阅读说明：本技术 预成型螺钉凸台 (Preformed screw boss ) 是由 圣地亚哥·耶佩斯加洛 瑞恩·莫维利 于 2020-10-15 设计创作，主要内容包括：本公开提供了“预成型螺钉凸台”。一种形成具有螺钉凸台的成型的聚合物零件的方法包括将螺钉凸台插入件定位在模具的销上。所述螺钉凸台插入件可以与所述模具的引导表面接触。在成型期间,在所述螺钉凸台插入件定位在所述销上时,聚合物材料沿着所述螺钉凸台插入件流动。所述聚合物材料可以结合到所述螺钉凸台插入件。所述螺钉凸台插入件可以包括一个或多个几何特征,所述一个或多个几何特征防止所述螺钉凸台插入件相对于周围聚合物材料旋转和/或轴向移动。(The present disclosure provides a "preformed screw boss. A method of forming a molded polymeric part having a screw boss includes positioning a screw boss insert on a pin of a mold. The screw boss insert may be in contact with a guide surface of the mold. During molding, polymeric material flows along the screw boss insert as the screw boss insert is positioned on the pin. The polymeric material may be bonded to the screw boss insert. The screw boss insert may include one or more geometric features that prevent the screw boss insert from rotating and/or moving axially relative to the surrounding polymeric material.)

1. A screw boss insert, comprising:

a body having first and second opposed ends and a first exterior surface portion adjacent the first end and a second exterior surface portion adjacent the second end;

wherein the lateral dimension of the first outer surface portion is greater than the lateral dimension of the second outer surface portion;

wherein the first and second opposing ends have first and second end surfaces, respectively, and wherein the second outer surface portion includes non-circular surface features;

the body also includes a cavity having an opening in the first surface, the cavity having an inner surface configured to receive a threaded fastener.

2. The screw boss insert of claim 1, wherein:

the screw boss insert comprises a one-piece continuously molded polymeric part, and wherein the inner surface comprises a molded polymer.

3. The screw boss insert of claim 1 or claim 2, wherein:

the first outer surface portion includes at least one outwardly opening annular groove and first and second cylindrical rib surfaces on opposite sides of the annular groove.

4. The screw boss insert of any of claims 1-3, wherein:

the non-circular surface feature includes at least one channel having a substantially flat base surface.

5. The screw boss insert of any of claims 1-4, wherein:

the first and second outer surface portions include first and second cylindrical outer surfaces.

6. The screw boss insert of any of claims 1-5, wherein:

the inner surface of the cavity is substantially cylindrical and the cavity has a single opening in the first surface.

7. The screw boss insert of any of claims 1-6, wherein:

the body includes a polymeric material.

8. The screw boss insert of any of claims 1-7, comprising:

a plurality of grooves on the first outer surface portion.

9. The screw boss insert of any of claims 1-8, wherein:

the recess is substantially annular.

10. The screw boss insert of any of claims 1-9, wherein:

a transition surface extending between the first and second outer surface portions and facing the second opposing end.

11. The screw boss insert of claim 1, wherein:

the non-circular surface features include at least one pair of substantially planar surfaces on opposite sides of the second outer surface portion.

12. The screw boss insert of claim 1, wherein:

the first outer surface portion includes an annular groove and cylindrical rib surfaces on opposite sides of the annular groove.

13. The screw boss insert of claim 12, wherein:

the annular groove includes at least two annular grooves with a first cylindrical rib surface between the at least two annular grooves, and a second cylindrical rib surface and a third cylindrical rib surface opposite the first cylindrical rib surface adjacent the at least two annular grooves.

14. A molded polymeric component comprising the screw boss insert of claim 1, wherein:

the molded polymeric component includes a polymeric material encapsulating the second exterior surface portion.

15. The shaped polymeric part of claim 14, wherein:

the molded polymeric component includes a polymeric material encapsulating the first outer surface portion.

