If you’re a CAD designer working onCNC加工 部品, small design errors can lead to big problems: broken tools, wasted material, or parts that don’t fit. 良いニュース? Most mistakes are easy to avoid once you know what to look for. このガイドはを分類します 6 most common CNC design blunders, 実際の例があります, データ, and step-by-step fixes to save you time, お金, そしてフラストレーション.
1. 間違い 1: Designing Walls That Are Too Thin
Thin walls might seem like a way to save material—but they’re a disaster for CNC machining. Thin sections vibrate during cutting, break easily, or lose precision.
Why It’s a Problem:
Low-stiffness materials (アルミニウムのように) are especially risky. 例えば, a 0.5 mm aluminum wall will twist or crack when a milling tool applies pressure. Even slightly thicker walls (0.6–0.7 mm) can warp, as the tool’s vibration bends the material.
Key Guidelines for Wall Thickness:
| 材料 | Minimum Recommended Thickness | Unofficial Industry Standard | Risk of Failure (If Too Thin) |
|---|---|---|---|
| アルミニウム (6061) | 0.8 mm | 0.794 mm | 70% (twisting or cracking) |
| 鋼鉄 (1018) | 1.0 mm | 0.794 mm | 50% (反り) |
| プラスチック (腹筋) | 1.2 mm | 0.794 mm | 80% (melting or breaking) |
本当の例:
A designer created a 0.6 mm thick aluminum bracket for a drone. During milling, 9 out 10 brackets broke because the tool’s vibration bent the thin walls. When they increased the thickness to 0.9 mm, the success rate jumped to 98%—and the bracket still weighed less than 5 グラム (no extra material waste).
それを修正する方法:
- Follow the h:t (Height to Thickness) 比率: Keep wall height no more than 5x its thickness (例えば。, a 1 mm thick wall should be ≤5 mm tall).
- If thin walls are required (例えば。, for a lightweight part), switch to sheet metal manufacturing instead of CNC machining—it’s cheaper and avoids vibration issues.
2. 間違い 2: Designing Features That Can’t Be Machined
CAD software lets you draw almost any shape—but CNC machines have physical limits. The most common mistake? Designingcurved holes (holes that bend or twist through the part).
Why It’s a Problem:
CNC tools move in straight lines (along X/Y/Z axes) or fixed rotations (A/B/C axes). They can’t follow a curved path for holes—trying to do so will either break the tool or leave an uneven, unusable hole.
本当の例:
A medical device designer added a curved hole to a stainless steel sensor housing (to route wires). The CNC mill couldn’t cut the curve, so the team had to scrap 20 プロトタイプ. They ended up redesigning the hole as two straight holes connected by a small channel—simple for the CNC to machine.
それを修正する方法:
- Avoid curved holes entirely for CNC parts. Use straight holes, or split the path into multiple straight sections.
- If you must have a curved feature (例えば。, for a custom pipe), 使用 電気放電加工 (EDM) その代わり. EDM uses electrical sparks to cut complex shapes—no straight tool paths required.
3. 間違い 3: Overusing Tolerances
公差 (the allowed variation in part size) are important for mating parts (例えば。, a lid that fits a box). But adding tight tolerances to every surface wastes time and money.
Why It’s a Problem:
- 厳しい許容範囲 (例えば。, ±0.001 mm) require slower cutting speeds, special tools, and extra quality checks—all of which increase cost.
- Most CNC machines can’t even hit extremely tight tolerances. 例えば, a basic 3-axis mill has a maximum accuracy of ±0.01 mm—any tolerance tighter than that is impossible.
Tolerance Guidelines by Machine Type:
| CNCマシンタイプ | 典型的な精度 (許容範囲) | に最適です |
|---|---|---|
| Basic 3-axis Mill | ±0.01 mm | プロトタイプ, non-mating parts |
| Advanced 5-axis Mill | ±0.005 mm | 航空宇宙部品, tight-fitting components |
| CNC旋盤 | ±0.008 mm | 円筒形の部分 (ボルト, シャフト) |
それを修正する方法:
- Only add tight tolerances to mating surfaces (例えば。, the hole where a bolt fits). Leave non-critical surfaces (例えば。, the outer edge of a bracket) with loose or no tolerances.
- Don’t assign numerical dimensions (like radius or diameter) to surfaces that don’t need precision. 例えば, a decorative notch doesn’t need a tolerance—just a general size.
4. 間違い 4: Designing Unnecessary Aesthetic Features
It’s tempting to add complex shapes (例えば。, 3D logos, 湾曲したエッジ) to make parts look nice—but these features often require extra machining time and material removal.
Why It’s a Problem:
- Aesthetic features like deep engravings or custom curves need 5-axis machining (more expensive than 3-axis) or multiple tool changes.
