Design Guide Global Leaders in PPS Technology
Contents
1. o 254 o 10 0 0 0 T T T T ii 1 0 0 590 600 610 620 630 640 650 Bx dd 25 33 eo o e o e o e WALL THICKNESS in mm STOCK TEMPERATURE F C R 4 230NA R 4 200NA mum R 7 120NA uu R 4 230NA R 4 200NA R 7 120NA Weld Lines Weld lines are formed when the melt front divides and then flows back together Typically the weld line interface is resin rich since glass fiber does not cross the interface This results in lower mechanical strength If possible the weld line should be eliminated or located in an area with lower load requirements Gate location is critical in determining weld line location If weld lines must bear stress the part design should compensate for typical strengths indicated in Figure 3 Weld line strength depends heavily on processing so the part and tool design should allow for rapid injection thorough packing and adequate venting at the weld Figure 3 Weld Line Strength for Ryton PPS Compounds 10 0 R 4 230NA 4 200 R 7 R 7 120NA BR111 A TENSILE STRENGTH Ksi N Part Design Fiberglass Orientation The orientation of the fiberglass reinforcement affects strength Ryton PPS is stronger in the direction of flow as compared to the transverse direction Fiberglass orientation should be utilized to enhance the strength requirements of the part Part design and gate location should minimize stress in the transverse direction In some cases wall thickne2. Conversely hot molded parts already have a high level of crystallinity and so exposure to temperatures above 400 F 204 C result in very little additional shrinkage Tool Steels Because of the abrasive nature of the glass and mineral fillers used in Ryton PPS compounds hard tool steels are required For long run production molds A 2 D 2 or D 7 tool steels hardened to Rockwell C 60 is recommended Of these A 2 is commonly used since itis a little more flexible and forgiving Many times cavity blocks of these harder tool steels can be inserted into a mold base of softer steel to minimize cost and make machining easier Because especially high rates of wear are typically encountered at gates removable replaceable gate blocks of D 2 steel are often used For low volume runs S 7 and H 13 are acceptable softer steels For complex electrical connector molds S7 is a good choice for core pins to minimize breakage because of the increased ductility Coatings and surface treatments are two methods for achieving higher wear resistance in long run production molds built from softer tool steels Coating Methods Recommended mold coating methods are slow deposition Dense Chrome and Electroless Nickel These coatings provide good mold release characteristics and fairly long life It is important to note that steels with a surface finish of 4 microinch 0 0001 mm or better experience extended service life Surface Treatments Successfully used su
3. e POLYPHENYLENE SULFIDE RESINS Design Guide Chevron Phillips Chemical Company LP Ryton PPS Design Guide Introduction 2 Mold Temperature 8 Ultrasonic Welding 16 Compound Selection 3 ShtiliKade s s aeu 8 Ultrasonic SAKING cond sai se esie Sag 17 Heat Staking 17 Tool Steel amp cssc ree 9 PartDesign x Eeer d Rivet Assembly 18 Wall Thickness 3 Surface 9 Adhesives 18 Weld Lines 4 Sprue Design 10 Tapped Threads for Bolts 19 Fiberglass Orientation 5 Runner Design 10 Self Tapping Screws 20 Variable Wall THEMES Lees 5 Venting 11 Ultrasonic 21 Molded In Threads 22 PME 6 Gate Geometries 12 Molded In Inserts 22 Ribs and Bosses 18 Interference Fit 22 Draft and Undercuts 7 GU EE 15 Machining 23 Typical 7 Draft abate ta 15 TEE 23 Introduction For many products designers are often told that their primary objective is to do more with less less material less manpower le
