Transparent plastic injection molding

Transparent plastic due to higher light transmission rate, which inevitably calls demanding surface quality of plastic products such like PC injection molding, PMMA injection molding, etc, can not have any markings, holes, white, fog halo, black spots, color, luster is not so good a result, the entire injection molding process on raw materials, equipment, molds, and even product design, we must pay great attention to a strict and even special requirements. Second, because of transparent plastic, mostly high melting point, poor mobility, so as to ensure the surface quality of products that often require a higher temperature, injection pressure, injection speed and other process parameters have to make minor adjustments to make when both full of plastic injection mold, Also does not produce the internal stress caused by deformation and cracking products.

PMMA injection molding

Therefore, from raw materials preparation, equipment and tooling requirements, raw material for injection molding processes and products must be strictly deal with several aspects of the operation.

(A) the preparation and drying of raw materials

Since any point in the plastic contains impurities, may affect the product transparency, and storage, transport, feeding the process must pay attention sealed to ensure a clean raw material. In particular, raw materials contain moisture, heat, might cause deterioration of raw materials, they must be dry. In the injection, the feeding must be used a dry hopper. Would also like to note that the drying process, the type of air should preferably be through a filter, dehumidification, in order to ensure no contamination of raw materials. The drying process the following table, transparent plastic drying process: material drying temperature (℃) drying time (h) Material thickness (mm) Remarks PMMA 70 ~ 80 2 ~ 4 30 ~ 40 PC 120 ~ 130> 6 <30 with hot air circulating dry PET 140 ~ 180 3 ~ 4 with continuous drying is better feeder

(B) the barrel, screw and its annexes clean

In order to prevent contamination of raw materials and in the screw and accessories depression there is old stuff, or impurities, in particular, the existence of thermal stability of the resin, so before use, stopping applications after they screw cleaning agent to clean the parts, so that it can not stick with impurities, when there is no screw when the cleaning agent can be used PE, PS and other resins cleaning screw. When the temporary shutdown, in order to prevent the raw materials at high temperatures to stay a long time, causing lower solution should be drying machines and barrel temperature decreases, such as PC injection molding, PMMA injection molding, etc. barrel temperature should be reduced to 160 ℃ below (hopper temperature for the PC should be down to 100 ℃ below).

(C) It should be noted on the mold design issues (including product design)

To prevent backflow of poor or uneven cooling caused by plastic molding bad, resulting in surface defects and deterioration in general in the mold design, should pay attention to the following points.

a) wall thickness should be uniform, stripping slope be large enough;

b) the transition part should be a smooth and gradual transition to prevent any sharp corners, sharp edges produce, especially in PC products must not have gaps;

c) gate, flow channel as large, chunky, and the condensation process of contraction set in accordance with gate location, if necessary, add cold material should be well;

d) die surface should be smooth, roughness low (preferably less than 0.8);

e) Vent. Trough must be sufficient, as well as air and melt when the exhaust gas;

f) In addition to PET, the thickness should not too thin, generally not less than 1 mm.

(D) injection molding process should pay attention to the issues (including injection molding machine requirements)

In order to reduce internal stress and surface quality defects in the injection molding process should pay attention to the following aspects.

a) should use special screws, with a separate temperature-controlled radio Tsui injection molding machine;

b) injection of the temperature in the plastic resin is not decomposed under the premise of injecting suitably high humidity;

c) Injection pressure: a general high melt viscosity in order to overcome the shortcomings, but the pressure is too high will produce stripping difficulties caused by internal stress and deformation;

d) Injection speed: In the case of filling to meet in general should low, it is best to adopt a slow-slow a fast multi-level injection;

e) holding pressure time and molding cycle: to meet the product filling and do not produce depression, the case of air bubbles; should as short as possible to minimize the melt residence time in the barrel;

f) screw speed and backpressure: in meeting the quality of plastics under the premise should be as low as possible and prevent the possibility of the lower solution;

g) Mold temperature: cooling products, good or bad, a great impact on quality, so mold temperature must be able to precisely control the process, if possible, die Wenyi higher good.

