention being paid to the electrical terminal selection and harness manufacturing by some of the major appliance manufacturers. Time will show if this practice continues, and reveal the benefits of pursuing these quality objectives. 10

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12 Since 1947 Old Values, New Ideas By Brian J. Stumm, Director of Engineering ETCO, Incorporated Engineered Products 25 Bellows Street Warwick, RI USA W W W. E T C O. C O M