4. NOZZLE LOCATING RING SPRUE BUSHING MOVING HALF Z PULLER EJECTOR PIN Runner Design It is most important that the runner system be designed so that the mold cavities fill uniformly and in a balanced fashion Runners of many types can be used successfully with Ryton PPS compounds Full round and trapezoidal runners are preferred Figure 15 Runners should be designed with cold slug wells Figure 15 Trapezoidal Runner Profiles 45 mm in mm 1 4 6 4 916 4 8 D 5 16 7 9 H 6 4 7 6 11 1 946 7 9 1 2 12 7 36 9 5 EQUIVALENT RUNNER DIAMETER D Multi cavity molds should have balanced runner systems On multi cavity molds with primary and secondary runners the primary runner should carry on beyond the intersection of the secondary runner in order to provide a cold slug well for the runner flow front Runner length however should be kept at a minimum Figure 16 Mold Design Figure 16 Balanced Runner and Cavity COLD SLUG WELL F Runner length should be kept at a minimum with runner diameter optimized for the compound to be used Suggested minimum runner diameters are listed in Table 1 The diameters listed in the table are suggested sizes starting at the gate and moving toward the sprue The diameter should be increased 20 at each 90 runner turn Where two secondary runners converge to form a larger secondary runner or main runner the dia
5. the cross section should be as symmetrical as possible Many Ryton PPS part applications have wall thicknesses as thin as 0 015 to 0 020 in 0 38 0 51 mm For example one battery pack cover measures 1 in by 0 500 in with 0 015 in walls 25 4 x 12 7 x 0 38 mm There are various connectors having 0 018 in 0 45 mm walls and some very small parts have walls as thin as 0 006 in 0 15 mm In very thick sections the surface stops shrinking as it solidifies while the interior bulk continues cooling and shrinking The difference in shrinkage can pull the material apart leaving sink marks and shrink voids which reduce overall strength Maximum allowable wall thickness depends on the Ryton PPS compound selected Most Ryton PPS parts should not have wall thickness greater than 0 375 in 9 52 mm Ryton PPS Design Guide Wall sections must be thick enough to allow adequate material flow into the tool Figures 1 and 2 illustrate the effect of wall thickness and stock temperature on spiral flow of Ryton PPS Since spiral flow is not packed at the end only 75 of this length should be used for design purposes Figure 1 Spiral Flow vs Wall Thickness at 600 E Figure 2 Spiral Flow vs Stock Temperature at 0 090 Maximum Injection Rate and 2 Second Fill Inch Thickness with 2 Second Fill 40 0 1016 50 0 MM E 900 s 40 0 762 z gt 30 0 200 G 508 C 4 200 amp 100
6. 40 346 4 76 2 0 2 1 0 1 9 1 0 164 729 40 0 0980 2 49 4 40 Die 7 94 4 0 5 2 0 2 15 1 7 477 2122 40 0 0980 2 49 6 32 4 6 35 9 1 0 6 0 7 b 2 1 359 1597 32 0 1160 2 95 6 32 Die 7 94 11 12 9 1 0 33 8 7 544 2420 32 0 1160 2 95 8 32 De 7 94 10 1 1 10 1 1 gt 50 55 6 612 2722 27 0 1440 3 66 8 32 12 7 21 24 21 2 4 55 6 1360 6049 27 0 1440 3 66 10 24 He 7 94 18 2 0 15 1 7 45 5 1 492 2188 20 0 1610 4 09 10 24 12 7 24 2 7 24 2 7 gt 50 gt 5 6 1103 4906 20 0 1610 4 09 10 32 De 7 94 28 3 2 28 3 2 gt 50 55 6 745 3314 20 0 1610 4 09 10 32 12 7 50 5 6 50 5 6 gt 50 55 6 1132 5035 20 0 1610 4 09 Table IV Self Tapping Screw Holding Power in Ryton PPS 6596 Glass Mineral Filled Compounds Screw Drill Thread Driving Undriving Stripping Pounds Force Size Size Engagement Torque Torque Torque N to Pull in mm in mm in mm inelbf Nm inelbf Nm inelbf Nm Out Screw 4 40 No 40 46 4 76 2 0 2 1 0 1 9 0 1 221 983 0 112 2 84 0 098 2 49 Die 7 94 4 0 5 3 0 3 14 1 6 448 1993 6 32 No 32 14 6 35 8 0 9 6 0 7 18 2 0 376 1672 0 138 3 51 0 116 2 95 Die 7 94 9 1 0 7 0 8 24 2 7 593 2638 8 32 No 27 De 7 94 10 1 1 8 0 9 gt 50 55 6 554 2464 0 164 4 17 0 144 3 66 15 12 7 16 1 8 15 1 7 gt 50 25 6 1263 5618 10 24 No 20 De 7 94 16 1 8 11 12 gt 50 55 6 502 2233 0 190
7. Chevron Phillips Chemical Company LLC CPC in the past it should not be considered as a substitute for your own specific knowledge and expertise Only you and your customers can know and influence the specific applications circumstances and facts pertaining to its individual situation which might be materially different from the circumstances or situation confronting CPC s employees The information set forth herein has been carefully compiled by Chevron Phillips Chemical Company LLC However there is no warranty of any kind either expressed or implied applicable to its use and the user assumes all risk and liability in connection therewith Information presented herein is given without reference to any patent questions which may be encountered Such questions should be investigated by the user Medical Caution Do not use this Chevron Phillips Chemical Company LLC CPC material in medical applications involving permanent implantation in the human body or contact with internal body fluids or tissues Do not use this CPC material in medical applications involving brief or temporary implantation in the human body or contact with internal body fluids or tissues unless the material has been provided directly from CPC under a contract which expressly acknowledges the contemplat ed use There is no warranty of any kind either expressed or implied concerning the suitability of this material for use in implantation in the human body or in contact with
