Mold sprue bush,AKA.The main runner refers to the melt flow passageway from the joint between the injection molding machine nozzle and the mold sprue bushing to the starting point of the branch runner.
–The design has to minimize melt temperature drop/pressure loss.
–Adopt the cone shape design, to facilitate removal of the condensed material
Forms of The Mold Sprue Bush
Fixing Methods of the Mold Sprue Bushing
The main runner is usually located along the center line of the plastic injection mold, overlapping with the axle of the injection molding machine nozzle.
In horizontal and vertical injection molding machines, the runner axle should be perpendicular to the parting surface.
To facilitate removal of condensed materials from the main runner, the main runner should be designed into the cone shape, with a cone angle of 2 – 6º; the diameter of the smaller end D ＞ d + (0.5~1mm), d refers to the diameter of the injection molding machine nozzle.
The internal surface roughness of the main runner Ra ＜ 0.4; and the length of the main runner usually ＜ 60mm.
The transition between the bigger end of the main runner and the branch runner should adopt an arc-shaped design, of which the corner radius is 1 – 3mm.
Since the main runner is the first contact point of the high temperature molten plastic, which also frequently make contact with the injection molding machine nozzle, damages by collision tend to occur. Generally speaking, the sprue bushing needs to be fixed to the fixed clamp plate. See the following figure for the structure of the sprue bush.
The hardness of the mold sprue bush should be lower than that of the injection molding machine nozzle.
In a mold structure, the cooling channel tends to leak at the joints between mold plates as well as those between the mold plate and the core insert due to the existence of joint gaps. To prevent this from happening, O-rings are often applied to seal the joints.
Mold structure design should take the following principle into consideration in case O-rings are applied:
Ensure sufficient positive pressure between the mold plate and the core/Cav insert.
The inclination of sliders should be kept between 15 and 25 degrees, and the inclination of the guide pin should be 2 degrees smaller that of the wedge. The available diameters of the guide pin are 6mm, 8mm, 10mm and 12mm, with the min and max values being 6mm and 12mm respectively. If a slider width is larger than 60 mm, deployment of 2 angle pins needs to be considered; if the width exceeds 80mm, a guide bar needs to be placed under the slider in middle.
If the injection mold sliders is too high, the starting point of the angle pin hole needs to be lowered, so as to ensure smooth travel of the slider. If slider open/close time needs to be delayed, the diameter of the guide pin hole will need to be enlarged.
When the injection mold sliders are deeper in the cavity than its own length, a wedge will not be necessary. The inclination can be designed on plate A directly. A R3 is required at the bottom. Besides, the slider doesn’t need a wear block.
When depth of the slider is mainly in the core, a wedge will be needed; if the part profile surface contacting the slider is large, or there’s kiss off or shut off on the slider, a reversed wedge should be applied and the inclination should be 10 degrees or above;
If the part profile surface contacting the slider is small, the slider can be designed as shown in Fig. 3.1.6, and the height of the wedge surface should be higher than 2/3 of the slider height.
The wear plate of the mold slider employs the 2510 steel, of which the hardness reaches up to HRC50°-52°. For all sliders with a thickness of over 50.0mm, wear blocks should be placed on the base and the back. These wear plates measure 5mm in thickness, and are 0.50mm higher than the mold base. And for all the sliders, a clearance is not needed along the travel direction of the slider (as shown in the following Fig.)
The width and height of the slider clamp – made from the 2510 steel with a hardness of up to HRC50-52 – are 20mm and 20mm respectively, while the length is dependent on slider.
For upward (including inclined ones) sliders, there are raised fine inserts and pins. When there’s an ejector pin under the slider, a spring can be applied to facilitate return.
Spring is built in the mold core and the slider (see 3.4.1A, 3.4.1B and 3.4.1C)
If the travel distance of the slider is long with an installation length of over 50mm, the spring may be mounted outside.
Air/Hydraulic Cylinder driving
If the height of the guide pin is larger than 100mm (see Fig. 3.7.1A) and the cavity slider needs to be lifted before A and B plates separate from each other, a Air/Hydraulic cylinder may be applied to drive it (see Fig. 3.7.2B).
Design Standard of Slider Inserts (Pins)
Design Standard of Slider Stops
For the undercut of a circular product with sliders on 4 sides, a stop needs to be mounted to the slider insert. It is better to design a separate stop for each individual product if there are multiple products in a single mold.
