Perfecting the Process: How BEC Tackles Moulding Challenges

In plastic injection moulding, precision matters. A fraction of a millimetre can mean the difference between perfect parts and an entire production run wasted.

When you’re making thousands of identical components, small defects quickly multiply into costly problems. The best manufacturers don’t claim to eliminate issues entirely – they anticipate potential problems and solve them before your production even starts.

Here’s how BEC handles the four most common moulding defects that keep engineers awake at night!

The Sink Mark Problem

Every plastic part designer fears those telltale depressions on otherwise smooth surfaces. Sink marks appear where thicker sections of plastic shrink internally after the outer surface has solidified – often near ribs, bosses, or changes in wall thickness.

BEC tackles sink marks by:

• Utilising Moldflow software during an initial design for manufacture report to highlight potential areas for sinkage
• Optimising wall thickness during design – maintaining consistent dimensions
• Adjusting cooling time and temperature for proper material solidification
• Modifying gate locations for even material flow
• Using structural ribs rather than solid sections to maintain strength

The result? Clean, smooth surfaces that meet both functional and aesthetic requirements.

Swerving Weld Lines

Weld lines represent one of the most challenging aspects in plastic injection moulding. They form when separate flows of molten plastic meet inside the mould but don’t fully bond together.

You can spot them as visible lines on finished parts – sometimes subtle, sometimes glaringly obvious. The real problem goes beyond appearances, though. These junctions create structural weak points that can crack under stress, potentially causing product failures in the field.

The physics behind weld lines is fascinating. As plastic flows through a mould cavity, it cools upon touching the metal surfaces. When two cooling flow fronts meet, they often lack enough heat energy to properly melt together, like trying to weld metal pieces that aren’t hot enough.

BEC’s engineers have perfected techniques to ensure materials meet with enough force and fluidity to create seamless joins.

Preventing Warpage

Anyone who’s opened a box of freshly moulded parts only to find they’ve twisted, bowed or curled knows the frustration of warpage. It happens when internal stresses cause components to distort after moulding, often making them unusable in precision assemblies.

This comes down to uneven cooling. When different sections of your part solidify at different rates, the resulting stress pulls the component out of shape. Thicker areas cool more slowly than thin ones, creating tension that distorts the final geometry.

Our production team controls this through precisely engineered cooling channels in the tool itself, ensuring heat dissipates evenly throughout the part.

We also calibrate holding pressure and cooling time for each specific material – small adjustments that make enormous differences in dimensional stability.

Stopping Flashing

Those thin feathers of excess plastic that form where the mould halves meet might seem trivial, but flash creates serious problems.

Beyond the obvious cosmetic issues, flash interferes with tight tolerances, creates sharp edges, and often means parts require expensive secondary operations.

Flash typically appears for several specific reasons:

• Worn or damaged mould surfaces that no longer meet precisely
• Insufficient clamping force to keep mould halves together under injection pressure
• Material viscosity issues from incorrect temperature or contamination
• Excessive injection pressure forcing material into the parting line

The root causes typically involve either worn tooling, insufficient clamping force, or excess injection pressure.

We regularly inspect and maintain mould surfaces, while balancing clamping pressure against material viscosity for each production run.

Quality Built Into Every Step

What truly sets BEC apart is our integrated workflow that bridges design, toolmaking and production under one roof.

This eliminates the communication gaps that often lead to problems. For clients, this means shorter lead times, reduced costs, and components that perform exactly as specified.

Whether you’re launching a new product or improving an existing one, BEC’s expertise ensures your plastic injection moulding projects deliver exceptional results.

Contact our friendly team to discuss how we can solve your toughest moulding challenges.

For more information on Perfecting the Process: How BEC Tackles Moulding Challenges talk to BEC Group