Technical Field

The present invention relates generally to screw bosses in molded parts, and in particular to screw boss inserts that may be positioned prior to molding.

Background

The molded polymeric component may have screw bosses for threaded fasteners. The molded screw boss may cause defects such as "sink". Sag is a jetting defect (e.g., a dimple) that may be caused by a cooling rate difference between the primary geometry and the attachment feature. In an effort to address the problems associated with screw bosses in injection molded polymer parts, various methods have been utilized, such as surrounding material modification and "dog house".

Disclosure of Invention

One aspect of the present disclosure is a method of forming a screw boss in an injection molded polymer part. The method includes providing a polymeric screw boss insert defining an axis and having first and second opposing ends. The polymeric screw boss insert has an outer surface extending between the first and second opposing ends and a pin cavity having an opening at the first end. A mold having a first mold part and a second mold part is provided. The mold parts form a cavity when the first and second mold parts are in a closed position relative to each other. At least one of the first and second mold parts has a boss cavity portion and a pin protruding into the boss cavity portion. The boss cavity portion defines an inner guide surface and at least one channel between the guide surfaces. The method also includes positioning the screw boss insert at least partially within the boss cavity portion, wherein the pin is received in the pin cavity of the screw boss insert, at least a first portion of the outer surface of the screw boss insert is in contact with the inner guide surface, and at least a second portion of the outer surface is spaced apart from the surface of the boss cavity portion at the channel to form a side passage extending along the at least one channel. The method also includes flowing molten polymer material into the cavity along the outer surface of the screw boss insert and into the side passage while the screw boss insert is positioned on the pin. Allowing the molten polymer material to solidify, whereby the polymer in the side passage bonds to the screw boss insert and retains the screw boss insert to solidify the polymer material in the main cavity.

Embodiments of the first aspect of the disclosure may include any one or combination of the following features:

the screw boss insert may optionally comprise a cylindrical outer surface portion.

The inner guide surface is optionally cylindrical.

The method optionally comprises contacting the cylindrical outer surface of the screw boss insert with the cylindrical inner guide surface.

The outer surface of the screw boss insert optionally comprises: a first outer surface portion adjacent the first end; a second outer surface portion adjacent the second end; and a transition surface between the first and second outer surface portions.

The screw boss insert optionally includes at least one non-circular surface feature.

The method optionally comprises flowing molten polymeric material into engagement with the non-circular surface feature, whereby the polymeric material prevents rotation of the screw boss insert when the polymeric material solidifies.

The first outer surface optionally comprises an annular groove and a cylindrical rib surface on the opposite side of the annular groove.

The boss cavity portion optionally comprises a cylindrical surface in contact with the cylindrical rib surface and spaced from the surface of the annular groove to form an annular passage connected to the side passage.

The method optionally comprises flowing molten polymeric material into the annular passage through the side passage.

The annular groove optionally comprises at least two annular grooves, wherein a first cylindrical rib surface is between the at least two annular grooves, and a second cylindrical rib surface and a third cylindrical rib surface are opposite the first cylindrical rib surface in the vicinity of the at least two annular grooves.

The at least two annular grooves are optionally connected to the side passage.

The method optionally comprises flowing molten polymeric material into the at least two annular grooves through the side passages.

The second end of the screw boss insert optionally comprises a cylindrical outer surface portion having a diameter less than a diameter of the cylindrical rib surface.

The cylindrical outer surface portion is optionally spaced from a surface of the auxiliary cavity to form an annular gap when the screw boss insert is positioned on the pin in the boss cavity portion.

The method optionally comprises flowing molten polymeric material into the annular gap around the second end of the screw boss insert.

The second end optionally comprises a second end surface, and the pin cavity optionally does not extend to the second end surface.

The method optionally comprises covering the second end surface with a molten polymeric material.

The side passage optionally extends across the cylindrical rib surface to form a gap.

The method optionally comprises flowing molten polymeric material into the side passage over the cylindrical rib surface to form a reinforcing rib as the polymeric material solidifies.