There are many types of guide pin structures in plastic injection mold application, among which the standard structural design is shown in the figure below. A guide pin has to serve as the cylindrical surface of concentric circles of different diameters. Based on structural dimensions and material requirements, a round steel bar with an appropriate size can be directly selected as the material. In addition, the technical requirements of guide pins need to be satisfied during the machining process.
Fig. 8-2 Structural Shape of a Guide Pin
Technical Requirements of Guide Pins
(1) At the joint between the guide pin and the fixed mold plate, the diameter concentricity tolerance should not exceed 1/2 of the diameter tolerance in the working portion.
(2) The cylindricity tolerance of the guide pin in the working portion should be kept within requirements.
(3) After being machined, the precision, surface quality and thermal treatment of each part of the guide pin should meet the requirements specified in the drawing. When applicable, the carburized layer on the working surface is required to be uniform usually with a thickness of 0.8 – 1.2mm.
Machining Process of Guide Pins
(1) Material Preparation & Cutting. The commonly used material of the guide pin is the 20 steel (or select materials as per the drawing). After cutting, an allowance of 3 – 5mm should be retained for facing; and an allowance of 3 – 4mm for cylindrical turning.
(2) Facing & Centering. Turn one end, retain a turning allowance of 1.5 – 2.5 mm, and drill the centered hole; turn the other end to specific dimensional requirements and drill the centered hole.
(3) Cylindrical Turning. Roughly turn the cylinder, and retain an allowance of 0.5mm on each side for grinding. When applicable, groove the guide pin to specification.
(4) Inspection. Inspect the finish sizes of the previous steps.
(5) Thermal Treatment. Follow the process, and ensure a carburization thickness of 0.8 – 1.2mm. After carburization, the quenching hardness is 58 – 62HRC.
(6) Lapping. Lap the centered hole on one end, and then lap the one on the other end.
(7) Grinding. Apply cylindrical grinder and centerless grinder to grind the cylinder. After grinding, an allowance of 0.01 – 0.05mm should be retained for lapping.
(8) Lapping. After machining, the surface of the cylinder needs to be lapped to reduce surface roughness, thus meeting the surface finish requirements.
(9) Inspection. Inspect the finish size of each step.
Texturing refers to the process that produces various patterns on the surface of a metal product through chemiosmosis, such as stripes, images, wood grain, leather pattern and stain, etc., while also including sandblasting, which means spraying glass sands directly onto the surface of a metal product.
The Purpose of Mold Texture
Improve product appearance. The texturing process is able to camouflage part of the shrinkage, welding line, parting line and steps of slider, etc.
Product surface strength can be improved via texturing and sandblasting.
Varieties of Mold Texture
Sand Pattern
Characteristics: Fast process, low cost and able to produce fine and 2D patterns.
Satin Pattern
Characteristics: Fast process and able to be applied to a plane surface. Twice as durable as the sandblasting process, and able to cover the weld lines and sagging marks on a rough surface.
Leather pattern and others
Characteristics: Durable. Product surface is abrasion resistant though cannot be fixed completely. Able to remove burnt and rust marks caused by chemical gases through surface treatment.
Other textures include stone/geometric patterns, HNDS and HN3D which are not commonly used. This time, we are going to do the satin pattern.
Procedure of Mold Texturing
Cleansing
Clean the mold cavity surface, to remove surface oil/grease.
Sealing
Apply adhesive paper or corrosion resistant coating to the cavity surface that does not need to be textured, so as to prevent corrosion. This is the most time consuming step, during which the 3 commonly used sealing materials include: Thick adhesive paper, to cover the majority part of the cavity surface; thin adhesive paper, to seal the details; and corrosion resistant coating, to cover the area that adhesive paper fails to cover, e.g. complicated curvy surfaces.
Drying
Dry the anti-corrosion coating.
Surface treatment
Carefully wipe the cavity surface to be textured using absorbent cotton, to make it free from any dirt, thus ensuring the texturing effect
Texturing
Apply a coating to the cavity surface to be textured and then soak it in the corrosive fluid. During this process, attention should be paid to the texturing status. Repeated soaking is required to get the desired textures.
Sandblasting
Sandblasting serves 2 purposes: A). To remove the residue liquid on the cavity surface after cleansing, with ammonia and pressure washer; B). To tune the gloss of the texture; different levels of gloss can be achieved by using different sands and different pressure levels.
