Location of Fiberglass Filtration Mesh

Fiberglass filtration mesh is used in foundries to filter molten metal before it enters the mold cavity. It helps capture slag, oxide films, refractory particles and other non-metallic inclusions while also helping regulate molten metal flow through the gating system.

The filter can be installed at different locations depending on the casting process, mold structure, pouring method, alloy type and required filtration efficiency. Common installation positions include the pouring cup, sprue, sprue base, runner, ingate and molten metal transfer system.

Correct filter placement is important. The filter should intercept inclusions before the molten metal reaches the casting cavity without excessively restricting flow or causing incomplete filling.

Widely used in automobile and motorcycle wheels, cylinder pistons, aluminum rods, aluminum materials, aluminum ingots, aluminum plates and precision casting of all types of aluminum alloy casting.

Effectively remove impurities, reduce turbulence and eliminate air bubbles, thereby improving the quality of castings and reducing costs. At the same time does not pollute the aluminum liquid and affect the chemical properties of the metal. Therefore, aluminum waste containing the filter mesh, aluminum liquid from sprue and the riser can be directly returned to the furnace for remelting, greatly reducing costs.

Common Installation Locations

1. Under the Pouring Cup

Fiberglass filtration mesh can be positioned directly below the pouring cup at the top of the sprue.

In this position, the molten metal passes through the filter immediately after pouring. This helps capture larger slag particles and other visible inclusions before they enter the main gating system.

This location is suitable for:

• Simple sand-casting molds

• Small and medium aluminum castings

• Castings requiring early-stage filtration

• Gating systems with sufficient metal head pressure

• Applications where the filter needs to be installed and inspected easily

The filter must be properly supported so that it does not move, fold or become displaced during pouring.

2. At the Bottom of the Sprue

Installing the filter at the bottom of the sprue allows molten metal to pass through it before entering the horizontal runner.

This is one of the most common locations for fiberglass casting filters because it combines filtration with flow control. It can help reduce the direct impact of molten metal entering the runner and promote a more stable flow pattern.

Typical applications include:

• Aluminum wheel casting

• Aluminum piston casting

• Automotive component casting

• Sand casting

• Gravity casting

• General aluminum alloy casting

A filter installed at the sprue base should have sufficient filtration area to prevent excessive flow restriction.

3. Inside the Runner System

A flat fiberglass mesh filter can be placed horizontally or vertically inside the runner.

Runner placement allows the filter to remove inclusions after the molten metal has entered the gating system but before it is distributed to the individual ingates.

This position is suitable for:

• Molds with long runner systems

• Multiple-cavity molds

• Castings with several ingates

• Large or complex aluminum castings

• Applications requiring more controlled metal distribution

The filter may be installed at the beginning, middle or end of the runner according to the gating design.

4. Before the Ingates

Placing fiberglass filtration mesh immediately before the ingates provides final-stage filtration before the molten metal enters the casting cavity.

This position can be useful for castings with strict surface-quality or internal-cleanliness requirements because inclusions generated or released inside the runner can still be captured before entering the product.

Typical applications include:

• Precision aluminum castings

• Thin-wall castings

• Structural components

• Automotive safety components

• Castings requiring machining or polishing

• Products with demanding surface-finish requirements

Because the filter is close to the mold cavity, it must provide adequate flow capacity to avoid cold shuts, misruns or incomplete filling.

5. In the Sprue Cup or as a Cap Filter

Fiberglass mesh can be formed into a cap, cup, bag or hat-shaped filter and installed in the sprue cup, at the bottom of the gate or inside a specially designed mold recess.

Cap filters provide a larger filtration surface than a simple flat sheet and can hold their position more securely in selected mold designs.

They are commonly used for:

• Aluminum pistons

• Automotive and motorcycle wheels

• Aluminum housings

• Small precision castings

• Gravity die casting

• Sand casting

• Repetitive production molds

The cap diameter, depth, flange size and mesh specification should be matched to the sprue and available mold space.

6. In Molten Aluminum Transfer Systems

Fiberglass filter mesh may also be used outside the mold during the transfer of molten aluminum.

Possible installation locations include:

• Transfer launders

• Holding-furnace outlets

• Ladle outlets

• Transfer funnels

• Furnace-to-mold transfer systems

• Aluminum ingot casting lines

In these applications, the filter removes inclusions before the molten aluminum reaches the casting station or mold.

Filter bags, cone filters and specially shaped mesh products may be used where a flat sheet is not suitable.

Application Locations by Casting Process

Sand Casting

In sand casting, fiberglass mesh filters can be installed:

• Below the pouring basin

• At the top or bottom of the sprue

• Inside the runner

• Before the ingates

• Inside a molded filter chamber

Sand casting systems should provide sufficient support around the filter to prevent sand erosion, mesh movement and molten metal bypass.

Permanent Mold and Gravity Casting

Permanent mold and gravity casting commonly use fiberglass filters in sprue bushings, runners and transfer channels.

