Abstract:
Manufacturing a reflex insert tool includes the steps of assembling optical pins in a bundle, and inserting same into a mold clamp assembly. The mold clamp assembly is placed into a vat, wherein an electroformed skin is developed which in turn is removed from the bath. A cold spraying technique is utilized applying a build up of material on the back surface of the electroformed skin. The back surface of the reflex insert is then machined and through wire EDM, configured to a desired shape and thereafter ready for insertion into a tool for injection molding plastic parts therefrom.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/796,002, filed 28 Apr. 2006. The disclosure of the above application is incorporated herein by reference. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a method of making a reflex insert tool which in turn is utilized to make an optical plastic part, such as a head lamp, or a tail lamp. 
       BACKGROUND AND SUMMARY OF THE INVENTION 
       [0003]    Automobiles routinely have optical components, such as a rear tail light lens, that are manufactured during an injection molding process. Often these plastic parts have reflective elements or prisms built into their surface, in order to aid in the reflectivity of the lens. During the injection molding process, these prisms become part of the tool&#39;s surface which results in the negative of the prisms being projected onto an interior surface of the completed plastic part. The present invention focuses on a method of making a reflex insert tool that is placed in the mold of an injection molding machine in order to make a plastic optical part. 
         [0004]    In the past, reflex insert tools were made by carefully organizing a group of highly machined individual reflex pins. A reflex pin is generally hexagonal or rectangular shaped having a precisely machined prism on one end thereof. The machined reflex pins are arranged in a clamp or a mandrel which in turn is inserted into an electroformed tank for approximately two weeks in order to produce a reflex skin that is a cast off of the prisms of the pins. This step creates what is generally known as an electroformed reflex skin. However, this skin is of insufficient thickness, lacks rigidity, and therefore is unreliable to be used as an insert tool. 
         [0005]    Thus, the next step has been to build up the back surface of the reflex skin. The thickness of the backing preferably is approximately 0.50 of an inch thick. The backing adds rigidity to the reflex insert tool so as to stabilize the insert tool when it is mounted into a mold. Thus, in order to build up the back surface of the reflex skin so as to have sufficient thickness, large electroformed tanks are utilized that are filled with an electroforming bath consisting of nickel, cobalt, etc. This bath produces lower densities than the skin bath and is easier to machine. This building up process takes about 6-7 weeks as the electroforming process is a very gradual process. 
         [0006]    Thus, the problem with utilizing the traditional electroforming process and their associated tanks of metal, is that the electroforming process is time consuming and labor intensive. As such, the traditional process of making a reflex insert tool takes up to twelve weeks. Moreover, the traditional electroforming process is extremely capital intensive as it requires large tanks of liquid electroformable metal that can be a caustic substance. These huge tanks consume large amounts of energy, require several people to operate and to manage, and the backing portion of the electroforming process takes six to seven weeks to complete. It would be desirable to eliminate or at least reduce this entire process. 
         [0007]    Accordingly, it would be desirable to provide an improved method of manufacturing a reflex insert tool which is less capital intensive, requires less manpower and plating time, less expensive machinery, substantially shortens the cycle time for making a reflex tool all the while maintaining photometric performance. It would also be preferred to utilize a cold spray technology during the backing process so as to reduce heat on the reflex skin so as to minimize heat damage and warp age. 
         [0008]    According to one aspect of the present invention, it would be desirable to speed up the process for manufacturing a reflex insert tool by entirely eliminating the electroplating process that was traditionally used to build up the backing on the insert skin. 
         [0009]    According to another aspect of the present invention, a method of manufacturing a reflex insert tool comprises the steps of machining optical pins having a predetermined prism configuration. Said pins are then arranged in a bundle. 
         [0010]    A clamp is provided which is operable to receive the arranged bundle of pins, and thus securely clamping the pins together. The loaded clamp is then placed into the electroformed tank to create an electroformed skin of about 0.140 of an inch thick. The clamp, with its associated electroformed skin, is then removed from the electroformed tank where the electroformed skin is then separated from the clamp. 
         [0011]    A cold spray low pressure technique is next utilized for applying lower density backing material to the underside of the electroformed skin. The cold spray process continues until a predetermined thickness, or build up, is generated on the underside of the reflex insert skin. After the backing material has cured, the backing material is machined to a predetermined thickness and configuration. Thereafter, the profile of the machined reflex insert can be cut by a wire EDM or CNC milling process, and the insert is then ready for insertion into a tool for injection molding an optical part. 
