سؤال “كيفية تصنيع قالب حقن البلاستيك” يبدو سهل. بيد أن الإجابة أكثر تعقيدًا بكثير. يتطلب هذا الأمر العديد من الخطوات والعمليات المدربة. وبالتالي، فإنها ليست من الأعمال التي يمكن لشخص أن يقوم بها بمفردها في عطلة نهاية الأسبوع. إنها وظيفة متخصصة تستلزم مهارات الهندسة. العملية تتعامل مع توظيف الكمبيوتر في إنشاء أدوات حقيقية، تقوم بتصنيع المطاط بطريقة مماثلة. هذه الأدوات يمكنها إنتاج عدد كبير من الأجزاء البلاستيكية المتطابقة.
معدل الحقن هو جزء ومقياس دقيق. يتمركز في القلب من عملية حقن البلاستيك process plastic injection molding. القالب هو كتلة من الصلب أو الألومنيوم بها مسافة مجوفة بالداخل. هذه المسافة هي الشكل المعاكس للجزء المراد تصنيعه. هذا الدليل سوف يوجهك في كل خطوة من الخطي. نبدأ من ملف الحاسوب إلى قالب نهائي. ليفهم كل شيء بصورة أفضل، ينبغي عليك قراءة All About the Basics of Plastic Injection Molding أولاً.
قبل البناء: مرحلة ما قبل الإنتاج والتصميم الصحيح
قالب رائع يبدأ بتصميم جزء رائع. لا يمكننا قطع أي قطعة معدن قبل أن ننهي التصميم. الانتهاء منها هو الخطوة الأولى لنقوم بتهيئها للتصنيع. وهي تدعى التصميم للاستخدام الصناعي (DFM). هذا هو الخطوة الأكثر أهمية. يحول الدورة إلى أداة يتجنب الأخطاء الفادحة.
تحليل DFM هو الشرط الذي يضمن بأن الجزء يمكن تشكيله بشكل سليم وبسعر منخفض. نناقش نموذج 3D. نحن نبحث عن المشكلات المحتملة. المعرفة بتصميمات critical design guidelines for injection molding صحيحة عند القاعدة المتبعة.
أهم قواعد DFM التي نتحقق منها دائمًا، هي:
- زاوية الميل: تقع هذه على شكل انحدار بسيط على جدران الجزء. الحاجة بها. إذا لم تكن هناك زوايا انحدار، فإن قطعة البلاستيك تميل إلى التصاق بالقالب. وبالتالي يزداد الأمر صعوبة أو حتى يصبح الخطر بالمكان.
- سماكة الجدار الموحدة: يجب أن تكون جميع الجدران من نفس السمك في المساحات المختلفة. إذا كانت بعض الأماكن أسمك بشكل كبير من غيرها، ستحدث مشاكل. سيتبخر البلاستيك بسرعات مختلفة. سيؤدي ذلك إلى علامات الخسارة والانحناء والضغط داخل الجزء.
- Geometric issues: An undercut is a feature that stops the part from being pulled straight out. These features need special moving parts in the mold, which adds a lot of cost and makes the tool more complex.
- Parting Lines: This is the place where the two halves meet. Our placement affects the appearance of the final product. Usually, we try to put it on an edge that is not visible. This will hide the very faint line it creates.
- Material Selection: This point is so important that the choice of plastic has a bearing on the design of the mold. Different types of plastic will shrink at different rates after the cooling period. Therefore, the mold machine must be built a little bigger, to begin with, that will be taking in the shrinkage from the plastic.
Professional Mold Making Process: 7-Step Breakdown
As soon as the part design is perfect we shift gears and begin the mold-making process. The route from a computer file to a steel tool itself is like a mathematical equation to be solved. Each new element depends on previous successes. The combined effort of skilled craftsmen and superior machinery is the only path to success.
1. Final DFM Review & Mold Flow Analysis
Our first step is running the DFM one last time. Next, we often run a mold flow simulating program. This shows how the melted plastic will flow into the mold. The program helps us solve design problems before we even start making the mold. Air traps or weak joining lines can be a problem also.
2. Mold Design (Tooling Design)
After the part is approved, our engineers start designing the mold. They use computer-aided design software to create a 3D model of the whole tool. The core and cavity make up the two halves of the tool which shapes the part. It also includes the runners system that guides the melted plastic. There are cooling channels that help keep the temperature in check and an ejector system that pushes the part out.
3. Material Procurement
The supplier is the next target we hit for buying materials. The choice of metal fully depends on the project. We normally use mold steels like H13 for high volume production. We may also use P20 pre-hardened steel for prototypes or low volumes. Aluminum can also be used, but it has to be of high quality.
4. Mold Machining (Core & Cavity Creation)
This is the phase in which the mold comes to life. We generally use two types of methods to cut so as to form core and cavity steel aluminum blocks.
High-speed China CNC machining services employing computer-controlled cutters, cut the main shape of the core and cavity. The machine cuts the steel with extreme precision according to the 3D design file.
Electrical Discharge Machining (EDM) is the second method we use for extra fine details. Internal sharp corners or deep ribs we also EDM. EDM is burner electricity which wears the metal off. It makes features that machines can’t uncut.
