Process, Materials, and Measurements

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03

Manufacturing Process

JOINING (PLASTIC)

The forming of plastic parts is usually followed by joining multiple parts together to

create assemblies with certain functionality, or to contain functional components. The

way parts are joined can vary widely based on functionality, forming processes, use

conditions, reparability, durability, and cost. Assembly is usually one of the most

costly aspects of producing a product. Therefore, carefully choosing the methods of

joining parts during the design process is critically important. The joining of parts is

determined well in advance of creating tooling, so that the appropriate features to aid

in specific joining methods can be designed into the parts. This section describes

common methods for joining plastic parts.

Adhesive bonding

is the process of joining two or more parts by using an adhesive.

Often when adhesive bonding is used, the parts include mechanical features that pre-

vent misalignment. Prior to bonding, parts are usually cleaned to ensure that mold

releases are removed to ensure a secure bond. Adhesive bonding is compatible with

most plastic-forming processes.

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ADHESIVE BONDING

Adhesive

Mechanical Interlock

Fasteners

, such as screws, are often used to attach components to housings and for

joining multiple housings. This method of joining allows parts to be disassembled for

repair or recycling. Injection-molded parts may have molded-in features (bosses) that

accept the screws. Self-tapping screws are often chosen when assembling plastic

parts because they tap into the plastic, creating a matching thread pattern. Thermo-

formed parts may require inserts to accept the screws.

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Job on:93996 CTP Title : RP_Process Material Measurements Client : Pro_Vision

Scn :

#

175 Size : 146.05(w) 209.55(h)mm _M2_Mac D

Dept : DTP D/O : 16.12.05 (Job on:000000 D/O : 00.00.01 Co: CM0)

Pantone

109 U

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03

52 PROCESS, MATERIALS, AND MEASUREMENTS

Snaps

are molded-in features that allow

parts to join by interlocking. Snaps are

designed into a molded part and take

advantage of the flexibility of plastic. This

method allows for the quick assembly of

parts at a ver y low cost. This type of fas-

tener is used for joining injection-molded

parts.

Ultrasonic welding

is the process of joining parts using ultrasonic vibration to create

friction between two parts, causing them to heat up, melt, and fuse together. The

edge of one of the mating molded plastic parts contains a thin ridge of plastic

(energy director), which focuses and controls the area of the weld. This method of

joining yields a strong bond, enhancing the rigidity of a housing assembly. Once parts

are welded, they cannot be disassembled. This is the process used for permanently

joining injection-molded parts.

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FASTENER

SNAPS

Boss

Flexible Snap

Job on:93996

Scn :

#

175 Si

Dept : DTP D/

2

Job on:93996 CTP Title : RP_Process Material Measurements Client : Pro_Vision

Scn :

#

175 Size : 146.05(w) 209.55(h)mm _M2_Mac D

Dept : DTP D/O : 16.12.05 (Job on:000000 D/O : 00.00.01 Co: CM0)

Pantone

109 U

p52

93996_PM&M_001-065.qxd5 16/12/05 11:18 AM Page 52