Post treatment
Cleanse the cavity surface and apply rust protection agent before delivering the mold parts back to the mold manufacturer.
Common Post-texturing Problems
Due to the fact that the mold cavity surface is roughened after texturing, the most common problems like scratches and stickiness to the cavity may arise. In some areas, the originally small draft angle will be made smaller after texturing, or even resulting in a negative draft angle sometimes, so scratches are often caused. During the ejection process, ejector marks tend to appear due to unfavorable mold release, thus greatly affecting the part appearance.
To resolve the problem of scratches and ensure smooth mold release, the textured surface usually needs to be sandblasted to reduce the texture depth and at the same time eliminate the acute angles caused by texturing. In the practical production scenario, it is very difficult to resolve the mold release problem by adjusting injection parameters, so release agent is usually applied to the textured surface to facilitate production. From the perspective of mold, the situation may be improved by increasing the draft angle in the scratched surface area/increasing the number of ejector pins.
1. Ejector pin holes should be at least 3/32” away from other holes;
2. At least a clearance of 1/32” for pin holes on the ejector plate;
3. At least a clearance of 1/64” for pin holes on the mold plate;
4. All ejector pins should adopt the standard dimensions; the ejector base cannot be ground lower;
5. During the injection molding process of nylon, LDPE or PP, the diamter of each ejector pin must be measured, because flash might occur when the clearanc between the pin and the hole is greater than 0.02mm
6. All ejector pin holes must be vertical and glossy (Ra ~ 0.25μm);
7. For plastic materials like PP, PE and Nylon, hole diameter = pin diameter + 0.01mm; for plastic materials like HIPS, PC and ABS, hole diameter = pin diameter + 0.02mm;
8. Ejector pin should pass through the base plate, ejector plate and mold components in a straight downward way;
9. After all ejector pins are installed, the ejector plate should be able to slide downwards freely;
10. Labels in the same direction should be provided near the location of all ejector pins and screw heads, so as to prevent wrong installation;
11. All pins need to come with dowels, to prevent wrong installation (the application of square-shaped pinhead should be avoided, unless the distance between ejector pins are very small; it cannot adopt the symmetric layout, but only the one-sided way. Usually, the 1st one should be applied; apply the 3rd when there is not sufficient space);
12. Upon installation of ejector pins, everything needs to be checked before covering the back panel;
13. After installation of the supporter, use a flashlight to examine each rib and hole from the direction of the mold core, to see if there is any problem with pins or sleeve ejectors. Cover the back panel when everything’s OK;
14. When designing the location of ejector pins, in addition to guaranteeing sufficient ejection force, it has to be ensured that the product can be ejected in a straightforward way;
15. There are two types of ejector pins, i.e. though-hardened and nitrided;
15.1 Though-hardened – surface hardness is 65 – 74HRC, and steel core hardness is 50 – 55HRC;
15.2 Nitrided – the nitrided surface hardness is 65 – 74HRC.
Design of Runner Ejector Pins
Purpose:
Eject the gate/runner from cavity.
Forms of Pins
2.1 Option 1 (for general purpose)
2.2 Option 2 (for general purpose)
2.3 Applied to transparent materials like PMMA
Design of Ejector Pin Location
Pin Locations
1.1 The ejector pin should be 0.040″ – 0.100″ away from the top edge of the upper mold;
1.2 Try to place the ejector pin at the bottom of the product, such as the Pin A shown below. Try to keep a distance of at least 0.010” from mold core. Don’t place on the top (Pin B)
1.3 If an ejector pin has to be placed on a slope, Location “A” is the first option,followed by “B” and “C”, because a product tends to dislocate on a slope, and the ejector force may decline due to the existenc of the slope. If “C” is the only choice, small blocks should be added to increase ejection force.
1.4 To avoid the upper mold from being damaged by the ejector pin, the ejector pin has to be placed in location “A”.
1.4.1 The pin has to be ground lower for 0.0005”, for venting purposes;
1.4.2 A spring is needed under the return pin.
1.5 When product is too high or draft angle is too large, draw the ejection path on a layout plan, to help avoid mistake when placing the ejector pin. When the product has a large R, draw the tangent of the R on a layout plan, as a boundary for ejector pin placement.
1.6 Place ejector pins under ribs
Among the above-mentioned 5 methods, 1 is the best, and 5 is the worst.
