You have carefully designed a metal shell with perfect functions and excellent appearance. You have repeatedly scrutinized the drawings and strived for perfection in details. However, when you received the manufacturing quotation with great expectations, the number was like a bucket of cold water – far exceeding the budget! What is the problem? Most likely, the problem does not come from your design itself, but is hidden behind a seemingly simple default selection: you may subconsciously check “CNC machining“, but your design is essentially a typical “sheet metal part“.
“CNC machining” and “sheet metal fabrication” – both words point to “metal manufacturing“, which sounds like the same thing. However, in the underlying logic of the manufacturing industry, they represent two completely different manufacturing philosophies, technical paths and cost structures. Confusing them or making the wrong choice inadvertently is often the root cause of project cost out of control, delivery delays and even design re-starts.
What is the difference between sheet metal fabrication and machining? This is not just a dispute over professional terms among engineers. A deep understanding of the essential differences, applicable scenarios, cost drivers and design constraints of these two mainstream metal forming technologies is the core knowledge that every decision-maker responsible for the transformation of a product from concept to reality must master. It is related to cost control, project cycle, and whether the product can be successfully implemented in the end. Choosing the right process is the first step to control the lifeblood of your project and avoid the nightmare of doubling your budget.
Quick Reference Table Of The Differences Between Sheet Metal Fabrication And CNC Machining
| Features | Sheet metal fabrication | CNC machining |
|---|---|---|
| Main materials | Metal sheets (steel, aluminum, etc.) | Metal blocks, bars, thick plates (aluminum, steel, copper, plastic, etc.) |
| Core processes | Cutting, bending, stamping, forming | Cutting (milling, drilling, turning) |
| Typical parts | Cases, brackets, chassis, cabinets | Part prototypes, complex parts, molds, fixtures, precision parts |
| Material thickness | Thin (usually < 6mm) | Thick (block/bar, can process thick plates) |
| Feature accuracy | Relatively low (affected by bending springback, etc.) | High accuracy (can reach micron level) |
| Complex geometry | Limited (mainly based on plane bending/punching) | Extremely strong (can process complex 3D surfaces) |
| Small batches | Cost-effective (simple molds) | Costly (long programming/clamping time) |
| Large batches | Very high (fast stamping speed) | Medium (long single-piece processing time) |
| Processing speed | Cutting/bending Fast; stamping Very fast | Relatively slow (depending on complexity and material) |
| Waste generation | Less (optimized nesting) | More (cutting to remove material) |
This guide will start with the basic principles and deeply compare the differences between the two processes in terms of precision, cost, and speed. Through real cases and design guidelines, it will ultimately help you establish a clear decision-making framework.
Here’s What You’ll Learn:
- The core working principles of sheet metal and CNC:In-depth analysis of how two completely different manufacturing philosophies, “bending and shaping” and “carving and removing”, can achieve part manufacturing.
- Key differences:Reveal the decisive differences and applicable scenarios between the two in core dimensions such as precision, cost, speed, geometric freedom, and material strength.
- Design Optimization Guide for Engineers:Design guidelines designed particularly for sheet metal and CNC to help you stay away from pitfalls and leverage process advantages to reduce costs. drastically.
- Practical Cost Optimization Case:Reveal the true account of how we reduced the cost of producing an industrial controller housing by 75% through the replacement of process (sheet metalization).
The Smarts of Hybrid Manufacturing:Find out how to skillfully combine the advantages of sheet metal and CNC to achieve perfectly balanced cost-versus-precision on one part. - Expert Quick Questions and Answers (FAQ):Clarify misunderstandings (such as “Is sheet metal always cheaper?”, “What is sheet metal processing?”) and provide expert advice on material selection.
Now, let’s take a deeper look at these two elementary processes that characterize today’s manufacturing and gain the insights to take the best decision for your project.
Why Should You Trust This Guide? LS’s Manufacturing Philosophy
In our factory, we handle thousands of parts every day. One profound experience is that good design does not mean manufacturing economy. A lot of costs are wasted at the “starting point” of design – such as over-reliance on the “stretch” command of CAD. A simple “stretch” operation may mean that this part can only be processed by expensive whole-piece CNC, and the material and time costs will soar.
LS’s core advantage is precisely this “cross-process” perspective. When we get the design drawing, we instinctively ask: “Can this part be folded out of a piece of metal plate?” Or, “Can it be disassembled into several simple parts and combined with more economical processes (such as stamping, bending, welding)?”
