plastic molded part with knit line blemish on top of half circular

Plastic Part Design Fundamentals: Gates and Parting Lines- plastic molded part with knit line blemish on top of half circular ,Parting Lines. A ‘parting line’ is the line of separation on the plastic part where the two halves of the plastic injection mold meet. The line actually indicates the parting ‘plane’ that passes through the part. Within more basic plastic part design plans this plane can be a simple, flat surface, but it is often a complex form that ...What are Parting Lines and Weld Lines in Plastic Injection MoldingDec 14, 2017·A weld line refers to a line, notch or color change that is created on the molded part caused by the convergence of two separate flows of molten plastic. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts.”. As these flow fronts come together on the ...



The Difference Between Knit and Meld Lines--and Why It Matters

Apr 16, 2021·A meld line is defined as the re-merging of two flow fronts after the plastic flow has been split by a feature within the part design. One way to think of this is to visualize merging onto the freeway after a long day at the office—all the vehicles are going the same direction and have to figure out how to get there without damage.

What are Injection Molding Defects and How to Control Them?

Knit / Weld Lines in Injection Molded Parts Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Weld Lines in Plastic Part

Plastic Injection Design Guidance | Plastic part design guide

Plastic Injection Molding Part Design Guidelines, Plastic part Design Guidance, Parting Line Draft Undercuts Wall Thickness & Uniformity Bosses Gussets and Ribs Radii and Corners Material Shrinkage Gating Ventings Knit/Weld Lines

Top-10 Injection Molding Defects And How To Fix Them

Flow Lines. Description: Flow lines are streaks, patterns, or lines - commonly off-toned in color - that show up on the prototype part as a consequence of the physical path and cooling profile …

What is a knit line in molding? | Welding Arc

Jul 31, 2022·The primary cause of knit lines is the way the plastic flow rejoins after it goes around a metal core in the mold. So for this reason there is a knit line (visible or not) downstream from every hole that goes through your part. And for similar reasons there is a knit line between every two gates on the part. What are knit lines in plastic? A ...

Injection Molding Troubleshooting: How to Avoid Knit Lines

When a product is produced through injection molding, a high-powered tool injects melted plastic into a custom, double-sided mold. A knit line, also called a weld line, occurs when the liquid plastic moves through the mold and hits more melted plastic and they don’t flow or fuse together. Instead, a line that looks like a seam forms.

Coping with Weak Weld Lines | Plastics Technology

Feb 26, 2013·Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld line. Glass filler improves strength over the neat resin but reduces weld line strength; it does not improve it. PROCESSING INFLUENCES

Cosmetic Appearance on Injection-Molded Plastic Parts

It’s simple physics: there are basic physical laws to the melting, flow, filling of the mold cavity, and solidification of resin; the geometry of the part governs how those physical laws manifest in your part’s appearance. Choice of Material …

Plastic Injection Molding Defects series-Flow Marks or Flow

Aug 23, 2019·If I can answer any questions you may have on optimizing the plastic part design, CNC plastic prototype, mold manufacturing, and injection molding or if I can be of any other help, please feel ...

Injection Molded Part Defects and Remedies - Basilius Inc.

Jun 19, 2019·Yellow / black marks at the end of fill on a molded part. Burning is most likely cause by air traps in the mold. As plastic fills the mold, the air needs to escape. If the air gets …

Plastic Injection Molding Defects series-Flow Marks or Flow

Aug 23, 2019·Flow marks, also known as flow lines, are surface defects in which circular ripples or wavelets appear near the gate. It also appears as a wavy pattern often a slightly different …

The Basics of Parting Line – SIDOTEK TECHNOLOGY

Jul 08, 2021·The form of parting line depends on the specific situation of the plastic part, but generally there are several types: vertical stepped, inclined, curved and integrated parting lines. 1. Vertical parting line The vertical parting line is commonly used. It is a plane perpendicular to the mold opening direction, as shown in the below figure. 2.

Knit Lines in Plastic Enclosures: What Are They and What …

Nov 25, 2009·Often called “weld lines” or “flow lines”, knit lines typically appear as faintly visible lines on molded plastic parts. What causes knit lines? Knit lines are formed when …

Top-10 Injection Molding Defects And How To Fix Them

Locate the gate at the thickest part of the molding. Switch to a less viscous plastic. This will ensure that less gas is trapped as air is able to escape more rapidly. Increase holding pressure as well as holding time. Ensure that mold parts are perfectly aligned. Surface Delamination

Guide to Injection Molding Parting Line: What is It, How to …

Aug 04, 2021·– Stepped parting line: machinists make the plastic parting line in a stepped shape. For this type of parting line, there is usually a large force on one side of the cavity. This …

The Plastic Troubleshooter Defect - Knit Lines

Solution: Increase the back pressure to raise the melt temperature and improve the ability for the fronts to unite. This is best accomplished by starting at the minimum of 50 psi and increasing …

Weld Line Defects in Plastic Injection Molding - Midstate Mold

Sep 25, 2019·In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares, the two or more fronts of molten plastic …

Injection Molding Troubleshooting: How to Avoid Knit Lines

When a product is produced through injection molding, a high-powered tool injects melted plastic into a custom, double-sided mold. A knit line, also called a weld line, occurs when the …

Eliminate Blemishes on Cosmetic Parts | Plastics Technology

Nov 01, 2005·Black specks on molded parts can be caused by poor screw design, material contamination, or processing missteps. Black specks, streaks, or poor color mixing are the most common problems that mar the appearance of cosmetic injection molded parts. Three likely culprits are resin degradation, equipment contamination, and processing errors.

Flow Lines Defect in Injection Molding Process

May 03, 2019·Mould Cause. LOW MOLD TEMPERATURE. Remedies: Increase the mold temperature to the point that the material has proper flow and packs out the mold. Start with the material suppliers recommendations and adjust accordingly. Allow 10 cycles for every 10-degree change for the process to re-stabilize. IMPROPER VENTING.

Injection Molding Troubleshooting: How to Avoid Knit Lines

When a product is produced through injection molding, a high-powered tool injects melted plastic into a custom, double-sided mold. A knit line, also called a weld line, occurs when the liquid plastic moves through the mold and hits more melted plastic and they don’t flow or fuse together. Instead, a line that looks like a seam forms.

Weld Line Defects in Plastic Injection Molding - Midstate Mold

Sep 25, 2019·What are Weld Line Defects? Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. As the polymer resin is injected into a mold, it flows through all parts of the mold. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex ...

Scary Plastic Part Defects and How to Avoid Them

Splay marks or silver streaks – Circular marks appearing where the molten plastic enters the mold cavity. This is often caused by excessive moisture in the resin. Common defects linked to the …

Eliminate Blemishes on Cosmetic Parts | Plastics Technology

Nov 01, 2005·Black specks on molded parts can be caused by poor screw design, material contamination, or processing missteps. Black specks, streaks, or poor color mixing are the …

13 Plastic Injection Molding Defects and How to Fix Them

Nov 23, 2018·It refers to the surface of the part that can be peeled off layer by layer. Causes: (1) Mixing other incompatible polymers (2) Excessive release agent used during molding (3) resin temperature is inconsistent (4) Excessive moisture (5) …

How to Avoid Knit Lines | Universal Plastic Mold (UPM)

Resin starts to cool as soon as it enters the mold. The faster the resin fills the mold, the less likely it is to cool enough to cause knit lines, so increasing the injection speed and pressure may help eliminate knit lines. Thicken Part Walls. With thicker part walls, plastic can move more easily through the mold.