By providing faster cycles, reducing downtime and maintenance costs, the \"3r\" approach provides a more efficient alternative to molding thread closure.
While plastic bottle covers have thousands of different styles, they can be classified according to three main molding methods: stripping, foldable core, and unscrew
For closed parts with internal threads, the manufacturing method is usually determined by the resin defined and used by the thread.
This article gives a brief introduction to the first two options for using internal threads for moldingclosures-
Peeling and foldable soft ribs.
It then delves into the options that are screwed down and proposes a new method for patent \"3R (
Rotating ratchet ring)design.
Stripping off normally, stripping off is produced on a simple mold, just press the molded product on the core.
This is the simplest and most effective way.
However, the part may produce threads with inconsistent dimensions and distortions (
When they pop up too early)
, And deformation wall caused by thread displacement.
Therefore, these parts are unacceptable due to cosmetic and performance reasons, and the efficiency of downstream capping may be reduced.
Part design is also limited.
Parts must be made of non-brittle materials such as polyethylene or polypropylene.
They must also have a shallow thread with a circular profile, usually no more than one lap thread.
Collapsible core needs a different approach to generate deeper and more defined threads.
Similar to the stripping thread mold, the collapsiblecore mold contains a stripping ring that pops the part up on the ore.
However, the core consists of three or more parts.
The center segment acts as a wedge.
In its front position, it maintains the position of the external part to produce the desired molding surface.
When the center part is retracted from the part, the external part is close to releasing the thread, allowing the stripping ring to pop up the part.
In some designs, the central part of the core does not weaken the direct reading.
This allows the center part to be removed from the part.
Therefore, it is not acceptable for closures to have an interrupted thread.
The fact that the movement of the outer segment does not allow the description of the sealing feature on the top surface of the core limits this method of lining closure.
Many different methods of forming parts have developed over the years.
They provide varying degrees of performance and reliability that can be categorized according to different methods of partremoval.
Either unscrew the core from the part or unscrew the core from the core.
The rotating CoreRotary core mold represents the most widely used method for mold thread closure.
In many variations that exist, so-
Molds known as \"gears and gears\" are the most common.
Figure 1 represents the typical section of the gear rack mold.
The order of injection is as follows: 1)
The rack moves in a linear direction and drives the gear connected to or belonging to the core. 2)
The resulting rotational motion unscrew the core from the part.
The ratchet ring passes through the small teeth embedded in the closed skirt to prevent the part from spinning with the core. 3)
When screwed, the ratchet ring passes through the cam forward index to maintain the engagement with the part.
Although there are many successful changes on this topic, most designs have some limitations inherent.
To compare with the new 3R unscredesign design: core cooling, these limitations are explored in depth.
In order to minimize the required pitch travel on the pitch and pinion molds, the drive gear on the core must be as small as possible.
This can limit the size of the larger cooling Channel
Diameter off. Rotary seals.
The core cooling fluid must be equipped with a sealing device.
Although the sealing design is constantly improving, they may be another source of water leakage even in the case of relatively short use time (
See explanation below). Core rotation.
The core rotation causes wear between the core and the taper closure of the ratchet ring.
Wear and tear will be treated as a vertical flash when closed (
See explanation below).
When the rotary seal is used to rotate the core mold, the presence of contaminants in the coolant is the main cause of the leakage.
Particles may exist in the form of sand or silt, or in the form of minerals, sulfuric acid, silica and phosphate buildings.
They may also be the result of corrosion.
Affect corrosion (MIC)
As a by-product, this has also generated scale deposits.
Chemical additives used to control corrosion can also attack rotating seals.
For all practical purposes, it is impossible for contaminants to be completely eliminated.
Particles can move between the seal and the diameter of the seal, eventually resulting in wear grooves
Even in a highly political situationchrome surface.
Even if there is no deposit, the rotating seal will be worn out. Back-
The upward seal is usually provided on the rotating core mold.
