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P.P.C'S large inventory of urethane compression springs are designed primarily for applications where corrosion, vibration, and magnetism prevent the use of conventional steel springs. Also, urethane springs have proven to be the safest, most efficient and reliable compression springs for punching, stamping and drawing dies.
As compared to conventional springs, the advantages of the urethane springs include the following:
- High load-carrying capability
- High dielectric strength and non-magnetic
- Protection against marring/galling
- Longer life
- Abrasion resistance
- Oil and solvent resistance
- Low noise
- Vibration damping and shock absorbence
- 100% load-bearing surface
- Bondable to mating parts
- Effectiveness between - 30º F and 180º F
An example of urethane material's load-carrying capability is shown in the following table which is presented in pounds that cause 1/8 inch deflection:
| Conventional heavy duty steel die spring |
Up to 500 Lbs. |
| Urethane springs |
Up to 2,600 Lbs. |
| Urethane bar stock |
Up to 90,000 Lbs. |
| Urethane slab stock |
Unlimited |
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Pressure Ratings of Die-Thane Bars |
Height
x
Width (inches) |
Length (inches) |
Pressure (LBS.) per
1/8" Deflection |
| DT-35 (80A) |
DT-25 (90A) |
DT-15 (95A) |
| 1" x 1" | 12 | 4,000 | 6,700 | 9,800 |
| 24 | 8,100 | 13,750 | 19,950 |
| 36 | 12,500 | 21,000 | 30,200 |
| 48 | 16,400 | 27,800 | 40,600 |
| 2 x 2 | 12 | 3,700 | 6,400 | 9,300 |
| 24 | 7,800 | 13,350 | 19,350 |
| 36 | 12,000 | 21,400 | 29,700 |
| 48 | 16,200 | 27,600 | 40,000 |
| 2 x 3 | 12 | 7,700 | 12,700 | 18,500 |
| 24 | 17,200 | 28,000 | 41,500 |
| 36 | 27,200 | 43,900 | 65,800 |
| 48 | 36,500 | 60,000 | 90,000 |
| 3 x 2 | 12 | 2,000 | 3,500 | 5,400 |
| 24 | 4,200 | 7,000 | 11,000 |
| 36 | 6,300 | 10,600 | 16,600 |
| 48 | 8,400 | 14,300 | 22,100 |
| Pressure Ratings for DT-25 (90A) Solid Rods |
| Cylinder Size |
Load for Deflecting by: |
| 1/8" |
1/4 |
3/8" |
| 1/2" Dia.x 1" height | 120 | 220 | - |
| 5/8" Dia.x 1-1/4" ht. | 170 | 295 | 460 |
| 3/4" Dia.x 1-1/2" ht. | 215 | 365 | 520 |
| 7/8" Dia.x 1-3/4" ht. | 250 | 430 | 610 |
| 1" Dia. x 2" height | 295 | 595 | 700 |
| 1-1/8" dia.x 2-1/4" ht. | 360 | 590 | 810 |
| 1-1/4" dia.x 2-1/2" ht. | 390 | 670 | 920 |
| 1-1/2" Dia.x 3" height | 520 | 820 | 1150 |
| 2" Dia.x 3" height | 920 | 1460 | 2000 |
| 3" Dia.x 3" height | 2060 | 3300 | 3650 |
| 4" Dia.x 3" height | 3700 | 5800 | 7100 |
Because of the exceptional load bearing capacity of urethane compression springs in the shape of tubes, cylinders, rectangular pads & sheets, urethane compression springs are used very successfully in various Engineering applications such as seismic bridge bearing blocks.
Urethane compression springs and bearings also outperform rubber in terms of load bearing capacity, abrasion resistance and resistance to ground level ozone.
One of the problems with rubber materials is their susceptibility to liquids and ground level ozone produced by the increasing number of automobiles or by electrical discharges. Over time rubber gradually cracks and deteriorates due to exposure to liquids and ozone.
Polyurethane, however, is far more resistant to liquid and ozone attack. In fact, testing shows that polyurethane can be exposed to at least five times longer to the high levels of ozone specified for rubber in chapter 18 of the AREA manual (ASTM D1149) without deteriorative effects.
P.P.C'S urethane spring material is a polyether-elastomer that reacts similarly to an incompressible fluid. The volume of material moved by compression is displaced laterally in the form of bulging sides. An approximation to the change in diameter of one of our standard cylindrical urethane springs can be made by incresing the diameter by the same amount of compression.
Example: A 2.00-inch long spring is to be deflected 15 percent or .30 inches. The diameter will then also increase approximately by .30 inches. This material's lateral expansion must be considered for many applications, especially when they have to fit inside cavities.
The recomended maximum free (unloaded) length is two-and-one-half time's the spring out side diameter, although springs may be stacked with guide rods and washer-shaped spacers, for taller applications.
Suggested maximum cyclic frequencies and deflection percentages of free length are summarized by the following, for 95A spring.
| |
Maximum Deflection |
Cycles Per Hour |
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| Slow speeds or short runs |
less than 25% |
200 |
| Intermittent |
up to 25% |
700 |
| Continuous |
up to 15% |
12,000 |
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P.P.C stocks urethane spring lengths as indicated on the following pages, plus a 24-inch length. We also cut to any desired length (up to 24 inches) although this material may be easily cut to length using a conventional band saw that has a suggested four-hook carbon blade with a raker set, or may be lathe cut with machine tool bits with a positive rake of from 5 to 10 degrees. For high volumes, we have CNC machines to accurately cut the tubes to any lengths economically.
P.P.C'S Softer Grades Compression Springs
Load-Deflection Curves
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Stock Number |
Inside Dia-d |
Outside
Dia-D |
Duro
Meter |
Free Length
Approx |
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U018-0500-60A
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0.17 |
0.69 |
60A |
0.5 |
U018-0750-60A |
0.17 |
0.69 |
60A |
0.75 |
U018-1000-60A |
0.17 |
0.69 |
60A |
1 |
U018-1250-60A |
0.17 |
0.69 |
60A |
1.25 |
U018-(length)-60A |
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Any to 12-1/2 |
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Stock Number |
Inside Dia-d |
Outside
Dia-D |
Duro
Meter
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Free Length
Approx |
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U018-0500-80A |
0.17 |
0.69 |
80A |
0.5 |
U018-0750-80A
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0.17 |
0.69 |
80A |
0.75 |
U018-1000-80A
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0.17 |
0.69 |
80A |
1 |
U018-1250-80A
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0.17 |
0.69 |
80A |
1.25 |
U018-(length)-80A
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Any to 12-1/2
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Stock Number |
Inside Dia-d |
Outside
Dia-D |
Duro
Meter |
Free Length
Approx |
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U018-0500-90A |
0.17 |
0.69 |
90A |
0.5 |
U018-0750-90A |
0.17 |
0.69 |
90A |
0.75 |
U018-1000-90A |
0.17 |
0.69 |
90A |
1 |
U018-1250-90A |
0.17 |
0.69 |
90A |
1.25 |
U018-(length)-90A |
0.17 |
0.69 |
90A |
Any to 12-1/2
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