This ability comes from our rich experience in both high-precision CNC (such as aerospace parts) and large-scale sheet metal (such as server chassis). We are well aware of the cost structure and limits of each process.
A typical case: A customer has a complex bracket, and the original design requires overall five-axis CNC machining, which is costly. We optimize and disassemble it into 3 simple sheet metal parts, which are completed by laser cutting, bending and welding. The result? Fully meet the functional requirements, and the cost is reduced by more than 70%!
This optimization comes from the fact that we did not accept the initial design by default, but used cross-process thinking to find a breakthrough in the sheet metal solution. At LS, we use this perspective every day to transform your design into a more competitive product. This is our manufacturing philosophy: good design, but also smart manufacturing.
Sheet Metal Fabrication In Depth: How Does It Work?
Sheet metal fabrication is a core manufacturing technology that transforms thin metal sheets into complex three-dimensional parts. Its core advantages lie in extremely high material utilization and extremely fast forming speed for simple geometric shapes. The process is a precisely controlled chain that goes far beyond simple bending operations.
Overview of the core steps of sheet metal fabrication
| Step name | Key equipment/method | Core purpose | Main technical points |
|---|---|---|---|
| Cutting | Laser cutting, plasma cutting, punching machine | Obtain the plane contour of the part from the plate | High-precision cutting of the two-dimensional unfolded diagram to maximize material utilization |
| Forming | Bending machine (V-type die/U-type die/air bending) | Convert the plane into a three-dimensional shape | Accurately control the bending angle, radius and sequence |
| Joining | Welding (MIG/TIG/spot welding), riveting, screwing | Combine multiple parts to form a complete structure | Select the connection method according to the strength and appearance requirements |
| Post-processing | Grinding equipment, spraying line, anodizing tank, etc. | Improve appearance, performance and durability | Deburring, weld treatment, anti-corrosion/decorative surface treatment |
Cutting: The starting point of the process. Using technologies such as laser (high precision, complex contours), plasma (thick plates, faster speeds) or CNC punching machines (batch, feature holes), large metal sheets are accurately cut into the two-dimensional plane unfolding diagram required for the parts. This step directly determines the material cost and the benchmark accuracy of subsequent processing (up to ±0.1mm).
Forming: The key to giving metal “life”. The core equipment is the bending machine, which forces the metal sheet to undergo plastic deformation on the die through huge pressure (tonnage).
- V-shaped bending: The most commonly used, the sheet is pressed into shape by the upper die (punch) in the V-shaped lower die, with high angle accuracy.
- U-shaped bending: Similar to V-shaped, but forming a U-shaped groove, requiring matching upper and lower dies.
- Air bending: The sheet only contacts the punch tip and the two lower die shoulders, and is suspended below. The angle is indirectly controlled by controlling the depth of the punch, which is highly flexible and versatile, and is the mainstream process.
Joining: When the design exceeds the forming limit of a single sheet, multiple sheet metal parts are combined.
Welding: (MIG/TIG/resistance spot welding, etc.) Provides high-strength, permanent connections, often used for structural parts, but will produce thermal deformation and require subsequent processing.
- Riveting: Mechanical connection, no thermal impact, suitable for different material combinations or non-weldable materials, reliable strength.
- Bolting/Screwing: Removable connection, easy maintenance or assembly, requires pre-processing of holes.
Post-processing: Improve the final quality of the product.
- Cleaning: Grinding to remove cutting burrs, sharp edges and welding spatter to ensure safety and beauty.
- Surface treatment:
- Spraying (powder spraying/painting): Provides color and protection (rust prevention, weather resistance).
- Anodizing (mainly used for aluminum): An electrochemical process that produces a hard, corrosion-resistant, colorable oxide film layer (5-25μm).
- Others: electroplating, passivation, etc.
Core advantages are highlighted:
- High material utilization rate: By optimizing nesting, the parts are arranged closely, which significantly reduces the scrap and reduces the cost of raw materials.
Fast forming speed (simple shape): For parts mainly composed of straight line bending, the bending machine usually completes a bend in a few seconds to tens of seconds in a single operation, which is much faster than casting or complex machining. Combined with efficient material cutting (such as laser cutting), the entire production cycle is extremely short.
It is through these interlocking and highly controllable steps that the sheet metal process efficiently and accurately shapes cold and hard metal sheets into countless key components that support modern industry and life. Its efficiency and flexibility make it indispensable in the manufacturing industry.