The second outer surface portion optionally comprises an outer surface spaced inwardly from the front outer surface portion.

The transition surface optionally extends laterally between the first and second outer surface portions.

The boss cavity portion optionally comprises an annular mould surface extending around and engaging the first outer surface portion adjacent the transition surface to prevent molten polymeric material from flowing between the annular mould surface and the first outer surface portion of the screw boss insert.

The auxiliary cavity optionally comprises a mould surface portion spaced from the second outer surface portion to form a gap therebetween.

The method optionally comprises flowing molten polymeric material into the gap around the second outer surface portion.

The non-circular surface feature optionally comprises at least one channel formed in the second outer surface portion, wherein the at least one channel has a non-circular base.

The non-circular surface features optionally comprise at least one pair of substantially flat surfaces on opposite sides of the second outer surface portion.

The pin chamber optionally has a substantially cylindrical inner surface.

After solidification of the molten polymeric material, a self-tapping threaded screw optionally engages with the inner surface to form a thread in the inner surface and interconnect the injection molded polymeric part with a second part.

Optionally using a robot to position the screw boss insert on the pin in the boss cavity portion.

According to another aspect of the present disclosure, a screw boss insert includes: a polymeric body having first and second opposing ends; and a first outer surface portion adjacent the first end; a second outer surface portion adjacent the second end; and a transition surface between the first and second outer surface portions. The first outer surface portion has a transverse dimension greater than a transverse dimension of the second outer surface portion, and the transition surface extends between the first and second outer surface portions and faces the second opposite end. The first and second opposing ends have first and second end surfaces, respectively. The second outer surface portion includes non-circular surface features. The body also includes a blind pin cavity having an opening in the first surface. The blind pin cavity has a generally cylindrical inner surface configured to receive a self-tapping threaded screw to form threads in the inner surface.

Embodiments of the second aspect of the disclosure may include any one or combination of the following features:

the screw boss insert optionally comprises a one-piece continuously molded polymeric part.

The inner surface optionally comprises a shaped polymer.

The first outer surface portion optionally comprises at least one outwardly opening annular groove and first and second cylindrical rib surfaces on opposite sides of the annular groove.

The non-circular surface feature optionally comprises at least one channel having a substantially flat base surface.

The first and second outer surface portions optionally comprise first and second cylindrical outer surfaces.

The transition surface optionally comprises an annular step orthogonal to the first and second cylindrical outer surfaces.

Another aspect of the present disclosure is a method of forming a screw boss in an injection molded polymer part. The method includes forming a polymeric insert by injection molding a thermoplastic polymeric material into a first mold cavity. The polymeric insert includes a plurality of recesses on an outer surface and a screw receiving opening. The polymer insert is positioned over the pin in the second mold cavity by inserting the pin into the screw receiving opening. The method also includes flowing molten thermoplastic polymer material around the polymer insert and into the plurality of grooves on the outer surface of the polymer insert. Allowing the thermoplastic polymer material to solidify around the polymer insert.

These and other aspects, objects, and features of the present disclosure will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

Drawings

In the drawings:

FIG. 1 is a partially exploded perspective view of a component including a screw boss according to one aspect of the present disclosure;

FIG. 2 is a cross-sectional view of the component of FIG. 1 taken along line II-II;

FIG. 3 is a cross-sectional view of the component of FIG. 1 taken along line III-III;

FIG. 4 is a cross-sectional view of a screw boss insert according to another aspect of the present disclosure;

FIG. 5 is an isometric view of a screw boss insert;

FIG. 6 is a partial schematic view showing the molding of the screw boss insert of FIG. 5;

FIG. 7 is a schematic view showing a screw boss insert in an injection mold;

FIG. 8 is an isometric view of a screw boss insert positioned in a mold; and is

Fig. 9 is a schematic diagram illustrating a mold and a robot configured to install screw boss inserts in the mold.

