Patent Application
20190084200
The present invention relates to a molded resin component on which outer surface a decorative pattern portion is formed, a method of manufacturing the molded resin component, and a printer having the molded resin component as an exterior surface of the printer.
In recent years, exterior components of electronic devices are often made with a molded resin component on which a decorative pattern is formed, for design, weight reduction, cost, and mass production. The molded resin component is obtained by filling a mold with a thermoreversible resin such as ABS or high impact polystyrene (HIPS), then transferring the shape of the mold, which includes a decorative pattern, to the resin by applying pressure to the resin, then cooling the resin, and then taking out the resin from the mold.
In particular, for exterior components, unevenness of the decorative pattern may significantly affect the external aesthetic appearance of the exterior components. Thus, it is desired to increase the accuracy of forming the decorative pattern. In conventional molded resin components, however, a step may be formed at a conspicuous position, visually impairing the aesthetic appearance.
One factor by which the step is formed is unevenness of a molding surface of a mold, which forms the decorative pattern. In the production of the mold, the molding surface is formed by cutting a base material with a cutting tool. In this case, because of durability of the cutting tool, the cutting tool may be replaced with another during formation of a single molding surface. When the cutting tool is replaced with the other, the shape of the molding surface may be changed, because the shape of the other cutting tool differs from that of the cutting tool having been replaced. Typically, the height of a base surface, which is a reference surface and on which a convex decorative pattern is formed, may be changed by the replacement of the cutting tool, at a position in the base surface. This may cause a visually conspicuous step (tools-originated step).
Another factor is a difference in position between pieces of the mold, which is produced at a boundary between the pieces. For example, a difference in position between a slide piece and a cavity piece causes a parting step, and a difference in height between an insert piece and the cavity piece causes a step which is formed at a boundary of the insert piece.
These steps are transferred to the molded resin component. Thus, if the steps are formed at visually conspicuous positions, the steps will cause quality deterioration in external appearance.
One solution to make the steps visually less conspicuous is to coat the surface of the molded resin component with paint, to reduce the height of the steps. When the molded resin component is partly or wholly covered with a sufficient thickness of paint, and the paint dries, the steps can be less conspicuous.
Another solution to make the steps less conspicuous is described in Japanese Patent Application Publication No. 2007-331233, which does not pertain to the field of the molded resin component. In this solution, a decorative sheet having a concave and convex pattern on its exterior surface is stuck to a material used for making an exterior surface, to camouflage a step of a joining end of the material for improving quality of the external appearance.
However, the above-described solution to coat the surface of the molded resin component with the paint needs an additional coating process which increases cost. In addition, since the coating decreases visibility of the decorative pattern transferred to the surface of the molded resin component, the aesthetic appearance in design will be impaired.
In addition, if the solution described in Japanese Patent Application Publication No. 2007-331233 is used for the molded resin component, the additional process for sticking the decorative sheet having the concave and convex pattern will increase cost. Moreover, the shape of the molded resin component may make it difficult to stick the decorative sheet to the molded resin component without producing any wrinkles.
According to a first aspect of the present invention, a method of manufacturing a molded resin component having a regular decorative pattern by filling a cavity with resin, the cavity being formed by a mold set including a first piece and a second piece, the regular decorative pattern having a convex portion, the method includes using a mold set in which a concave part is formed along a boundary portion between the first piece and the second piece, the concave part being used to form one portion of the convex portion of the regular decorative pattern, or using a mold set including a first base surface, a second base surface which positioned higher than the first base surface, a concave part between the first base surface and the second base surface, and a step formed by a cutting tool being replaced at a position where the concave part is to be formed, the concave part being used to form one portion of the convex portion of the regular decorative pattern.
According to a second aspect of the present invention, a molded resin component having a regular decorative pattern, the regular decorative pattern including a convex portion, the molded resin component includes a step in one portion of the convex portion of the regular decorative pattern.
According to a third aspect of the present invention, a printer having a molded resin component on an exterior surface thereof, the molded resin component including a regular decorative pattern, the regular decorative pattern including a convex portion, the printer includes a step in one portion of the convex portion of the regular decorative pattern.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, some embodiments of the present invention, that is, a molded resin component, a method of manufacturing the molded resin component, and a printer having the molded resin component as an exterior surface of the printer will be described with reference to the accompanying drawings. The present invention can be applied to resin components having decorative patterns. Examples of the resin components include exterior components of home electrical products and electronic products, and exterior and interior components of vehicles such as automobiles.