5. Polishing and Assembly
After the machining process, the work surfaces get tool marks. The surfaces need special hand polishing to achieve desirable finished surfaces. The wanted finish can range from matte to mirror-like polish.
After polishing is done, the skilled workers assemble all components together. This includes fitting the core into the oil mold base, connecting the ejector pins, slides, and lifters, and running the cooling lines.
6. Mold Trial & Validation (T1 Sampling)
The big day of testing the mold is the first trial; we call it ‘T1’. We put the new mold in an injection molding machine and produce the first plastic parts. This is an important step to learn how to make a plastic injection mold work properly.
We check all T1 samples thoroughly. We measure them against the computer file. We also find common problems in the mold. This includes short shots that occur when the mold does not fill completely, flash is the additional plastic that leaks out, sink marks are the small dents in the surface, and weld lines mark the place where the two separated plastic flows met.
7. Revisions and Texturing (If Needed)
Of course, it is normal to make small adjustments after the T1 trial. We might have to modify the mold based on the parts we saw. This could be a change in dimension or the addition of new features which improve the product. This incremental approach is a key aspect of professional injection mold making.
Only after the mold has made the perfect parts and gets the go-ahead from the customer, do we proceed to add the textures. It could be a slight grain or heavy texture. We use chemical etching or laser engraving for this.
Selecting the right mold material: Steel vs. Aluminum vs. 3D-Printed
The material used to mold a product will impact on its cost, life cycle, and lead time. Understanding the differences is revolutionary. The first step is to select the right mold material. You basically have two options.
| Mold Type | Material | Production Volume | Lead Time | Relative Cost |
|---|---|---|---|---|
| Production Molds | Hardened Steel (H13, S7) | 500,000 – 1,000,000+ cycles | Long (8-12+ weeks) | High |
| Prototype Molds | P20 Steel, Aluminum | 5,000 – 50,000 cycles | Medium (4-8 weeks) | Medium |
| Rapid Molds | 3D-Printed Polymer | Under 100 cycles | Short (1-5 days) | Low |
Hardened steel molds like h13 hardened steel ones, are the masstdard for production; they are quite expensive but can do over a million shots.
Aluminum molds are ideal for prototyping and small batch production. They are faster and are cheaper to cut compared to steel. Although they are worn down in no time which is usually under 100,000 cycles.
3D-printed molds are the ones used for very fast and cost-effective prototyping. They have limited usage of fewer than 100 shots and only certain low-temperature plastics can be used with them.
Why to Partner with an Expert for Mold Making?
As you can see, to how to make a plastic injection mold involves way more than cutting a piece of metal. It requires a good command of part design, material science, and precision machining. Also, it is about having engineering process knowledge. The investment is in a high-quality steel mold.
Each part you make is directly influenced by the quality of the mold. The consistency and cost of the part are also affected. A lot of issues in production would happen if the mold were badly built. This results in the high scrap rate and also in a final product that fails to meet expectations.
Thus, teaming-up with an experienced manufacturer is indeed a clever choice. It mitigates the risk for your project. Guarantees you the best possible result. A reliable partner like Mekalite should be the one to supply you with the state of the art machines and expertise that will take your project all the way from the design stage to successful mass production.
FAQ: How to Make a Plastic Injection Mold
How long does it take to make an injection mold?
This period sees a lot of fluctuation. A basic single aluminium cavity mold will more or less require 4 to 6 weeks, And a multi-cavity, hardened steel mode with complex features will likely take more than 12 weeks depending on the size and features.
What is the most expensive part of making a plastic injection mold?
Precision machining and skilled labor are the biggest points in this case. CNC and EDM methodologies are still very expensive. Hand polishing and assembly require highly skilled employees. If the designs are complex, this will be charged separately, as well as fast tolerances, which can also increase costs by requiring more complicated tooling.
Can I make a plastic injection mold myself using a 3D printer?
Sure, you can 3D-print a very small prototype mold. You can only check these molds for less than 100 parts. They can work only with low-temperature plastics. Their lifespan is very short. They can not run at all.
What is the difference between a single-cavity and a multi-cavity mold?
A single-cavity mold is capable of producing just one part in one cycle of the molding process, thus is suitable for low-volume initial prototyping. The tooling cost will be lower. On the other hand, a multi-cavity mold will make two or more parts in one cycle, thus reduce the cost. An upfront multi-cavity mold is usually higher.
What is a mold base?
A mold base is the steel frame that holds all the mold parts together. It acts as the foundation. It has the core and cavity inserts, the ejector system, and cooling channels. It also has leader pins. Mold bases are often standard items that toolmakers buy and then customize.
Conclusion
To learn how to make a plastic injection mold is to learn about a manufacturing system as well. It is not a single task. It is a series of steps that are carefully planned and executed. The process of combining digital design, precision engineering, and handcrafting.
The road from a computer file to a finished mold is intricate. Nonetheless, it is the only route to achieve high-precision production of plastic parts. You can undergo this process confidently with the help of a proficient manufacturing partner. You can make your product idea a reality bit by bit with this method.
