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Pom pom injection molding process
by：CSSSLD
2021-01-23
Polyoxymethylene (
POM）
Is a very important engineering plastics, the small gear on the printer, we use it, today we have detailed understanding pom pom injection molding process points.
It is at the raw material such as formaldehyde aggregate income.
POM-
H(
Polyoxymethylene homopolymer)
，POM-
K(
Polyoxymethylene copolymer)
Is high density, high degree of crystallinity of thermoplastic engineering plastic.
Have good physical, mechanical and chemical properties, especially have excellent friction resistance.
POM is a crystalline plastics, melting point, once reached melting point, the melt viscosity drops rapidly.
When the temperature exceeds a certain limit or melt heating time is too long, can cause decomposition.
POM small water imbibition, general is 0. 2% - 0. 5%. Under normal circumstances, POM can processing does not need to dry, but the damp raw material must be dry. The drying temperature above 80 ℃, for 2 hours, should be in accordance with the supplier details. Reworked material use proportion is generally not more than 20 - 30%. But depends on the product type and end use, sometimes can reach 100%. POM screw without stagnation expected zone in addition to the requirements, the injection molding machine have no special requirements, general injection molding.
common mold temperature control is 80 - There are 3-90 ℃, the runner diameter 6 mm, gate length is zero. 5 mm, the gate size depends on adhesive thickness, circular runner diameter should be at least product thickness of 0. 5 - 0. 6 times, the width of the rectangular gate is usually 2 times or more, the thickness of the depth of wall thickness of 0. 6 times, draft 40 & prime; - 130′ In between.
the cause of the appearance is not beautiful, Pom products are mainly the expansion of the melt in the filling time is not to stabilize the flow before the extension, but with disturbance formation caused by turbulence. And the expansion of the melt can form stable when filling flow, in addition to related to mould design, molding process, is also associated with the thermal physical properties of the melt.
1, POM, specific heat, cooling the heat released when many, this is the injection molding POM mould and products of high temperature and hot.
2, POM thermal conductivity and thermal diffusion coefficient is low. Low thermal conductivity shows that POM on the surface of the melt and mold heat slow, frozen layer is thinner. Low thermal diffusion coefficient showed that the melt of internal heat transfer ability is poor, even the surface of the melt temperature is reduced, and can quickly lead to the center layer of the melt temperature is lower, the center layer of high temperature of the melt is still with good liquidity. When the melt in the filling, it is easy to break through the thin skin layer, the formation of turbulence.
3, the melt index of POM. Although a range is given in the table, the discretion of the melt index related to the size of molecular weight. General production stylus product of this request is not high, can choose low price, low molecular weight and material, so the relatively high melt index of POM has higher liquidity. The several ways of integrated performance, is to use POM material molding handwritten pen, difficult to steady filling, prone to disturbance, turbulence, it is difficult to molding the beautiful appearance to
mould design, gate design as far as possible much larger, avoid a jet flow. Injection molding process adjustment, should try to reduce the fill speed, the formation of steady filling. But injection machines under the low speed stability is bad, the injection speed is too low when the screw forward trembling would appear, therefore the melt will be shock vibration producing lines, and sometimes as filling speed slightly faster filling instead of good appearance.
through the above analysis it can be seen that the POM injection molding process forming the appearance of the stylus is difficult to obtain qualified, and use PC/ABS, PC, ABS material is very easy to do through process adjustment, it is because the thermal properties of several materials, to the contrary, specific heat, thermal conductivity and thermal diffusion coefficient is high, the melt index is low, the melt filling time can obtain steady state flow.
more excellent articles: injection molding plastics processing parameters, click directly.
http://www。 csssld。 cn//html/2017/Info_0727/642。 HTML
nantong on suye's official website: http://www. csssld。 Cn / /
more wonderful articles, immediately search: changshu da plastic products factory smoothly
POM small water imbibition, general is 0. 2% - 0. 5%. Under normal circumstances, POM can processing does not need to dry, but the damp raw material must be dry. The drying temperature above 80 ℃, for 2 hours, should be in accordance with the supplier details. Reworked material use proportion is generally not more than 20 - 30%. But depends on the product type and end use, sometimes can reach 100%. POM screw without stagnation expected zone in addition to the requirements, the injection molding machine have no special requirements, general injection molding.
common mold temperature control is 80 - There are 3-90 ℃, the runner diameter 6 mm, gate length is zero. 5 mm, the gate size depends on adhesive thickness, circular runner diameter should be at least product thickness of 0. 5 - 0. 6 times, the width of the rectangular gate is usually 2 times or more, the thickness of the depth of wall thickness of 0. 6 times, draft 40 & prime; - 130′ In between.
the cause of the appearance is not beautiful, Pom products are mainly the expansion of the melt in the filling time is not to stabilize the flow before the extension, but with disturbance formation caused by turbulence. And the expansion of the melt can form stable when filling flow, in addition to related to mould design, molding process, is also associated with the thermal physical properties of the melt.
1, POM, specific heat, cooling the heat released when many, this is the injection molding POM mould and products of high temperature and hot.
2, POM thermal conductivity and thermal diffusion coefficient is low. Low thermal conductivity shows that POM on the surface of the melt and mold heat slow, frozen layer is thinner. Low thermal diffusion coefficient showed that the melt of internal heat transfer ability is poor, even the surface of the melt temperature is reduced, and can quickly lead to the center layer of the melt temperature is lower, the center layer of high temperature of the melt is still with good liquidity. When the melt in the filling, it is easy to break through the thin skin layer, the formation of turbulence.
3, the melt index of POM. Although a range is given in the table, the discretion of the melt index related to the size of molecular weight. General production stylus product of this request is not high, can choose low price, low molecular weight and material, so the relatively high melt index of POM has higher liquidity. The several ways of integrated performance, is to use POM material molding handwritten pen, difficult to steady filling, prone to disturbance, turbulence, it is difficult to molding the beautiful appearance to
mould design, gate design as far as possible much larger, avoid a jet flow. Injection molding process adjustment, should try to reduce the fill speed, the formation of steady filling. But injection machines under the low speed stability is bad, the injection speed is too low when the screw forward trembling would appear, therefore the melt will be shock vibration producing lines, and sometimes as filling speed slightly faster filling instead of good appearance.
through the above analysis it can be seen that the POM injection molding process forming the appearance of the stylus is difficult to obtain qualified, and use PC/ABS, PC, ABS material is very easy to do through process adjustment, it is because the thermal properties of several materials, to the contrary, specific heat, thermal conductivity and thermal diffusion coefficient is high, the melt index is low, the melt filling time can obtain steady state flow.
more excellent articles: injection molding plastics processing parameters, click directly.
http://www。 csssld。 cn//html/2017/Info_0727/642。 HTML
nantong on suye's official website: http://www. csssld。 Cn / /
more wonderful articles, immediately search: changshu da plastic products factory smoothly
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