Abstract:
A method is provided for meeting anticipated parts demands, by controlling substitute part inventory coverage based on percentage requirements. The method is characterized by substitution sets determined as a ratio of the current PN level. In one embodiment, current parts of specified type and substitute parts functionally equivalent to the current parts are respectively kept in inventory. This embodiment includes specifying a maximum percentage of demand for the current parts that is allowed to be filled using substitute parts. The number of additional parts needed to cover a demand is determined, when the demand specifies a total number of current parts exceeding the number thereof in inventory. A number of substitute parts is then assigned from inventory to cover the demand, up to a number that does not exceed the specified maximum percentage of the specified total number. When the number of additional parts needed is greater than the number of assigned substitute parts, a number of current parts equal to the difference therebetween is then purchased.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention disclosed and claimed herein generally pertains to a method for analyzing demand coverage, in view of forecast or anticipated demand for parts of specified types. More particularly, the invention pertains to a method of the above type wherein the inventory contains both current parts of the specified type, and substitute parts that are functionally equivalent to the current parts. Even more particularly, the invention pertains to a method of the above type for optimizing substitute part usage, maximizing the potential for on-hand inventory to meet serviceability requirements, and minimizing the potential for inventory carrying costs. 
         [0003]    2. Description of the Related Art 
         [0004]    It is frequently necessary to introduce a modified form of a manufactured part that complies with certain regulations, in order to use the part on certain products or to ship it into certain countries or jurisdictions. For example, a country may decide to demand compliance with ROHS (Restriction of Hazardous Substances) standards, so that a certain material can no longer be used in a particular type of part. Accordingly, the part manufacturer will design a modified part that is functionally equivalent to the previous parts, but no longer uses the material. Typically, the new part will become the “current” part of that particular part type. 
         [0005]    When the new current part is introduced, it is likely that there will still be a number of older parts, and possibly a very large number, remaining in inventory. Since these parts and the new current parts are functionally equivalent to one another, the older parts can still be readily substituted for the new current parts, for many applications. Thus, if some countries are not concerned about the ROHS material that led to the new current parts, the older parts can continue to be used for products sent to those countries. At least some of the time it is beneficial to substitute older parts for the current parts, when this is permitted. As a result, it has become common, when analyzing future or upcoming demand for a particular part, to consider the portion of the demand that must be covered using current parts, and the portion that is allowed to be covered using older parts. For example, it may be determined, based on experience and other factors, that 60% of the anticipated demand for a particular part type will need current parts, whereas the older parts can be used as substitutes to meet 40% of the demand. 
         [0006]    Present planning systems such as the Manufacturing Resource Planning (MRP) have no capability for automatically ensuring that percentages of the above type will be considered, when planning demand coverage that apportions between current new parts and equivalent older substitute parts. As a result, significant manual planning effort may be required, in order to ensure that current part percentage requirements are complied with. This deficiency may also result in ineffective application in the use of substitute parts. 
         [0007]    One present solution to this problem is to supplement MRP recommendations with significant manual planning. This approach uses existing MRP recommendations and substitution logic, and then augments this with miscellaneous demands to procure specific required parts. However, this solution tends to result in excess inventory and scrap, as well as significant manual effort to independently manage the miscellaneous demands on a part-by-part basis. 
         [0008]    A further solution is to manually override the MRP results, in order to adjust purchasing recommendations on a part-by-part basis. This is very manually intensive, and would be subject to change based on the demand and inventory levels, both in manufacturing and at the vendor, for every MRP run. 
         [0009]    Another approach is to release a new Bill of Material for a new current part, and manage it independently from the equivalent older parts that can be substituted for the new part. This, however, tends to drive the purchasing of incorrect parts in the substitute structure, and also drives significant inventory increases. 
         [0010]    Yet another solution would be to simply break in a new current part, and allow for no substitutions using older parts. This, however, would lead to increased inventory and/or scrap costs to the product. 