8. PPS compounds The graph of minimum gate diameter or thickness versus overall part volume that is shown in Figure 19 depicts the relative need for increasing the gate diameter or thickness as overall part volume increases The Minimum Gate Diameter for round gates shown in Figure 19 may also be considered the minimum gate thickness for typical rectangular gates having a width of two times the gate thickness A good guideline for larger parts is for the gate diameter or thickness to be about 60 to 75 of the maximum wall thickness of the part Success has been shown with center sprue tab flash round disk submarine and spoke gates The placement of the gate is essential in determining the potential strength and dimensional stability of the part Small parts can usually be gated in a single location to prevent weld lines If the part cannot be molded without weld line s the weld line s should be placed in the thickest section of the part or in areas where there is minimal stress Figure 19 Minimum Gate Diameter 0 160 4 00 e 0 140 3 50 g 0 120 300 c 9 0 100 250 S S OQ 0 080 2 00 2 amp 0 060 150 5 0 040 1 00 E 0 020 050 E t 0 000 0 00 0 1 1 10 100 1000 Part Volume cc The following list represents the majority of gating choices available Where it is applicable the gate land length should be kept as short as possible or 0 030 in maximum Center Sprue Ga
9. ultrasonic staking and has many of the same advantages plus greater strength Testing has demonstrated that amorphous parts cold molded stake more easily and exhibit more strength than crystalline hot molded parts The rate of heat transfer is controlled by adjusting the interdependent variables of the tip temperature and downward pressure Too much pressure and or too low a temperature will crack the post before melt deformation can occur The optimum process conditions for a typical 1 8 in 3 18 mm diameter post might be for an amorphous part a tip temperature of 590 F 310 C For a crystalline part use a tip temperature of 620 F 327 C The downward force is typically 150 Ibs 68 kg applied for 40 seconds Since the staked area will be amorphous after the melt deformation the assembly should be annealed at 400 F 204 C for 2 hours if the application requires a fully crystalline part The heat staking tip is designed in the same manner as the horn head for an ultrasonic staking unit However since all glass reinforced compounds can be abrasive we recommend the staking tip be made of a hardened steel with a Rockwell C rating of 60 or greater Ryton PPS Design Guide Snap Fit The most convenient method of assembling plastic parts is the snap fit The savings in assembly costs more than offset the increase in tooling costs required by this technique Studies have shown that the high strength and ridgity of Ryton PP
10. 08 0 025 in 0 2 0 6 mm AFTER WELD Assembly Methods Ultrasonic Staking Ultrasonic staking is an assembly method that uses the controlled melting and reforming of a plastic stud or boss to capture or lock another component of the assembly The plastic stud protrudes through a hole in the component then the high frequency vibrations of the ultrasonic horn are imparted to the top of the stud The stud melts and fills the volume of the horn cavity to produce a head locking the component in place The progressive melting of plastic under continuous but generally light pressure forms the head Ultrasonic staking does cause some reduction in tensile strength of the reformed stud The advantages of ultrasonic staking include short cycle time tight assemblies with virtually no tendency for recovery the ability to perform multiple stakes with one horn repeatability and control over the process design simplicity and the elimination of consumables such as screws There are two head forms that will satisfy the requirements of a majority of applications Figure 31 The first generally considered standard produces a head having twice the diameter of the original stud with a height 1 2 the stud diameter The second referred to as a low profile has a head diameter 1 1 2 times the stud diameter with a head height 1 4 the size of the head diameter Figure 31 Ultrasonic Staking Methods Heat Staking Heat staking is very similar to