         [0012]    It will be appreciated that this process results in a reflex insert tool that can be used for making an assortment of optical parts. This novel process takes substantially less time than does conventional methods that were used in the past to make optical reflex insert tools. This novel process further utilizes less natural resources, less capital intensive machinery, and is safer to manufacture. This novel process increases the number of reflex inserts that can be manufactured while maximizing the use of existing electroforming tanks, and other resources. For example, because the electroforming tanks are not used for the electroforming the back surface of the skin, the tanks are now freed up for making new skins that can be in turn used to make more reflex inserts. The electroforming tanks are only needed for about two weeks in total for each reflex insert. 
         [0013]    Further areas of applicability of the present invention will become apparent from the detailed description provided herein. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It will be appreciated that the present invention can be utilized wherever it is desirable to make a tool for an optical part. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of an optical pin that is used for a reflex insert; 
           [0015]      FIG. 2  is a perspective view of a cluster of optical pins; 
           [0016]      FIG. 3  is a perspective view of the bundle of optical pins organized together and positioned within a clamp, with a portion of the clamp broken away; 
           [0017]      FIG. 4  is a side elevational view of the clamp filled with pins positioned within a tank of electroforming material; 
           [0018]      FIG. 5  is a side elevational view of the newly created electroformed skin once it is separated from the clamp; 
           [0019]      FIG. 6  is a schematic illustration of the cold spray process of applying backing material to the back side of the electroformed reflex insert skin; 
           [0020]      FIG. 7  is a schematic diagram illustrating machining the back side of the electroformed skin; 
           [0021]      FIG. 8  is a schematic diagram illustrating a wire EDM processes cutting out a preferred profile in the machined electroformed skin; 
           [0022]      FIG. 9  is a side view of the finished reflex insert tool in its final form ready to be positioned into a mold; 
           [0023]      FIG. 10  is a side view illustrating a finished molded lens and the reflex insert tool after having been injection molded using the reflex insert depicted in  FIG. 9 ; and 
           [0024]      FIG. 11  is a flow chart illustrating the steps for this method of making an optical reflex insert tool. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    With respect to  FIG. 1 , an optical pin  10  has an elongated steel shaft with a precisely machined prism  12  on one end thereof. The prism  12  is specially configured to take on an optical surface configuration which in turn, is imparted onto an electroformed skin. 
         [0026]      FIG. 2  illustrates a bundle  14  of optical pins  10  that are arranged together in a predetermined configuration. The configuration illustrated is exemplary in nature and it will be appreciated that the bundles can be arranged in a variety of profiles as desired. The bundle of pins  14  are arranged so as to have the respective prisms adjacent to one another. 
         [0027]      FIG. 3  illustrates the bundle of pins  14  secured within a two-piece clamp  16 . The clamp has a first half  18  and second half  20 . The clamp  16  is shown with a cut-away section with the bundle  14  of pins shown positioned within an opening  22  located in the center of the clamp  16 . The clamp  16  has a back surface  24  and a front surface  26 . The clamp  16  is made preferably of stainless steel. Collectively, the clamp  16  and the bundle of reflex pins  14  create a clamped bundle of pins  28  that are ready for insertion into an electroforming tank. In this clamped state, the prisms of the reflex pins create a protruding surface  30  comprising an optical prism surface  32  collectively extending above the front surface  26  of the clamp  16 . 
         [0028]    With reference to  FIG. 4 , the clamped bundle of pins  28  is next positioned within an electroforming tank  34 . The clamped bundle of pins  28  is secured via a bracket  36  to a vertical wall  38  of the tank. The tank  34  is filled with electroform bath  40  to a level substantially above the optical prism surface  32 . The preferred electroform bath  40  includes cobalt, nickel and/or a formulation of same. The electroform bath  40  preferably has a sufficiently high density material so as to add rigidity to the electroformed skin. An electroformed skin  42  is shown built up off of the front surface  26  and off of the optical prism surface  32 . The process of forming the electroformed skin accrues over a period of two weeks, in the preferred embodiment. The electroformed skin  42  takes on substantially the same configuration as the front surface  26  and its adjoining optical prism surface  32 . A prism surface  44  is created on the back side  46  of the electroformed skin. A finish surface  48  represents the side opposite the back side  46 . 
         [0029]    With reference to  FIG. 5 , the electroformed skin  42  is shown separated from the clamped bundle of pins  28 . The electroformed skin  42  is approximately 0.140 inches thick being preferably made of nickel, or cobalt or an amalgamation of same. The finished side  48  of the electroformed skin now has a negative prism configuration  50  which will be used as the finished surface for molding optical lens parts. 