         [0011]    There is currently no known automated process that allows a variable percentage of parts substitution while minimizing needed inventory. The labor to manage such situations manually is excessive, and can significantly impact inventory by driving costs and serviceability issues. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    The invention generally provides a new process for meeting anticipated parts demands, by implementing a variable percentage and nested based schema for controlling substitute part inventory coverage. Key elements of the process include a new model containing variable substitution sets, and a method of recursively evaluating the new variable substitution model and enforcing variable (percentage) netting of demand to on-hand inventory. Also, a new netting logic is applied to alter and/or determine the correct parts and quantity that need to be purchased. The new model is characterized by substitution sets determined as a ratio of the current part number (PN) level, which is the primary purchased part level. The model is able to group substitutions into multiple sets as well as on a PN-by-PN basis, in order to allow like grouping and application. Also, the model can sequence the evaluation order of the substitution groups, and can nest such groups. One embodiment of the invention is directed to a method for planning parts coverage, wherein current parts of the specified type and substitute parts that are functionally equivalent to the current parts are respectively kept in inventory. The method includes specifying a maximum percentage of demand for the current parts that is allowed to be filled using substitute parts, wherein the percentage can be less than 100%. The number of additional parts that are needed to cover a given anticipated demand is then determined, when the given demand specifies a total number of current parts that exceeds the number of current parts then in inventory. The method further includes assigning a number of substitute parts from inventory to cover the given demand, up to a number that does not exceed the specified maximum percentage of the specified total number. When the number of additional parts needed is greater than the number of assigned substitute parts, a number of current parts to be acquired is determined that is equal to the difference between the respective additional and assigned numbers of parts. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0014]      FIG. 1  shows an informational chart for use in illustrating an embodiment of the invention. 
           [0015]      FIGS. 2A and 2B  are schematic diagrams illustrating concepts of the prior art and the invention, respectively. 
           [0016]      FIG. 3  is a flow chart illustrating an embodiment of the invention. 
           [0017]      FIG. 4  is a flow chart illustrating a further embodiment of the invention. 
           [0018]      FIG. 5  is a block diagram showing a data processing system for use in implementing embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    In planning the coverage of a forecast demand for a particular part, it is conventional industry practice to assume that substitute parts, as described above, can be used to supply up to 100% of the needed current parts. Such coverage planning thus disregards the requirement that some percentage of the total parts demand must be limited to current parts only. Accordingly, embodiments of the invention provide a demand coverage planning method that is based on or takes into account the ratios or percentages that must be apportioned between current and substitute parts, respectively, in view of percentage requirements of the type described above. 
         [0020]    Referring to  FIG. 1 , there is shown a chart that uses an example to illustrate significant benefits of the method of the invention. Rows (A)-(C) respectively indicate a part forecast demand of  300 , and further indicate that there are 10 current parts and  350  substitute parts in inventory. For simplicity, it is assumed that there is only a single type of part available as a substitute for the current part. It is further assumed that for the particular part type, 20% of the demand coverage mandates current parts, and 80% of the coverage is permitted to be substitute parts. 
         [0021]      FIG. 1  further shows two columns, one labeled Industry and the other labeled Variable. Rows (D)-(I) of the Industry column disclose results of following conventional industry practice, whereas rows (D)-(I) of the Variable column indicate the results provided by an embodiment of the invention. 
         [0022]    As discussed above, present conventional practice allows 100% of a demand for current parts to be satisfied with available substitute parts. Since there are 350 substitute parts in inventory, the entire demand of 300 parts could be covered with substitute parts under conventional practice. With 10 current parts in inventory, the remaining demand requirement could be satisfied with 290 of the substitute parts from inventory. It would therefore not be necessary to purchase any additional parts, as shown by row (H). Only current parts, of course, can be purchased or otherwise acquired, whenever there is a need to obtain parts that are not available in inventory. Substitute parts are generally no longer being produced. 
         [0023]    Referring further to  FIG. 1 , rows (D)-(H) of the Variable column show that only 80% of the 300 part demand, or  240 , can be substitute parts. Thus, with the 10 current parts, only a total of 250 current and substitute parts are available from inventory, to cover the 300 part demand. It is therefore necessary to purchase  50  additional current parts. 
         [0024]    Row (I) of the chart in  FIG. 1  emphasizes the significant difference between conventional industry practice and the method of the invention. The industry approach overuses substitute parts, since it does not account for the mandatory current part percentage requirement. As a result, it will be necessary to make plans at some later time to acquire 50 current parts, in order to avoid impacting product shipment capability. Typically, such acquisition will require substantial and inefficient manual effort. In contrast, the method of the invention automatically accounts for the mandatory current part percentage. Accordingly, row (I) of the chart in  FIG. 1  shows that it will not be necessary to purchase additional current parts at some time in the future. 
         [0025]    To illustrate a more complicated example,  FIGS. 2A and 2B  show a current part set  202  that has a current Part A of part number (PN), resulting from an engineering change (EC) to a part of particular type.  FIGS. 2A and 2B  further show that a number of different parts B-E, included in substitute part sets  204 - 210 , respectively, can be used as substitute parts for current part A. Parts E of substitute part set  210  may be the oldest of the particular part type still in inventory. Alternatively, part E may have the lowest ranking, for some other reason, in a sequential order in which each of the parts B-E is ranked. Parts C and D of sets  206  and  208  were introduced after the parts E, and parts B of set  204  were introduced after parts C and D. All the parts of substitute part sets  204 - 210  are functionally equivalent to current part A of part set  202 , and can thus be used as substitute parts therefor, whenever substitute parts are allowed. Moreover, each of the substitute part sets may include several part variations. For example, substitute part set  208  includes part variations D 1 , D 2 , and D 3 . 
