runner components of injection mold

Runner components between the two mold plate and three plate mold because there are different functions of these components, but there are several components that can be used in general without looking at the type of mold construction.

1.Runner lock pin
The main function of the runner lock pin (RLP) is an pulling runner so
the gate can be disconnected/cut from the product, RLP fitted with a straight gate position, the head planted on the top plate, while in the body mounted on the cavity plate (3) up to the top
plate (1). RLP does not move during the injection process lasts, mold base plate
moves accordance with the mold opening sequence, the tip of the runner lock pin is the part that greatly affects the success or failure of the gate runner cutting process. Greater the undercut which is the stronger the ability of RLP to attract runners from the gate, the type of plastic material also influenced for selection of RLP.
2.RLP Lock
RLP lock have function to maintain RLP order not to loose from its position, there are various ways to lock them RLP
* closed with a locating ring or sprue bush or heat insulation board.
* using a plate
* use a screw plug
3. Bushing RLP
high cycle time mold or need durability are advised to use the bushing,the benefits include easy maintenance of RLP, more resistant to wear due to friction so it's can avoid direct contact between RLP and mold plate that can caused wears, this method will shorten maintenance time.
4. Ejector runner
Only used if the runners stuck on the stripper plate mold base or stuck on the cavity mold bases, the use of the runner ejector can help the runner release from the place that was not supposed to stick. Other components are collar to the head of RLP, and change flow components

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using mold base become locking block of slider unit

moldbase sometimes can be used for the locking block on the slider unit, this is basedon several reasons, for example, to reduce cost, by reducing the insert locking block, the other reason is required surface area for the locking block.

illustration picture above shows the angular pins are bolted to the mold base and the mold base made pocket instead of locking block,

to keep the process easy to do maintenance, should be installed oil slide plate, so when it can wear easily replaced without the need to change their plate slider block.
This model is widely used for large parts and molds with a tonnage greater than 350 tons, other advantage is the size of the mold base to be more compact and small, so the cost for the mold base can also be reduced, and if the size is smaller base can mold into tonnase also smaller

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Loose core for ejecting undercut at injection mold

Picture above shows the loose core, or often also called slope ejectors or inclined pin, loose cores is one method to overcome the undercut on the product, particularly undercut the core position facing into the bottom (towards the sprue bush-center of mold) that undercut it can not be made simply by using slider method, part of the loose core complete with mold base include:

1. Top clamping Plate
2. stripper plate
3. cavity plate
4. core plate
6. support plate
7. top ejector plate
8. bottom ejector plate
9. bottom clamping plate
10. loose core rod
11. loose slide unit
12. bushing

for more details look at the picture below, which shows the current position of loose cores prior to the occurrence of loose core ejecting position after ejecting process, shortly after the mold is closed and the injection process, loose cores in the closed position (note the closed mold), after the injection process is complete done, at the push of ejector rod, ejector plate both upper and lower parts helped push out through the ejector, while the loose-core because it has a certain slope (generally 8-15) when driven will move slowly into center with the aid of friction on inclined leader pin bushings, so the position Loose cores are separated from the undercut product (mold opened)

 

Slide the unit mounted on the ejector plate is always on the top or at the bottom, and the main mover of the loose core are ejector rod simultaneously with the process of ejecting, points to consider in designing the loose core is strokes and angles used, too little angle of it can reduce the occurrence of abrasion (wear) but required a long stroke.

If angle is too large can cause the inclined pin (loose core) broken because of the occurrence of high abrasion, but required a shorter stroke. The angle that is used is usually between 8-15 0, while the stroke must be exceeded 5 mm or more to keep the loose core is certain regardless of the undercut in the product.

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Loose cavity inner undercut release method in injection Molding

one way to release the undercut is to loose cavity, the opposite of loose cores, loose inner cavity is used to remove the undercut in the cavity area, note the image below for more details,

1 = top plate
2 = runner stripper plate
3 = cavity plate
4 = core plate
5 = locking block for loose cavity
6 = angular pin for loose cavity system
7 = loose insert cavity

 

some designers also say that with the inner mold cavity slider, whatever his name is, in essence, functions and works the same way. when the first opening between the top runner stripper plate (2) with the cavity plate (3) top plate will pull locking block (5) together with the angular pin (6), aided by the spring on the insert cavity, this movement causes the loose insert cavity to move straight straight to the angular movement of the pin, as a result of friction between the angular pin with a hole in the loose insert cavity.

when construction is used, ie if your product has undercut formation on a position in the cavity region, angular corners and locking block commonly used ranged from 8 to 20 degrees, above the angle can cause angular cartilage pin was broken, because the force that fought too large.
Another thing to note is the stroke, you must ensure that the stroke of movement of loose cores must be secure, which is about the length undercut products coupled with the 5-10 mm.