Detailed Description

For purposes of the description herein, the terms "upper," "lower," "right," "left," "rear," "front," "vertical," "horizontal," and derivatives thereof shall relate to the disclosure as oriented in fig. 1. It is to be understood, however, that the disclosure may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

Referring to fig. 1, component 1 may comprise an injection molded polymer (e.g., polypropylene, ABS, or other suitable thermoplastic or thermoset polymer) having a body 2 and screw bosses 5 and 5A. The screw boss 5 and/or 5A may optionally include a reinforcing rib 6. Referring to fig. 2, the screw boss 5 includes a screw boss insert 10 (see also fig. 5) that is molded into a screw boss post 12 of the component 1. The screw 15 is threadedly engaged with the screw boss insert 10 to retain the second component 14 to the screw boss 5 of the component 1. As shown in fig. 3, the screw boss 5A is similar to the screw boss 5 except that the screw boss 5A is configured to support the first and second components 14 and 14A, respectively, via screws 15 that threadedly support the screw boss inserts 10 of the screw boss 5A.

With further reference to fig. 4, the screw boss insert 10 may also be used in a screw boss 5B that does not include a rib 6. The screw boss insert 10 includes an upper (first) end portion 22 and a lower (second) end portion 24 (fig. 5). When the screw boss insert 10 is utilized in the screw boss 5B, the molded polymeric material 18 around the end 24 of the screw boss insert 10 has an outer surface 19 that may be substantially flush with the outer surface 21 of the screw boss insert 10. The outer surface 19 is optionally cylindrical.

With further reference to fig. 5 and 6, the screw boss insert 10 comprises a molded polymeric material having an upper portion 22 and a lower portion 24. The lower portion 24 has a reduced transverse dimension (e.g., diameter) relative to the upper portion 22. The upper portion 22 includes ribs 26 and grooves 28 formed between the ribs 26. The ribs 26 and grooves 28 may be annular and extend around the perimeter 30 of the upper portion 22 of the screw boss insert 10. The rib 26 includes an outer surface 27. The outer surface 27 may be cylindrical. The shoulder 32 of the upper portion 22 has a cylindrical outer surface 33 that may have the same transverse dimension (e.g., diameter) as the cylindrical outer surface 27 of the rib 26. The upper portion 22 of the screw boss insert 10 may be generally symmetrical about the centerline "C" of the screw boss insert 10.

The screw boss insert 10 may be formed by injection molding using a mold 40 comprising mold halves 42A and 42B (fig. 6) having mold cavities 43A and 43B, respectively. The cavities 43A and 43B have a shape corresponding to the outer surface of the screw boss insert 10. When the mold halves 42A and 42B are closed, the pin 38 is positioned in the cavity formed by the cavity portions 43A and 43B, and then the polymeric material is injected into the mold cavity such that the pin 38 forms the opening 35 in the end surface 36 of the screw boss insert 10. Examples of suitable thermoplastic polymer materials are polypropylene and ABS. However, the present disclosure is not limited to these materials, and the insert 10 may comprise a wide range of materials, such as thermosetting polymers or metals.

The lower portion 24 of the screw boss insert 10 includes a cylindrical outer surface portion 44 having a reduced transverse dimension (e.g., diameter) relative to the transverse dimension (diameter) of the cylindrical surface 33 of the upper portion 22. The transverse surface 45 extends between the cylindrical surface 33 and the cylindrical surface 34 of the shoulder 32. The transverse surface 45 may be substantially flat and substantially orthogonal to the axis C of the screw boss insert 10. The lower portion 24 may include a non-circular feature to prevent rotation of the screw boss insert 10 when a screw is engaged with the opening 35. For example, the plurality of slots 46 have a flat base surface 47. When the polymeric material 18 of the component 1 is molded around the screw boss insert 10, the flat base surface 47 is asymmetric about the centerline C, thereby preventing rotation of the screw boss insert 10. The end surface 48 (fig. 6) of the screw boss insert 10 may be curved (e.g., hemispherical). As shown in fig. 4, the opening 35 is a blind hole having a cylindrical (or slightly conical) inner surface 39 and a flat inner end surface 37. The surface 39 may be cylindrical or tapered such that the surface 39 has a larger diameter adjacent the opening 35 and a smaller diameter adjacent the inner end surface 37. For example, the surface 39A adjacent to the end surface 36 may be tapered (conical).

