No. 6555 Songze Avenue, Chonggu Town, Qingpu District, Shanghai, China
Rigid vs. Flexible Resins: Finding the Best Shore Hardness for Your Prototype
Introduction: The Spectrum from Rock‑Solid to Rubber‑Like
Hi, I’m Barry Zeng, a manufacturing engineer at Shanghai Yunyan Prototype & Mould Manufacture Factory. One of the most common questions I get about Flexible Resins 3D Printing is: “How flexible is it? Will it feel like rubber or like stiff plastic?” The answer lies in Shore hardness — a measure of a material’s resistance to indentation. In this guide, I’ll explain the spectrum of SLA resins from rigid (Shore D 80–85) to flexible (Shore A 30–80) to elastic (Shore A 00–30). You’ll learn how to choose the right hardness for your prototype: rigid resins for structural parts, flexible resins for grips and seals, and elastic resins for gaskets and soft‑touch surfaces. I’ll also share a case study where we replaced a silicone mold with a 3D printed flexible resin part, saving weeks of lead time. Whether you’re prototyping a phone case, a medical device handle, or a soft robotic actuator, understanding Shore hardness will help you select the best material for Flexible Resins 3D Printing.
Chapter 1: What Is Shore Hardness?
Shore hardness measures how resistant a material is to indentation. Two scales are common in Flexible Resins 3D Printing:
- Shore D: For rigid to semi‑rigid materials (plastic‑like). Range: 30D (soft plastic) to 85D (hard plastic).
- Shore A: For flexible to rubber‑like materials. Range: 00 (gel‑like) to 100A (very firm rubber). Typical flexible resins: 30A to 80A.
A higher number means harder material. For comparison: a car tire is ~70A, a pencil eraser is ~40A, a hard hat is ~75D. Understanding these numbers helps you specify exactly what you need.
Chapter 2: Rigid Resins (Shore D 70–85) – For Structural Parts
Rigid resins are the “standard” SLA materials. They are stiff, strong, and accurate. Typical Shore D: 75–85. These are not Flexible Resins 3D Printing materials — they are the opposite. Use rigid resins for:
- Enclosures and housings.
- Brackets and structural supports.
- Jigs and fixtures.
- Master patterns for molding.
Rigid resins have elongation typically <5%. They will snap rather than bend. If your prototype needs to hold shape under load, choose rigid.
Chapter 3: Flexible Resins (Shore A 50–80) – Rubber‑Like Feel
Flexible resins are true elastomers — they bend, stretch, and return to shape. Typical Shore A: 50–80. For Flexible Resins 3D Printing, these are the workhorses. Common applications:
- Soft‑touch grips (Shore A 60–80): Handles, tool grips, phone cases.
- Gaskets and seals (Shore A 50–70): Compression seals, O‑ring substitutes.
- Overmolding patterns: Test fit before investing in injection tooling.
- Vibration dampers: Flexible mounts and bushings.
Popular flexible resins: Formlabs Flexible 80A (Shore 80A), Liqcreate Flexible-X (Shore 60A), and Photocentric Flex (Shore 70A).
Chapter 4: Elastic Resins (Shore A 30–50 / Shore 00) – Ultra‑Soft
Elastic resins are even softer — Shore A 30–50 or Shore 00 (gel‑like). These are for applications requiring high flexibility and low compression set. For Flexible Resins 3D Printing, elastic resins push the boundaries of what SLA can do.
- Soft robotic actuators: Inflatable chambers that bend or expand.
- Medical models: Simulating soft tissue or blood vessels.
- Custom earbud tips: Conforming to ear canals.
- Wearable device straps: Comfortable, skin‑safe materials.
Elastic resins have elongation of 150–300% and can be stretched repeatedly without tearing. Examples: Formlabs Elastic 50A (Shore 50A), Liqcreate Rebound (Shore 35A).
Chapter 5: Shore Hardness Comparison Table
Chapter 6: How to Choose the Right Shore Hardness
Selecting the right hardness for Flexible Resins 3D Printing depends on your prototype’s function:
- Does it need to hold its shape under load? → Rigid resin (Shore D).
