TPU (Thermoplastic Polyurethane) offers an incredible range of flexibility, from rubber-band elastic to nearly rigid. Understanding Shore hardness ratings helps you select the perfect material for your application. This guide covers everything from Shore 85A to 98A.
Understanding Shore A Hardness
The Shore A scale measures the hardness of flexible materials. Lower numbers indicate softer, more flexible materials:
- 85A: Very soft, extremely flexible
- 90A: Soft, moderate flexibility
- 95A: Medium-soft, some rigidity
- 98A: Semi-rigid, limited flexibility
Compared to TPE, TPU offers better layer adhesion and easier printing.
Shore 85A: Maximum Flexibility
Characteristics
- Extremely soft and rubbery
- Excellent elongation (>500%)
- High elasticity and recovery
- Most challenging to print
Best Applications
- Gaskets and seals
- Phone cases with maximum grip
- Vibration dampeners
- Wearable devices
Printing Considerations
- Requires direct drive extruder
- Very slow speeds (10-20mm/s)
- Minimal retraction
- 220-240°C nozzle temperature
Like nylon, TPU benefits from dry storage.
Shore 90A: Balanced Flexibility
Characteristics
- Soft but manageable
- Good elongation (400-500%)
- Excellent recovery
- Moderate print difficulty
Best Applications
- Flexable hinges
- Footwear soles
- Protective bumpers
- Flexible couplings
Printing Considerations
- Direct drive recommended
- Moderate speeds (15-25mm/s)
- Standard retraction settings
- 220-235°C nozzle temperature
Shore 95A: Semi-Flexible
Characteristics
- Noticeable stiffness
- Moderate elongation (300-400%)
- Good dimensional stability
- Easier to print
Best Applications
- Functional prototypes
- Twistable components
- Semi-rigid seals
- Impact-resistant parts
Printing Considerations
- Can work on Bowden setups
- Normal speeds (20-30mm/s)
- Standard settings mostly work
- 225-240°C nozzle temperature
Shore 98A: Nearly Rigid
Characteristics
- Minimal flexibility
- Low elongation (200-300%)
- High dimensional accuracy
- Easy to print
Best Applications
- Semi-rigid enclosures
- Functional brackets
- Snap-fit components
- Impact protection
Printing Considerations
- Works on most printers
- Normal printing speeds
- Standard settings acceptable
- 230-245°C nozzle temperature
Application Selection Guide
| Application | Recommended | Reason |
|---|---|---|
| Gaskets | 85-90A | Maximum sealing |
| Phone cases | 90-95A | Balance of grip and protection |
| Hinges | 90-95A | Flexibility without fatigue |
| Bumpers | 95-98A | Impact absorption |
| Snap fits | 95-98A | Predictable flex |
| Tires | 85-90A | Maximum grip |
Frequently Asked Questions
Can I print 85A TPU on a Bowden extruder?
It’s possible but challenging. Direct drive is strongly recommended.
Does TPU hardness affect strength?
Yes, harder TPU generally has higher tensile strength but lower elongation.
How do I know which hardness I need?
Start with 95A if unsure. It’s the most versatile and easiest to print.
Frequently Asked Questions
Why is my print quality inconsistent?
Multiple factors affect quality: temperature stability, filament quality, and machine calibration. Test systematically.
How can I improve my print success rate?
Start with proper calibration, quality filament, and appropriate settings for each material.
What maintenance does my printer need?
Regular nozzle cleaning, belt tensioning, and lubrication of moving parts.
