Flow marks, troubleshooting

A flow mark or halo, is a surface defect in which circular ripples or wavelets appear near the gate.

Ripples, a similar defect, appear as small fingerprint-like waves near the edge or at the end of the flow.

Causes

• Material freezing near the gate. Low melt or mold temperature, and low ram speed can result in cold material entering the cavity. This can cause the partly solidified material to take on the form of the flow pattern.

  
  
  

  Ripples caused by low temperature

  .

  a normal fountain flow with no ripples, b flow causing ripples (R).

• Insufficient material compensation. Early gate freeze-off or low packing pressure may not pack the cavity properly. The material near the gate then freezes while maintaining the form of the flow pattern.

Remedies

• Optimize the cold well. Design the cold well in the runner system to trap the cold material during the filling phase. The proper length of the cold well is usually equal to that of the runner diameter.

• Optimize the runner system design. A restrictive runner system design can result in premature gate freeze-off. It can however, increase shear heating for better melt flow.

• Increase the mold and melt temperature.

• Optimize packing pressure.

Solving one problem can often introduce other problems to the injection molding process. Each option hence requires consideration of all relevant aspects of the mold design specification.

 

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Unbalanced flow, troubleshooting

Unbalanced flow is plastic completely filling some flow paths in the mold before other flow paths have filled.

Unbalanced flow can be the cause of many molding problems such as flashing, short shots, high cycle time, density differences throughout the part, warpage, air traps and extra weld lines.

Flow is balanced when all the extremities of the mold fill at the same time.

To recognize unbalanced flow, you need to recognize the different flow paths in the mold. These are the different routes that the plastic takes throughout the cavity.

The following part contains three fundamental flow paths (shown as red arrows).

Each flow path is of a different length. Therefore, if the part has uniform thickness, flow path 1 will fill first, followed by flow path 2, followed by flow path 3.

To identify unbalanced flow, use either the fill preview or the fill time result.

What to do

By altering the thickness of regions within the part, flow can be hastened or delayed in certain directions to help balance flows. In the above diagram, varying the part thickness and creating flow leaders and deflectors, thinning flow path 1 and thickening flow path 3, is the answer. These variations in thickness are known as Flow Leaders or Flow Deflectors.

In other examples it is often necessary to consider the position of the polymer injection location, or the number of polymer injection locations.

For example, if you choose a single injection location that defines some flow paths to be three or four times the length of others, then it is almost impossible to balance flows. Try moving the polymer injection location to a position that will define similar length flow paths. Alternatively, visualize the cavity in smaller, more manageable sections. Then use multiple injection locations, one per sub-section.

For a multi-cavity part, balance flows in each cavity first, then proceed to alter runner dimensions to ensure that:

• All cavities fill at approximately the same time, with the same pressure.

• The temperature at the end of fill shows uniform distribution in each cavity, predicting uniform shrinkage, and acceptable weld line quality.

• The shear stress in each cavity (ignore runners) is less than the recommended limit for the material chosen.

 

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Troubleshooting flow problems

 

Troubleshooting Melt flow problems

 

Flow problems manifest themselves in a variety of ways, including overpacking, insufficient packing, and visual defects.

Topics in this section

• Hesitation
  Hesitation, which occurs when the melt flow slows down or stops along a particular flow path, can lead to asymmetrical and unpredictable flow patterns.
• Volumetric shrinkage
  Volumetric shrinkage is the contraction of polymer due to the change in temperature from melt temperature to ambient temperature.
• Shear stress
  Shear stress is stress that is experienced by the melt as it flows through the mold. It occurs as a result of friction between layers of plastic flowing in the cavity.
• Overpacking
  Overpacking occurs when extra material is compressed in one flow path while other flow paths are still filling.
• Racetrack effect
  The racetrack effect occurs when flow races through thick sections of the cavity before the thin sections have filled.
• Unbalanced flow
  Unbalanced flow is plastic completely filling some flow paths in the mold before other flow paths have filled.
• Underflow
  Underflow is when a flow front reverses direction.

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THUẬT NGỮ CHUYÊN NGÀNH NHỰA - PLASTIC

