1、c- r“ MIL-P-46872A 14 M 7797706 0438876 M I INCH-POUND 16 July 1990 . . SUPERSEDING MIL-P-46872(MI) 14 December 1973 MILITARY SPECIFICATION POTTING AND MOLDING OF CABLE ASSEMBLIES, PROCESS FOR This specification is approved for use by the US Army Missile Command, Department of the Army, and is avail
2、able for use by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification covers the potting and molding process for cable assemblies using elastomeric compounds. 2, APPLICABLE DOCUMENTS 2.1 Government documents. 2.1.1 Specifications, standards, and handbooks.
3、 The following e sPecificatiKstandards. and handbooks forrn a Part of this document to the extent specified herein. *Unless otherwise specified, the issues of these documents are those listed in the issue of the Department of Defense Index of Specifications and Standards (DODISS) and supplement ther
4、eto, cited in the solicitation. SPECIFICATIONS ivl I L I TARY MIL-t4-24041 - Molding and Potting Compound, Chemically Cured, Polyurethane Beneficial coinments (recornrnendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Cornr
5、nander, US Army Missile Command, ATTN: AMSMI-RD-SE-TD-ST, Redstone Arsenal, AL, 35898-5270 by using the self- addressed Standardization ocument Improvement Proposal (UD Form 1426) appearing at the end of this document or by letter. AMSC N/A FSC 14GP DISTRIBUTION STATEMENT A. Approved for public rele
6、ase; distribution is unlimited, a Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-(Unless otherwise indicated, copies of the federal and mi 1 i tary specifications, standards, and handbooks are available from the Naval Publications and Forms Center,
7、(ATTN: NPODS), 5801 Tabor Avenue, Philadelphia, PA 19120-5099.) this document to the extent specified herein. Unless otherwise specified, the issues of the documents which are DoD adopted are those listed in the issue of the DODISS cited in the solicitation. of documents not listed in the DODISS are
8、 the issues of the ciocuments cited in the solicitation. 2.2 Non-Government pblications. The following document forins a part of Unless otherwise specified, the issues AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTIPI) ASTM D 740 - Standard Specification for Methyl Ethyl Ketone (Application for cop
9、ies should be addressed to the American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19O3-1187.) (Non-Government standards and other publications are normally available from the organizations that prepare or distribute the documents. These documents also may be available in
10、or through libraries or other informational services.) 2.3 Order of precedence. In the event of a conflict between the text of this document and the references cited herein, the text of this document shall take precedence. Nothing in this document, however, supersedes applicable laws and regulations
11、 unless a specific exemption has been obtained. 3. REQUIREMENTS 3.1 Materials and equipment. 3.1.1 Materials. The potting and molding compounds and primers used shall conforni to MIL-M-24041, Category 13, type optional. The sealant shall be compatible with the potting and rnolding cornpounds and sha
12、ll be procured from the same manufacturer. 3.1.2 Equipment. - 3.1.2.1 Vacuum system. A vacuum system capable of producing a differential Essure of not less than 29.5 inches of mercury (in/hg siiall be used to remove entrapped air from the potting and molding compounds. 3.1.2.2 Mixing containers. Mix
13、ing containers shall be of a nonporous material. 3.1.2.3 Air pressurization equipment. Air pressurization equipinent shall be capable of delivering moisture-free air at not less than 90 pound-orce per square inch gage (psiy). 2 Provided by IHSNot for ResaleNo reproduction or networking permitted wit
14、hout license from IHS-,-,- - MIL-P-46872A 14 977790b 0438898 L = 3.1.2.4 Brushes. Brushes shall have natural, nonmetallic bristles. 3.1.2.5 Cable molds, Cable molds shall be easy to assemble, impervious to temperature change, strong and solid in construction, and easy to remove after the potting or
15、molding compound has set. operated caulking gun with a disposable liner and nozzle. 3.1.2.6 Injection gun. The injection gun shall be a manual or air- 3.1.2.7 Thermometer. The thermometer shall be of the immersion type with a temperature range of zero to 100“ Celsius (Cl (32 to 212“ Fahrenheit FI).
