The so-called adjustment of the machine refers to the constant adjustment of various parameters of the beer machine for the specific mold, until the qualified plastic parts are produced.
The various parameters of the plastic beer machine can be roughly classified as follows:
1. Preliminary comprehensive parameters:
For a set of specific molds, the following three parameters need to be considered before the mold is made:
1.1 Die size:
is Moho×Move× (Mothmi~Mothma) of injection molding machine. Its items must be greater than the corresponding items of the mold: Mwid×Mlen×Mthi (width×height×thickness)
1.2 Maximum injection volume:
is the maximum plastic weight SHWT(g) that can be injected by the injection molding machine. The total weight per beer of the plastic must be less than (or equal to) 85% SHWT and greater than (or equal to) 15% SHWT. (When the total weight of each beer>85%SHWT will reduce the efficiency of injection molding).
1.3 Clamping force:
is the maximum separation force that the mold can withstand after the mold is closed. Its size is approximately proportional to the projected area of the plastic part. The rough calculation formula is as follows:
clamping force (tons) = projection surface of cavity (inch 2) × material pressure coefficient
The material pressure coefficient of PS, PE, PP is 1.7; ABS, AS, PMMA is 2; PC, POM, NYLON is 3. For specific molds, the actual clamping force is ≤ rated clamping force of the beer machine × 90%. Excessive clamping force is not beneficial to the beer machine and will cause mold deformation.
2. Temperature parameter (T):
The temperature in the production process of beer is set according to different rubber materials. It can be divided into the following types:
2.1 Material temperature:
Beer production requires the water content in the raw materials to be dried to below a certain percentage, which is called the raw material. Because the water content is higher than a certain proportion of the raw materials will cause defects such as air blooming and peeling.
2.2 Barrel temperature:
The barrel from the hopper to the nozzle can be divided into: conveying section, compression section, metering section, the heating temperature of each section is collectively called barrel temperature
Spend. The barrel temperature is from low to high. In addition, the nozzle temperature is usually slightly lower than the temperature at the metering end.
2.3 Mold temperature:
refers to the surface temperature of the mold cavity. The set temperature is different according to the shape of each part of the mold cavity. Generally, the mold temperature of the part where the glue is difficult to remove is required to be higher, and the temperature of the front mold is slightly higher than that of the rear mold.
When the temperature of each part is set, the temperature fluctuation is required to be small, so it is often necessary to use auxiliary equipment such as thermostats and chillers to adjust the mold temperature.
3. Position parameters:
3.1 Screw position (S):
The segmental switching position of the injection speed and pressure of the screw is called the screw position.
The specific segments are as follows: S0 S1, S2, S3, SS. Among them, S0, SS are equal to the amount of melt required for one beer, and SS cannot be less than 10mm (usually between 15-20mm); S0, S1, S2, S3, and SS are the screw position segments, according to the flow of melt The position of the mold cavity is specifically set, S0, S1, S2, S3, SS are injection sections. Among them, S3 and SS are the pressure holding section.
3.2 SUCK BACK:
When the screw stops rotating after returning the material, the screw has a backward evacuating action, which is called rubber pumping, and the distance of the pumping is the rubber pumping distance. Generally, it is below 5mm. The purpose of evacuation is to prevent the melt glue from flowing in the nozzle; the evacuation should be appropriate, and too much evacuation will cause defects such as air blooms and bubbles in the finished product.
3.3 Mold opening position:
The distance between the back mold surface and the front mold surface is called the mold opening distance. Its size is so that the plastic parts can be taken out smoothly.
It is advisable to extend the cycle time after the conference.
3.4 Position of thimble:
is the distance from the mold surface after the ejector pin of the mold is ejected. Push the product away from the back mold surface
It is better to be able to win smoothly. Be careful not to make the thimble to the end, and there must be enough margin to avoid breaking the slingshot of the mold thimble plate.
Four, pressure parameters:
4.1 Injection pressure (IP):
The driving force given by the screw to the melt is called the injection pressure. According to the various segments of the screw position, different propulsive forces of the screw can be set to melt glue.
Such as S0 S1 is IP1; S1 S2 is IP2; S2 S3 is IP3. The setting of the propulsion force of each section mainly depends on the position where the melt flows in the mold cavity. When the flow through the mold cavity is complicated in shape and the glue position is thin, the resistance of the melt is large, and greater advancement is required. Force; when the flowing position has a simple shape and the resistance of the melt is small, a small propulsive force can be set to reduce the loss of the beer machine.
4.2 Holding pressure (HP):
After the melt fills the mold cavity, in order to compensate for the space formed by the mold cavity and compact the rubber material due to the cooling and shrinkage of the rubber material, at this time the screw still needs to give the melt glue a certain propulsion force, which is the pressure holding.
The position movement of the screw here is: S3 SS. Holding pressure is represented by HP. Generally, medium pressure is used for large rubber parts, and low pressure is used for small rubber parts. (Under normal circumstances, HP is less than IP).