- Removing extra material for looks increases scrap—for example, a 1 kg aluminum block might become a 0.5 kg part with unnecessary cuts, wasting $10–$20 per part.
本当の例:
A consumer electronics brand added a 3D engraved logo to the back of an aluminum phone case. The logo required 2 extra tool changes and 15 minutes of machining time per case. When they switched toエレクトロポリッシング (a post-processing step that smooths the surface) and a simple printed logo, they cut production time by 25% そして保存されました $5 ケースごと.
それを修正する方法:
- 聞く: “Is this feature necessary for function?」 そうでない場合, skip it.
- Use post-processing for aesthetics: エレクトロポリッシング (smooths surfaces), 陽極酸化 (adds color), or laser engraving (速い, cheap logos) are better than machining complex shapes.
5. 間違い 5: Designing Too Deep Cavities
キャビティ (hollowed-out sections) are useful for lightweight parts—but CNC tools have a limited cutting length. Too-deep cavities cause tool failure or poor quality.
Why It’s a Problem:
- Milling tools work best when cavities are 2–3x the tool’s diameter. 例えば, a 15 mm tool can safely cut cavities up to 35 深さmm (2.3x its diameter).
- Deeper cavities lead to:
- Tool deflection: The tool bends under pressure, leaving uneven walls.
- Chip buildup: Debris gets stuck in the cavity, scratching the part.
- Tool breakage: The tool protrudes too far from its holder and snaps.
本当の例:
A designer created a 50 mm deep cavity in a plastic part using a 15 mm tool (3.3x the tool’s diameter). The tool deflected, making the cavity walls 2 mm thicker on one side—rendering the part useless. They fixed it by reducing the cavity depth to 35 mm and adding a small ledge (no loss in functionality).
それを修正する方法:
- Follow the tool diameter rule: Keep cavity depth ≤3x the tool’s diameter.
- より深い空洞の場合:
- Use a longer tool holder (to reach the bottom without bending).
- Cut in small increments (1–2 mm at a time) to reduce tool stress.
- Use high-pressure coolant to flush out chips.
6. 間違い 6: Designing No Radius for Internal Corners
CNC milling tools are cylindrical—they can’t cut sharp internal corners. Designing sharp edges forces the machine to use smaller tools (もっとゆっくり, より高価です) or leaves uneven corners.
Why It’s a Problem:
- A sharp internal corner requires a tool with a tiny diameter (例えば。, 1 mm) to fit into the corner. Small tools cut slowly and break easily.
- Even if you design a sharp corner, the CNC will automatically leave a small radius (equal to the tool’s radius)—so your part won’t match the CAD design.
Internal Corner Radius Guidelines:
| Cavity Depth | Minimum Recommended Corner Radius | Tool Size Needed |
|---|---|---|
| 10 mm | 3 mm (1/3 of depth) | 6 mm tool |
| 20 mm | 7 mm (1/3 of depth) | 14 mm tool |
| 30 mm | 10 mm (1/3 of depth) | 20 mm tool |
それを修正する方法:
- Aを追加します corner radius to all internal corners in your CAD design. Make the radius slightly larger than the tool’s radius (例えば。, a 6 mm tool needs a 3.5 mm corner radius).
- If you need a sharp edge (例えば。, for a part that fits into a rectangular slot), design an アンダーカット (小さなノッチ) その代わり. Undercuts let the tool reach the corner without leaving a radius.
7. Yigu Technology’s Perspective on CNC Design Mistakes
Yiguテクノロジーで, we’ve seen every one of these mistakes delay projects or waste money. The biggest takeaway? Design for manufacturability first. Before finalizing a CAD model, 聞く: Can a CNC machine actually cut this? Is this tolerance necessary? Small tweaks—like adding a corner radius or simplifying a curved hole—save time and avoid rework. We often work with designers early on to review plans, catching issues before they become costly problems. By aligning design with CNC capabilities, you’ll get parts that work right the first time.
8. よくある質問: Common CNC Design Questions
Q1: What’s the thinnest wall I can safely design for CNC aluminum parts?
Stick to a minimum of 0.8 mm for aluminum (6061). Thinner walls (0.6 mm or less) will vibrate and break during machining. If you need something thinner, use sheet metal instead.
Q2: Can I use EDM for all impossible-to-machine features?
EDM works for complex shapes like curved holes or sharp internal corners, but it’s slower and more expensive than CNC. Use EDM only when CNC is impossible—for most parts, simplifying the design (例えば。, straight holes) より良いです.
Q3: Do I need to add tolerances to every surface of my CNC part?
いいえ! Only add tight tolerances to mating surfaces (例えば。, holes for bolts). Non-critical surfaces (例えば。, the top of a bracket) can have loose tolerances or no tolerances at all—this cuts machining time and cost.