Normally, the term “injection mold” or “plastic mold” refers to a tool used primarily for plastic injection molding. Steel plates and other mold components are combined to create an injection molding tool. To create the desired shape for the project, these components are fitted together to form an overall mold, which is then installed in an injection molding machine and filled with thermoplastic resin. Plastic products are most commonly made with molds. Plastic molds fall into two categories: thermoplastic molds and thermosetting molds
How to estimate the cost of plastic mold
No matter whether you operate a job or captive shop, mold making costs must be estimated, either for bidding on jobs or accounting to manufacturing or staff departments. It is extremely difficult to generalize about cost estimating in plastics fabrication. Since most plastic mold making is hand work, mold making time is highly dependent on the workers involved. The time required for a worker to do a given job differs greatly, consequently this factor must be analyzed carefully in estimating mold making costs. In estimating, the more important factors to be considered are
- type of plastic mold, i.e., size, degree of complexity and required accuracy,
- method of fabrication to be used, and
- type of materials to be used. Basically, casting materials are estimated on volume cost/cu in.; laminates are figured by the square foot with relation to the thickness of laminate and variable contours involved. Labor on flat lay-up laminating runs about 20 to 25 sq ft/man hour. More intricate shapes and contours may run twice that amount. The best procedure for accurately estimating costs is to study individual workers in your own shop and estimate their productivity in terms of salary for your particular type of worker in your geographic locality.
The design software:
Raw Plastic Material:
|ABS (Acrylonitrile Butadiene Styrene)||PS (Polystyrene)||PA6 (Polyamide 66)||PA6 (Polyamide 66)|
|PET (Polyethylene Terephthalate)||PC (Polycarbonate)||POM (Acetal)||PP (PolyPropylene)|
|PVC (Polyvinyl Chloride)||TPR (Thermoplastic Rubber)||PE(Polyethylene)||Acrylic|
plastic mold steel specification:
|General plastic mold steel application|
|DIN standard||AISI standard||JIS standrad|
|General preharden plastic mold steel||618||638||PXZ(27-34HS)|
|Precise Mirror-effect Preharden Plastic Mold Steel||718S||2311||P20||NAK55|
|Pre-harden Mirror effect Rust-prevent Plastic Mold Steel||S-136H||2316||420||S-STAR|
|Anneling Mirror-effect Rust-prevent Plastic Mold Steel||S-136||2083||420ESR|
|Die Casting Plastic Mold Steel||8407||2344||H13||SKD61|
|Anneling||Quenching temp1020||Quenching temp1020||Quenching temp1020|
|Quenching temp||Quenching temp||Quenching temp|
|Quenchingtemp820||Quenchingtemp||Quenching temp||Quenching temp|
|Toughness High Chromium Steel||XW-41||2379||D2||SKD11|
|Quenching temp||Quenching temp||Quenching temp||Quenching temp|
|wear-resist High Chromium Steel||XW-5||2080||D3||SKD1|
|Quenching temp||Quenching temp||Quenching temp||Quenching temp|
Cost function and costs similarity
In mold-making shops the quotations are generally determined with the help of prognosis procedures. From the literature two general basic methods for predicting costs are known : cost function and costs similarity.
- The first method: the cost function starts with the assumption that there is a dependency between the costs of a mold and its characteristics. This dependency is expressed in a mathematical function. The characteristics are the independent variables or affecting quantities, which determine the costs.
- The second method is the cost similarity. Starting with an injection mold to be calculated and its characteristics, another existing plastic injection mold with similar characteristics is looked for in the shop. The costs for this mold are generally known and can now be used for the new object. In doing so one can fall back on existing data such as the system of classification.
Both methods have their advantages and disadvantages. The cost function provides accurate results only if the affected quantities have nearly the same effect on costs. This is rarely the ease with the variety of injection molds today.
With the similarity method one can only fall back on molds which are designed in the same way and, thus, have similar cost-effective quantities. To make use of the specific benefits of both methods a combination of them presents itself ，this can be achieved by grouping similar injection molds or structural components of the same kind together and determining a cost function within each group.
The basic requirements for injection mold design can be summarized as follows:
Ensure the product quality and dimensional stability
The product quality includes appearance quality and internal quality.
The excellent appearance quality includes complete and clear structure shape, surface roughness (including etching and sandblasting, etc.) that meets the requirements,
And no injection molding defects such as weld lines, silver streaks, black spots and black spots.
Excellent internal quality M includes no plastic injection defects such as loose tissue, bubbles and bright spots.
The dimensional accuracy and stability of the product depends on the manufacturing accuracy of the plastic mold, the mold design and the injection molding parameters.
However, the dimensional stability of the product usually depends only on the design and injection molding setting.
The dimensional instability of the product is usually due to the shrinkage.
In order to control the shrinkage of products, not only should there be an appropriate injection molding process, but also the following points should be followed:
(1) A good temperature regulation device makes the temperatures of all parts section of the mold approximately equal;
(2) For the multi-cavity injection mold, the cavity and cooling channel arrangement should make the mold achieve temperature and pressure balance;
(3) Choose a reasonable gating system from the product structure and size.
(2) The mold should be a safe and reliable tool in production.
The mold is a tool for high frequency production.
In each production, its actions must be correctly coordinated, stable and reliable.
Mechanisms to ensure safe and reliable molds include the following:
(1) the fixed-distance parting unit in the three-plate plastic mold;
② Lateral core pulling mechanism;
(3) the first reset mechanism of the push rod plate;
(4) transmission mechanism and anti-rotation mechanism of products in the inner pattern demoulding mechanism;
⑤ Secondary pushing mechanism.
(3) The service life of the mold convenient for maintenance is very long. In order to facilitate future maintenance, the mold shall be designed as follows:
(1) the fragile cymbals are assembled and spliced to facilitate replacement after being damaged;
(2) the direction of the side core pulling should give priority to choose both sides;
(3) cooling water to enter the internal mold insert through the mold frame;
(4) oblique push rod should not slide directly on the push rod panel;
(5) the pressing block on the sliding block is made into a combined pressing block, etc.;
⑥ the fixed-distance parting mechanism in the three-plate die shall preferably adopt the external type.
(4) To meet the requirements of mass production, mold is characterized by being able to repeatedly produce the same product or products, usually requiring hundreds of thousands or even millions of lives. In order to achieve this, the following points must be paid attention to indie design:
(1) the formwork must have sufficient strength and rigidity;
(2) the internal mold insert material must have sufficient hardness and wear resistance;
(3) The mold must have a good heat exchange system to shorten the injection cycle of the mold;