4.3 BACK PRESS:
When the glue injection and pressure holding are completed, the screw starts to rotate. In this way, the rubber material in the screw groove and the hopper is pressed into the front end of the barrel (metering chamber) through the screw groove, and the melt has a reaction force on the screw. Forcing the screw to retreat is called material return.
In order to increase the density of the molten glue at the front end of the barrel (metering chamber) and adjust the screw retreat speed, an adjustable thrust must be added to the screw. This force is called back pressure. Adjusting the back pressure can adjust the mixing degree of the toner and the plastic raw material, and affect the plastic effect. Proper back pressure can reduce the defects of color mixing, bubbles, uneven gloss, etc., but the back pressure should not be too large. Too much back pressure will cause the melt to decompose, which will cause the plastic parts to change color, black lines and other defects. In addition, increasing the back pressure will inevitably prolong the production cycle and increase the loss of the beer machine, which is generally about 10kg/cm2.
4.4 MOLD PROTECT PRESS:
is also known as low pressure protection, which is the protection device of the beer machine to the mold. From the protection position of the mold to the moment when the front and rear mold surfaces are attached, during this period, the force of the clamping mechanism to push the back mold of the mold is relatively low. The mold will automatically open to stop the clamping action, so that if there is a foreign object between the front and rear molds during mold clamping, the mold can be protected.
The low pressure of mold clamping is generally that the mold with the row position is larger than the mold without the row position, and the value is 10-20kg/cm2.
4.5 MOLD CONTACT PRESS:
is also called mold clamping pressure. When the mold is closed to make the front and rear mold surfaces fit, the mold clamping force is automatically changed from low pressure to high pressure. The purpose is to have a certain pressure when the front and back mold surfaces are bonded, so that the mold position can be moved in place. The clamping pressure can not be too high, too high will crush the mold surface; when adjusting, make sure that the front and rear mold surfaces have a certain pressure, generally 80-100kg/cm2. (Generally, the whole clamping state: slow, high speed, low pressure Low-speed, high-pressure mold clamping).
4.6 Thimble pressure:
The ejection force applied by the beer machine behind the ejector plate of the mold is suitable for pushing down the plastic parts.
5. Speed parameters:
5.1 Injection speed (V):
When the beer machine is injecting glue, the screw pushes the moving speed of the molten glue. The injection speed is mainly affected by the injection pressure, the resistance of the mold cavity to the melt, and the viscosity of the melt itself. The injection speed can be set when the injection pressure is greater than the cavity resistance and the melt viscosity. Give full play.
For example: S0 and S1 are V1, at this time melt filling cavity requires low speed and medium pressure; S1 and S2 are V2, at this time melt filling cavity requires high speed and high pressure; S2, S3 are V3, melt filled plastic parts At the periphery, medium speed and low pressure are required, and the injection speed will slowly decrease as the filling resistance of the cavity increases, until it is zero. The setting of the specific injection speed of each section depends on the shape of the melt flowing through the mold cavity.
5.2 Screw speed (R):
The rotation speed of the screw feeding the barrel measuring chamber is called the screw rotation speed. It affects the retreat speed of the screw. When the back pressure is set, the higher the screw speed, the greater the retreat speed. Adjusting the screw speed can adjust the plasticizing effect of the rubber material, and improve the uneven color tone and color mixing of the product. However, if the screw speed is too high, the rubber material will be over-sheared and decomposed. The product generates bubbles.
PC, PE, PVC, POM, PMMA and other heat-sensitive plastics with high viscosity are not suitable for high screw speed. The screw speed is represented by R1 and R2. Generally, R1 uses medium speed and R2 uses low speed, which has a protective effect on the beer machine.
5.3 Glue drawing speed (SB.SPEED):
The retreat speed of the screw when it is evacuated is called the rubber pumping speed. Generally, medium and low speeds are appropriate.
5.4 Opening and clamping speed:
The mold opening speed is expressed by: MO1, MO2, MO3. Generally, the slow speed is used when the front and rear mold faces are separated, so the molds with different templates have different settings. Two-platen general settings: slow, fast, slow; three-platen general settings: medium, slow, slow. The clamping speed is represented by: MC1, MC2, MC3. Generally, the slow speed is used when the front and rear mold surfaces are in contact, so the two-plate mold
settings: medium, fast, slow; three-plate mode settings: medium, slow, slow.
5.5 ejector speed (EJ SPEED):
The speed at which the ejector pin pushes out the rubber is called the ejector speed. The rubber parts of different structures have different settings, and medium speed is generally adopted.
Six. Time parameter (t):
6.1 Game time:
Different compounds require different time. I 6.2 INJ-HOLD TIME:
The time required for the screw to move from S0 to S3, its setting must be consistent with the screw position movement.
6.3 Holding time (HT):
The time from S3 to the start of the screw feed is generally 1-2 seconds, not too long, too long will waste time.
6.4 COOLING TIME:
The cooling time is the period from when the screw starts to feed back to when the mold is ready to open. The cooling time should not be less than the return time.
6.5 Cycle time (CYCLE TIME):
The time required for the beer machine from the start of the beer to the beginning of the next beer. The requirement is that under the premise of producing qualified plastic parts, the shorter the better.