How Is a CNC Machining Quotation Calculated? Um guia passo a passo

If you’re sourcing CNC-machined parts for your project, understanding how quotations are calculated is key to avoiding overpaying or misinterpreting costs. A CNC machining quotation isn’t a random number—it’s a detailed sum of tangible factors like material use, tempo de usinagem, e trabalho. This guide breaks down the calculation process, principais fatores de influência, and practical examples to help you verify and optimize quotes.

1. 8 Core Factors That Shape a CNC Machining Quotation

Every line item in a CNC quotation ties back to specific cost drivers. Abaixo está um detalhamento detalhado de cada fator, with real numbers to illustrate how they impact the final price:

(1) Custo do material

Material cost forms the base of the quotation and is calculated by the part’s weight or volume. Different materials have vastly different unit prices, directly affecting this component:

Observação: Scrap material (typically 10–20% of the raw material weight) is often included in the quotation to account for cutting waste.

(2) Machining Time Cost

Machining time is the single largest variable in most quotations, as it combines equipment and labor charges. It includes three key phases:

• Tempo de programação: 0.5–2 hours for simple parts (Por exemplo, a flat block) and 3–8 hours for complex parts (Por exemplo, parts with 3D curved surfaces). Programmers typically charge 80–150 RMB/hour.
• Actual Machining Time: Depends on cutting speed, tool path, and part size. A small aluminum part (5cm × 5cm) may take 1–2 hours, while a large stainless steel part (20cm × 20cm) could take 4–8 hours.
• Aperto & Tool Change Time: 0.2–1 hour per part. Multi-sided machining (Por exemplo, 4-axis work) can double this time, adding 0.4–2 hours to the total.

Equipment hourly rates vary by type:

• Ordinary 3-axis CNC machines: 50–100 RMB/hour
• High-end 5-axis CNC machines: 150–300 RMB/hour

(3) Equipment Depreciation

CNC machines cost tens of thousands to millions of RMB, so depreciation is spread over their 5–10-year lifespan and included in the quotation. Por exemplo, um 500,000 RMB 3-axis machine has an annual depreciation of 50,000–100,000 RMB, which translates to 20–40 RMB/hour added to the equipment cost.

(4) Manutenção & Desgaste da ferramenta

Ferramentas (Por exemplo, Mills finais, exercícios) wear out after repeated use and need replacement. A standard carbide end mill costs 50–200 RMB and lasts for 20–50 hours of machining—adding 1–10 RMB/hour to the quotation. Other maintenance costs (lubricating oil, filter changes) add an extra 5–15 RMB/hour.

(5) Labor Cost

Labor covers operators, quality inspectors, and sometimes programmers. Hourly rates vary by region and skill:

• Entry-level operators: 50–80 RMB/hour
• Skilled operators (for 5-axis machines): 100–150 RMB/hour
• Quality inspectors: 80–120 RMB/hour

For a part that takes 3 horas para máquina, labor cost typically ranges from 150–450 RMB.

(6) Post-Processing Cost

Most parts require post-processing to meet functional or aesthetic standards, and each step adds to the quotation:

(7) Complexidade da parte & Precisão

Complexity and precision directly increase machining time and skill requirements, pushing quotes higher:

• Peças Simples (block shapes, tolerances ±0.1mm): Lower time and skill needs—quotes are 50–150 RMB/part.
• Partes complexas (paredes finas <2milímetros, tolerâncias ± 0,01 mm): Require slower cutting speeds and more programming—quotes jump to 200–1,000 RMB/part.

Exemplo: A stainless steel part with ±0.01mm tolerance costs 3x more than the same part with ±0.1mm tolerance.

(8) Volume do pedido

Batch size unlocks descontos por volume, como custos fixos (programação, configurar) estão espalhados por mais partes. Here’s how volume affects unit quotes for a simple aluminum part:

2. 3 Common Methods to Calculate CNC Machining Quotations

Suppliers use different formulas to compile quotes, depending on part type and order size. Abaixo estão os métodos mais comuns, with step-by-step examples:

Método 1: Time-Based Quotation (Most Common for Complex Parts)

This method focuses on total machining time, combining equipment, trabalho, and other time-related costs.