11. 4 83 0 161 4 09 15 12 7 31 8 5 24 2 7 gt 50 gt 5 6 1297 5769 10 32 No 20 De 7 94 28 3 2 25 2 8 gt 50 25 6 762 3389 0 190 4 83 0 161 4 09 15 12 7 gt 50 25 6 41 4 6 gt 50 25 6 1345 5983 Accurate readings could not be obtained above 50 ine lbf 5 6Nm of torque Failures resulted from brittle fracture of Ryton PPS Table V Torque Retention of Self Tapping Screws in Ryton PPS 40 Glass Filled Compound Unscrewing Torque After 24 h at 160 F 71 C Unscrewing Torque Application Torque After 24 h at Room Temp ineoz Nm ineoz Nm ineoz Nm 13 0 092 12 3 0 087 11 7 0 083 16 0 113 14 3 0 101 12 0 0 085 20 0 141 17 7 0 125 16 7 0 118 Screw Data Height of Head 0 071 in 1 80 mm Head Diameter 0 118 in 3 0 mm Contact Area of Head 0 007 in 2 4 5 mm Screw Length 0 196 in 4 98 mm Screw Diameter 0 073 in 1 85 mm Drilled Hole Size 0 059 in 1 50 mm Ryton PPS Design Guide Ultrasonic Inserts Like other thermoplastics Ryton PPS can be conveniently assembled using ultrasonic inserts Table VI shows how a 0 625 in 15 9 mm Ryton PPS 65 glass mineral filled compound slab was used to develop pull data on three common sizes of inserts Inserts of these types are recommended when repeated disassembly is required and good pull out strength is desirable Figure 34 shows design recommendations for other common inserts The ta
12. S compounds provide good holding strength with a minimum of flex and interference Figure 32 details the guidelines for the design of snap fit members for different Ryton PPS compounds Typically Ryton PPS snap fit applications involve only one time assembly Figure 32 Snap Fit Design Parameters CALCULATE MAXIMUM DEFLECTION BY el 8 WHERE A DEFLECTION AT BREAK EE LENGTH D I i THICKNESS e 0 018 FOR R 4XT R 4 200 0 014 FOR R 4 R 4 230 0 010 FOR R 7 R 7 120 BR111 USE 75 FOR ONE TIME ASSEMBLY USE 50 FOR MULTIPLE ASSEMBLIES Rivet Assembly Ryton PPS can be successfully assembled using semi tubular style rivets The definition of a semi tubular rivet is a rivet whose mean hole depth measured on the wall does not exceed 11296 of its mean body diameter This design will put less stress on the molded parts especially if the distance between the hole and the underside of the head is the same as the combined material thickness In order to ensure that minimum stress is placed on the molded parts during riveting operations it is essential that the rivet setter be adjusted to exert the minimum impact required to clinch the rivet Even more successful are the Tommel rivet setting machines that round over the metal on the bottom of the rivet This places even less stress on the part Refer to Figure 33 Figure 33 Example Rivets SOLID HOLLOW SEMI TUBULAR Adhesives Adhesive bonding is a versatile me
13. d for a variety of common threads ranging from 4 40 to 1 4 20 bolts The three hole sizes chosen were one hole size smaller one hole size larger and the recommended hole size for steel threads as shown in the Machinery s Handbook for each bolt The bolts were then screwed into the hole to three depths four bolt diameters except the 1 4 20 two bolt diameters and three turns Samples were then pulled in an Instron to measure the force required either to pull the bolt from the hole or to break the bolt The data in Table 1 demonstrates that tapped holes in Ryton PPS glass mineral filled compounds have excellent bolt holding power Bolts screwed in to a depth of four bolt diameters equaled or exceeded the tensile strength of brass and mild steel bolts Bolts screwed in three turns and those at two bolt diameters also had excellent strength Table Bolt Holding Strength in Ryton Glass Mineral Filled Compounds Pound Force N Bolt Size Drill Size Bolt Depth to Pull Out Bolts 4 40 Mild Steel No 43 3 Turns 184 818 0 112 in 2 84 mm 0 089 in 2 26 mm 0 224 in 5 69 mm 413 1837 0 448 in 11 38 mm 392 1744 6 32 Brass No 36 3 Turns 244 1085 0 138 in 3 51 mm 0 106 in 2 69 mm 0 276 in 7 01 mm 572 2544 0 522 in 13 26 mm 599 2664 8 32 Brass No 29 3 Turns 236 1050 0 164 in 4 17 mm 0 136 in 3 45 mm 0 328 in 8 33 mm 761 3385 0 625 in 15 88 mm 761 3385 10 24 Mild Steel No 25 3 Turn