As mold designers, we are all aware that, in normal circumstances, lifters are created for inner undercuts and sliders are created for outer undercuts. However, when we have undercuts on all 4 sides of a product, which makes it impossible to release the product by force, how should the mold be designed? See the following figure for the product. Shall we create lifters or sliders? Now, let me explain the mold design solutions for such products to all of you.
Design analysis
When coming across such products, we will firstly consider whether it is possible to create lifters. However, analysis shows that the undercuts in the 4 corners will not be able to be released with the help of lifters (lifters in the arrow direction).
Solution
Since lifters are not able to ensure complete release of the undercuts, we have to think about the design scheme that combines lifters and inner sliders. As shown in the figure below, green parts are inner sliders, and pink parts are lifters.
How it works
Mold core and cavity open a bit, then the slope of the wedge drives the sliders to move towards the center, so as to release the undercuts from the 4 corners of the product. At the same time, the lifters eject the product out while the undercuts are released completely. Finally, you can take the product out and close the mold for the next production run.
By virtue of its enormous benefits, such as light weight, outstanding toughness, easy molding and low cost, plastic is gaining more and more popularity in modern industry and the production of daily necessities, because it is an ideal substitute for glass. Especially, in the fields of optical devices and the packaging industry, it has witnessed an exceptionally rapid development. However, due to the fact that such plastic materials are required to be extremely transparent(clear), with great abrasion resistant and impact resistant features, a great deal of effort is needed in the aspects of plastic ingredients, as well as the technology, equipment and molds throughout the entire plastic injection molding process, so as to make sure that these glass substitute materials (hereinafter referred to as transparent plastics) possess an outstanding surface finish, thus meeting the application requirements.
Currently, the commonly used transparent plastic materials on the market include polymethyl methacrylate (commonly known as acrylic or acrylic glass, abbr. PMMA), polycarbonate (abbr. PC), polyethylene terephthalate (abbr. PET), transparent nylon, acrylonitrile-styrene copolymer (abbr. AS) and polysulfone (abbr. PSF), etc., among which the 3 most commonly used ones are PMMA, PC and PET. Now, we will take these 3 materials as an example, to discuss the characteristics and the injection molding process of transparent plastics.
Performance of transparent plastic materials(clear plastics)
Above all, transparent plastic materials have to be highly transparent, and then they need to be strong enough to resist abrasion, impact, heat and chemicals, with a low water absorption rate. This is the only way to guarantee that the materials can meet the transparency and durability requirements for application. The following table I shows the performance comparison among PMMA, PC and PET.
From table I we can tell, PC is an ideal choice, but the raw materials are costly and not easy to process. As a result, PMMA is the main choice (for average products). PET needs to be stretched to obtain a desired mechanical performance, so it is usually used for production of packages and containers, etc
Common problems that need to be addressed during the injection molding process of transparent plastics.
Inevitably, due to their high light transmission rate, stringent requirements are imposed on product surface finish defects like pores, black spots, discoloration and low glossiness have to be completely eliminated. Therefore, to guarantee product surface finish, throughout the entire process, close attention should be paid to raw materials, equipment, mold and even product design, with stringent or even special requirements in place. Secondly, since transparent plastic materials normally have a high melting point and poor fluidity, subtle process parameter adjustments including mold temperature, injection pressure and injection speed are usually required to make sure that the mold can be fully injected, and product deformation or cracks that are caused by internal stress can be completely eliminated.
In the following paragraphs, we will discuss the considerations for transparent plastic injection molding from the perspectives of raw material preparation, equipment/mold requirements, the injection process and raw material processing, etc.
（1）Raw material preparation and drying:
Due to the fact that even the smallest amount of impurities in the plastic may greatly affect product transparency. Therefore, during the storage, transport and feeding processes, special attention should be paid to sealing, so as to keep the raw material clean. In particular, if the raw material contains moisture, it may deteriorate after being heated. So, the raw material has to be dried during the molding process, and a dry hopper must be used for material feeding. Also note that, during the drying process, the air blown in has to be filtered and dehumidified to keep the raw material from contamination.
（2）Cleansing of barrel, screw and accessories
Before and after the molding process, in order to prevent the raw materials from contamination, and keep the recessive parts of the screw or the accessories free from used materials or impurities (in particular the resins with a poor thermal stability), each part has to be cleansed by using the screw detergent to protect it from any impurities. If there is no screw detergent, resins like PE and PS can be used to clean the screw. If the machine has to be shut down temporarily, to prevent raw material degradation caused by long time staying in the high temperature environment, the temperatures of the drier and the barrel need to be lowered. For example, barrel temperature for PC and PMMA need to be reduced to below 160℃ (for PC, the hopper temperature should be lower than to 100℃).