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Top 6 Injection Molding Company

it's difficult to list all company that provide any solution about injection machine, include manufacturer, injection molder, machine maker, and injection design, based on the survey is limited to friends and colleagues associated with the injection mold, which many ads appear on Google, and companies that contribute most in the book and seeing appear in the books of injection mold, here I will be showing 6 of the most famous course according to my own version, because I do not have complete data. assessment should be based on the type of machine made, proceeds, income per year, the number of employees, average employee welfare, customer satisfaction and how many problems that arise from the resulting product.



1. HUSKY,
if you often read a book mold, of course, will easily recognize these companies from Canada,
Husky designs and manufactures the industry’s most comprehensive range of complete, integrated injection molding systems for a variety of key markets. Our systems include Hylectric, HyPET, HyPAC and HyCAP
    * Hylectric  – our base platform on which we've build a wide range of specialized systems for a variety of applications including closures, thinwall/IML, pails, and cutlery
    * HyPET – lightweight PET preforms
    * HyCAP – high output beverage closure manufacturing
    * HyPAC – high performance thinwall packaging


2.SUMITOMO DEMAG
Sumitomo (SHI) Demag is one of the leading manufacturers of plastic injection moulding machines anywhere in the world together with its Japanese parent group. More than 3,000 workers come up with and produce outstanding machines and solutions at 4 production locations in Germany, Japan and China.
 develop and manufacture a range of all-electric,hybrid and hydraulic injection moulding machines with clamping forces ranging from 180 kN to 40,000 kN.


3. ARBURG
is one of the leading global manufacturers of injection moulding machines. Robotic systems, complex production cells and other peripherals are also included in our product range.

4. NISSEI
This company is very famous in world injection machine, because kepresisianya especially for products with small tonnage, nissei producing machine with a capacity of 7 tons to 1500 tons, penjualanya many areas of Asia and America


5. DONGSHIN

Dongshin Hydraulics has continually striven to be one of the
premier manufacturers of injection molding machines world-wide through our continual investment in reserch and development-with 38 years of acquired technology and the closest co-operation with our customers.
since its establishment in 1960 the company was growing rapidly and could become the best performing companies in Korea in 2007, the marketing is a broad range ranging from southeast asia, korea, china to India and Africa.


6. JSW
As a leader in the industry, JSW provides a full line of injection molding machines, ranging from small to ultra-large models, which offer ease of operation, safety, and environment-friendly improvements such as energy- and space-saving features. Moreover, we offer technical support in line with customer needs, including consulting service and systems for factory automation. JSW has established a global network which covers the United States, Europe, and Asia

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wall thickness and sink mark estimation

Uniform wall thickness in plastic part design is critical.Non-uniform wall thickness can cause serious warpage and dimensional control problems.One of the easiest ways to cure this problem is change the part geometry by adding ribs. The use of ribs is a practical way and economical means of increasing the structural strength of a part.  it is more economical to use ribs than increase wall thickness, But there are guidelines that govern adding ribs without causing sink marks or surface blemishes to your parts. in parts requiring good surface appearance, ribs should be avoided as sink marks on the opposite surface will surely appear.

The wall thicknesses of an injection-molded part generally range from 2 mm to 4 mm (0.080 inch to 0.160 inch). Thin wall injection molding can produce walls as thin as 0.5 mm (0.020 inch).

Rib thickness should be less than wall thickness. A rib thickness of 60% to 80% of nominal wall thickness is recommended. (plastics1.com)

using finite element software or relevant software for injection mold like, Mold flow, C-Mold, Etc, we can estimate the sink mark that will appear, picture below for example, with different rib we can see that sink mark result also different, first rib (from left) have 0.6 * thickness part, second rib thickness same with part thickness, 

Thick sections cool slower than thin sections. The thin section first solidifies, and the thick section is still not fully solidified. As the thick section cools, it shrinks and the material for the shrinkage comes only from the unsolidified areas, which are connected, to the already solidified thin section (efunda.com)

non uniform wall thickness also can cause voids and non-uniform shrinkage, for example in a sharp outside corner and a properly filleted inside corner could present problems due to the increased wall thickness at the corner. to prevent that we can add additional radius or shape like picture below 

How About Bosses?

Bosses are used for locating, mounting, and assembly purposes. There are boss design guidelines that must be followed to insure the highest quality in molded parts. Again, one of the main points to consider is nominal wall thickness. Too many times bosses are designed with thick wall sections that can affect the appearance of the plastic part and the final product. (plastic1.com)

As a rule, the outside diameter of a boss should be 2 to 3 times the hole diameter to ensure adequate strength. The same principles used in designing ribs pertain to designing bosses, that is, heavy sections should be avoided to prevent the formation of voids or sink marks and cycle time penalty.Less good design of bosses can lead to sink marks.

to prevent that, design the boss like picture below is preferred

Rule of thumb: the wall thickness around a boss design feature (t) should be 60% of the nominal part thickness (T) if that thickness is less than 1/8". If the nominal part thickness is greater than 1/8" the boss wall thickness should be 40% of the nominal wall
.Boss diameter, wall thickness, and height design parameters. While boss heights vary by design, the following guidelines will help avoid surface imperfections like sink marks and voids: the height of the boss should be no more than 2 1/2 times the diameter of the hole in the boss.

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