With further reference to fig. 7-9, during manufacture of the component 1, the screw boss insert 10 is positioned on the pin 54 of the mold component 50A. The mold parts 50A and 50B define a mold cavity 52 when closed, as shown schematically in FIG. 7. The mold part 50A includes one or more boss cavities 56 and a pin 54 protruding into each boss cavity 56. The mold part 50B may optionally include one or more boss cavities 56 and pins 54.

During manufacture of part 1, a robot 60 having a robot arm 65 may be utilized to position one or more screw boss inserts 10 on pins 54 in boss cavities 56 of mold part 50A prior to forming mold parts 50A and 50B together into mold cavity 52 having a shape corresponding to part 1. The pin 54 may have a lateral dimension (e.g., diameter) that is slightly larger (e.g., about 0.0005 inches to about 0.001 inches or more) to provide a friction and/or interference fit to ensure that the insert 10 does not dislodge from the pin 54 (e.g., if the pin 54 protrudes downward). The outer surface 54A of the pin 54 may optionally include a raised annular ridge 54B or other surface feature that engages and/or deforms the surface 39 of the bore 35 of the insert 10 to retain the insert 10 on the pin 54. After positioning the screw boss insert 10 on the pin 54, the mold parts 50A and 50B are brought together and a molten thermoplastic polymer material 64 is injected into the mold cavity 52 by an injection molding machine 66 through one or more passages 68 in the mold parts 50A and/or 50B. After solidification of the polymer material forming part 1, the mold parts 50A and 50B are moved apart to the open position (fig. 9). It should be understood that the number, size and location of the passages 68 may be varied as desired to properly fill the mold cavity 52.

Referring to fig. 7 and 8, the boss cavity 56 of the mold part 50A may include a cylindrical surface 70 that extends around the lower portion 24 of the screw boss insert 10 to form an annular gap 72 that is filled with the molten (or unsolidified) polymer material 64 during the injection molding process. One or more passageways 74 in the mold part 50A also receive the molten polymer material 64 during the molding process. Specifically, during the injection molding process, the molten polymer material 64 flows into the gap 72, into the passageway 74, and into the groove 28 of the screw boss insert 10, thereby forming a ring 76 of polymer material. The molten polymer material in the passages 74 solidifies to form the ribs 6 (fig. 2 and 3). The cylindrical die surface 70 may fit tightly over the surfaces 27 and 33 of the screw boss insert 10 such that these surfaces are exposed in the final screw boss 5, 5A (fig. 2 and 3). The side wall 70 forms a cylindrical polymer surface 78 in the screw boss 5, 5A.

During the injection molding process, molten (or unsolidified) polymer material also flows into the slots 46 of the end 24 of the screw boss insert 10. Due to the flat surface 47, the slot 46 is asymmetric with respect to the centre line C of the screw boss insert 10, and when the screw 15 is screwed into the opening 35 of the screw boss insert 10, the slot 46 prevents the screw boss insert 10 from rotating in the component 1. If the screw boss 5 or 5A includes a rib 6 (e.g., fig. 2 and 3), the passage 74 may extend substantially the entire length of the screw boss insert 10, as shown in fig. 2 and 3, to form the rib 6. However, during formation of the screw boss 5B without ribs (fig. 4), a mold 50A including only the annular space 72 (without the passageway 74) may be utilized, thereby forming the molten polymeric material 64 into the surrounding polymeric material 18 (fig. 4). As discussed above, the polymeric material 18 has an outer surface 19 that is substantially the same diameter as the outer surface 21 of the screw boss insert 10. In the screw boss 5B of fig. 4, when a threaded fastener is inserted into the opening 35 of the screw boss insert 10, molten polymer material flows into the slot 46, thereby securing the screw boss insert 10 and preventing the screw boss insert 10 from rotating.