         [0026]    Even though there are differences between parts that can be substituted for current part A, the present practice of industry is to consider all substitute parts as being the same, and to disregard any differences therebetween in selecting substitute parts as replacements for the current part. This industry practice is illustrated by  FIG. 2A . However, in an embodiment of the invention depicted in  FIG. 2B , parts of different substitute part sets are treated in a hierarchical or ranked sequential manner. That is, it is recognized that whenever a new part was introduced to become the current part, there may have been a percentage applied to the older part that was being replaced. For example, when part D of substitute part set  208  became the current part, there could have been a requirement that up to 50% of a demand for the then current part D could be covered by substituting parts E, from substitute part set  210 . 
         [0027]    Referring further to  FIG. 2B , there are shown substitute part sets  204 - 210  arranged in a nested configuration to illustrate a procedure comprising a series of sequences. Each sequence is based on a demand percentage requirement associated with a substitute part that may have previously been the current part, or is a substitute part for some other reason. To further illustrate the procedure, it is assumed that there is a demand of 500 parts for current part A of part set  202 . 
         [0028]    During a processing Sequence 1 of the procedure,  FIG. 2B  shows that up to 70% of the 500 part demand, or 350 parts, can be any combination of parts B 1  or B 2  from substitute part set  204 . However, because of the equivalency between parts B and C, up to 30% of the coverage for parts B can be parts C 1  from substitute part set  206 . Accordingly, during Sequence 2 it is determined that in covering the 500 part demand for current part A, a maximum of 30% of 70% of 500, or 105 parts, can be parts C 1  from part set  206 . Similarly, up to 20% of the coverage for parts B can be parts D 1 , D 2  or D 3  from substitute part set  208 . Sequence 3 therefore determines that coverage from substitute part set  208  for the current part demand can be at most 20% of 70% of 500, or 70 parts, wherein the 70 parts may be any combination of D 1 , D 2  and D 3 . Finally, Sequence 4 determines that coverage of D parts provided by E 3  parts of substitute part set  210  can at most be 50%. Thus, E parts can provide up to 50% of 20% of 70% of the 500 part demand, or 35 parts. It is thus seen that the procedure described in connection with  FIG. 2B  determines the maximum number of parts that are allowed to come from each of the substitute part sets  204 - 210 , for a given demand for current parts A. 
         [0029]    Referring to  FIG. 3 , there is shown a flow chart pertaining to an overall method that uses the above procedure of  FIG. 2B . At step  302  of  FIG. 3 , a forecast demand is provided for a number of parts having the PN of current part A, such as the 500 part demand described above. At step  304 , the number of parts specified by the demand is compared with information from inventory  306 , wherein such information indicates the total number of current parts A then in inventory. If the number of such parts is at least equal to the demand number, the demand is covered, and the method shown by  FIG. 3  comes to an end. However, if the number of current parts in inventory is not sufficient to cover the demand, the method of  FIG. 3  moves to step  308 . 
         [0030]    At step  308  the procedure of  FIG. 2B  is carried out, to provide the maximum number of parts that are allowed to come from respective substitute part sets  204 - 210  for the particular demand. The hierarchically ranked part sets are collectively represented as  310  in  FIG. 3 . After determining the maximum number of each substitute part (B)-(E) that can be used to satisfy the particular demand, information is obtained from the inventory to determine the actual numbers of substitute parts (B)-(E) that are respectively contained therein. From this information and the maximum numbers for respective substitute parts, a suitably programmed processor can readily determine whether the total available substitute parts (B)-(E) are sufficient to cover any difference between the forecast demand for current parts A, and the number of current parts A that are available in the inventory  306 . 
         [0031]    The sufficiency of the substitute parts to cover demand is considered at step  312 . If the sum of current parts and substitute parts in inventory can cover the demand, subject to respective mandatory percentage requirements, the method of  FIG. 3  comes to an end. Otherwise, an additional number of current parts to cover demand is purchased at step  314 . 
         [0032]    Referring to  FIG. 4F  there is shown an embodiment of the invention directed to a method for analyzing and planning coverage of a parts forecast demand  402 , wherein demand  402  pertains to a multiplicity of part types having different PNs. The different part types of demand  402  are considered sequentially, by PN. Thus, at step  404  information for a particular current part PN, including the needed quantity (QTY) of such part, is pulled from the demand  402 . 
