The main difference between LD18, LD33, and LD45 foam is their density. LD18 foam has a density of 18kg/m^3, LD33 foam has a density of 33kg/m^3, and LD45 foam has a density of 45kg/m^3. This means that LD18 foam is the least dense and LD45 foam is the most dense.

In general, higher density foam is firmer and more supportive, while lower density foam is softer and more cushioning. The choice of foam density will depend on the specific application and desired level of comfort and support.

Custom foam typically refers to foam products that are specifically designed and manufactured to meet certain specifications or requirements. Custom foam can come in various densities, colors, sizes, shapes, and materials, depending on the needs of the customer.

Some common examples of custom foam products include:

• Custom-cut foam inserts for packaging, cases, or displays

Custom foam products are often used in industries such as packaging,  automotive, aerospace, and medical devices. They are tailored to provide optimal performance and meet specific functional and aesthetic requirements.

When deciding between waterjet cutting and CNC foam cutting for foam materials, there are several factors to consider:

1. Precision: Waterjet cutting is known for its high level of precision, as the water jet can cut intricate shapes with very tight tolerances. CNC foam cutting is also precise but may not offer the same level of precision as waterjet cutting.

2. Speed: Waterjet cutting tends to be faster than CNC foam cutting, especially for thicker foam materials. Waterjet cutting can cut through foam quickly, while CNC foam cutting may be slower, depending on the complexity of the design.

3. Material Compatibility: Waterjet cutting is versatile and can cut through a wide range of materials, including foam, rubber, plastics, metals, and composites. CNC foam cutting is specifically designed for foam materials and may not be suitable for cutting other materials.

4. Cost: Waterjet cutting machines are generally more expensive than CNC foam cutting machines. The operating costs of waterjet cutting, including water and garnet abrasive, also tend to be higher than those of CNC foam cutting.

5. Maintenance: Waterjet cutting machines require regular maintenance and replacement of components such as high-pressure seals, abrasives, and nozzles. CNC foam cutting machines may require less frequent maintenance and have lower operating costs.

Ultimately, the choice between waterjet cutting and CNC foam cutting will depend on the specific requirements of the project, including the desired level of precision, speed, material compatibility, cost considerations, and maintenance needs.