14. e Figure 20 Sprue Gate SPRUE POLISH TO A Eh SPHERICAL RADIUS PART MOLD PARTING y LINE Figure 22 Fan Gate A RUNNER A GATE RUNNER o0 SECTION A A Figure 24 Spoke Gate PART WALL SECTION A A EJECTOR PIN Figure 26 Edge Gate 0 020 in 0 51 mm SEE MINIMUM GATE SIZE Figure 21 Pin Gate PLATE x CAVITY _ RETAINER PLATE RUNNER T DRAFT 1 3 LAND LENGTH Figure 23 Diaphragm Gate A A EJECTOR PIN PART WALL DIAPHRAGM SPRUE SECTION Figure 25 Flash Gate GATE A A RUNNER 0e X SECTION A A Figure 27 Tunnel Gate KNOCKOUT PIN 1 1 2D Mold Design Coring Thick part sections should be cored to provide uniform wall thickness This design practice will avoid sink marks and voids reduce stress and cycle time and offer material savings Cores which extend into the cavity will be subject to high pressure therefore these cores should generally have a minimum diameter of D 0 050 in 1 27 mm and should not extend more than 2D unless they pass entirely through the cavity Refer to Figure 28 Figure 28 Coring Problems and Solutions BEFORE CORING REDESIGN CORE EQUALLY FROM BOTH SIDES Draft Ryton PPS compounds flex very little during ejection Therefore the part design should provide sufficient draft to eject the part without flexure Short cores and shallow cavities of 3 16 in 4 76
15. e Material Selection e Flow Analysis e Shrink Evaluation e Molding Optimization e Finite Element Analysis For more complete and detailed information contact your nearest Account Manager or call one of our Service Centers listed on the back page Conclusion These design guidelines are intended to help designers maximize the versatility of PPS engineering thermoplastics in their products Our suggestions are the result of direct experimentation and our Technical Service staff s experiences in helping customers For more complete and detailed information contact your nearest Account Manager or call one of our Service Centers listed on the back page e POLYPHENYLENE SULFIDE RESINS P O Box 4910 Nihonbashi IT Bldg 9F The Woodlands TX 3 9 Nihonbashi Muromachi 3 Chome 77380 4910 Chuo Ku Tokyo 103 0022 1 877 RYTON66 81 3 5200 0511 ryton cpchem com rytonjp cpchem com Haendorpweg 21 Tuas Avenue 3 1 Haven 1227 Singapore 639417 B 9130 Kallo Belgium 65 6861 6991 32 3 70 2611 rytonsa cpchem com rytonea cpchem com Another quality product from 3 Lockhart Road 2001 or Wanchai Hong Kong Gan 85 2 2 9789800 Chevron rytonhk cpchem com Phillips Chemical Company B LP The Woodlands Texas 500 CMS Rev 6 04
16. hat increasing depth of insertion or increasing the area of surface contact can be more effective at improving pull out force than increasing interference Ryton PPS Design Guide Machining Because of its exceptional mechanical properties Ryton PPS can be readily machined with conventional metal working tools A high degree of precision can be obtained with Ryton PPS while using moderate cutting speeds and fast feed rates It is recommended that carbide tipped tools be used for machining all Ryton PPS compounds In general the best surface speed will be in the range of 300 to 700 SFM 1 5 to 3 5 m s for turning operations 100 to 200 SFM 0 5 to 1 0 m s for milling operations and 200 to 300 SFM 1 0 to 1 5 m s for drilling and reaming The rate of travel should be relatively fast A slow feed results in excess abrasion by the tool and will tend to give poor surface appearance If a coolant is desired ethylene glycol antifreeze works well Although fairly deep cuts of up to 1 8 in 3 17 mm can be made finish cuts should take off no more than 0 005 in 0 127 mm of material Computer Aided Engineering CAE Our Computer Aided Engineering services include a full complement of analysis programs prepared to assist at any stage of the development cycle From design to testing you can be assured that your product is being evaluated with state of the art programming by people who know the material e Computer Aided Design