In a first embodiment, there will be described an example in which the present invention is applied to an exterior component of a printer having a document reader.
The external surface of the document cover 12 is provided with the lattice-like pattern illustrated in
For aesthetic appearance, the base surface is a mirror surface, or has a high flatness which is almost the same as that of the mirror surface. Preferably, the base surface is a glossy surface. In the present embodiment, the base surface is a mirror surface.
A first base surface 30 forms a basic shape of a curved portion of the document cover 12. In
The first to the third base surfaces 30 to 32 are provided with a convex portion 33, as a decorative pattern, such that the convex portion 33 is formed like a lattice when viewed from above.
A boundary line 34 indicates a parting step produced in the convex portion 33 having the decorative pattern. In addition, the second base surface 31 and the third base surface 32 are different in height in a Z direction. A boundary line 35 indicates a boundary between the second base surface 31 and the third base surface 32. Specific shapes of the vicinities of the boundary lines 34 and 35 will be described later.
Next, there will be described a method of manufacturing the document cover 12.
In
Next, a configuration of the mold set having the pieces will be more specifically described.
In
Next, the parting step of the present embodiment will be described in detail. The parting step is produced along the boundary line 34 illustrated in
In the present embodiment, the parting step 69 is formed in the convex portion 33 having the decorative pattern. For describing this formation,
The cavity piece 52 is provided with a concave portion 67, as a mold to form the decorative convex pattern on the top surface of the molded resin component 50. Here, the top surface is an external surface of the molded resin component 50. The depth of the concave portion 67 is equal to the height 613 of the convex pattern, measured from the base surface of the external surface of the molded resin component 50.
In addition, the slide piece 53 is provided with a concave portion 68, as a mold to form the decorative convex pattern on the external surface of the curved portion of the molded resin component 50. The depth of the concave portion 68 is equal to the height 613 of the convex pattern, measured from the base surface of the external surface of the molded resin component 50.
Thus, the cavity piece 52 and the slide piece 53 are provided with the concave portions arranged with regularity and corresponding to the decorative convex pattern. At the boundary between the cavity piece 52 and the slide piece 53, one portion of a concave portion is formed at an edge of the cavity piece 52, and the other portion of the concave portion is formed at an edge of the slide piece 53. Thus, when the cavity piece 52 and the slide piece 53 are joined with each other, the one portion and the other portion form a single convex pattern.
In the present embodiment, the parting step 69 as illustrated in
Here, the parting step produced between the cavity piece and the slide piece will be further described with reference to
For allowing the slide piece 73 and the cavity piece 72 to slide, an allowance is provided in a boundary plane 75 between the slide piece 73 and the cavity piece 72. The allowance and the pressure applied by the resin in the mold will change a relative position of the slide piece 73 to the cavity piece 72, producing a step in the boundary between the slide piece 73 and the cavity piece 72. The step is transferred to the molded resin component, and a parting step 77 is produced. The height of the parting step 77 is not constant, and changes depending on many factors, such as molding conditions, precision of making the mold, and type of resin. Thus, it is actually difficult to eliminate the step by making the mold in consideration of the step. If the parting step 77 appears in the base surface, which is a reference surface of the external shape, the parting step 77 becomes highly visible, and significantly reduces quality of external appearance of the component.
In the present embodiment, as illustrated in
Next, a shape of the vicinity of the boundary line 35, as illustrated in
The mechanism of the occurrence of the step will be more specifically described.
Next, the reason why the cavity piece is formed in this manner will be described.
When the main spindle 102 moves and rotates at the number of rotations, feed speeds in those axes, and feeds per stroke in those axes, which are contained in the NC data 108, the cutting tool 103 can cut the workpiece 104. Thus, when the cutting tool 103 is attached to the main spindle 102 of the machining center 101, and the cutting tool 103 is moved relative to the workpiece 104 in a state where the main spindle 102 is rotating, the workpiece 104 can be machined into a predetermined three-dimensional shape.
When a molded resin component having a large external surface is molded with a mold, the number of parting steps increases as the number of pieces used to form the external surface increases. Thus, the less number of pieces is desirable, but causes each of the pieces to become larger. When a large cavity piece, enlarged due to the above-described reason, is made by using the above-described machining center, the cutting tool 103 wears during the cutting of the workpiece 104. Thus, the cutting tool 103 needs to be replaced with a new cutting tool in a sequential manner.
When the cutting tool 103 is replaced, the machining characteristic of the machine tool changes, causing difference in shape of the machined workpiece. Thus, the difference in shape becomes a step. In the following description, the difference in shape of the machined workpiece may be referred to as a tools-originated step.