The screw boss insert 10 may be made of a thermoplastic polymer material that is substantially the same as the polymer material of the component 1. The temperature and pressure of the mold 50 may be set or adjusted to cause the molten polymer material of the component 1 to combine and fuse/intermix with the thermoplastic material of the screw boss insert 10. This may partially melt the polymer material of the screw boss insert 10 to provide a strong integral bond between the screw boss insert 10 and the polymer material of the component 1. Alternatively, the screw boss insert 10 may be made of a different material (e.g., a thermoplastic polymer with a higher melting temperature, a thermoset polymer, etc.) so that the material of the screw boss insert 10 does not melt and does not intermix with the polymeric material of the component 1. However, the slots 46 and ribs 26 of the screw boss insert 10 mechanically secure the screw boss insert 10 in the material of the component 1 during the injection molding process, thereby ensuring that the screw boss insert 10 does not rotate or pull out when the screw 15 is screwed into the screw boss insert 10. Furthermore, the present disclosure is not limited to injection molding thermoplastic polymers in the mold 50. For example, thermosetting polymers or other suitable materials may also be used to fabricate the components in which the insert 10 is molded.

It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present disclosure, and further, it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

According to the present invention, a method of forming a screw boss in an injection molded polymer part comprises: providing a polymeric screw boss insert defining an axis and having first and second opposing ends, an outer surface extending between the first and second opposing ends, and a pin cavity having an opening at the first end; providing a mold having a first mold part and a second mold part, the mold parts forming a cavity when the first and second mold parts are in a closed position relative to each other, at least one of the first and second mold parts having a boss cavity portion and a pin protruding into the boss cavity portion, wherein the boss cavity portion defines an inner guide surface and at least one channel between the guide surfaces; positioning the screw boss insert at least partially within the boss cavity portion, wherein the pin is received in the pin cavity of the screw boss insert, at least a first portion of the outer surface of the screw boss insert is in contact with the inner guide surface, and at least a second portion of the outer surface is spaced apart from the surface of the boss cavity portion at the channel to form a side passage extending along the at least one channel; flowing molten polymer material along the outer surface of the screw boss insert into the cavity and into the side passage while the screw boss insert is positioned on the pin; allowing the molten polymer material to solidify, whereby the polymer in the side passage bonds to the screw boss insert and retains the screw boss insert to solidify polymer material in the main cavity.

In one aspect of the invention, the screw boss insert includes a cylindrical outer surface portion; the inner guide surface is cylindrical; and comprises: bringing the cylindrical outer surface of the screw boss insert into contact with the cylindrical inner guide surface.

In one aspect of the invention, the outer surface of the screw boss insert comprises: a first outer surface portion adjacent the first end; a second outer surface portion adjacent the second end; and a transition surface between the first and second outer surface portions, and wherein the screw boss insert has at least one non-circular surface feature; flowing molten polymer material into engagement with the non-circular surface feature, whereby the polymer material prevents rotation of the screw boss insert when the polymer material solidifies.

In one aspect of the invention, the first outer surface comprises an annular groove and cylindrical rib surfaces on opposite sides of the annular groove; and comprises: the boss cavity portion including a cylindrical surface in contact with the cylindrical rib surface and spaced apart from the surface of the annular groove to form an annular passage connected to the side passage; flowing molten polymeric material through the side passage into the annular passage.

In one aspect of the invention, the annular groove comprises at least two annular grooves with a first cylindrical rib surface between the at least two annular grooves and a second cylindrical rib surface and a third cylindrical rib surface opposite the first cylindrical rib surface adjacent the at least two annular grooves, wherein the at least two annular grooves connect to the side passage; and comprises: flowing molten polymeric material through the side passage into the at least two annular grooves.