Typical products include:

• Aluminum wheels

• Brake components

• Engine housings

• Cylinder heads

• Pistons

• Pump housings

• Transmission components

Rigid or preformed fiberglass filters may be selected where a loose mesh sheet could move under the force of the molten metal.

Low-Pressure Aluminum Casting

In low-pressure casting, molten aluminum rises through a stalk tube and enters the mold under controlled pressure.

A suitably designed rigid fiberglass filter may be installed in the sprue bushing or metal-flow path. The filter must remain stable during the pressure cycle and should not create an excessive pressure drop.

This configuration is commonly used in aluminum wheel and automotive component production.

Aluminum Ingot, Slab and Rod Casting

Fiberglass filtration products can be used in molten aluminum transfer and distribution systems before the metal enters ingot, slab or rod molds.

Typical products include:

• Aluminum ingots

• Aluminum slabs

• Aluminum billets

• Aluminum rods

• Aluminum plates

• Continuous-casting products

Filter bags and transfer-system filters can be used to intercept inclusions during furnace-to-mold metal transfer.

Typical Casting Applications

Fiberglass filtration mesh is widely used for the production of:

• Automobile wheels

• Motorcycle wheels

• Aluminum pistons

• Cylinder heads

• Engine and transmission housings

• Pump and valve housings

• Aluminum rods

• Aluminum billets

• Aluminum ingots

• Aluminum slabs

• Aluminum plates

• Precision aluminum alloy castings

• Decorative aluminum castings

• General industrial components

The appropriate filter material must be selected according to the molten metal and pouring temperature.

Standard treated fiberglass mesh is mainly used for aluminum and lower-temperature non-ferrous casting applications. High-silica fiberglass mesh or another high-temperature filter material should be selected for cast iron, steel, copper and higher-temperature alloys.

How Filter Location Affects Casting Performance

No single installation position is suitable for every casting. The location should be selected according to the gating design, casting size, pouring rate and required metal cleanliness.

How to Select the Correct Filter Location

Before deciding where to install fiberglass filtration mesh, foundries should evaluate:

Molten Metal Type

Confirm whether the filter will be used for:

• Aluminum

• Aluminum alloy

• Copper alloy

• Cast iron

• Steel

• Another molten metal

The filter material must withstand the actual pouring temperature.

Casting Process

Specify whether the application uses:

• Sand casting

• Permanent mold casting

• Gravity casting

• Low-pressure casting

• Investment casting

• Continuous ingot or slab casting

Different processes may require flat mesh, cap filters, bags or rigid preformed filters.

Pouring Rate

The filter must provide enough open area for the required volume of molten metal to pass through without interrupting mold filling.

A filter that is too small or too fine may increase filling time and create incomplete casting defects.

Inclusion Level

Molten metal containing a high level of slag or oxide inclusions may require:

• A larger filtration area

• More suitable mesh size

• Improved upstream melt treatment

• Multiple-stage filtration

• More frequent filter replacement

A filter should not be used as a substitute for proper furnace cleaning, degassing and melt-handling practices.

Gating-System Design

The sprue, runner, ingates and filter chamber should be designed as one system.

Important considerations include:

• Available filter-support area

• Metal head height

• Flow direction

• Runner cross-section

• Distance from the mold cavity

• Risk of filter movement

• Risk of metal bypass

• Required mold-filling time

Filter Shape and Size

Available fiberglass filter forms include:

• Cut mesh sheets

• Mesh rolls

• Round filters

• Square filters

• Rectangular filters

• Cap filters

• Cone filters

• Filter bags

• Custom-shaped filters

The filter should cover the complete metal-flow path without gaps around its edges.

Benefits of Correct Filter Placement

Correctly selected and positioned fiberglass filtration mesh can help:

• Remove slag and non-metallic inclusions

• Reduce oxide films entering the mold cavity

• Stabilize molten metal flow

• Reduce excessive turbulence

• Improve casting surface quality

• Reduce internal inclusion defects

• Improve machining performance

• Reduce rejected castings

• Improve production consistency

• Reduce unnecessary cleaning and reworking

The final result depends on the filter specification, gating design, molten metal condition and pouring process.

Custom Fiberglass Filtration Mesh Solutions

We can supply fiberglass filtration mesh in different:

• Mesh sizes

• Fabric weights

• Coating types

• Temperature grades

• Sheet dimensions

• Roll widths

• Cap diameters

• Bag shapes

• Custom-cut profiles

To recommend a suitable product and installation location, please provide:

• Molten metal type

• Pouring temperature

• Casting process

• Casting weight

• Pouring time

• Sprue and runner dimensions

• Required filter shape

• Current casting defects

• Annual consumption

Request a Filtration Recommendation

Send us your casting process, molten metal type, pouring temperature and gating-system drawing. Our team can recommend a suitable fiberglass filtration mesh type, size, shape and installation location for your foundry application.