The Up seal is generally not designed for dry operation and may fail before the main seal.
Continuous monitoring is required.
If the coolant does leak the seal, it causes widespread corrosion damage to the bearing, which is usually located next to the seal.
Another factor that causes water leakage is the rotation of the core.
The rotation is affected by many factors, including the internal clearance of the bearing;
Clearance in bearing installation;
The position of the bearing relative to the rack and the distance from the other racks;
Prominent parts other than bearings;
Dislocation between bearing plates; and wear.
All of these factors allow the core to oscillate during rotation, thus continuously compressing and decompressing the seals.
The faster the core rotates, the faster the seal reacts to changing gaps.
By reducing the rack speed, the risk of leakage can be reduced, but the cost is to increase the cycle time.
Any oscillation of the core during rotation can lead to wear and tear when the core and the ratchet ring are tapered off.
The alignment bushing between the gear ring and the ratchet ring is usually provided, but the bushing will wear out and need to be monitored.
The water pressure corresponding to the inside of the core exerts constant pressure, forcing the core to move forward.
Any clearance in the bearing or gasket used for axial alignment will allow the core to move forward when rotating.
This maintains the engagement with the ratchet cone during the initial rotation and can accelerate the wear of the cone.
Since the cam mechanism design is usually used for mostrack and pinion molds, any wear on the Cam, Cam follower, or wear platform can result in premature mating that becomes thinner during the delay and reset period of the time-varying thinner when unscrewed.
As a result, the part of the core rotation is completed as the bonding becomes thinner.
Again, this can accelerate taper wear.
Another option for rotating the core die is to unscrew the part from the core.
This can be achieved in two ways: by building the unscrew function in the mold, or by using a machine that performs the unscrew function outside the molda so-
Screw down system based on mold with two core half part and three half parttie-
Bar machine with unscrew mechanism.
The core part is mounted on a swing plate that rotates around one of the iron bars.
The cavity is semi-installed on a fixed template.
The pop-up order is as follows: 1)
The parts are formed on the first set of cores. 2)
Then the plate swings 180 [degrees]
Near the tie bar. 3)
Then, when the first group is connected by unscrewing the Chuck, the part is formed on the second group of cores. 4)
The Chuck holds each part from the outside and screws it down from the core. 5)
The Chuck then indexes and pops up the part.
This method removes all moving and rotating components from the old component.
The mold is simplified and the maintenance requirements are reduced.
Removal of the rotary shut-off valve eliminates vertical flash, static O-replaces rotary sealrings.
Because the bearings, gears and bearings have been removed and the best water channel scanning is used to minimize cooling, Grease is not required.
Because the mold is very simple, the maintenance required is much less, and because the molding cycle is faster, this method is proved to be an economical method compared to the traditional unscrewed mold.
Economy, that is, as long as the product meets this method and the production requirements are high enough, it can be proved that the initial cost is high. 3R (
Rotating ratchet ring)
A new method for unscrewing parts from a fixed core
The mold is screwed down by the mechanism, which is the 3R method for obtaining a patent.
Figure 2 represents a typical cross section of the 3R mold.
The following is the olding order: 1)
When the mold is opened, the air piston moves the bearing platform forward, occupying a small space between the Cam and the Cam follower.
This provides the initial clearance between the core tapers and the hot ratchet ring. 2)
The hydraulic cylinder pulls the Cam and the rack, which in turn drives a series of small gears. 3)
Each pinion drives a set of four rotating ratcheting rings that are screwed into the closure by embedding the small teeth of the closing skirt. 4)
When the part is screwed down, the forward movement of the bearing plate maintains this grip.
The rate of movement of the support plate is controlled by the CAM and Cam follower device. 5)
At the end of the movement of the bearing plate, compressed air helps to insert the part. 6)
Before the mold is closed, the bearing plate is returned by the air piston before repositioning the rack/cam mechanism. 7)
The one-way clutch in the drive gear allows to reset the rack and Cam structure after the mold is closed.
