Online Urethane Casting (Vacuum Casting) Service

Requirement	Specification
Standard lead time	Up to 50 copies within 3-5 working days
Standard accuracy	±0.3% (with a lower limit on ± 0.3 mm on dimensions smaller than 100 mm)
Minimum wall thickness	To ensure that the mold is filled properly, a wall thickness of at least 0.75 mm is necessary. For best results, we recommend a wall thickness of at least 1.5 mm
Maximum part dimensions	The size of the mold is limited by the dimensions of the vacuum chamber (1900 x 900 x 750 mm) and by the volume of the product (maximum volume: 10 liters)
Typical quantities	Up to 25 copies per mold (depending on the mold’s complexity and the casting materials)
Surface structure	High-quality surface finish comparable to injection molding

Requirement

Specification

Standard lead time

Up to 50 copies within 3-5 working days

Standard accuracy

±0.3% (with a lower limit on ± 0.3 mm on dimensions smaller than 100 mm)

Minimum wall thickness

To ensure that the mold is filled properly, a wall thickness of at least 0.75 mm is necessary. For best results, we recommend a wall thickness of at least 1.5 mm

Maximum part dimensions

The size of the mold is limited by the dimensions of the vacuum chamber (1900 x 900 x 750 mm) and by the volume of the product (maximum volume: 10 liters)

Typical quantities

Up to 25 copies per mold (depending on the mold’s complexity and the casting materials)

Surface structure

High-quality surface finish comparable to injection molding

FAQ's

What is injection molding?

Injection molding is a manufacturing process used to create plastic parts in large quantities. Molten plastic material is injected into a mold or cavity, which is then cooled and solidifies into the desired shape. The process involves feeding plastic pellets into a hopper, which are then heated to a molten state and injected into the mold under high pressure. This pressure ensures that the material fills the mold completely and uniformly, resulting in a high-quality finished product. Injection molding is commonly used to create products such as toys, automobile parts, packaging materials, and medical devices.

What materials can be used in injection molding?

A variety of materials can be used in injection molding, including thermoplastics, thermosets, and elastomers.

Thermoplastics: These are the most commonly used materials in injection molding, including polyethylene (PE), polypropylene (PP), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), and polyvinyl chloride (PVC).

1. Thermosets: These materials are harder, more rigid, and more heat-resistant than thermoplastics. Examples include epoxy resins and phenolic resins.

2. Elastomers: These are rubber-like materials with high elasticity and flexibility. Examples include silicone, natural rubber, and styrene-butadiene rubber (SBR).

The choice of material depends on the specific application and requirements for the finished product. Properties such as strength, durability, flexibility, heat resistance, chemical resistance, and color can be tailored by using different materials and additives in the plastic pellets. In addition, recyclable and biodegradable materials are becoming increasingly popular in injection molding as part of a sustainable production process.

What are the different types of injection molding machines?

Single-shot injection molding and multi-shot injection molding are both methods used for producing plastic parts, but they differ in the way that the plastic material is injected into the mold.

Single-shot injection molding: This is the most common method of injection molding. It involves injecting a single material into the mold, which solidifies to form the final part. The mold is typically designed to have a single cavity or multiple cavities, enabling multiple identical parts to be produced simultaneously.

Multi-shot injection molding: This method uses multiple materials to create a single part. It is also known as overmolding. Depending on the design of the mold, two or more materials can be injected into the mold in a single operation. Multi-shot injection molding allows for the creation of parts with multiple colors or materials, or for the creation of parts with rigid and flexible sections.

There are two main types of multi-shot injection molding:

1. Sequential injection molding: This involves injecting one material into the mold cavity and allowing it to partially solidify before injecting the second material. The process can be repeated with additional mold cavities to create more complex parts.

2. Co-injection molding: This involves injecting two materials simultaneously into the mold cavity. This method is typically used for creating parts with a core and skin structure, for example, plastic cups with foam insulation.

The choice of single-shot or multi-shot injection molding largely depends on the specific requirements of the part and the manufacturing process. Multi-shot injection molding is more complex and can be more expensive, but it allows for greater design flexibility and the creation of parts with multiple materials or colors.

What is the maximum injection molding capacity of a machine?

The maximum injection molding capacity of a machine depends on several factors, including the volume of the mold cavity, the shot size, and the material being used. The machine's clamping force and injection pressure also play a role in determining the maximum injection molding capacity.

Injection molding machines can range in size from small benchtop machines with a maximum injection capacity of a few grams to large machines capable of producing parts that weigh several kilograms. High-capacity, industrial-grade machines can have a maximum injection capacity of up to 60,000 grams (or 60 kilograms), depending on the manufacturer and model.

The maximum injection molding capacity of a machine is typically specified in terms of the shot size, which is the maximum volume of material that the machine can inject into the mold with a single injection stroke. The shot size can range from a few grams to several kilograms, depending on the machine's size and capacity.