17. hods in Ryton PPS 6596 Glass Mineral Filled Compounds Pound Force Fastening Fastener Thread Size Drill Size Engagement N to Pull Method Type in mm in mm in mm from Sample Ultrasonic Dodge 6 32 Insert Ultrasert 11 0 138 0 188 0 250 383 3 51 4 78 6 35 1704 Ultrasonic Dodge 10 32 Insert Ultrasert 11 0 161 0 249 0 375 785 4 09 6 32 9 53 3492 Molded 1 4 20 Threads 0 250 0 500 1633 6 35 12 7 7264 Molded Yardley Brass 1 4 20 Inserts Standardized 0 250 0 500 3087 6 35 12 7 13731 Molded In Inserts Because of the excellent processability of Ryton PPS molded in inserts can be designed into many parts Molded in inserts may be used when repeated assembly and disassembly of parts is required Since Ryton PPS easily molds around inserts excellent pull out strengths should be expected Inserts are recommended when an appreciable amount of preload is desired The insert should be designed such that the load is carried through the metal insert and not the plastic Flanged type inserts work well for highly loaded applications Interference Fit The strength and modulus of Ryton PPS compounds makes them suitable for retention of interference fit components however molded in inserts are generally perferred especially for larger components such as hubs or bearings To prevent cracking the degree of interference should typically not induce more than about 0 5 hoop strain Tests have shown t
18. internal body fluids or tissues Part Design 3 Compound Selection There are two basic series of Ryton PPS compounds from which to select The Fiberglass Reinforced Series This series includes Ryton PPS R 4 R 4 200 R 4 220 and R 4 230 The most common determining factors for selection between these compounds are flow length mechanical strength and hot water resistance Typical glass filled PPS applications include electronic connectors under hood automotive components high heat appliance parts and a wide variety of industrial products The Fiberglass and Mineral Reinforced Series This series includes Ryton PPS R 7 R 7 120 R10 110 and BR111 In addition to the 500 F 260 C Heat Deflection Temperature HDT at 264 psi and excellent mechanical strength these compounds provide enhanced electrical properties This feature allows glass and mineral filled Ryton PPS compounds to be used in a wide range of applications including electronic devices switches and high density interconnection devices Please refer to the Engineering Properties Guides for all the specific mechanical physical electrical chemical thermal etc data for each of the Ryton PPS compounds Part Design Part design is a critical aspect of any successful product Balancing functional requirements of the part with a material s capabilities is the first step The designer must take into consideration the strength of the part utilizing proper wall thic
19. ints including relative dimensions are shown in Figures 29 and 30 When welding shear joints use high power with a high amplitude booster low pressure and slow horn speed When welding the parts caution should be used since too high an amplitude and or too long an application time could destroy the part Refer to Figure 29 Shear joints are usually not recommended for parts with a maximum dimension of 3 5 inch or greater sharp 90 turns or irregular shapes due to the difficulty of holding the required molding tolerances Ryton PPS may extend these limits however since it can hold tight molding tolerances Figure 29 Shear Joint for Ultrasonic Welding PERFORE WELD Some of the more common joint design mistakes to avoid are 1 Joints which are too tight or too close together which prevent adequate vibration 2 The section transmitting the ultrasonics being too thin as it may crack under the Sen high amplitude level MINIMUM Too large a step requiring a high instant power which may destroy the part A 4 assembly in which the highest part does not vibrate zi 5 An energy director design which will prevent a homogenous weld 0 4 0 8 mm Figure 30 Step Joint for Ultrasonic Welding INTERFERANCE BEFORE WELD 0 012 0 015 in SEH I 0 3 0 4 lt CLEARANCE Ww 0 002 0 005 in a 0 05 0 13 mm H w3 AFTER WELD 0 002 0 005 0 05 0 13 mm 0 0
20. kness and fiber orientation and also consider the ability to fill the required mold A well designed part will incorporate uniform wall thickness adequate corner radii ample draft sufficient venting and a gate location that minimizes the effects of weld lines Incorporating proper design elements will result in a part that can be economically manufactured and reproducible to very tight molding tolerances Wall Thickness Material cost and cycle time are directly related to wall thickness Optimum part design balances minimum wall thickness versus sufficient strength The minimum wall section must be thick enough for the material to fill the mold under typical processing conditions With Ryton PPS as