As with the rotary core and foldable core methods, the 3R design has the advantage of running in a standard machine.
However, it does have some additional benefits compared to these methods: * the thread on the closure device is usually the thickest wall segment and tends to adjust the cycle.
If the closure is screwed too early, the friction experienced on the thread can overcome the internal strength of the part.
This causes the thread to swell and twist, resulting in a capping problem.
With the 3R method and the elimination of any restrictions on core cooling, the dimensions of the cooling channel can be increased and closer to the forming surface.
Therefore, parts can pop up faster.
* Since the core is no longer rotating, the physical demand for the core material is reduced, and it is possible to emphasize more thermal conductivity when selecting the core material (e. g.
This can bring significant additional improvements in heat dissipation and further shorten the cycle time.
* Like the screw down system described above, the fixed core of the 3R method allows the replacement of the rotating seal with staticO-rings.
This greatly reduces the maintenance requirements and the risk of water leakage.
* If the humidity level is high, condensation can also occur on thecooled core.
If the aligned bearing is in contact with the core, bearing corrosion may occur.
The 3R design places the aligned bearing on the ratchet ring away from any potential moisture build-up.
* The 3R design reduces the risk of wear between the core and the ratchet ring tapering and subsequent vertical flashes by: 1)
Before the rotation, provide the initial clearance between the core and the ratchet ring cone (
See pop-up order). 2)
Clutch, which allows the ratchet ring toremain to stand still during Cam and rack reset. 3)
Reverse the cam mechanism to allow the bearing plate to follow the cam instead of being driven by the CAM.
This ensures that even after Cam wear and Cam follow wear, the forward movement of the bearing plate will not be delayed. 4)
Alignment has been improved because the needle bearing at the end of the ratchet eliminates any protruding part.
* The reverse implementation of the one-way clutch and cam mechanism allows the reset of the rack and Cam after the mold is closed.
This eliminates any delay in the cycle (rack reset)
Allow the flexibility of the double ejection stroke if required.
* Another benefit of using a one-way clutch is that in the unlikely event of an attack (
Or exceed the torque design standard)
, Before any damage to the gear teeth, the clutch will slip and no torque will be transmitted.
* The fixing core also allows the thread to start to align with the precise rotation of the cavity.
* Gear ratio, drive gears, and ratchet rings can cause a deceleration stroke for most of the closures.
* The number of racks required is reduced by half compared to the rotary core design, which allows the hydraulic cylinder to be placed between racks.
Since the rack and Cam are located behind the core, the hydraulic cylinder can also sink into the mold shoe
Air and water services required at the core.
The benefits of repositioning the hydraulic cylinder include reducing the overall height of the mold and thus making it easier to handle;
Reduce the risk of part contamination in case of hydraulic leakage;
And shorter racks and cameras (
Also need to reduce the result of rack travel).
* Another major benefit is the increased accessibility of module components.
This allows for quick replacement and replacement of the product without removing the mold from the molding machine.
The tilt of the front bearing plate exposes most of the main components, including the ratchet ring, the drive gear, the clutch mechanism, the pinion, the wear plate, the positioning bearing, the thrust gasket, the air piston and the seal.
Rotating Core and 3R mold, producing the same 38-
Both the mold and hot runner are manufactured by samesupplier and tested on the same husky LX300 machine with an auxiliary screw injection device.
All process setting parameters are the same. Part weight: 5.
Number: 2110 mn50 color: white;
% Concentrate: 3% mold process temperature: 10 [degrees]
CResults: 3R molds are able to produce acceptable parts at Cycle Time 1. 5 sec (18. 3%)
Faster than rotating core mold.
Most cycle improvements are due to shorter retention and cooling times (0. 9 sec).
Another reason for the improvement is faster pop-up and mold closing time (0.
6 seconds fast). See Fig. 3. ReferenceP.
\"Thread closure molding: an alternative,\" speantec Tech.
34 papers, 264 (1989).
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