7 Essential Rules for Beginner Sheet Metal Design to Avoid Costly Mistakes

Created on 08.26

Are you a beginner in sheet metal design who’s tired of making costly errors? Do your designs often lead to delayed projects, wasted materials, or extra rework when sent to a custom machining factory? You’re not alone. Many new designers struggle with sheet metal design because it requires a mix of practical knowledge and attention to detail—especially when aiming for fast, accurate, and cost-effective custom machining results.​At Marigold Rapid (www.marigold-rapid.com.cn), a one-stop custom machining factory, we’ve seen countless beginner mistakes slow down projects. To help you save time, money, and frustration, we’ve put together 7 simple, easy-to-follow rules. These rules focus on real-world needs: avoiding rework, matching machining capabilities, and ensuring your design works for rapid prototyping and full-production runs.

​

1. Know Your Material Thickness (And Stick to Standard Sizes)​

One of the most common mistakes? Ignoring material thickness limits. Thin materials might bend or break during machining, while overly thick ones can make bending or cutting impossible with standard equipment.​

Fix: Use standard material thicknesses (e.g., 0.5mm, 1mm, 1.5mm for aluminum; 0.8mm, 1.2mm for steel). Our custom machining factory works with popular metals like aluminum, stainless steel, and mild steel—check our material guide to pick the right size. This avoids extra costs from custom material orders and ensures smooth production.​

2. Add Clear Bend Allowances (No Guesswork!)​

Bends are key in sheet metal design, but forgetting bend allowances ruins dimensions. If you design a part to be 100mm long with a bend, the actual length after bending will be shorter—this leads to parts that don’t fit.​

Fix: Use basic bend allowance formulas or tools (many free online!) to calculate how much space a bend takes. For example, a 90-degree bend in 1mm steel usually needs a 1.5mm allowance. At Marigold Rapid, we share our bend allowance charts with clients to keep designs on track.​

3. Keep Holes Away from Edges (Prevent Cracks!)​

Drilling holes too close to sheet metal edges is a recipe for cracks—especially during bending or assembly. New designers often miss this, leading to scrapped parts.​

Fix: Make sure the distance from any hole to the edge is at least 1.5 times the material thickness. For 2mm aluminum, that means holes should be 3mm or more from the edge. This small step stops parts from breaking and reduces rework.​

4. Avoid Sharp Corners (Use Fillets or Radii)​

Sharp corners in sheet metal design cause two big problems: they’re hard to machine (slowing down production) and they’re unsafe (risk of cuts during assembly).​

Fix: Add small fillets (rounded edges) or radii (curves) to all corners. A 1mm radius works for most parts—simple to design, easy for our custom machining team to produce, and safer for everyone.​

5. Simplify Your Design (Less Complexity = Lower Costs)​

Beginners often overcomplicate designs with too many curves, slots, or custom shapes. While unique parts are great, extra complexity means longer machining time and higher costs.​

Fix: Stick to simple shapes (squares, rectangles, basic slots) when possible. If you need a custom feature, ask your machining factory (like Marigold Rapid) first—we can suggest ways to keep it simple without losing function. This helps with fast turnaround and keeps budgets in check.​

6. Check for Machinability (Don’t Design What Can’t Be Made)​

Nothing is more frustrating than finishing a design, only to learn it can’t be machined with standard equipment. This leads to delays while you redo the design.​

Fix: Work with your one-stop machining factory early. At Marigold Rapid, we offer free design reviews for clients—we’ll tell you if a feature (like a super narrow slot or a deep hole) is hard to make, and suggest fixes. This saves you time and ensures your design is production-ready.​

7. Label Everything Clearly (Avoid Misunderstandings)​

Vague labels or missing dimensions lead to wrong parts. If your design doesn’t say “bend here” or “hole diameter: 5mm,” the machining team might guess—and guess wrong.​

Fix: Add clear dimensions, bend directions, and material notes to every part of your design. Use simple labels (e.g., “Bend 90 degrees up” or “Material: 304 Stainless Steel, 1.5mm”). Our team at Marigold Rapid uses these labels to make exact parts, so you get what you need the first time.​

Why These Rules Matter for Your Projects​

Following these 7 rules isn’t just about avoiding mistakes—it’s about getting high-quality, custom sheet metal parts fast and at a fair price. Whether you’re working on a prototype or a full production run, these simple steps align with what every custom machining factory needs to deliver great results.​At Marigold Rapid (www.marigold-rapid.com.cn), we specialize in one-stop custom machining for sheet metal parts. From design reviews to rapid prototyping and production, we help beginners and experts alike turn their ideas into real parts—without the headaches. If you have a design ready, or need help getting started, contact our team today.