16、3.1.2.8 Abrasive paper. The abrasive paper shall be number 40 to 60 3.1.2.9 Curing apparatus. The curing apparatus shall be an air- grit. circulating oven, infrared equipment, heater strips, or rods. The apparatus shall be capable of maintaining the curing temperature within * 2C (k 3.6“F), and shal
17、l have incorporated a means of preventing hot spots (see 6,2.3) during the curing process. 3.2 Potting and molding facility. 3.2.1 Dimensions and location. The dimensions of an acceptable potting and molding area shall be governed by the volume of work. They shall be of sufficient size to permit pro
18、per processing of cables without the cables being piled or walked on by personnel. and supplies to prevent the need for an overlap of operations. The putting and molding facility shall be isolated from all other activities that could result in contamination (see 6.2.1) such as dust, metallic particl
19、es, water, oil, and grease. 3.2.2 Ventilation. The potting and molding facility shall be provided with adequate ventilation to accommodate the volume of compounds, solvents, and primers being used per hour. Forced-draft ventilation where vapors are generated is necessary, and fumes shall be drawn aw
20、ay from the operator and vented to the outside. The responsible safety agency shall be consulted to determine the proper ventilation requirements in relation to the quantity of material being used. molding area shall be maintained at 24“ f 2C (75.2“ f 3.6“F). humidity shall be not greater than 55 pe
21、rcent. The environment of the area shall be subject to examination and test at all times by an authorized quality assurance representative. A hygrometer (see 6.2.4) and thermometer of sufficient quality to record an accuracy of * 5 percent relative humidity and 11C (* 1.8“F) shall be installed withi
22、n the potting and molding area, The hygrometer and thermometer records shall be maintained for six months and shall be made. avai 1 able to the procuring activity upon request during this The area shall contain sufficient equipment 3.2.3 Environmental conditions. The temperature of the potting and T
23、he relative per i od. e 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-P-46872A 14 W 777770b 0438879 3 . . e 3.3 Compound storage life. Storage life of the potting and molding compounds shall be in accordance with MIL-M-24041. 3.4 Health and s
24、afety precautions. When carelessly handled, the chemicals utilized for potting and molding may cause severe physiological reactions. personnel, and when the following precautions are carefully observed: The chemicals involved are safe when properly handled by trained a. b. C. Avoid contact of solven
25、ts, primers, and compounds with the skiti. Special care shall De taken to prevent contact with open breaks on the skin. Inhaling and injection of vapors shall be avoided. If the eyes are accidentally contaminated, flush with water and obtain medical attention immediately. Areas of the skin exposed t
26、o solvents, primers and compounds, shall be cleaned with an approved cleaner and then with a non- abrasive soap and clean water. Cleanser jars, bottles, tools, or containers chal 1 be used individually, never coinmorily, by Dersonnel. Personnel shall not smoke or eat until after a thor- ough cleansi
27、ng of exposed skin areas. No smoking or open flames shall be allowed within 25 operation where compounds, primers, and solvents are NO SMOKING signs shall be displayed in conspicuous p CAUTION feet of an being used. aces. Methyl-ethyl-ketone (MEK) shall not be stored in, or used from, an open contai
28、ner. agency shall be used. Only containers approved by the responsible safety The material shall have no adverse effect on the health of personiiel when used for its intended purpose. Questions pertinent to this effect shall be referred by the contracting activity to the appropriate departmental med
29、ical service who will act as an advisor to the contracting agency. 3.5 Examination (prior to potting or molding). The cable assemblies shall bear a tag indicating that examination for workmanship, electrical continuity, and short circuits has been performed. 3.6 Preparation of cable assemblies. Befo
30、re preparation, the type of sheath material used shall be determined. The cable and primer shall be prepared in accordance with the requirements for the applicable material, the cable j,acket termination shall be sealed with an elastomeric sealant (see 3.1.1). The sealant shall be processed in accor
31、dance with the manufacturers instructions. 3.6.1 Wicking. To prevent wicking during the cable molding operation, 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-U 4 MIL-P-LIb872A LLJ 79999Ob OLI38900 b m prepared as a. MIL-P-46872A(NI) 3.6.2 Prepar
32、ation of sheath material. The sheath material shall be I follors: Reinove all grease, oil, wax, and dirt with NEK conforming to ASTM D 740 from the ar2a to be covered by the potting or molding compound b. C. d. e. f. 9. Abrade the sheatil 0.125 f 0.062 inch above the area to be covered by the pottin
