In the world of plastic product manufacturing, there is a multitude of different processes which makes it confusing on which process is the best process for your produce you unique product. On this page, we will explain some of the most used processes, the material used in each, and the strengths and limitations of each. This will allow you to select the process that meets your unique MOQ, Engineering/Design, manufacturing, and COST requirements. The plastic manufacturing processes we will discuss are:
When machining plastic in Plastic Product Manufacturing are relatively endless machining process possibilities to machine plastics as long as the plastic is rigid. Most in the thermoplastics plastic with a few thermosetting plastics have the ability to be machined.
Any standard machining process can be used. This is one of the most underutilized processes since 3D printing became readily available. This is because it is a common thought that if you want a prototype utilizing 3D printing is the lowest cost. For smaller parts, one, two our five parts this might be true, however larger more complex parts with runs from 3-25 machining can be the more economical and quicker
Can be economical for quantities of 1-25 in 1-3 weeks
Parts will have machining marks and better suited for machine shops who specialize in the machining of plastics with the availability of powder coating to give the part a more cosmetically pleasing look.
They are relatively endless as long as they are rigid mostly in the thermoplastics plastic with a few thermosetting plastics with the ability to be machined.
Plastic injection molding uses “thermoplastics”, plastics that melt with heat, and inject the melted plastic into a mold cavity to create a cavity image, the finished plastic part. A typical plastic injection unit can be broken out an explained in three specific areas
A. The Thermoplastic Injection Unit
B. The Mold
C. The Clamp
The Plastic Injection Unit is comprised of 5 major parts:
In the plastic injection molding process, the plastic pellets are first put into the hopper which feeds the pellets into the plastic injection unit’s barrel. As the reciprocating screw turns the pellets are pushed forward and are mixed by the flutes/flights on the screw. The screw diameter increases closer to the mold and with the combination of the friction of the screw action and heat distributed by the heating bands the plastic melts and is fed into the chamber in front of the screw. Then the hydraulic ram pushed the screw forward injecting the mold sprue with the melted plastic in a matter of seconds. Most times in less than seconds the plastic component is ejected out of the mold and the process repeats itself. For larger plastic components and plastic housings, the timing will be longer.
The Plastic Injection Mold is comprised of
The Thermoplastic Mold Process in Plastic Product Manufacturing: The molding process starts when the Injection Unit injects the melted thermoplastic into the sprue, the inlet that feeds the thermoplastic into the mold cavity in a closed plastic mold. Cooling water is circulated in the mold through water channels to help speed up the Thermoplastic solidification. Once solidified the mold will only slightly open a 1/64″-1/32 to break the vacuum for a couple of seconds the open all the way. The ejector plate and backplate move forward pushing the ejector pins which in turn pushed the finished plastic part, ejects it, from the mold cavity. Them the ejector assembly moves back, and the mold is closed, and the operation repeats itself.
Mold Design: When designing a part and having a plastic injection mold designed and manufactured to produce your part you need to have a more detailed understanding of design and mold components considerations to:
These considerations are (see the Mold Diagram):
In the thermoplastic injection unit, the clamp houses the mold. Before the injection process, the two halves of the mold must be mounted to the “clamp”. On either side of the clamp, there is a large stationary plate called the platen. Each side of the mold must be mounted to the corresponding platen. The front half of the mold, the mold cavity, is mounted to the front plate aligning with the injection unit nozzle. The rear plate, the core half of the mold, is mounted to the rear platen that operates, moves the mold utilizing a large hydraulic ram.
Thermoplastics come in pellets that can be mixed to get the desired color or transparency:
Although the processes vary slightly between the manufacturers of the LSR injection machines typically the LSR (Liquid Silicon Rubber) Injection Molding starts with 2 buckets are barrels of different silicone components. These components are then pumped into a mixer. The mixed material is COLD. The LSR is then sent to a screw. Sometimes the screw will directly inject the LSR into the mold or send the mixed LSR to a separate plunger that then injects the mixed LSR into a HOT (275F-390F) mold that then rapidly solidifies the LSR part and then the part is removed.
Rubber/Silicone Compression Molding: This is one of the oldest a very simple molding process. Rubber/Silicone Compression Molding only has two major components:
A. The Mold
The process is also relatively simple. A premeasured amount of un-vulcanized rubber or silicone material, slug, is placed in one half or both halves of the mold. The mold is closed and heated to a predetermined time, and the rubber or silicone is vulcanized.
First, for selecting the correct plastic component manufacturing process, it comes down is what material you require, NRE cost you can recuperate and the physical geometry of the part to be manufactured.
Second, the last two items you must consider are a “Cradle to Grave” and a FULL-SERVICE COMPONENT CONTRACT MANUFACTURER.
FULL-SERVICE means the contract manufacturer can provide you with a finished cast part including machining, PEM/Fastener installation, silk screening/engraving and metal components if required, a “one stop shop“, eliminating having to resend out your part for a secondary process to a separate multiple vendors. This makes controlling processes errors from multiple sources difficult.
“Cradle to Grave” means as your product matures, we will continually give you suggestions, (process changes, material changes, sub-assemblies) to reduce your cost giving you an improved sales advantage. An example would be per at the beginning of marketing your product, PROTOYPING, your volumes are low, and you do not want to make the investment in molds and manufacturing quantity, Ionthis could make your finished part or parts from machining from a solid block or unitize an aluminum mold. Your NRE investment would be low but part price might be higher but absorb-able. When your volume gets high enough to justify the NRE then Ionthis can move you into a high production molds. This is “Cradle to Grave”.
For a DFM/Analysis and recommendations of your Die Cast, Investment Cast and Sand Cast component or assembly, feel free to contact Ionthis at email@example.com