It's important to note that while a machine may have a high maximum injection molding capacity, the actual production rate will depend on the complexity of the part being produced, the cycle time, and the number of cavities in the mold.

Plastic Part Cosmetic Defect – Black Specks | Definition, Causes & Inspection Criteria

1. Definition

Black specks refer to black spots or streaks present on molded parts. Any black discoloration visible on the component surface is defined as BS (Black Specks).

2. Visual Characteristics

Typically appear as black dot-like or linear foreign inclusions

Mostly found on the part surface

Negatively impacts cosmetic uniformity

3. Potential Causes

Degraded / Burnt resin

Carbonized resin

Material stagnation residue inside barrel

Contamination from foreign debris

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Inspection Criteria

Observe color and distribution pattern

Verify whether the defect is a foreign contaminant

Distinguish between surface residue and embedded inclusions

Retain photos and defective samples

Plastic Part Cosmetic Defect – Pitting (Pockmarks) | Definition, Causes & Inspection Criteria

1. Definition

Pockmarks are small depressions formed on thick-section molded areas, caused when molten resin fails to fully adhere to the mold cavity surface.

2. Visual Characteristics

Tiny indentations on the part surface, generally small in size

Commonly found on thick wall sections

3. Main Causes

Pockmarks can stem from multiple factors; the primary contributor is insufficient pack pressure.

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Inspection Criteria

Observe the location and density of indentations

Focus inspection on thick wall regions

Distinguish pockmarks from contamination or impact marks

Document size, affected zones and quantity

Plastic Part Cosmetic Defect Training – Simple Reference for Quality Inspectors

Plastic Part Cosmetic Defect – Weld Lines (Knit Lines) | Definition, Causes & Inspection Criteria

1. Definition

Weld lines form where separate resin flow fronts converge. They inevitably develop around perforations and appear as distinct linear marks on the surface.

2. Typical Locations

Surrounding holes, resin convergence zones, handles and folded angular geometries.

3. Favorable Conditions for Defect

More likely to occur at low mold temperatures, and become more pronounced when resin flow front merging is poor.

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Inspection Criteria

Confirm position of linear marks

Evaluate impact on aesthetics and mechanical strength

Analyze in conjunction with hole locations, corners and melt flow direction

Take photos for archiving

Plastic Part Cosmetic Defect Training – Simple Reference for Quality Inspectors

Plastic Part Cosmetic Defect – Gas Burn | Definition, Causes & Inspection Criteria

1. Definition

Gas burn describes scorched discoloration that appears on molded part surfaces during injection.

2. Formation Mechanism

Burn marks occur at melt flow end positions, most often associated with inadequate mold venting.

3. Typical Risks

Impairs surface appearance, local mechanical performance and perceived quality by customers. Severe cases are accompanied by carbonized traces.

Inspection Focus Points

Prioritize checking flow ends, corners and wall thickness transition zones

Confirm discoloration depth and affected area

Retain defective samples

Timely escalate venting concerns for mold optimization

Plastic Part Cosmetic Defect Training – Simple Reference for Quality Inspectors

Plastic Part Cosmetic Defect – Root Cause of Gas Burn | Definition, Causes & Inspection Criteria

Local black or dark brown scorch marks appear on molded components.

Defect Formation Mechanism (3-stage process)

1. Normal Venting As resin fills the mold cavity, trapped air and gases generated by the molten material escape through mold vents.

2. Venting Blockage If vents become clogged, or no vents are present at melt flow ends, gases cannot be discharged smoothly.

3. Compression Heating & Burning Trapped gases are compressed, creating extreme localized high temperature, which scorches the resin.

Improvement Actions

Clean Vents

Regularly clean mold vent grooves and vent ports to ensure unobstructed ventilation.

Verify Venting at Flow Terminations

Install vents at melt flow end positions, avoid blind end sections without venting.

Optimize Fill Speed & Packing Pressure

Set appropriate filling speed and packing pressure to reduce gas entrapment and compression.

Inspect Mold Design & Maintenance Status

Periodically check mold structure, wear and clogging issues to maintain reliable venting performance.

Plastic Part Cosmetic Defect Training – Simple Reference for Quality Inspectors

Plastic Part Cosmetic Defect – Glass Fiber Bloom | Definition, Causes & Inspection Criteria

Glass Fiber Bloom (Glass Fiber Exposure)

The root causes for glass fiber bloom are identical to those for poor surface gloss.

Refer to the “Poor Surface Gloss” section for full details.

Figure 1: Glass fiber bloom on 120 square flat panel (Example 1)

Figure 2: Glass fiber bloom on 120 square flat panel (Example 2)

Definition / Appearance

Glass fibers emerge onto the molded part surface; localized whitening, fuzziness, rough texture or distinct fibrous grain patterns can be observed.

Relationship with Poor Surface Gloss

Glass fiber bloom shares the same root causes as poor surface gloss. Fundamentally, both defects originate from inadequate surface replication and abnormal surface layer conditions.