Trainees explain: The process of plastic injection molding

For economic reasons, the injection molding process is best suited to plastic parts in standard sizes that are in high demand on the market. In this process, the granular raw material is given its final shape by injecting it into a closed mold that determines the geometry of the plastic part. The advantages of the injection molding process are Automated production Large series can be produced cost-effectively High quality standard But how does the process actually work? The injection molding process basically consists of 6 individual steps. It is a so-called forming process with high precision of the manufactured parts. Plasticization of the granulate The plastic granulate is liquefied by heat in an elongated cylinder and homogenized by a rotating screw inside. Injecting the liquefied plastic The plasticized plastic is injected under high pressure into the closed injection mold by pushing the screw very quickly towards the tool and forcing the hot, liquid plastic through a channel into the mold cavity. Continue pressing during the cooling phase The screw remains in the front position until the hot plastic melt has solidified in the cooled mold. In this way, the shrinkage of the plastic caused by cooling is compensated by pressing the plastic into the mold. The injection mold is constantly cooled with water, but sometimes it is also brought to a certain temperature. This depends on the plastic being processed. When the hot and liquid plastic then touches the cool mold wall, the plastic solidifies again and the component retains its shape. Dosing After the pressure has been maintained and during the cooling phase, the screw rotates again and builds up a hot mass cushion that can be injected into the closed mold again during the next cycle. Demolding and starting a new cycle Once the plastic part has cooled to form stability and shrinkage has stopped, the mold can be opened and the plastic molded part demolded. In most cases, small ejector pins protrude from the mold and push the plastic part out of recesses. The molded part usually falls down into a basket or onto a conveyor belt. The mold is only open for a very short time because a new production cycle begins when the mold is closed. video Hier finden Sie die ausführliche Anwort.

Apprentices explain: Plastic blow molding

The blow molding process is used to create hollow objects such as canisters and barrels, as well as household items such as watering cans or PET bottles. Blow molding combines two plastic processing methods. First, a hot plastic tube must be formed using extrusion. To do this, the granular starting material is liquefied as in classic plastic extrusion and pressed vertically downwards through an extrusion tool (also called a nozzle). It is important to ensure that the tube has a certain degree of dimensional stability, but at the same time is not too cold to be reshaped. The tube is then lowered from above between the two open parts of the blow molding tool, which only forms the outer contour of the blow molded part. The wall thickness of the blow molded part is determined by the thickness of the tube and the degree of stretching during inflation. The hose must be long enough so that it can be squeezed together at the top and bottom when the tool is closed. A needle is inserted into the heated hose from above, and air is blown into the hose. The excess pressure generated causes the hose to inflate like a balloon until the hose, which is still hot, completely touches the wall of the cooled tool. There, the plastic material cools and solidifies until it is dimensionally stable enough. After opening the tool, the blow molded part can be demolded. After the hollow body has been demolded, a processing step follows in which the remains of the hose are removed. In the case of hollow bodies with handles, the excess, squeezed-out material in the area of the handle is ideally punched out at the same time. Depending on the customer's wishes and the degree of automation of the process, further manual steps can follow, such as reworking the pinch seam with a deburring knife. The blow molded part usually takes up significantly more space for storage and shipping due to its larger dimensions. Video Hier finden Sie die ausführliche Anwort.