         [0030]    With reference to  FIG. 6 , the step of applying backing material to the electroformed skin  42  is illustrated. It will be preferred that a cold spray welding process be utilized. It is preferred to utilize a cold backing process so as to minimize heat and thus warp age on the negative prism configuration surface  50 . Thus, layers of backing material  52  are built up on the backside  46  of the electroformed skin  42 . This may be accomplished by a cold spray process wherein metal is disbursed in even presentations to the back of the electroformed skin. This may be done by the delivery of metal by a nozzle  54  that is connected to a machine, not shown. It will be preferred that the metal that is used for the backing buildup to have a low density property such that its density is lower than the density of the material comprising the electroformed skin  42 . For example, the backing material  56  could be made of the group consisting of aluminum, zinc, or an amalgamation of same. It is also possible that the metal  56  be a powder mixture when applied. It is preferred that the backing portion  52  be approximately 0.50 of an inch thick. 
         [0031]    With reference to  FIG. 7 , a machining step is illustrated showing the removal of the uneven backing portion  52  after the cold spraying step has been completed. It is necessary to provide a smooth surface  58  on the backing portion  52  so that the final reflex insert tool may be properly installed within a mold. A CNC Machine  60  is shown having a tool  62  for cutting away the excess backing material  56 . The electroformed skin  42  is not machined during this step. It will be appreciated that the machining step can be accomplished through other means, as desired. 
         [0032]    With reference to  FIG. 8 , the machined reflex insert  64  is now ready for the final machining so that the profile of the insert tool is created. This next step is accomplished by a wire EDM or CNC mill  66  passing through the machined reflex insert  64  so as to cut a desired profile for an insert tool. This causes undesirable material  68  to be cut away from the final reflex insert which ultimately will be placed within a tool for injection molding. 
         [0033]    With regards to  FIG. 9 , a finished reflex insert  70  is illustrated and is now ready for insertion into the injection molding tool shown in  FIG. 10 . A finished insert  70  has an electroformed skin portion  42  and the associated backing portion  52 . As can be seen in  FIG. 10 , the finished reflex insert  70  is located within a core  72  of an injection molding tool  74 . An injected molded plastic optical part  76  is shown having been molded from the tool  74 . The optical part  76  has an optical surface  78  of superior photometric qualities, thus ready for use after trimming and finishing. 
         [0034]    It will be appreciated that the optical part  76  can be utilized in automotive, aeronautical, or wherever it is desirable to produce a part having a highly reflective optical surface of superior photometric qualities. 
         [0035]    With regards to  FIG. 11 , the steps for manufacturing a reflex insert tool  70  will be presented. The first step  80  includes manufacturing the optical pins to a desired configuration so as to have an optimal optical surface. The next step includes bundling  82  the optical pins together in an arrangement of a desired configuration. The next step includes clamping  84  the bundled optical pins, so as to securely hold them together for the electroforming stage. The next step includes locating  86  the assembled clamp into an electroformed bath. The clamp containing the pins must be sufficiently submerged within the electroformed bath so as to allow proper material buildup. The electroformed bath preferably includes material such as cobalt and nickel. 
         [0036]    The next step includes building up  88  the electroformed skin to a desirable thickness. It is preferred to continue this electroforming process until the skin has reached approximately 0.140 inches in thickness. The next step includes removing  90  the clamp from the electroformed bath which concludes the step of generating the electroformed skin. The next step includes separating  92  the electroformed skin from the clamp. The clamp retains the bundle of optical pins. The electroformed skin now has an optical surface configured therein that is a take off of the plurality of prisms. 
         [0037]    The next step includes building up  94  a material on the back of the electroformed skin. This is preferably accomplished by applying a cold spray material to the back side of the skin in a rapid manner under a low pressure condition. It will be appreciated then the buildup material be comprised of material such as aluminum or zinc. It is preferred that the backing material have a density less than that of the density of the electroformed material. Providing a lower density backing material aids machining of same, yet providing rigidity to the insert tool. It is preferred that the backing step take a few hours to less than one week. 
         [0038]    The next step includes machining  96  the backing material to a desired thickness and a uniform plane. The last step includes CNC machining  98  the profile of the reflex insert to a desired configuration. The result is a completed finish reflex insert  70  that is ready for insertion to an injection molding tool  74 . 
         [0039]    It will be appreciated that the aforementioned steps may be modified, yet still be within the spirit of the scope of the present invention. It will also be appreciated that the step of applying cold spray material to the electroformed skin substantially reduces the time over conventional methods, for building up the backing portion. It is preferred that the step of applying cold spray material be completed within approximately a one hour time period from beginning to end.