The so-called machine adjustment refers to the continuous adjustment of various parameters of the brewing 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 upper mold is made:
1.1 Mold size:
It 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:
It is the weight SHWT(g) of the maximum plastic that the injection molding machine can inject. The total weight of each beer of the plastic beer must be less than (or equal to) 85% SHWT, 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:
That is, the maximum separation force that the mold can bear after the mold is closed. Its size is approximately proportional to the projected area of the molded part. The rough calculation formula is as follows:
Clamping force (ton) = projection surface of cavity (inch 2) × material pressure coefficient
Among them, the material pressure coefficient of PS, PE, PP is 1.7; ABS, AS, PMMA is 2; PC, POM, NYLON is 3. For a specific mold, the actual clamping force ≤ the 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 beer production process is set differently according to different rubber materials. It can be divided into the following types:
2.1 Local material temperature:
During the production of beer, it is necessary to partially dry the moisture content in the raw materials below a certain percentage, which is called partial material. Because the moisture content is higher than a certain proportion of raw materials, it will cause defects such as air flowering and peeling.
2.2 barrel temperature:
The barrel can be divided into conveying section, compression section and metering section from the hopper to the nozzle. The heating temperature of each section is collectively referred to as the barrel temperature. Barrel temperature 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 mold cavity surface temperature. The set temperature is different according to the shape of each part of the mold cavity. Generally, the mold temperature of the parts that are difficult to glue 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 a constant temperature machine and a chiller to adjust the mold temperature.
3. Position parameters:
3.1 Screw position (S):
The segmental conversion 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 and SS are equal to the amount of melt glue required for one beer, and SS cannot be less than 10mm (generally between 15-20mm); The position of the mold cavity is specifically set, and S0, S1, S2, S3, and SS are the injection sections. Among them, S3 and SS are pressure-holding sections.
3.2 Glue pumping position (SUCK BACK):
When the screw stops rotating after returning the material, the screw has a backward pumping action, which is called glue pumping, and the distance that is pumped out is the glue pumping distance. Generally, it is less than 5mm. The purpose of evacuation is to prevent the melt from flowing at the nozzle; the evacuation must be appropriate, and too much evacuation will cause defects such as air marks 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 to be able to take out the plastic parts smoothly.
It is advisable to extend the cycle time if it is too large.
3.4 Ejector position:
It is the distance from the mold surface after the ejector pin of the mold is ejected. Make the product lift off the rear mold surface
And it is advisable to win it smoothly. Be careful not to let the thimble reach the end, and there must be enough margin to avoid breaking the slingshot of the ejector plate of the mold.
4. Pressure parameters:
4.1 Injection pressure (IP):
The driving force given by the screw to the melt is called the injection pressure. According to each segment of the screw position, different propulsion force of the screw can be set for the melt. The setting of the propulsion force of each section mainly depends on the position where the melt flows in the mold cavity. When the shape of the mold cavity flowing through is complex and the glue position is thin, the resistance to the melt will be large, and a larger propulsion is required. When the shape of the flowing position is simple and the resistance of the melt is small, a small propulsion force can be set to reduce the loss of the beer machine.
4.2 Holding pressure (HP):
When the melt glue fills the mold cavity, in order to compensate for the space formed by the mold cavity and compact the glue material due to the cooling and shrinkage of the glue material, the screw needs to give a certain propulsion force to the melt glue, and this force is the holding pressure.
The position movement of the screw rod here is: S3 SS. Pressurization is indicated by HP. Generally, medium pressure is used for large rubber parts, and low pressure is used for small rubber parts. (Generally HP is less than IP).
4.3 Back pressure (BACK PRESS):
When the injection and pressure keeping are completed, the screw starts to rotate, so that the rubber material originally 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 glue has a reaction force on the screw at this time Forcing the screw to retreat is called back material.
In order to increase the density of the melt at the front end of the barrel (metering chamber) and adjust the speed of the screw to retreat, an adjustable thrust must be added to the screw, which is called back pressure. Adjusting the back pressure can adjust the mixing degree of the toner and the plastic material, and affect the plastic effect. Appropriate back pressure can alleviate defects such as color mixing, air bubbles, and uneven gloss of the plastic parts, but the back pressure should not be too large, as excessive back pressure will cause the melt to decompose, causing discoloration, black lines and other defects of the plastic parts. In addition, increasing the back pressure will inevitably prolong the production cycle and increase the loss of the beer machine, generally about 10kg/cm2.