（3）Considerations for mold design
To prevent product defects and/or deteriorations caused by poor backflow or uneven cooling, the following points need to be paid attention to when designing a mold.
a）A consistent wall thickness, and a big-enough draft angle;
b）A smooth transition, to avoid the occurrence of pointed angles or sharp edges. Especially for PC products, no gap is allowed;
c）The gate and runner need to be wide and short, and the gate position needs to be defined based on the solidification shrinkage process; Set up a cold slug well when necessary;
d）The mold surface should be glossy, with a low roughness;
e）Adequate venting slots, to expel the air and/or gases in the molten plastic in a timely manner;
f）Except PET, the wall thickness cannot be too thin – usually, it should be thicker than 1mm;
（4）Considerations for the plastic injection process (including requirements on injection machine)
To reduce internal stress and surface defects, the following aspects of the injection molding process should be paid close attention to.
a）Select the injection machine designed with a special-purpose screw and a separate thermostatic nozzle;
b) The higher the injection temperature is, the better, but keep in mind that the temperature should be controlled below the decomposition point of the resin materials;
c）Injection pressure: Usually higher pressure is applied to cope with the high viscosity of the molten plastic. However, if the pressure is too high, internal stress will occur, leading to difficult mold release or product deformation;
d）Injection speed: Usually, the injection speed should be lower on condition that complete filling can be guaranteed. It is better to employ the slow – fast – slow multistage injection;
e）Pressure holding time & molding cycle: Keep both as short as possible on condition that complete filling can be guaranteed, and no dents or bubbles will occur, so as to minimize molten material’s staying time in the barrel;
f）Screw speed & backpressure: Keep both as low as possible on condition that plasticization quality can be guaranteed, so as to prevent the possibility of degradation;
g）Mold temperature: Product cooling effect plays an important role in determining product quality, so mold temperature has to be accurately controlled during the molding process. Whenever possible, keep the temperature as high as it can be.
If you want to know more about plastic material,please visit our plastic list.
The proportional injection speed control system is extensively adopted by injection machine manufacturers. In this article, we are going to explain the benefits of applying the multi-speed injection molding process, while offering an overview on the role it plays in eliminating product defects, such as short shot, entrapped air and sink marks, etc.
By virtual of its close relation with product quality, plastic injection speed has become one of the key parameters of plastic injection molding. By defining the front, center, and rear of the feeding speed segmentation, and realize smooth transition from one set point to another, a steady molten plastic surface speed can be guaranteed to turn out the desired product.
We suggest the following speed segmentation principles:
1). The flow surface speed should be a constant;
2). Apply high-speed injection to avoid molten plastic solidification during the injection process;
3). To set the injection speed, we need to take both the fast feeding of critical areas (e.g. the runner) and the slower speed at the gate into consideration;
4). The plastic injection speed needs to ensure that the injection process immediately stops after the mold cavity is filled up, so as to avoid over flow, flash and residual stress, etc.
The several considerations for speed segmentation settings include geometric shape of the mold, other flow limitations and some uncertainties. To set the speed properly, we need to have a good understanding of the injection molding process as well as the materials, or it will be hard to control product quality. Though it is not easy to measure the speed of the molten plastic directly, we can gauge the speed indirectly via the measurement of screw moving speed or cavity pressure.
The characteristics of a material are of great importance, because polymers may decompose under a different stress, and mold temperature rise may lead to vigorous oxidation and chemical structural degradation, but at the same time, shear may lower the level of degradation, because the higher temperature has reduced material stickiness and therefore the shear force. Undoubtedly, the multistage injection speed control is very helpful for the molding process of thermally sensitive materials like PC, POM, and UPVC, as well as their ingredients.
The shape of a mold is another defining factor: the thin-walled area needs the fastest injection speed, and the thick-walled part needs the slow – fast – slow speed curve to avoid defects; to bring part quality up to standard, the setting of injection speed needs to make sure that the speed at the forefront of the molten plastic is constant. The flow speed of the molten plastic is so important that it will influence the molecular orientation and surface status of the final part. When the forefront of the molten plastic comes to an intersection, the speed should be decreased; for a complex mold with a radial expansion, we need to ensure that the throughput of the molten plastic increases in a balanced manner; as for the long runner, fast injection is needed to lessen molten plastic forefront cooling. However, the injection of high stickiness materials like PC is an exception, because if the speed is too high, the cold slug will be brought into the cavity via the gate.
