Detailed Explanation of Foam Mold Design

Detailed Explanation of Foam Mold Design

The mold for foam molding is a plastic foam mold. The foamable resin is directly filled into the mold, heated and melted to form a gas-liquid saturated solution, through nucleation, a large number of tiny bubble nuclei are formed, and the nuclei grow to form a foam plastic part. There are three commonly used foaming methods: physical foaming, chemical foaming and mechanical foaming. Let's take a look at the design principle of the foaming mold. I hope it will be helpful to everyone's study!

1. The principle of foaming mold

1. Types of foaming raw materials: EPS, EPP, EPE, EPO, etc.

2. Molding principle: mold closing, feeding, steam heating, cooling, demoulding

2. Overall structure of EPS foam mold

Design the mold according to the type of the customer's machine, and match it with the customer's machine.

1. Water tank (steam chamber): three-piece mold, the customer has a standard water tank. Taiwan machine, Fangyuan machine, and other machines do not have a standard water tank, and the water tank must be determined according to the mold arrangement of the product, which is also called one-piece mold.

2. The three-piece mold has three plates, which are called convex template, concave template, and gun plate. The convex template is used to fix the convex model cavity, and the concave template is used to fix the concave model cavity. Back plate, mainly equipped with ejector rod cover and material gun.

3. Pressing material: A structure designed for the cooperation of the punch and the die, which is convenient for pre-opening and feeding, so that the material does not run out during pre-opening and feeding. Calculated according to the mold clamping steps and templates of the water tank, there are two kinds of pressing materials: free space and no space. If there is no space, the pressing material of the concave and convex molds is the same. If there is space, the pressing material of the concave mold plus the space is equal to the pressing material of the punch. , Die pressing material is not less than 10 mm.

4. Flange side: that is, the space between the die and the die formwork, which is convenient for installing screws. It is determined according to the steps of the water tank mold clamping and the formwork. Generally, it is suitable to be about 15 mm, not less than 10 mm. There is another kind, Set from the bottom of the formwork to the top, called reverse support, the height of the reverse support is determined according to the thickness of the formwork, such as the Coulter model, which generally adopts the reverse support type, and the Japanese model generally adopts front installation with flange sides.

5. Wall thickness: The wall thickness of EPP molds is generally about 15 mm, the wall thickness of EPS molds and EPO molds is between 8 and 10 mm, and the wall thickness of EPE molds is generally 15 mm, unless the customer specifies otherwise.

6. Shrinkage: The shrinkage of general foaming mold EPS material is 0.3% (domestic) and 0.4% abroad. Customers with low ratios require 0.25%, 0.2%, etc. EPO materials are generally between 0.9% and 1.0%; EPP, EPE material shrinks differently according to different magnifications; EPP and EPE materials are divided into JSP raw materials, cardboard raw materials, etc., and the shrinkage is different. Therefore, the shrinkage of EPP, EPE and other materials is provided by the customer, or it can be provided by the raw material manufacturer. Such as two domestic raw material companies, JSP and Kaneka;

7. Air core: air core ∮4, ∮6, ∮8, ∮10, ∮12 and other specifications, there are two types of strip type and pinhole, and there is also a non-porous air core, stuffy air core; according to the requirements of the general Air core, special air core, such as strip type, the strip type straight seam is 0.25mm~0.4mm is a special air core, generally made by wire cutting; the ordinary strip type straight seam is 0.8 mm ~0.7mm; EPS raw material Molds use more pinhole air cores, and EPP, EPE and other raw material molds use more bar-shaped air cores, which generally use pinholes for planes and sides; air cores are divided by material, including aluminum air cores, copper air cores, and stainless steel air cores. Core, aluminum gas core is commonly used, others are determined according to customer requirements.

8. Drilling the air core: first use a drill to make a good hole. Generally, the drill bit is selected to be 0.3~0.4 mm smaller than the air core, and the air core is evenly distributed. EPS generally adopts a 25×25 space between the air core and the air core. EPP and EPE generally use the air core The space between the gas core and the gas core is 20×20, unless the customer requires it. To flatten the air core, the air core must be knocked in place three times. The air core that is knocked flat once is loose. , plus the pinhole between ∮0.6~0.8mm.

9. To find the parting line, the parting line should be made according to the maximum shape of the product, and then the pressing material should be made to separate the concave and convex mold cavities, and the processing technology should be analyzed to facilitate processing, inflating cores, polishing, etc.; if it is difficult to do it properly, do it locally It is best to make blocks, and it is best to make a limit for the block, which is convenient for installation; the product has an undercut and a perforation on the side, and it is used as a slider for core pulling; according to the cavity of the concave and convex molds, the wall thickness of the mold is made, and the wall thickness according to the customer's requirements To do it, remove the excess material on the back of the cavity, try to make the wall thickness uniform, and make the demoulding slope as far as possible on the back, so that the wood sample can be easily demoulded when sanding. For the positions of the ribs and pillars on the back, you can first make a 2D layout diagram, and design the position of the ejector rod, material gun, and pillars.

10. Name plate: made according to the drawing requirements.

11. Release top: If there is a gap between the concave formwork and the convex formwork, a release top must be installed. It can be made of ∮30 aluminum rods and fixed with screws. It is made according to the height of the release space. The distribution is even, about 200~ The spacing of 250mm is appropriate and installed on the concave formwork.

12. Locating pins: According to customer requirements, install locating pins to facilitate the mold to play a guiding role when closing the mold and prevent the mold from being damaged.

13. Clamping system: Foreign molds and Ehrenbach models are often equipped with a mold clamping system, which fixes the convex formwork and the concave formwork for easy hoisting. After installation, open the clamping lever, which is generally not used for domestic molds.

14. Feed gun: generally equipped with the customer, the mold is made according to the customer's feed gun, and the hole of the feed gun is made, which is 0.2~0.5mm larger than the feed gun mouth. Some need to be limited, and some do not need to be based on customer requirements Do.

15. Ejector: Generally, customers have ejectors with fixed specifications, and design molds according to customer requirements. If customers want to match ejectors, we can provide a complete set of ejectors, such as ejector sleeves, sealing rings, push rods, springs, and pins. , Ejector head.

16. Pillars: There are convex mold pillars and concave mold pillars, which are made according to the height of the water tank of the client machine. The pillars are generally arranged evenly, with a distance of about 150mm. The distance between EPP molds can be smaller, and the distance between EPS molds can be larger. Try not to If the section exceeds 200mm, the pillar can be fastened with fastening screws, flat base, inner and outer hexagonal screws, depending on the mold structure, and the thickness of the plate; if the pillar is connected with the gun plate with screws, the gun plate has been drilled through holes There must be a sealing ring to prevent air leakage, and the screws should be as large as possible, such as M10 mm.

17. Water pipes: According to the mold layout diagram, design the water pipes by leaving the ejector rod, material gun, and pillars open. The distance between the nozzles on the water pipes is 100~120 mm. Try to let the water spray to every place on the surface of the mold. After cooling completely, the mold is very fast. If it is high, you can add a small water pipe. Generally, it is equipped with a concave mold water pipe, and the convex mold water pipe is generally available on the client machine. The water connector is made according to the data of the client machine. The structure of the foaming mold is roughly like this. The mold should be designed according to the customer's machine, and the designed mold must be convenient for the customer to install.

3. Types of foaming molds: Most of the domestic molds are Kurt Japan Daisen, Japan Sekisui, Fangyuan Machine, Juxin Machine, Taiwan Machine, and most foreign countries are Kurt and Allenbach.