(V) other aspects of the

In order to prevent the upper surface due to deterioration in the quality, generally when you minimize the use of injection mold release agent; When we go back to the materials used shall not be greater than 20%.

For addition to PET, the product should be carried out post-processing to eliminate stress, PMMA injection moulding should be 70-80t hot air circulation drying 4 hours; PC should be clean air, glycerin, liquid paraffin, and other heating 110-135 ℃, time as a product may be the highest need for more than 10 hours. The PET must be bi-oriented processes in order to get good mechanical properties.

Case Study

We have been with ST plastics since Royston and Bob took the reins some 3-4 years ago. ST have designed injection moulding tools to our specifications for over 20 product lines and supply us with a continuous stream of plastics which are used in our product and exported globally. Staying on shore and particularly with ST has proved to be a very smart management and fiscal move. Their co-operation, liaison, reliability, communication and willingness to accommodate change far outweigh any perceived savings one might achieve using resources off shore. Not to say ST are not competitive, they are, but the quality and reliability from the ST team are second to none.

plastic moulding

managing director

Roger

I have had dealings with ST for the past 5 or so years, and the service and response to any given problem is truly fabulous. I design machinery for a living, and plastics and associated materials form a very important part of the design process. Most important to the process is, I find, the need to obtain advice and assurances that a certain design is possible, and this is often required very early in the design process. I have found that ST Plastics are very capable of this, and it saves many days , even weeks in design work.

Their early evaluation of the design and how it might be cast in what product has been close to faultless. This is, in my opinion, what sets them apart from the typical toolmaker who often requires detailed drawings before you can get past the front door.

Their tool making expertise has been very good, allowing and preempting the shrinkage rates and distortion that will occur with many moulding procedures.

Very Very impressed with your entire business and service. Regards Paul Willett, Managing Director,

I am writing to endorse and highlight ST plastics .Bob & Royston have provided us with fantastic service right from the first contact , besides being professional and friendly they have made themselves available to us , which can be very reassuring .

Our line of work is in commercial construction, so time lines and installation schedules are tight & limited. Taking this into account Bob &Royston not only took the projects on but created working drawings & helped with design issues together with managing to supply us the finished product before the due date, enabling us latitude to complete our manufacture. In closing I can do nothing but recommend ST plastics to anyone that is in the market for their services. Dealing with them is easy & you can be confident of the service & outcome you require which makes them a perfect choice to help grow & improve product lines & productivity.

Yours thankfully

director

Shaun

I have had a long business relationship with ST Plastics and have always been happy with their service and expertise. Since taking over the business a few years ago, Royston and Bob have worked hard to take the company to another level. Their commitment to service, quality and customer satisfaction is honest and real. If you have need of injection mouldings look no further.

Brad

Managing Director

As manufacturers of the Odalog Gas Logger and Gas Detector range, Thermofisher Scientific, like our customers, demand only the highest quality and accuracy from our high-end gas instruments. Our instruments meet the needs of their industry, whether in a rugged underground mining environment or in the corrosive wastewater monitoring, so we need to be sure that the plastic parts that house our compact electronics are up to the job. At ST, our extremely high standards are completely understood and catered for with high quality, precision and repeatability of our ‘unconventional’ plastic moulding – even in small batches. With the experience, technical advice and superior customer service ST offer, we wouldn’t consider going anywhere else.

plastic molding

Design Engineer (Mechanical Engineer / Industrial Designer)

I have to compliment you, and all others of your company – and I don’t hand out compliments freely. As you might expect, in looking for a company to do this work for us, I contacted multiple Australian companies who advertise on the net claiming a high tech capability for tooling and production of prototype runs. All other replies I received demonstrated incompetence (at least in communication) or just plain disinterest.

You replied with intelligent communication and followed up with a phone call. Subsequently you have been most courteous in all contacts with me, and have demonstrated a high level of competence in the quality of the samples received today. Thus, in my view, ST sets a benchmark to which others should aspire. May your company enjoy well deserved success.

Geoffrey Wickham A.O.

Bioengineer