Previous Page 142 4 Mold Selection gate must be opened to access the mold for servicing. The rear gate is usually either screwed locked, or does not have safety features such as drop bars. Opening the rear gate often stops the operation of the machine completely, even shutting down the hydraulic pumps. Over the years, with these safety features in molding operations, the number of personal injury-accidents has greatly decreased. Referring back the Fig. 4.54, plates (a) and (c) must be locked together solidly even though they are clamped together during injection by the clamping force of the machine. If plastic is injected...

Selection of an Appropriate Mold Because of the better cooling, the, mold will cycle faster for higher productivity Interchangeability of components is easier to achieve and repairs are less costly. Heat expansion is not a problem; by having the cores mounted to float a limited amount to self-align with the cavities, regardless of any temperature difference between the plates, the size of the mold (number of cavities) is not limited. If this design is used for molding products that can only be ejected with air, it becomes a really simple mold, with very few mold shoe components. This method is of...

Selection of an Appropriate Mold Self-degating is somewhat more expensive than edge gating and while an insert for the gate area adds some cost, it may be necessary for long running molds to avoid expensive repairs later. The somewhat higher mold cost may be well worth it in the long run. There is a number of different designs for tunnel gates [5]. The size of the tunnel gate is determined the same way as the size for any other gate; however, there is a limit to the size that the can be sheared off cleanly. ...

Mold Selection Selection of an Appropriate Mold Once a good product design has been achieved and it is decided where the product will be made and how many cavities are required, we must consider the available alternatives for the molds. Dedicated Mold, Universal Mold Shoe “Dedicated mold” means a complete mold that is used for one purpose only. After use, the mold is put into storage until it is used again.

Schematic of ejection timing with added MO time Multi-Cavity Molds Especially with multi-cavity molds, it may not be possible to clear all molded pieces out of the molding area in time and some MO time will have to be added. The need for this MO time should be closely scrutinized; while it is sometimes not possible to avoid MO time, it is quite common that the setup persons add extra MO time “just to be sure” that the pieces have cleared, rather than to ensure that the ejection, including air assist, is properly adjusted and timed as intended. ...

Required Shot Size of the Mold Shot size is an important characteristic of the molding machine, which affects the molding cycle. But first, what is the difference between “shot size” and “rated shot size”? “Rated shot size” is the amount (in grams or ounces) of polystyrene (PS) that the injection system (ram screw or two-stage) can inject at every cycle, and is indicated in all machine specifications. “Shot size” depends on the mass (W) of the molded product (in grams).

A mold’s productivity is ultimately measured by how many good parts it can produce over time. A mold that runs very fast but is frequently down for maintenance or repair will not produce at lowest part cost and highest productivity. Conversely, a mold that runs too slow but produces parts consistently over time is not optimal. The same can be said for each component in the injection molding system. One way to quantify productivity is to measure the total equipment productivity (TEP): TEP = Production hours (auto cycling) Parts made Scrap parts × × Available hours Hour Parts produced...

General Appearance of the Product Parting Line Flash Good molds have venting around most of, if not the whole length of the parting line. As long as the stack and the vents are designed properly, there should never be flash on the parting line. If flashing does occur despite a properly designed and built mold, there could be a number of other causes: The selected molding machine has not enough clamp force (tonnage) for the projected area of the cavity and the required injection pressure or was not adjusted properly. ...

Fitting Surfaces of Mold Parts This applies to all surfaces of mold parts that abut on other mold parts, but are not in touch with plastic. Usually, grinding or fine machining surfaces are required where the dimensions stack up and their sum must be held to close tolerances. Otherwise, ordinary turning and milling surfaces are sufficient. We have dwelled on the finishing of mold parts to highlight the importance of properly specifying how and where a mold (mold part) needs to be finished (polished) because of the cost....

Are Special Fits with Matching Products Required? Often, certain dimensions of a product are specified with unnecessary close tolerances, when all the designer wanted to convey is that the product should fit suitably on another product (tightly or loosely), typically, a container and a matching lid. This requirement must be clear. Especially, when molding plastics with high shrinkage factors (e.g., PP or PE), it can be difficult to arrive at the proper “steel” dimensions, and some experimenting may be required to achieve the required fit. ...

Plastics have evolved to be a very useful material. Today, plastics are used in almost every area, from small bottle caps, disposable cutlery, and packages for dairy products, to large containers, such as laundry baskets and garbage pails. Plastics have transitioned from a “cheap” substitute for metal and glass to the material of choice providing almost unlimited design freedom, unique properties, and significant cost savings. Figure 2.1 shows various industrial containers and house wares that create durable products in cycles from 10–30 seconds....

Today, injection molding is probably the most important method of processing plastics in the production of consumer and industrial goods, and is performed everywhere in the world. Once the decision has been made to use injection molding for a new product, a number of difficult choices are ahead which will be addressed later in more detail: Number of cavities Stack design, which is the purely technical aspect of how to mold the product.

AND lệnh này sẽ thực hiện một phép và logic trện hai toán hạng đích và nguồn đạt kết quả vào đích

Các số không dấu được định nghĩa như những dữ liệu mà tất cả mọi bit của chúng đều được biểu diễn dữ liệu và khó có bit dành cho số âm hoặc dương

CPC có thể truy cập dữ liệu theo nhiều cách khác nhau . Dữ liệu có thể ở trong một thanh ghi hoặc trong bộ nhớ hoặc được cho như một giá trị tức thời các cách truy cập dữ liệu khác nhau được gọi là các chế độ đánh địa chỉ

Mặc dù các thành viên của họ 8051 đều có các kiểu đóng vỏ khác nhau , chẳng hạn như hàng chắn DIP dạng vỏ dẹt vuông QFP và dạng chíp không có chắn đỡ

Tham khảo tài liệu 'lập trình 8051 : các lệnh nhảy , vòng lặp và lệnh gọi', kỹ thuật - công nghệ, tự động hoá phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả

Trong mục này chúng ta bàn về nhu cầu đối với các bộ vi điều khiển và so sánh chúng với các bộ vi xử lý cùng dạng chung như Pentium và các bộ vi xử lý x 86 khác

Tài liệu giúp các bạn tìm hiểu nội dung các chương sau: chương 1 phương pháp tính và tự động hóa tính toán thiết kế tàu, chương 2 tính toán nối và tính ổn định tàu, chương 3 sức cản vỏ tàu, chương 4 thiết kế chân vịt tàu thủy, chương 5 thiết kế tối ưu tàu thủy.

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