         [0033]    At step  406 , information is obtained from parts inventory  408  indicating the number of particular current parts then contained in inventory. Such information is used to determine whether there are sufficient particular parts in inventory to satisfy the quantity thereof required by the demand. If the demand is satisfied, the method returns to step  404 , and pulls down demand information for the next current PN, that follows the particular part in demand  402 . 
         [0034]    If the demand for the particular current part is not satisfied, step  410  determines whether or not there are any substitute part sets that are defined for the particular current part. If there are none, step  412  is carried out, to arrange for purchase of sufficient particular current parts to cover the unsatisfied demand. Also, the method returns to step  404 , and pulls down demand information for the next current PN. 
         [0035]    If it is determined at step  410  that one or more substitute part sets are defined for the particular current part, the method of  FIG. 4  proceeds to step  414 . This step reads or acquires information identifying each part in the first defined substitute part set, including parameters pertaining thereto, from a substitution model  416 . For example, if the first set was substitute part set  204 , described above in connection with  FIG. 2B , the acquired information would indicate that any combination of parts B 1  and B 2  could be substituted, for up to 70% of the total current part demand. At step  418  such information would be analyzed, together with the numbers of parts B 1  and B 2  that were then in inventory, as provided by inventory  408 . The analysis would indicate whether or not the number of parts B 1  and B 2  in inventory would satisfy the uncovered demand, subject to the current part percentage requirements as described above in connection with  FIG. 2B  and  FIG. 3 . 
         [0036]    In accordance with step  420 , if it is determined that parts of the first substitute part set are able to meet the uncovered demand, the method returns to step  404 . Demand information is then pulled down for the next following current PN, as described above. However, if it is determined at step  420  that current part demand is still uncovered, the method of  FIG. 4  proceeds to step  422 , and reads information pertaining to the substitute part set that next follows the first substitute part set. This information is also supplied by model  416 . Thus, if the next set was substitute part set  206 , as described above, the acquired information would indicate that part C could be substituted for up to 30% of total part demand that could be supplied from the immediately preceding substitute part set. 
         [0037]    At step  424 , information for the next following substitute part set is routed back to step  418 , and analyzed in view of the percentage requirements and availability of parts in inventory for such part set. Again at step  420 , if it is determined that parts of the substitution part set are able to meet the uncovered demand, the method returns to step  404 . Otherwise, information for the next substitute part set is read for model  416  at step  422 . 
         [0038]    It will be seen from  FIG. 4  that steps  418 - 424  collectively define a looped process that sequentially considers each of the substitute part sets associated with a particular current part. This process continues until (1) the demand is fully covered by the substitute parts, whereupon the method returns to step  404 , or (2) the demand is still uncovered, and it is determined at step  424  that there are no more substitute part sets for the particular current part. When this occurs, plans are made at step  412  to purchase current parts to meet the uncovered demand. Also, the next current part is pulled at step  404 . 
         [0039]    Referring to  FIG. 5 , there is shown a block diagram of a generalized data processing system  500  which may be used in implementing embodiments of the present invention, such as by carrying out methods and procedures as described in connection with  FIGS. 2B ,  3  and  4 . Data processing system  500  exemplifies a computer in which code or instructions for implementing the processes of the present invention may be located. Data processing system  500  usefully employs a peripheral component interconnect (PCI) local bus architecture.  FIG. 5  shows a processor  502  and main memory  504  connected to a PCI local bus  506  through a Host/PCI bridge  508 . PCI bridge  508  also may include an integrated memory controller and cache memory for processor  502 . 
         [0040]    Referring further to  FIG. 5 , there is shown a local area network (LAN) adapter  512 , a small computer system interface (SCSI) host bus adapter  510 , and an expansion bus interface  514  respectively connected to PCI local bus  506  by direct component connection. Audio adapter  516 , a graphics adapter  518 , and audio/video adapter  522  are connected to PCI local bus  506  by means of add-in boards inserted into expansion slots. One or more I/O adapters  524  may also be inserted into PCI bus  506  as plug-in devices. SCSI host bus adapter  510  provides a connection for hard disk drive  520 , and also for CD-ROM drive  526 . 
         [0041]    An operating system runs on processor  502  and is used to coordinate and provide control of various components within data processing system  500  shown in  FIG. 5 . The operating system may be a commercially available operating system. Instructions for the operating system and for applications or programs are located on storage devices, such as hard disk drive  520 , and may be loaded into main memory  504  for execution by processor  502 . 
         [0042]    The invention can take the form of an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc. 
         [0043]    Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any tangible apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. 
         [0044]    The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD. 
         [0045]    A data processing system suitable for storing and/or executing program code will include at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution. 
         [0046]    Input/output or I/O devices (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. 
         [0047]    Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters. 
         [0048]    The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.