- Does it need to grip without slipping? → Flexible resin (Shore A 60–80).
- Does it need to seal against pressure? → Flexible resin (Shore A 50–70).
- Does it need to bend repeatedly without taking a set? → Elastic resin (Shore A 30–50).
- Does it need to feel like soft silicone? → Elastic resin (Shore 00).
When in doubt, order a sample kit. We provide Shore hardness sample sets so you can feel the difference before committing to a full print.
Chapter 7: Case Study – Overmolding Prototype with Flexible Resin
A consumer electronics company needed a soft‑touch overmold for a handheld scanner. The traditional process: injection mold the rigid base, then overmold with TPE — 12 weeks and $15,000 tooling. We proposed an alternative: print the rigid base in standard resin, then print the overmold in Flexible Resins 3D Printing (Shore 70A) and assemble. The prototype was ready in 3 days for $300. The client tested the ergonomics, validated the design, and then committed to tooling. This hybrid approach saved 11 weeks of development time.
Chapter 8: Design Guidelines for Flexible Resins
Designing for Flexible Resins 3D Printing is different than rigid resins:
- Add generous fillets: Sharp corners concentrate stress and can tear.
- Design for support removal: Flexible resins are more difficult to sand. Place supports on non‑cosmetic surfaces.
- Avoid thin walls (<0.8 mm): Thin flexible walls are too delicate.
- Consider assembly: Flexible parts can be snapped or stretched over rigid parts. Design with interference fits (0.2–0.5 mm).
- Test compression set: If your part will be compressed for long periods, request compression set data from the resin manufacturer.
Chapter 9: Limitations of Flexible Resins
While Flexible Resins 3D Printing is powerful, it has limits:
- Lower tear strength: Flexible resins are easier to tear than molded silicone or TPE. Not suitable for high‑stress dynamic seals.
- Higher cost: Flexible resins are 2–3× more expensive than standard resin.
- Longer print times: Flexible resins require slower peel speeds and longer exposures.
- Limited temperature range: Most flexible resins soften above 60°C.
For production volumes >1,000 parts, injection molded TPE or silicone may be more economical.
Chapter 10: Summary – Shore Hardness Selection Checklist
- ☐ Rigid (Shore D 75–85): Structural parts, enclosures, brackets.
- ☐ Flexible firm (Shore A 70–80): Grips, seals, overmolding patterns.
- ☐ Flexible medium (Shore A 50–70): Gaskets, vibration dampers, soft handles.
- ☐ Elastic soft (Shore A 30–50): Soft robotics, medical models, wearable straps.
- ☐ Request sample kit to feel hardness before printing.
Conclusion: Match Hardness to Function
Choosing the right Shore hardness for your prototype is about matching material properties to function. Rigid resins for structure, flexible resins for grip and sealing, elastic resins for softness and stretch. We offer a full range of rigid, flexible, and elastic resins for Flexible Resins 3D Printing. Send me your CAD file and application. I’ll recommend the optimal Shore hardness, provide a free DFM report, and quote your project — within 24 hours. Let’s print the feel you need.
👇 Need Help Choosing the Right Shore Hardness?
Send me your CAD file and tell me how your part will be used. I’ll recommend the optimal Shore hardness — rigid, flexible, or elastic — and provide a free DFM report and quote.
📞
Call Barry
Direct engineering line
(I answer Shore hardness questions)
+86 138 1894 4170
🌐
Visit Our Site
Download “Shore Hardness Selection Guide”
(Material comparison, design tips)
Not sure what Shore hardness you need? Just say: “Barry, here’s my part — how flexible should it be?” I’ll guide you.
🧪 Flexible Resins 3D Printing — Find the Perfect Feel 🧪
P.S. Mention “shore guide” when you email, and I’ll send you a Shore hardness sample kit request form and material datasheet bundle.
Barry Zeng
Senior Manufacturing Engineer, Shanghai Yunyan Prototype & Mould Manufacture Factory
(10+ years printing rigid, flexible, and elastic resins — from Shore D 85 to Shore A 30. Let me help you choose the right hardness.)