Trainees explain: Plastic extrusion

In the first step, the plastic to be processed is fed into the cylinder in the form of granules via a funnel. If large quantities are required, the granules are fed into the funnel via hose lines. The plastic granulate is continuously melted and liquefied with the help of heating bands and the resulting frictional energy on the inner wall of the cylinder. The rotating screw conveys and compacts the melt granulate and constantly puts it under pressure. This homogeneous, hot mass is then pressed through the extrusion tool. The shape geometry of the extrusion tool is actually never identical to the cross-sectional geometry of the profile to be produced. The mold maker must take into account that the hot plastic melt swells a little after leaving the mold and that the shape and position can therefore change more or less significantly. To prevent the profile from collapsing, it must be cooled over a certain period of time. Depending on the complexity of the geometry, the profile sometimes runs through a longer or shorter distance in a cooling medium until it is completely dimensionally stable and dimensionally accurate. For less complex profile geometries, the profile usually only runs through a water bath to cool down. For complex profile geometries, the still hot profile must run through a so-called calibration section in which the walls of the profile are cooled in a controlled manner, but at the same time are supported with air or sucked onto cooling fins with a vacuum in order to achieve the required position and dimensional tolerances. Conveyor belts or caterpillar pull-offs used to pull the extruded profile ensure that the cooling profile runs at a consistent speed. Fluctuations in speed affect dimensional accuracy. After the take-off, a winding or cutting unit usually follows to wind the previously endless profile onto spools or cut it to the desired length. In the first step, the plastic to be processed is fed into the cylinder in the form of granules via a funnel. If large quantities are required, the granules are fed into the funnel via hose lines. The plastic granulate is continuously melted and liquefied with the help of heating bands and the resulting frictional energy on the inner wall of the cylinder. The rotating screw conveys and compacts the melt granulate and constantly puts it under pressure. This homogeneous, hot mass is then pressed through the extrusion tool. The shape geometry of the extrusion tool is actually never identical to the cross-sectional geometry of the profile to be produced. The mold maker must take into account that the hot plastic melt swells a little after leaving the mold and that the shape and position can therefore change more or less significantly. To prevent the profile from collapsing, it must be cooled over a certain period of time. Depending on the complexity of the geometry, the profile sometimes runs through a longer or shorter distance in a cooling medium until it is completely dimensionally stable and dimensionally accurate. For less complex profile geometries, the profile usually only runs through a water bath to cool down. For complex profile geometries, the still hot profile must run through a so-called calibration section in which the walls of the profile are cooled in a controlled manner, but at the same time are supported with air or sucked onto cooling fins with a vacuum in order to achieve the required position and dimensional tolerances. Conveyor belts or caterpillar pull-offs used to pull the extruded profile ensure that the cooling profile runs at a consistent speed. Fluctuations in speed affect dimensional accuracy. After the take-off, a winding or cutting unit usually follows to wind the previously endless profile onto spools or cut it to the desired length. Video Hier finden Sie die ausführliche Anwort.

General topics FAQs

Trainees explain: The process of plastic injection molding

For economic reasons, the injection molding process is best suited to plastic parts in standard sizes that are in high demand on the market. In this process, the granular raw material is given its final shape by injecting it into a closed mold that determines the geometry of the plastic part.

The advantages of the injection molding process are

Automated production
Large series can be produced cost-effectively
High quality standard

But how does the process actually work?

The injection molding process basically consists of 6 individual steps. It is a so-called forming process with high precision of the manufactured parts.

Plasticization of the granulate The plastic granulate is liquefied by heat in an elongated cylinder and homogenized by a rotating screw inside.
Injecting the liquefied plastic The plasticized plastic is injected under high pressure into the closed injection mold by pushing the screw very quickly towards the tool and forcing the hot, liquid plastic through a channel into the mold cavity.
Continue pressing during the cooling phase The screw remains in the front position until the hot plastic melt has solidified in the cooled mold. In this way, the shrinkage of the plastic caused by cooling is compensated by pressing the plastic into the mold. The injection mold is constantly cooled with water, but sometimes it is also brought to a certain temperature. This depends on the plastic being processed. When the hot and liquid plastic then touches the cool mold wall, the plastic solidifies again and the component retains its shape.

Dosing After the pressure has been maintained and during the cooling phase, the screw rotates again and builds up a hot mass cushion that can be injected into the closed mold again during the next cycle.
Demolding and starting a new cycle Once the plastic part has cooled to form stability and shrinkage has stopped, the mold can be opened and the plastic molded part demolded. In most cases, small ejector pins protrude from the mold and push the plastic part out of recesses. The molded part usually falls down into a basket or onto a conveyor belt. The mold is only open for a very short time because a new production cycle begins when the mold is closed.

video
Apprentices explain: Plastic blow molding

The blow molding process is used to create hollow objects such as canisters and barrels, as well as household items such as watering cans or PET bottles.