In one aspect of the invention, the second end of the screw boss insert has a cylindrical outer surface portion having a diameter less than a diameter of the cylindrical rib surface and spaced from a surface of the boss cavity portion to form an annular gap when the screw boss insert is positioned on the pin in the auxiliary cavity; flowing molten polymer material into the annular gap around the second end of the screw boss insert.

In one aspect of the invention, the second end has a second end surface and the pin cavity does not extend to the second end surface; and comprises: covering the second end surface with a molten polymeric material.

In one aspect of the invention, the side passage extends across the cylindrical rib surface to form a gap; and comprises: flowing molten polymer material into the side passage over the cylindrical rib surface to form a reinforcing rib as the polymer material solidifies.

In one aspect of the invention, the second outer surface portion has an outer surface spaced inwardly from the front outer surface portion; the transition surface extends laterally between the first and second outer surface portions; the boss cavity portion comprising an annular mold surface extending around and engaging the first outer surface portion adjacent the transition surface to prevent molten polymeric material from flowing between the annular mold surface and the first outer surface portion of the screw boss insert, the auxiliary cavity further comprising a mold surface portion spaced apart from the second outer surface portion to form a gap therebetween; and the method further comprises: flowing molten polymer material into the gap around the second exterior surface portion.

In one aspect of the invention, the non-circular surface feature comprises at least one channel formed in the second outer surface portion, wherein the at least one channel has a non-circular base.

In one aspect of the invention, the non-circular surface features include at least one pair of substantially flat surfaces on opposite sides of the second outer surface portion.

In one aspect of the invention, the pin cavity has a substantially cylindrical inner surface; and after the molten polymeric material solidifies, engaging a self-tapping threaded screw with the inner surface to form a thread in the inner surface and interconnect the injection molded polymeric part with a second part.

In one aspect of the invention, the pin forms an interference fit when inserted into the pin cavity of the screw boss insert; and comprises: positioning the screw boss insert on the pin in the boss cavity portion using a robot.

According to the present invention, there is provided a screw boss insert having: a polymeric body having: first and second opposed ends and first and second outer surface portions adjacent the first and second ends; and a transition surface between the first and second outer surface portions; wherein a transverse dimension of the first outer surface portion is greater than a transverse dimension of the second outer surface portion, the transition surface extending between the first and second outer surface portions and facing the second opposing end; wherein the first and second opposing ends have first and second end surfaces, respectively, and wherein the second outer surface portion includes non-circular surface features; the body also includes a blind pin cavity having an opening in the first surface, the blind pin cavity having a generally cylindrical inner surface configured to receive a self-tapping threaded screw to form a thread in the inner surface.

According to one embodiment: the screw boss insert comprises a one-piece continuously molded polymeric part, and wherein the inner surface comprises a molded polymer.

According to one embodiment: the first outer surface portion includes at least one outwardly opening annular groove and first and second cylindrical rib surfaces on opposite sides of the annular groove.

According to one embodiment: the non-circular surface feature includes at least one channel having a substantially flat base surface.

According to one embodiment: the first and second outer surface portions comprise first and second cylindrical outer surfaces, and the transition surface comprises an annular step orthogonal to the first and second cylindrical outer surfaces.

According to the present invention, a method of forming a screw boss in an injection molded polymer part comprises: forming a polymeric insert by injection molding a thermoplastic polymeric material into a first mold cavity; wherein the polymeric insert comprises a plurality of grooves on an outer surface and a screw receiving opening; positioning the polymer insert over the pin in the second mold cavity by inserting the pin into the screw receiving opening; flowing molten thermoplastic polymer material around the polymer insert and into the plurality of grooves on the outer surface of the polymer insert; and allowing the thermoplastic polymer material to solidify around the polymer insert.

In one aspect of the invention: the polymeric insert includes a flat outer surface; and comprises: contacting molten polymeric material with the flat outer surface.