How to Choose the Right Sheet Metal Process: A Comprehensive Guide

1，Introduction

When manufacturing products from sheet metal, material selection, finish and production technology need to be considered at the design stage. The choice of production process affects a number of aspects such as part price, tolerances and geometry. This blog will introduce the common sheet metal fabrication processes, as well as their advantages and characteristics, and teach you how to choose.

2， Types of sheet metal working processes

1. Laser Cutting
Process principle
Laser cutting uses a high-power industrial laser to cut metal sheets into the required shape and size, which is divided into two categories: melting cutting and ablation laser cutting.
Modern laser cutting machines are mainly CO2 lasers and fiber lasers; CO2 lasers use infrared light to cut the material, less power, slower, but the surface is smoother when cutting thicker materials; fiber lasers are faster, more powerful, and able to cut thicker overall material.
Advantages
Faster and more efficient than mechanical cutting.
Surface finish is superior to mechanical and most other computer-controlled methods.
Highly accurate and able to accommodate tight tolerances.
Multiple shapes can be obtained without the need for custom molds.
Suitable for a wide range of metals and other materials.
Suitable for a wide range of material thicknesses.
Ideal for metal annealing, etching and engraving serial numbers.
Complex individual cuts and complex production runs are possible with the help of modern CNC controls.
Disadvantages
Materials may undergo thermally induced structural changes that can affect the final product.
Reflective materials are difficult to cut.
Not suitable for most plastics or wood.
Adjustments are required when cutting different thicknesses of sheet metal.
Edge hardening may require additional treatment.
Other cutting methods may be more suitable for mass production.

2. Plasma Cutting
Process Principle
Plasma cutting uses an accelerated jet of hot plasma to cut electrically conductive materials such as metals. Compressed gas is injected into the cut material in the form of a high-speed jet, generating an electric arc in the gas between the electrode and the conductive material, which ionizes the gas to form a plasma jet that is heated enough to melt the cut material, at temperatures of 20,000°C and above.
Advantages
Very neat edges can be obtained.
Faster cutting speeds than many alternative cutting methods.
Narrow kerf widths.
High accuracy.
Cheaper than laser cutting and water jet cutting.
Disadvantages
Not suitable for non-conductive materials.
High temperatures can cause problems with the material being cut, not suitable for thin and medium-thin sheet metal parts.
Generates radiation and requires staff to wear protective equipment.
Less accurate and slower than laser cutting.
May require post-processing at the cut edge.

3.Water Jet Cutting
Process Principle
Water jet cutting uses a mixture of high-pressure water and abrasives to cut metal. The water is pressurized to 60,000 psi by a hydraulic pump and cuts the metal surface by abrasive action in the form of a fine jet.
Advantages
Highly accurate, allowing for complex cuts.
Avoids the effects of thermally induced structures on the sheet metal.
Small kerf widths.
Suitable for a wide range of metals and other materials.
Smooth cutting edges, reducing the need for post-processing.
Cost-effective in mass production.
Can cut thicker metal blocks.
Can be combined with software to automatically manage complex production runs.
Disadvantages
Cutting times are slower than other methods.
Thick cuts are not as clean as other methods and edges are often tapered.
Requires post-processing for best results.
Can be more expensive than other cutting methods.
Less suitable for small scale production due to cost and setup time.
Manufacturers with water jet cutting equipment are harder to find.
Less suitable for engraving and annealing.

4. Mechanical Cutting
Process principle
Mechanical cutting uses machines with power-driven moving cutting edges to shape the metal to design specifications, removing the material from the sheet metal by mechanical action. Common mechanical cutting machines include lathes, mills, drills, grinders, saws and planers.
Advantages.
Mechanical cutting methods can be set up quickly and are suitable for small production runs.
Modern cutting machines are highly accurate and suitable for high precision requirements.
Can be used on a wide range of metals and other materials.
Customized tooling is usually not required.
Easy to produce prototypes with mechanical cutting methods.
Some mechanical cutting methods reduce the effects of thermally induced structures on sheet metal parts.
Disadvantages
May require a combination of several different mechanical cutting processes to complete the part.
Post-cutting processes are often required.
May require specialized labor.
Slower processing times make it unsuitable for mass production runs.
Parts may vary depending on production method.

5. CNC Plate Bending Machine
Process principle
CNC plate bending uses CNC presses or bending machines to bend metal into two- or three-dimensional shapes. It can be used in the early stages of manufacturing or to adjust the finished product.
Advantages
High-precision process for parts requiring high precision.
Large quantities can be produced in a short period of time.
Low cost, with minimal tooling costs.
Suitable for high or low volume production.
Multiple customized shapes can be created by series bending process.
Standard punches and dies are available.
Disadvantages
May create indentations or marks at product bend points.
Labor intensive and not well suited for high volume production.
Custom dies are required for specialized bending projects.
Sheet metal parts need to be positioned to prevent slipping when bending.
Hard metals tend to break when bent parallel to the rolling direction.
Features such as holes and slots near the bend may be deformed.

6. Shearing

Process Principle
Shearing applies force to the sheet metal by means of a die, punch or blade to fracture and separate it at the desired position, usually used for straight line cutting, but can also produce angular cutting.
Advantages
Produces long straight strips.
Suitable for soft metals.
Cost effective for high volume projects.
Ideal for cutting small lengths or different shaped materials.
Disadvantages
Cutting type and complexity is limited, mainly for straight cuts.
Burrs or other defects can occur at the cut end.
Not suitable for all materials, including hard metals and large diameter parts.
Slower and less accurate than other cutting methods.