For making a mold having such a shape, there are the following two methods, for example. A first method first forms a base surface by cutting a base material by using a tool suitable for the mirror-surface machining, and then forms the concave portion by using another tool having a different shape and suitable for the concave-portion machining. A second method forms the base surface and the concave portion together by cutting the base material by using a single tool, which is capable of forming the mirror surface and the concave portion. In the first method, since the tool for forming the base surface wears when used for a mold having a considerable size, the tool is required to be replaced with a new tool during the formation of the base surface. Also in the second method, since the tool wears when used for a mold having a considerable size, the tool is required to be replaced with a new tool during the machining.
Conventionally, when the machining center cuts the workpiece 104 to make the cavity piece, a position where a worn cutting tool is replaced with a new cutting tool is not controlled in the positional relationship between the position and the decorative pattern.
Thus, in both the first and the second methods, the cutting tool is often replaced with another during the formation of the base surface for a molded resin component. This replacement changes the machining characteristic; and causes a tools-originated step, having the height 90, to be formed in the base surface, as illustrated in
When a molded resin component for the document cover 12 is made by using the cavity piece made in this manner, a step is formed in the base surface which serves as a reference of the outer shape. The step is visually conspicuous, and reduces quality of the external appearance.
Thus, it is desirable that the step is not formed in the production of the cavity piece. However, for a large molded resin component, it is actually difficult to make a corresponding cavity piece without replacing the cutting tool.
In the present embodiment, the step produced by the change in machining characteristic is prevented from being formed in the base surface, which serves as a reference of the outer shape, by adjusting a timing at which the cutting tool is replaced. That is, when a mold is made for molding a molded resin component having a decorative pattern, which is arranged on the base surface with predetermined regularity, the timing at which the cutting tool is replaced is adjusted so as not to replace the cutting tool when the cutting tool is cutting a surface of the mold corresponding to the base surface of the molded resin component. In other words, the cutting tool is replaced at a timing at which the cutting tool is cutting a portion of the mold corresponding to the decorative pattern, that is, a timing just before the cutting tool cuts the portion, a timing in a period of time in which the cutting tool cuts the portion, or a timing just after the cutting tool has cut the portion.
In the present embodiment, the cutting tool 103 is replaced with another at a timing at which a surface of the mold, corresponding to the convex portion 33 having the decorative pattern, is cut. As illustrated in
By using the cavity piece made in this manner, the molded resin component illustrated in
In other words, even though base surfaces on both sides of the convex portion 933 having the decorative pattern are different in height, the difference is visually less conspicuous.
Here, as described in later-described examples, for aesthetic appearance, the ratio of the difference 90 in height to the height 97 of the convex portion is preferably 60% or less, and more preferably, 50% or less.
Hereinafter, specific examples of the molded resin component, used as a component of a printer and having a decorative pattern on its exterior surface, will be described.
Next, a method of forming a cavity surface and a slide surface of pieces of the mold will be described.
Pieces of mold sets of examples and pieces of later-described comparative examples were made by using a machine tool including the three-axis control machining center 101, the main spindle 102, and the cutting tool 103, which are illustrated in
The cavity piece 111 and the slide piece 110 illustrated in
In the examples to evaluate the parting step, the size of the cavity piece 111 was 300 mm×200 mm, and the size of an area to which the decorative pattern was added was 250 mm×160 mm. The size of the slide piece 110 was 40 mm×200 mm, and the size of an area to which the decorative pattern was added was 20 mm×160 mm.
In these areas, the decorative pattern was formed by cutting the slide piece 110 and the cavity piece 111, by using an end mill. As illustrated in
In the examples to evaluate the parting step, the lattice-like decorative pattern was adjusted in position so that the boundary between the mating surfaces 115 of the cavity piece 111 and the slide piece 110 is positioned in the lattice pattern. In addition, the height 613 of the decorative pattern illustrated in
The tool used was a ball end mill having a ball-like tip, and the cutting was performed under a condition in which the shape of the tool is sufficiently transferred to the mold.
In the examples to evaluate the tools-originated step, the size of the cavity piece 111 to which the decorative pattern was added was 340 mm×200 mm, and the size of an area to which the decorative pattern was added was 250 mm×180 mm. In these areas, the decorative pattern was formed by cutting the cavity piece 111, by using an end mill.
As illustrated in a plan view of
Next, a method of making a mold which was used for Examples 7 and 9 will be described.