In-depth Analysis Of CNC Machining: The Secret Of Precision Cutting
Contrary to the ‘shaping’ philosophy of sheet metal, CNC machining is an art of ‘carving’, the core of which lies in precise material removal.
Overview of the core steps of CNC machining
| Steps | Core content | Key objectives |
|---|---|---|
| 1. Programming | CAD model → CAM software → G code | Generate precise tool path instructions |
| 2. Setup | Metal blank fixed on the machine table | Ensure stable machining process without displacement |
| 3. Machining | The rotary tool removes material layer by layer along the path | “Carving” out the design shape |
| 4. Finishing | Deburring/Sandblasting/Anodizing/Precision Inspection | Achieving final surface requirements and quality verification |
Programming: It is initiated from a CAD 3D model. CAM software is used by engineers to convert the model into a G-code sequence of instructions that the machine tool can perform based on material properties, tooling type and accuracy requirements, and accurately trace the path of motion of the tool, speed and feed rate.
Setup: The raw material in metal form (Billet) is securely clamped on the machine tool table (often a vise, vacuum suction cup or fixture). Clamping stability is essential, and any displacements will make the part scrap.
Machining: The spindle spins to move the tool at high speed, and by the multi-axis linkage of the table or tool, the redundant material is removed exactly as per the G-code commands. The most typical methods are:
- Milling: Material is removed from the stationary workpiece by the revolving tool, which is suitable for complicated contours/cavities.
- Turning: The rotating workpiece is touched by the stationary tool, and is adept at machinings rotating bodies.
- Multi-axis machining: 3-axis (regular plane machining) → 4-axis (addition of rotation, side machining) → 5-axis (simultaneous multi-directional rotation, achieving single-clamping and single-molding of complex curved surfaces, with higher precision and efficiency).
Finishing: The parts after cutting must be further processed: deburring and edge sharp removal, sandblasting/polishing to improve appearance and feel, anodizing for improving hardness and resistance to corrosion, and finally strict dimensional and tolerance test by precision measurement (e.g., three-coordinate measuring machine).
Key advantages: The major advantage of CNC machining is its extremely high accuracy (to micron range), the ability to create intricate geometrical shapes (such as aircraft parts, precision medical devices), and the ease of small-lot production and rapid prototype validation without the cost of specialty moldings. It is a master engraver of today, converting solid metal billets into precise engineering parts with precision.
Key Differences: One Table Shows The Trade-off Between Cost, Speed And Accuracy
As we now understand how each process works, let’s directly compare them head-to-head along metrics that most concern engineers.
| Comparison Dimension | Sheet Metal | CNC Machining | Expert Practical Comments |
|---|---|---|---|
| Precision Tolerance | The typical range is ±0.1mm~±0.5mm. Bending springback may cause tolerance fluctuations. | Conventional ±0.025mm~±0.05mm, High-precision Equipment Can Reach ±0.005mm | CNC machining must be selected for micron-level precision requirements, such as bearing seats or optical components; sheet metal is suitable for conventional tolerance parts such as chassis and brackets |
| Cost Structure | Low material waste rate (through nesting optimization) Unit cost is significantly reduced in mass production High initial cost of molds and fixtures | No mold costs (suitable for prototype verification) Material waste rate is usually over 30% (whole material cutting) Unit cost increases linearly with processing time | Small batch verification gives priority to CNC; mass production of more than 5,000 pieces of sheet metal has obvious cost advantages. CNC is more economical for less than 500 pieces |
| Production speed | Simple parts can be stamped in seconds/bent in minutes Welding and assembly may become bottlenecks | Processing time is usually measured in hours, and complex parts need several days | Single-piece delivery cycle is stable Sheet metal is recommended for urgent orders: 100 chassis can be delivered in 1 day; CNC parts of the same complexity require superimposed processing and queuing time |
| Geometric freedom | The design is limited to the two-dimensional unfolding structure, relying on bending and welding to achieve a three-dimensional shape Good at hollow thin-walled components | Can manufacture any complex three-dimensional solid (curved surface/cavity/special-shaped hole) Deep and narrow cavities and internal right-angle structures are difficult to process | Sheet metal is used for flat unfolded structures (such as radiator shells); CNC must be used for biomimetic curved structures (such as turbine blades) |
| Material strength characteristics | The bending area has increased local strength due to work hardening There is a risk of fatigue failure at the welding point The overall impact resistance is good | The material maintains the original homogeneous structure (isotropic) No seam stress concentration problem Cutting may destroy the material fiber orientation | Use sheet metal welds with caution for high-cycle fatigue loads; CNC integral parts are preferred for load-bearing frames; sheet metal for shells is more cost-effective |
| Typical application scenarios | Electrical cabinets, mounting brackets, equipment housings, ventilation ducts | Engine blocks, injection molds, orthopedic implants, aircraft structural parts | Sheet metal dominates the field of electronic and electrical/industrial equipment; CNC cannot be replaced in power systems/precision medical parts |
Practical Case Study: Cost Optimization Of Industrial Controller Housing
Background: Recently, we served an automation equipment manufacturer who commissioned us to customize a rugged aluminum housing for a new industrial PLC controller. The customer’s initial design required the housing to be manufactured by CNC milling from a single piece of 6061 aluminum alloy.