The adjustment of injection speed is able to help eliminate product defects caused by the slower speed at the gate. When the molten plastic arrives at the gate via the sprue and the runner, the surface of its forefront may have solidified, or the molten plastic comes to a standstill because the runner suddenly narrows. It will not move forward until enough pressure is built up to push the molten plastic through the gate. In this instance, the pressure that passes through the gate will show a peak shape. The high pressure may do harm to the material and lead to surface defects like flow marks and burnt streaks on gate, etc. This can be resolved by slowing down the speed right before the molten plastic enters the gate, because it is able to prevent over shear at the gate location. After that, restore the injection speed to the original value. Since it is difficult to precisely slow down the injection speed at the gate location, it is a better solution to slow down the speed in the final section of the runner. We can reduce or even avoid product defects like flash, burnt marks and entrapped air by controlling the injection speed in the final section. Also, slowing down in the final section can help prevent overflow, thus avoiding flash and reducing residual stress. The entrapped air caused by poor ventilation in the final section of the mold flow path or feeding problems can also be resolved by slowing down the air venting speed, especially the air venting speed in the final section of plastic injection.
Short shot occurs because of the too low speed at the gate or the local flow blockage caused by plastic solidification. The issue can be resolved by increasing injection speed when the molten plastic is passing through the gate or when local flow is blocked.
Product defects like flow marks and burnt streaks on gate which tend to appear on thermal sensitive plastic materials are usually caused by the over shear occurring when the flow passes through the gate.
The production of smooth-surfaced parts is dependent on injection speed, yet glass fiber filled materials are even more sensitive, especially nylon. Streaks (wrinkles) are caused because the flow is not steady due to stickiness changes. A twisted flow may lead to wrinkles or uneven fog-like patterns, among which the specific defect is dependent on the level of flow unsteadiness.
When the molten plastic passes through the gate, a high injection speed will lead to high shear, causing thermal sensitive plastics to burn. The burnt plastic will then go through the cavity, reach the forefront of the flow, and finally appear on product surface.
To prevent jetting marks, injection speed setting must guarantee that the flow is able to fill the runner area quickly and then passes through the gate slowly. Essentially, the key is to find the transition point. If too early, filling time will be overextended; if too late, the excessive flow inertia will lead to jetting marks. The lower the stickiness of the molten plastic and the higher the barrel temperature, the more likely jetting marks will occur. Due to the fact that the small size gate requires high-speed and high pressure injection, it is another important factor that causes flow defects. Sink marks can spread under pressure, so the problem can be improved by reducing the pressure. Flow distance will be greatly shortened in the scenario of low mold temperature and slow screw speed, so increasing injection speed will be able to compensate for the distance. A high speed flow is able to minimize heat loss. In addition, the high shear heat will produce frictional heat, causing molten plastic temperature to rise, which helps reduce the thickening speed on the outer layer of the part. An adequate thickness must be guaranteed for the intersections inside the cavity, so as to prevent excessive pressure loss, or sink marks will appear.
In a word, most of the injection molding defects can be resolved through injection speed adjustment. Hence, the trick of adjusting the plastic injection molding process is to appropriately set the injection speed and its segmentation.
Injection molding temperature is very important for plastic injection molding,right injection molding temperature is a guarantee of product quality and production effciency.we will show what is the best injection process for different plastic material.
Front:The suck-back section is located at the forefront of the barrel, where the nozzle is situated. The temperature here should be a little lower than that of the plasticization area. Its main purpose is to prevent the molten plastic from flowing back through the nozzle under internal pressure. However, the temperature cannot be too low, or additional plasticization pressure will be required.
Center:The plasticization area is located in the middle of the barrel, where the temperature will gradually rise above the melting point. The purpose of this section is mainly to melt the plastic material. However, if the temperature is too high, the plastic material will be prone to decomposition; if the temperature is too low, it will not be helpful for the plasticization process, and screw torque will also increase.
Rear :The feeding area is close to the hopper. Usually, its temperature is set to be lower to around the melting point of the plastic material. The purpose of this section is mainly to pre-heat the material. So, if the temperature is too high, the plastic will be melted, causing screw slippage and thus affecting material delivery. However, if the temperature is too, screw torque will increase.
