Static Seal Vulcanized O-Rings and Profile Extrusions Tolerances

Extrusions: The five most common materials vulcanized are:

Chloroprene "CR";,
Ethylene Propylene "EP";,
Nitrile (Buna-N) "NBR",

Silicone "VMQ", and
Fluorocarbon "FKM"

Extrusion Compound: To be a vulcanizing extrusion grade rubber. Extruder shall not use any "Extrusion Aids" that will impart:

White Bloom

Foreign materials; salt, talc, wax, etc.

RMA Tolerances for Extruded Rubber:

RMA Class 2, Drawing Designation "E2". For OD, ID and Wall Thickness.
Dimension in Inches	Tolerance	Dimension in Inches	Tolerance
0.00 to 0.06	± 0.010	0.39 to 0.63	± 0.031
0.06 to 0.10	± 0.014	0.63 to 0.98	± 0.039
0.10 to 0.16	± 0.016	0.98 to 1.57	± 0.051
0.16 to 0.25	± 0.020	1.57 to 2.48	± 0.063
0.25 to 0.39	± 0.027	2.48 to 3.94	± 0.079

Vulcanizing: Cut to length extrusions are prepared for vulcanizing by applying uncured rubber to both ends. Parts are then put into dies that apply heat and pressure for a specific cure time.

RMA Tolerances for Cut Lengths:

RMA Class 2, Drawing Designation "L2"
Length in Inches	Tolerance	Length in Inches	Tolerance
0 to 1.6	± 0.04	16.0 to 25.0	± 0.16
1.6 to 2.5	± 0.05	25.0 to 40.0	± 0.20
2.5 to 4.0	± 0.06	40.0 to 63.0	± 0.25
4.0 to 6.3	± 0.08	63.0 to 100.0	± 0.40
6.3 to 10.0	± 0.10	100.0 to 160.0	± 0.50
10.0 to 16.0	± 0.13	160.0 and over	± 0.32 %

Uncured Rubber: An adhesive mixture is prepared by adding a solvent of the rubber to make a spreadable adhesive that can be applied to both ends of the rubber extrusion. The adhesive is distributed evenly to the extrusion ends. In order to minimize voids, gaps, and non-fill areas a secondary coat may need to be applied and put into the heated die for a second cure cycle.

NOTE: Only uncured rubber is used for vulcanization; NO substitutes such as fast cure cyanoacryalate adhesives are to be used.

Imperfections: Acceptable criteria per ISO 3601-3, Quality grade "N" general purpose.

O-Ring Cross-Section Diameter:
	.031-.089	.089-.124	.124-.177	.177-.248	.248-.331
Flash/Bonding Residue:	.004	.005	.0055	.006	.007
Mismatch: (Die pressure marks)	.003	.004	.005	.006	.006
Non-Fills:
Deep:	.003	.003	.004	.004	.005
Wide:	.024	.032	.039	.051	.067

Splice Strength Testing: Reference ASTM D2527-83 (2006)

(4.1) Upon visual inspection, the splice joint shall not show any signs of separation.

(5.1) The splice shall meet ultimate elongation of 20%

RMA Designation for Extrusion Finish and Appearance:

RMA Class 3, Commercial, Drawing Designation "F3".

Product shall have loose dust and foreign matter removed but a natural finish is (not washed) acceptable.
The surface of the rubber extrusion will conform to Good Extrusion Processes, No micro - inch finish will be specified, as this is a commercial finish.

A.Q.L. 2.5: Inspection for "Commercial" Items, RMA drawing designation Q-6.

Lot Size	Sample Size	Lot Reject Number
0 - 25	5	1
26 - 50	8	1
51 - 90	13	1
91 - 150	20	1
151 - 280	32	2
281 - 500	50	3
501 - 1200	80	4
1201 - 3200	125	6
3201 - 10,000	200	9
10,000 and up	315	13

Example: For a shipment of 1000 pieces, 80 samples are selected at random and inspected for physical and dimensional characteristics. This lot shall be considered acceptable if the sample lot does not yield more than 4 rejects.