Blow molding combines two plastic processing methods. First, a hot plastic tube must be formed using extrusion.
1. To do this, the granular starting material is liquefied as in classic plastic extrusion and pressed vertically downwards through an extrusion tool (also called a nozzle). It is important to ensure that the tube has a certain degree of dimensional stability, but at the same time is not too cold to be reshaped. The tube is then lowered from above between the two open parts of the blow molding tool, which only forms the outer contour of the blow molded part. The wall thickness of the blow molded part is determined by the thickness of the tube and the degree of stretching during inflation.
2. The hose must be long enough so that it can be squeezed together at the top and bottom when the tool is closed.
3. A needle is inserted into the heated hose from above, and air is blown into the hose. The excess pressure generated causes the hose to inflate like a balloon until the hose, which is still hot, completely touches the wall of the cooled tool.
4. There, the plastic material cools and solidifies until it is dimensionally stable enough.
5. After opening the tool, the blow molded part can be demolded.
After the hollow body has been demolded, a processing step follows in which the remains of the hose are removed. In the case of hollow bodies with handles, the excess, squeezed-out material in the area of the handle is ideally punched out at the same time. Depending on the customer's wishes and the degree of automation of the process, further manual steps can follow, such as reworking the pinch seam with a deburring knife.

The blow molded part usually takes up significantly more space for storage and shipping due to its larger dimensions.

Video
Trainees explain: Plastic extrusion

In the first step, the plastic to be processed is fed into the cylinder in the form of granules via a funnel. If large quantities are required, the granules are fed into the funnel via hose lines.

The plastic granulate is continuously melted and liquefied with the help of heating bands and the resulting frictional energy on the inner wall of the cylinder. The rotating screw conveys and compacts the melt granulate and constantly puts it under pressure. This homogeneous, hot mass is then pressed through the extrusion tool.
The shape geometry of the extrusion tool is actually never identical to the cross-sectional geometry of the profile to be produced. The mold maker must take into account that the hot plastic melt swells a little after leaving the mold and that the shape and position can therefore change more or less significantly.
To prevent the profile from collapsing, it must be cooled over a certain period of time. Depending on the complexity of the geometry, the profile sometimes runs through a longer or shorter distance in a cooling medium until it is completely dimensionally stable and dimensionally accurate. For less complex profile geometries, the profile usually only runs through a water bath to cool down. For complex profile geometries, the still hot profile must run through a so-called calibration section in which the walls of the profile are cooled in a controlled manner, but at the same time are supported with air or sucked onto cooling fins with a vacuum in order to achieve the required position and dimensional tolerances.

Conveyor belts or caterpillar pull-offs used to pull the extruded profile ensure that the cooling profile runs at a consistent speed. Fluctuations in speed affect dimensional accuracy.
After the take-off, a winding or cutting unit usually follows to wind the previously endless profile onto spools or cut it to the desired length.

In the first step, the plastic to be processed is fed into the cylinder in the form of granules via a funnel. If large quantities are required, the granules are fed into the funnel via hose lines.
1. The plastic granulate is continuously melted and liquefied with the help of heating bands and the resulting frictional energy on the inner wall of the cylinder. The rotating screw conveys and compacts the melt granulate and constantly puts it under pressure. This homogeneous, hot mass is then pressed through the extrusion tool.
2. The shape geometry of the extrusion tool is actually never identical to the cross-sectional geometry of the profile to be produced. The mold maker must take into account that the hot plastic melt swells a little after leaving the mold and that the shape and position can therefore change more or less significantly.
3. To prevent the profile from collapsing, it must be cooled over a certain period of time. Depending on the complexity of the geometry, the profile sometimes runs through a longer or shorter distance in a cooling medium until it is completely dimensionally stable and dimensionally accurate. For less complex profile geometries, the profile usually only runs through a water bath to cool down. For complex profile geometries, the still hot profile must run through a so-called calibration section in which the walls of the profile are cooled in a controlled manner, but at the same time are supported with air or sucked onto cooling fins with a vacuum in order to achieve the required position and dimensional tolerances.
4. Conveyor belts or caterpillar pull-offs used to pull the extruded profile ensure that the cooling profile runs at a consistent speed. Fluctuations in speed affect dimensional accuracy.
5. After the take-off, a winding or cutting unit usually follows to wind the previously endless profile onto spools or cut it to the desired length.
  
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