       THUẬT NGỮ CHUYÊN NGÀNH NHỰA - PLASTIC

Tiếng Việt	Anh
Phụ gia	Additive
Chất chống oxy hóa	Antioxidant
Tác nhân chống tĩnh điện	Antistatic agent
Nòng xy-lanh	Barrel
Thổi khuôn	Blow molding
Thổi màng	Blown Film
Cán láng (xuất tấm)	Calandering
Chất xúc tác	Catalyst
Đùn kết hợp	Co-extrusion
Dây chuyền đùn kết hợp	Co-extrusion Line
Chất tạo màu	Colourant
Vật liệu composite	Composite Material
Hợp chất	Compound
Polymer đồng trùng hợp	Copolymer
Xử lý bề mặt theo công nghệ Corona (điện hóa)	Corona Treatment
Tính chất phân hủy	Degradable
Khuôn tạo hình	Die
Thiết bị	Equipment (Machine)
Polystyrene trương nở được	Expandable Polystyrene (EPS)
Đùn	Extrusion
Sợi	Fibre
Chất hãm cháy	Flame Retardent
Polymer nền fluorocarbon	Fluoropolymers
Bọt xốp	Foam
Chất dẻo gia cường bằng sợi thủy tinh (FRP)	Glass Fibre Reinforced Plastics
Phễu	Hopper
Rãnh dẫn nhựa nóng	Hot runner
Độ bền va đập	Impact Strengths
Chất ức chế	Inhibitor
Ép phun – thổi	Injection Blow Moulding
Ép phun – đúc ép	Injection Compression Moulding
Ép phun	Injection Moulding
Máy ép phun	Injection Moulding Machine
Cán mỏng	Laminate
Chất bôi trơn	Lubricant
Hạt màu masterbatch	Masterbatch
Chỉ số chảy	Melt Flow Index
Khuôn	Mould
Tác nhân chống dính khuôn	Mould Release Agent
Tạo hạt	Pellet
Hạt màu	Pigment
Chất hóa dẻo	Plasticizer
Chất dẻo	Plastics
Polyacetal (POM)	Polyacetal (POM)
Polyamide (PA)	Polyamide (PA)
Polyamide Imide (PAI)	Polyamideimide (PAI)
Poly Butylene Terephthalate (PBT)	Polybutylene Terephthalate (PBT)
Polycarbonate (PC)	Polycarbonate (PC)
Poly Ester	Polyester
Polyether Etherketone (PEEK)	Polyether Etherketone (PEEK)
Poly Ête Imide	Polyether Imide
Polyetherssulphone (PES, PESU)	Polyetherssulphone (PES, PESU)
Polyethylene (PE)	Polyethylene (PE)
Polyethylene Terephthalate (PET)	Polyethylene Terephthalate (PET)
Polymethylmethacrylate (PMMA)	Polymethylmethacrylate (PMMA)
Polyphenylene ether (PPE)	Polyphenylene ether (PPE)
Polypropylene (PP)	Polypropylene (PP)
Polystyrene (PS)	Polystyrene (PS)
Polytetrafluoro Ethylene (PTFE	Polytetrafluoro Ethylene (PTFE)
Polyurethane (PU)	Polyurethane (PU)
Polyvinyl Chloride (PVC)	Polyvinyl Chloride (PVC)
Công nghệ Pultrusion	Pultrusion
Nguyên liệu	Raw Material
Tái sinh	Recycle
Chất dẻo được gia cường	Reinforced Plastics
Nhựa	Resin
Cứng, không linh động	Rigid
Đúc khuôn quay	Rotational Moulding
Tấm	Sheeting, Sheet
Co rút	Shrinkage
Dung môi	Solvent
Chất ổn định	Stabaliser
Lỗ xốp cấu trúc	Structural Foam
Tạo hình nhiệt	Thermoforming
Nhiệt rắn	Thermoset
Máy đùn 2 trục vít	Twin Screw Extruder
Tạo hình chân không	Vacuum Forming
Độ nhớt	Viscosity
Hàn	Welding

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MP1200- MFI MEASUREMENT MACHINE -TINIUS OLSEN

 TINIUS OLSEN - MP1200

MFI MEASUREMENT MACHINE 

                  

  Model : MP1200

  Made in : USA- TINIUS OLSEN 

  Applications: Measure the Melt Flow Index  of a resin. Other option MVR    

  Standards: Equipment meets and exceeds international standards ASTM D1238 and D3364, ISO 1133-1 and 2, BS 2782, DIN53735, JIS K7210

 Description:

• The newly designed oven allows for superior heat control with 3 heating zones that meet ISO 1133-2.

• The MP1200 has a user-friendly LCD touch screen display. The user can configure the machine with the available options and set other features such as language, unit, alarm ... Independent tests can be set up and stored for calls. out when needed.

• Results are automatically displayed at the end of each test and saved or printed when the printer is connected to the MP1200 via USB.       

Other  parameters:

 
    * Operating temperature: 450 ° C max

    * Temperature control: +/- 0.1 ° C

    * Spatial temperature change: +/- 0.1 ° C

    * Temperature controller: 3-zone PID control

    * Thermal sensor: Platinum RTDs (3)

    * Timer accuracy: 0.001 seconds

    * Display: 7.1 ”LCD touch screen, 800x480 resolution

    * Data access: touch screen display.

    * Connection port: USB

    * Dimensions: 458 mm x 394 mm x 521 mm (width x depth x height)

    * Weight: 21 kg (excluding load and other accessories)

    * Power supply: 230 VAC +/- 10%, 50/60 Hz, single phase.

 

 

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