4.4 MOLD PROTECT PRESS:
Also known as low-voltage protection, it is a protection device for the beer machine to the mold. From the mold protection position to the moment when the front and rear mold surfaces are attached, during this period, the force of the clamping mechanism to push the rear mold of the mold is relatively low, and when a resistance higher than the driving force is encountered during the advancement process, The mold will be opened automatically to stop the mold clamping action, so that if there is any foreign matter between the front and rear molds during mold clamping, the mold can be protected.
The mold clamping low pressure is generally larger than the mold without rows, and the value is 10-20kg/cm2.
4.5 MOLD CONTACT PRESS:
Also known as clamping pressure, when the mold is closed to make the front and rear mold surfaces fit together, the clamping force will automatically change from low pressure to high pressure. The clamping pressure should not be too high, otherwise it will damage the mold surface; when adjusting, it is enough to make the front and rear mold surfaces have a certain pressure, generally 80-100kg/cm2. Low speed, high pressure clamping).
4.6 Ejector pressure:
The ejection force applied by the beer machine to the back of the ejector plate of the mold should be large enough to eject the plastic parts.
5. Speed parameters:
5.1 Injection speed (V):
When the beer machine is injecting glue, the screw drives the moving speed of the melt. The injection speed is mainly affected by factors such as the injection pressure, the resistance of the mold cavity to the melt, and the viscosity of the melt itself. When the injection pressure is greater than the cavity resistance and the viscosity of the melt, the set injection speed can be achieved. Full play.
For example: S0, S1 is V1, at this time, the melt glue fills the cavity, and low speed and medium pressure are required; S1, S2 is V2, and the melt glue fills the cavity at this time, and high speed and high pressure are required; S2, S3 is V3, and the melt glue fills the plastic parts Periphery, medium speed and low pressure are required, and the injection speed decreases slowly with the increase of cavity filling resistance until it reaches zero. The specific setting of the injection speed of each section depends on the shape of the melt flowing through the cavity.
5.2 Screw speed (R):
The speed at which the screw feeds material to the barrel metering chamber is called the screw speed. It affects the backward speed of the screw. When the back pressure is set, the higher the screw speed, the greater the backward speed. Adjusting the screw speed can adjust the plasticizing effect of the rubber material and improve defects such as uneven color tone and color mixing of the product. However, if the screw speed is too high, the rubber material will be decomposed due to excessive shearing, and at the same time, air will be mixed into the barrel, causing 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 pumping speed (SB.SPEED):
The retreat speed when the screw is evacuated is called the glue pumping speed, and it is generally advisable to choose a medium or low speed.
5.4 Opening and clamping speed:
Mold opening speed is represented by MO1, MO2, and MO3. Generally, the slow speed is used when the front and rear mold surfaces are separated, so the settings of molds with different templates are different. General settings for two-plate molds: slow, fast, and slow; general settings for three-plate molds: medium, slow, and slow. Clamping speed is expressed by: MC1, MC2, MC3, generally slow speed is used when the front and rear mold surfaces are in contact, so the setting of two-platen mold: medium, fast, slow; the setting of three-platen mold: medium, slow, slow.
5.5 Ejector speed (EJ SPEED):
The speed at which the thimble ejects the plastic part is called the thimble speed. The glue parts of different structures have different settings, and the medium speed is generally used.
6. Time parameter (t):
6.1 Round material time:
Different compounds require different times.
6.2 Injection time (INJ-HOLD TIME):
The time required for the screw to move from S0 to S3 must be set to match the position of the screw.
6.3 Holding time (HT):
The time from screw S3 to the start of feeding is generally 1-2 seconds, and it should not be too long, otherwise it will waste time.
6.4 Cooling time (COOLING TIME):
The cooling time is the time from when the screw starts feeding back to when the mold is ready to open. The cooling time cannot be less than the return time.
6.5 Cycle time (CYCLE TIME):
The time required for the brewing machine to start the brewing process and start the next brewing process. The requirement is that the shorter the better on the premise of producing qualified plastic parts.