7. Roll Forming
Principle of the process
In roll forming, a long strip of sheet metal passes through a series of pairs of rolls, each pair of rolls partially bending the sheet metal until it reaches its final shape, and then cutting it into finished products.
Advantages
Fast production speeds.
Low cost of production on a large scale.
Fewer post-processing requirements.
Can incorporate secondary processes such as punching.
Better results than some sheet metal extrusions.
Highly complex shapes can be produced through a relatively simple production process.
Provides an alternative when stamping is not possible.
Disadvantages
Production set-up process is complex and can be expensive.
Metal springback can cause production difficulties.
Some shapes cannot be formed by rolling.
Sheet metal strip end pieces may be of poor quality.
Large production facility footprint.
May not be suitable for narrow or short sections.

8. Precision Hand Stamping
Process Principle
Stamping uses mechanical or hydraulic presses to form metal, dies are used for bending, stamping, etc. to process metal parts, custom dies are created for individual production runs and need to be accurately manufactured.
Advantages
Medium to large volume production is fast and cost effective.
Precise production of complex shapes.
Large quantities of identical parts can be produced quickly after the mold is made.
Suitable for high precision production of small parts.
Versatile process that allows for a variety of processes such as punching.
Surplus material can be recycled.
Disadvantages
Long pre-production time for custom molds, which can take more than 45 days.
Tooling changes are expensive and impact production schedules.
Stamping tools are relatively fragile and susceptible to repeated changes in life.
Tooling errors can lead to complete production errors.
Parts may require additional sheet metal processing.
Small order production is not cost effective.
Stamping tools require regular maintenance and monitoring.
Materials need to be sufficiently ductile.

9. precision progressive stamping
Process Principle
In Precision Progressive Stamping, a metal strip is processed in multiple stages through a series of stamping presses with sequentially arranged dies, and finally cut into finished products.
Advantages
More complex shapes can be created than with manual stamping or other methods.
Cost effective for high volume production with low cost per piece.
Accurate production of complex shapes.
Fast production speeds.
Suitable for high precision production of small parts.
Can reduce scrap rates.
Disadvantages
Custom molds are time-consuming to produce and can take more than 50 days to deliver.
Molds and tooling are costly to produce, with a large upfront investment.
Changes to molds after they are created are expensive and disruptive.
Stamping tools are fragile and their lifespan can be compromised.
Tooling errors can lead to complete product errors.
Parts may require additional sheet metal processing.
Stamping tools require regular maintenance and monitoring.
Materials need to be ductile enough.

10. CNC Punching
Process Principle
CNC punching uses a punch to push a sheet of metal into a die to create a hole or cutout, which can also be used for secondary operations.
Advantages
Strong cutting power, suitable for a wide range of metals.
Fast and efficient punching for shapes such as squares.
Suitable for medium to large quantities.
High accuracy and even cutting levels.
Standard punches available.
Can produce complex designs.
Disadvantages
Not suitable for complex shapes.
Burrs on edges may require secondary finishing.
Hole diameter should generally not be smaller than sheet metal gauge.

3，How to choose sheet metal processing?

When selecting a sheet metal cutting and forming process, a number of factors such as design requirements and production constraints need to be considered. Different processes produce sheet metal parts with different physical properties and also involve different costs, time and manufacturing difficulties. Usually, the process that can meet the design requirements with minimum cost, on-time delivery and as little hassle as possible should be selected.

1.Process Cost
Cost is often a key factor in selecting the right process. Generally should choose the production method that can meet the minimum quality standards of parts at the lowest cost. However, cost selection can be complicated by production volumes and manufacturer capabilities.
Volume is an important factor, and some production methods such as stamping and progressive stamping are inexpensive for high volume production but expensive for low volume. Manufacturers who specialize in certain production methods may be able to reduce costs accordingly.

2.Tolerance
The level of accuracy required for the finished sheet metal part needs to be considered when selecting the process, as this is critical to the performance of the finished part and subsequent calibration of the assembly.
3、Tooling Requirements
Some sheet metal cutting and forming processes require customized tooling, such as stamping which almost always requires customized tooling. Customized tools can be costly and are required to ensure accuracy, with lengthy qualification processes.

3.Thickness Requirements
The thickness of the sheet metal to be processed is an issue that needs to be taken into consideration, mainly whether or not thick sheet metal needs to be processed. Of the common processes, only laser cutting and CNC bending can be used for sheet metal sections over 4mm.

4.Minimum order quantities
Minimum order quantities need to be discussed with the manufacturer. Some processes are not suitable for small quantities, such as stamping, which is often unsuitable for small batches because of the time and expense involved in creating customized tooling and planning the production process. Progressive stamping, on the other hand, is suitable for high volume sheet metal applications.

5.Lead Time
Lead time is related to production requirements. No need to customize tools and setup procedures for simple processes with short lead times, such as laser cutting can be directly entered into the design production, the lead time is very short. Processes that require planning, customized tooling, specialized equipment or staff training have long lead times. Larger orders may also require longer lead times.

4，Summary

Choosing the right sheet metal processing process is significant for sheet metal product manufacturing. This paper describes a variety of sheet metal cutting and forming processes, such as laser cutting. Factors such as process cost, tolerance, tooling requirement, thickness requirement, minimum order quantity and lead time need to be considered when selecting a process. Different processes have their own advantages and disadvantages as well as applicable scenarios. The most suitable process should be selected based on the design requirements and production constraints with the objective of minimizing cost and on-time delivery.