Challenges and our findings: After evaluating the process based on the customer’s original design drawings, we calculated the CNC milling manufacturing cost to be $180 per housing. We realized that although this solution met the functional requirements, there was significant room for optimization from a manufacturing economic perspective.
Our professional advice and solutions: With our professional experience in metal processing technology, we took the initiative to contact the customer and proposed an innovative alternative: “sheet metalizing” the design. Specifically, we suggested using 3mm thick 5052-H32 aluminum alloy sheet as the raw material, and achieving the same function and structural strength through a combination of sheet metal processes such as laser precision cutting, precision bending, local welding and fine grinding.
Results and value: After adopting our sheet metal solution, the manufacturing cost of a single shell was significantly reduced to US$45, a 75% reduction compared to the original solution! This case clearly demonstrates the core value of LS as a manufacturing partner: we not only strictly produce according to the drawings, but also actively use our process expertise and manufacturing experience to deeply review the design, identify potential optimization points, and propose practical alternatives, ultimately bringing customers significant direct cost savings (75% in this case) and improved supply chain efficiency.
Core revelation: Choosing LS, you get not only a processing service provider, but also a deep manufacturing partner who is committed to creating the greatest value for your products and optimizing the cost of the entire life cycle.
Design Optimization Guide For Engineers
After choosing the right process, the next step is to optimize your design for that process, which can further reduce costs and improve quality.
Sheet Metal Design Key Points (Do’s & Don’ts)
Do:
- Uniform wall thickness: Simplify processing and reduce deformation.
- Reasonable bending radius (R ≥ sheet thickness T): Avoid cracking and wrinkling.
- Sufficient flange length (recommended ≥ 4T + R): Ensure bending stability.
Don’t:
- Design a closed body that cannot be expanded: It must be able to be processed from a flat plate.
- Opening holes and grooves at/near bends: High risk of deformation (hole edge distance recommended ≥ 2T + R).
CNC Machining Design Key Points (Do’s & Don’ts)
Do:
- Use standard tools/threads: Reduce costs and delivery time.
- Sufficient inner corner radius (R ≥ tool radius): Allow large diameter and high-efficiency tools.
- Reasonable width-to-depth ratio (depth D ≤ 3-4 times width W): Convenient for rigid tool processing.
Don’t:
- Design deep and narrow pockets (D >> W): Require slender tools, poor rigidity, low efficiency, and easy tool breakage.
- Require extremely small internal corner radius: Force the use of fragile micro-diameter tools, which increases costs and is easy to damage.
- Design internal features that cannot be reached by tools: Add special tooling, multiple clamping or impossible to process.
Core: Understand process limitations (material deformation, tool physics), follow DFM principles, use standard parameters, and avoid extreme designs (too small, too deep, too narrow). Early communication with manufacturers can significantly improve efficiency and benefits.
Hybrid Manufacturing: When Sheet Metal Wisdom Meets CNC Precision
The essence of the most advanced manufacturing solutions is often not an either-or choice, but a wise fusion of different processes. Hybrid manufacturing is an outstanding practice of this concept – it uses sheet metal forming and CNC machining technology on a single component, cleverly combining the strengths of both and breaking through the limitations of a single process.
What is hybrid manufacturing?
Its core lies in breaking down process barriers and allowing economical and efficient sheet metal to work with precise and flexible CNC machining. Sheet metal is good at quickly building lightweight main structures and complex surfaces with significant cost-effectiveness; while CNC machining can achieve ultra-high precision features, strict tolerances and excellent surface finish. Hybrid manufacturing allows both to show their strengths on the same component through reasonable planning, creating a solution with excellent performance and cost.