Formula: Total Quotation = (Equipment Hourly Rate + Labor Hourly Rate) × Total Machining Time + Custo do material + Post-Processing Cost

Exemplo:

• Equipment hourly rate: 100 RMB (3-eixo cnc)
• Labor hourly rate: 60 RMB (operator + inspector)
• Total machining time: 4 horas (1 hour programming + 2.5 hours machining + 0.5 hours clamping)
• Custo do material: 40 RMB (0.5kg aluminum alloy × 80 RMB/kg)
• Post-processing cost: 80 RMB (Anodizando)

Total Quotation = (100 + 60) × 4 + 40 + 80 = 160 × 4 + 120 = 640 + 120 = 760 RMB

Método 2: Material-Based Quotation (Common for Simple Parts)

This method starts with material cost and adds a fixed or variable machining fee.

Formula: Total Quotation = (Material Unit Price × Part Weight) + Machining Fee + Post-Processing Cost

Exemplo:

• Material unit price: 50 RMB/kg (aço carbono)
• Part weight: 1kg → Material cost: 50 × 1 = 50 RMB
• Machining fee: 200 RMB (includes equipment, trabalho, and depreciation for a simple block part)
• Post-processing cost: 50 RMB (perfuração 2 buracos)

Total Quotation = 50 + 200 + 50 = 300 RMB

Método 3: Fixed Quotation (For Standardized Parts)

For simple, peças repetíveis (Por exemplo, spacers, standard fasteners), suppliers often offer a fixed quote that includes all costs. Por exemplo:

• A standard aluminum spacer (10mm × 5mm) may have a fixed quote of 20–30 RMB/piece for orders of 100+.
• A stainless steel bolt (M10 × 20mm) could have a fixed quote of 15–25 RMB/piece.

3. How to Verify and Optimize a CNC Machining Quotation

Once you receive a quote, you can cross-check its 合理性 (reasonableness) and reduce costs with these steps:

1. Break down the quote: Ask the supplier to itemize costs (material, tempo de usinagem, pós-processamento) to identify overcharges. Por exemplo, if the material cost for a 0.5kg aluminum part is listed as 80 RMB (well above the 25–50 RMB market range), clarify the reason.
2. Otimize o design da peça: Simplify geometry (Por exemplo, replace curved surfaces with straight lines) to cut machining time by 10–30%. Add hollow structures to reduce material weight by 15–25%.
3. Negotiate volume discounts: Even if you need 20 peças agora, ask for a “future batch” discount (Por exemplo, 15% off if you order 50+ dentro de 6 meses).
4. Adjust precision requirements: Use ±0.05mm tolerance instead of ±0.01mm if the part doesn’t need ultra-high precision—this can lower machining time by 20–40%.
5. Choose cost-effective post-processing: Skip unnecessary steps (Por exemplo, polishing internal surfaces that won’t be seen) to save 50–150 RMB/part.

Yigu Technology’s Perspective on CNC Machining Quotations

Na tecnologia Yigu, acreditamos transparency is the foundation of trust in CNC machining quotations. Many clients struggle with “black-box” quotes that lack itemized costs, levando à confusão. We always break down quotes into material, tempo de usinagem, trabalho, and post-processing costs, so clients understand exactly where their money goes. We also proactively suggest optimizations: por exemplo, if a client requests a stainless steel part with ±0.01mm tolerance for a low-load application, we’ll recommend aluminum alloy with ±0.05mm tolerance—cutting the quote by 30–50% without sacrificing performance. Adicionalmente, we offer flexible volume discounts, Mesmo para pequenos lotes, by aggregating orders from multiple clients. Our goal is to help clients get fair, cost-effective quotes that align with their actual needs.

Perguntas frequentes

1. Why is scrap material included in the material cost of a CNC quotation?

Scrap material (10–20% of the raw material weight) is included because CNC machining produces waste (Por exemplo, estacas, leftover raw material after shaping). Suppliers factor this in to cover the full cost of the raw material they purchase, even if not all of it ends up in the final part.

2. Can I negotiate the machining time cost in a CNC quotation?

Yes—if you can show that the machining time is overestimated. Por exemplo, if the quote lists 5 hours for a simple aluminum block (which typically takes 1–2 hours), provide a 3D model or drawing to prove the part’s simplicity. Suppliers may adjust the time to 2–3 hours, lowering the total quote by 40–60%.

3. What’s the difference between a “time-based” and “material-based” quotation?

A time-based quotation focuses on total machining time (combining equipment and labor) and is better for complex parts with variable machining needs. A material-based quotation starts with material cost and adds a fixed machining fee, making it simpler for basic parts (Por exemplo, blocos, spacers) where machining time is predictable. Choose the method that matches your part’s complexity for the most accurate quote.