As illustrated in
The tools used were ball end mills having a ball-like tip. The cutting was performed under a condition in which the shapes of the tools are sufficiently transferred to the mold.
The cavity piece and the slide piece, which had been made, were combined into a mold; and the molded resin components were obtained by performing the molding, by using the mold. In the molding, injection molding was performed by using white resin which was a PS material made by Toray Industries, Inc.; and the decorative lattice pattern formed in the cavity piece and the slide piece of the mold was transferred to the molded resin components. The molding machine used was an injection molding machine of J180EL3 (made by THE JAPAN STEEL WORKS, LTD.). The molding was performed under a molding condition which allows the decorative lattice pattern formed in the cavity piece surface and the slide piece surface of the mold to be sufficiently transferred.
In the examples to evaluate the parting step, a plurality of molded resin components were made. The molded resin components were made different in the parting step, that is, in the difference 612 in height between the base surface of the cavity piece 52 and the base surface of the slide piece 53, by adjusting positions of the cavity piece 52 and the slide piece 53 of
In the examples to evaluate the tools-originated step, the tools-originated step 144 of the examples was 0.025 mm in Example 7, and 0.05 mm in Example 9. The pattern height 97 of
In Comparative Example 1, the line interval 129 of the lattice-like pattern was 5 mm, as in the examples.
In Comparative Example 2, the molded resin component 70 was made by molding resin by using the mold of
In Comparative Example 3 of the tools-originated step, there was made a molded resin component whose tools-originated step was formed outside the convex portion having the decorative pattern, that is, on the base surface.
In Comparative Example 4, as illustrated in an enlarged sectional view of
The molded resin components of Examples 1 to 13 and Comparative Examples 1 to 4, obtained by using injection molding, were evaluated by five skilled workers who routinely check the external appearance. In the evaluation, whether the parting step, which is produced between the cavity piece and the slide piece, and the tools-originated step can be visually recognized was evaluated in five grades. When a step was more difficult to recognize, a higher grade was given. The evaluation criterion was as follows: grade C was given when the average of five evaluation results was 2 or less, grade B was given when the average of the five evaluation results was 3 to 4, and grade A was given when the average of the five evaluation results was 5. Table 1 indicates the evaluation results.
As can be seen, since the parting steps of Examples 1 to 4 and 10 to 11 were each integrally formed with the convex portion having the decorative pattern, they were more difficult to recognize than Comparative Examples 1 to 2, even though the height of the steps is large.
In addition, since the tools-originated steps of Examples 5 to 9 and 12 to 13 were each integrally formed with the convex portion having the decorative pattern, they were more difficult to recognize than Comparative Examples 3 to 4, even though the height of the tools-originated steps is large.
In the examples, the evaluation was excellent when the ratio of the height of the step to the height of the convex portion having the decorative pattern was 60% or less, and more excellent when the ratio was 50% or less.
As described above, the present invention produces the effect in which the aesthetic appearance in design is prevented from deteriorating, by adjusting the arrangement of the decorative pattern so that the step, produced in a molded resin component having a decorative pattern, is formed in a visually less conspicuous position.
The present invention, however, is not limited to the above-described embodiments and examples. Thus, embodiments of the present disclosure may be appropriately modified or combined.
For example, the decorative pattern is not limited to the lattice pattern illustrated in
Here, the regularity typically means repetition of the same shape and the same interval, but is not limited to this. For example, in the regularity, the area, the shape, or the interval of a pattern may be gradually changed at a predetermined rate of change.
In the above-described embodiments, in order to form the parting step in the convex pattern, both pieces are each provided with one portion of a single concave portion, used to form a corresponding convex pattern, at an edge of each piece so that the single convex portion is formed when both pieces are joined with each other. However, for reducing the visibility of the parting step, the parting step may be formed not at a center of the convex pattern, but at an edge of the convex pattern. Thus, the concave portion used to form the convex pattern may be formed at an edge of one of two pieces, which contact with each other via the boundary between the two pieces.
In addition, the parting step to which the present invention is applied is not limited to the step between the cavity piece and the slide piece. For example, even for a step in a boundary portion of another piece, such as a step produced when an insert piece is set to the cavity piece, the visibility of the step can be reduced by forming a mold such that a corresponding decorative pattern is formed along the boundary portion.
In addition, the molded resin component of the present invention is not limited to exterior components of printers, and may be any of exterior components of other home electrical products and electronic products, or exterior or interior components of vehicles such as automobiles.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-180811, filed Sep. 21, 2017, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-180811 | Sep 2017 | JP | national |