Typical application scenarios:
High-precision mounting point: Precisely weld a CNC-finished aluminum or stainless steel mounting block on the main body of the formed economical sheet metal chassis. The module provides perfect flatness and precise holes, and is directly used to fix sensitive electronic components or motors, eliminating the need for additional mounting plates, ensuring that core components are stable and reliable.
Complex interface integration: The ends of large sheet metal structures (such as racks or housings) often need to be connected to other systems. At this time, CNC machining a flange with a precision O-ring sealing groove, complex threaded holes or special contours, and then welds or fastens it to the sheet metal, which perfectly solves the sealing and connection problems.
Post-processing improves accuracy: For sheet metal parts that have been bent and formed, ordinary stamping or laser cutting may not be able to meet the extremely high tolerance requirements of certain key holes or contours. Post-processing through CNC milling or drilling can easily achieve these features, giving the formed sheet metal a new dimension of accuracy.
LS’s one-stop advantage:
Coordinating different suppliers of sheet metal and CNC is not only time-consuming and labor-intensive, but also prone to matching errors. LS is well aware of this and provides a truly one-stop hybrid manufacturing service. From design collaboration, process planning to seamless production and quality inspection, we control the entire process to ensure the perfect integration of sheet metal parts and CNC machined parts, eliminate interface risks, significantly shorten your product launch cycle, and give full play to the advantages of hybrid manufacturing.
Hybrid manufacturing is a symphony of intelligently connected processes, allowing the efficiency of sheet metal and the precision of CNC to resonate harmoniously on the same component, creating higher-value products.
FAQ – Quick Questions And Answers About Sheet Metal And Machining
1. Is sheet metal always cheaper than CNC machining?
Not always. Sheet metal machining is usually more economical for thin parts and large-scale production because its processes (such as stamping or bending) are fast, have high material utilization and low cost; but CNC machining may be more cost-effective for small batches, complex geometries or high precision requirements because it does not require special molds and can handle thick materials. The final cost depends on the complexity of the design, the output, the material selection (such as stainless steel or aluminum), and the post-processing requirements. It is recommended to compare the quotes of the two in specific projects and give priority to simplifying the design to reduce costs. Generally, sheet metal is suitable for simple parts and CNC is suitable for customized parts.
2. What is “sheet metal machining”? Is there a problem with this term?
There is nothing fundamentally wrong with the phrase “sheet metal machining” itself. It is an industry-standard term that refers to the manufacturing process of metal sheets (such as steel or aluminum), including cutting, bending, stamping and welding. However, it may cause misunderstandings, such as being mistakenly believed to involve only manual operations rather than automation, or being confused with “machining” (such as CNC), which targets solid blocks. When using it, it is recommended to clarify its scope in the context to avoid ambiguity; it is widely accepted in the professional field, but beginners can clarify it by consulting standard definitions (such as ISO standards).
3. How do I choose the right material for my design?
Selecting materials requires a comprehensive assessment of design requirements: first consider functional factors such as load strength, weight restrictions, corrosion resistance (such as humid environments) and temperature tolerance; secondly, analyze cost budget, processability (such as aluminum or stainless steel for easy bending of sheet metal) and aesthetic requirements. Common options include aluminum (lightweight, low cost), stainless steel (high corrosion resistance), and carbon steel (high strength). It is recommended to refer to material data sheets, conduct prototype testing, and consult suppliers or engineers to match application scenarios (such as high-strength steel for automotive parts and anti-corrosion aluminum for electronic housings) to ensure a balance between performance and manufacturability.
Conclusion
Sheet metal fabrication and CNC machining are not mutually exclusive, but indispensable complementary processes in modern manufacturing. Accurately grasping the core geometric features of your parts is the key to optimizing process selection and effectively controlling project costs and cycles.
Is your part more suitable for sheet metal or CNC machining? Why guess! At LS, we have both top-notch sheet metal and CNC machining equipment and a senior engineering team. Just upload your CAD file to our smart platform:
- Get an accurate CNC machining quote instantly.
- Our engineers will proactively evaluate the feasibility of sheet metal fabrication.
- Let us tailor the most economical and efficient manufacturing solution for you!
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📧 Email:info@longshengmfg.com
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Disclaimer
The content appearing on this webpage is for informational purposes only. LS makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through LS’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please contact to our for more information.
Team LS
This article was written by various LS contributors. LS is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding,metal stamping and more.