33、g or molding compound. Clean the abraded area with a dry, natural, non-metallic bristled brush. For a neoprene sheath, wipe the abraded area with a clean, lint- Free cloth or disposable wiper dampened with MEK, changing the wipiny area of the cloth or wiper as it becomes soiled. Dry the sheath with
34、a clean, lint-free cloth, disposable wiper, or a jet of clean, dry air. For a polyvinyl chloride (PVC) sheath, brush or wipe the sheath 0.125 f 0.062 inch above the area to be covered with pottiny or molding compound with uncontaminated MEK until the surface becomes tacky. For other sheath materials
35、, follow tne manufacturers instructions for cleaning. If a primer is required, prime the abraded sheath area with the correct primer for the approved cofiipound. 0.062 k 0.031 inch above tne area to be covered with potting or molding compound. Al low to dry in accordance wi tn the manufacturers inst
36、ructions. Apply the primer 3.6.3 Preparation of connector. The connector shall be prepared as follows: a. Use a small nonmetallic bristled brush or a lint-free cloth, dampened with MEK to clean the connector and wiring. CAUTION Wiring insulation shall not be exposed to the cleaning solvent to the ex
37、tent that swelling or other forms of degradation occur. b. If a primer is required, apply as recommended by the manufacturer to areas of the connector that will contact the molding compound. 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-P-9b8
38、72A 34 m 999790b 0438903 8 m MIL-P-46872A(MI ) c. Prior to potting or assembling into a mo d, inspect electr cal connectors for binding of the coupling r ng. The coupling ring shall rotate freely for proper connector engagenent. Examine the connector for bent or misaligned pins. Attach a mating conn
39、ector or mating device to all connectors with wire sizes of American Wire Gage (AWG) 10 and larger. 3.7 Mold preparation. Molds shall be prepared as follows: a. Examine and clean the mold cavities and vent ports as necessary. b. If required, apply niold release to all surfaces of the cavity mold and
40、 dry in accordance with the manufacturers instructions. 3.8 Assembly for molding. The mold shall be assembled, as follows, to receive the mol ding compound: a. Examine the cable assembly to determine that preparation procedures for the applicable sheath material are compatible as specified in 3.6. b
41、. Assemble the two half-sections of the mold around tne cable a s s em b 1 y c. d. Examine the assembly for correct alignment and positioning of the cable and connector, and then tighten the clamping screws. Place the mold in a molding position with the cable connector down. 3.9 Preparation of riott
42、ina and moldina compounds. 3.9.1 Liquid, The liquid compound shall be two-part units, consisting of base resin and activator, and shall be prepared as follows: a. Determine that the material has been acceptance tested and meets the requirements specified in MIL-M-24041, and that the shelf life has n
43、ot expired. CAUTION Use premeasured kits as supplied by the manufacturer. use broken or partially used kits. Do not I b. C. Examine the contents of the base resin and activate for solidification. If e that ther part has thickened, solidified, or crystallized, heat part to 90“ * 5C (194“ f 9F). 6 Pro
44、vided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. Use a thermometer (see 3.1.2.7) to determine the actual material temperature. Occasional stirring is essential during heating to assure uniformity and to hasten the niolding process. return to room tempe
45、rature before mixing. Place the base resin and activator in a clean, dry, nonporous container having at least five times the volume of the combined parts. Blend parts thoroughly, avoiding fast stirring and whipping that may entrap excessive air. Allow to d. e. Place the container in a vacuum chamber
46、 and apply a vacuum of not less than 29.5 inches Hg. foaming subsides. The foaming should subside within 20 minutes, If foam is still present after 30 minutes, the compound should not be used. Maintain the pressure until f. Transfer the degassed compound into the injection gun cartridge, using care
47、not to entrap air. Place the plunger in the cartridge next to the potting and molding material. inserting the plunger. g. Exercise care not to entrap air while 3.3.2 Thawing of premixed frozen cartridges. It is essential that the e thawing time and temperature of frozen cartridges be closely control
48、led to obtain sufficient application life. An increase in either thawing time or temperature will reduce application life, and a decrease in either thawing time or temperature will reduce application life, and a decrease in either thawing time or temperature will result in an inconplete thaw. steps
49、shall be followed for thawing premixed frozen cartridges. a. The following Remove the cartridge from storage and thaw for 30 minutes at 49“ i 2C (120.2 i 3.6“F). The thawing methods used shall not cause degradation of the compound, b. -Complete thawing and check the plunger to make sure that no air is entrapped. c. When once thawed, premixed frozen cartridges shall not be refrozen. The cartridges shall not be used after application life has expir