with all resins it is important to strive for uniform wall thickness When this is impractical parts should be designed to fill from thick to thin areas Uniform wall thickness is also desirable to minimize internal stresses Where wall thickness must vary it should differ by no more than 40 of the thickest wall Likewise intersections should have a radius of 60 of the thinner wall Wall thickness variations can affect the direction of material flow and therefore shrinkage Due to the fiberglass and molecular orientation transverse shrinkage is roughly double the flow direction shrinkage For this reason it is important that the wall thickness be symmetrical through the cross section of the part If thick sections are required to fill the part
21. low the same rules avoid thick sections and provide sufficient radius at the base Figure 9 shows the recommended boss design for Ryton PPS parts Figure 8 Recommended Rib Design Figure 9 Recommended Boss Design 2 5 TOS3D H bs D t 0 6T 0 6 T Drafts and Undercuts Ryton PPS compounds replicate mold surfaces very well and flex little during ejection Therefore the part design should avoid undercuts and provide sufficient draft to eject the part without flexure Short cores and shallow cavities of 3 16 in 4 76 mm or less should have at least 1 4 draft per side As cavity depth and core length increases to one or two inches the draft angle should increase up to 2 per side Polishing the core and cavity will improve release so a surface finish of 4 microinch 0 0001 mm or better should be specified Polish marks should parallel the direction of part ejection In special cases an undercut can be useful to retain parts on the core or cavity during mold opening The interference should range from 0 0005 to 0 001 in 0 0127 0 0254 mm Since Ryton PPS compounds are very stiff any undercut areas in a mold will experience high wear rates Typical Tolerances Typically Ryton PPS exhibits very low shrinkage Dimensional tolerances are very reproducible therefore Ryton PPS compounds can be molded to tolerances as tight as 0 0001 in in in optimally gated small part
22. meter should be increased 4096 In addition for eight cavity or higher molds the use of a melt flipper should be considered For specific details about the melt flipper technology please call our Technical Service Engineers or contact the manufacturer Beaumont Runner Technologies Inc www meltflipper com Table I Minimum Runner Diameter In mm R 4 R 4 XT BR111 R 4 230 R 4 200 R 7 120 L 5 127 0 125 3 175 0 188 4 775 0 188 4 775 L 10 254 0 188 4 775 0 250 6 350 0 250 6 350 L 15 381 0 250 6 350 0 313 7 950 0 313 7 950 Generally it is good practice with engineering thermoplastics to not use family mold layouts because of differences in filling patterns These differences are sometimes difficult to control and may produce parts with differing physical and mechanical properties However if a family mold must be used a rotating runner shut off should be incorporated into the runner design in order to allow individual cavity molding Venting To successfully mold Ryton PPS compounds proper venting is essential Poor or improper venting results in hard to fill parts and burning of the part in areas where gas is trapped In addition trapped gas leads to accelerated mold wear Venting can be accomplished with 0 0003 to 0 0005 in 0 0076 0 0127 mm deep by 0 250 in 6 35 mm wide channels cut on the parting line Figure 17 Flattened ejector pins can also be used as vents Stationary vent pins are not reco
23. mm or less should have at least 1 4 draft per side As cavity depth and core length increases to one or two inches draft angle should increase up to 2 per side Polishing the core and cavity will improve release so specify a surface finish of 4 microinch 0 0001 mm or better Polish marks should parallel the direction of part ejection This is typically referred to as draw polishing Assembly Methods Most products incorporate several functions that require different levels of performance or dimensiona precision In many cases Ryton PPS compounds can meet all these requirements allowing the designer to combine these functions into a single molding When part geometry or functional needs necessitate more than one molding or material the components should be designed to minimize the cost and complexity of assembly procedures Ryton PPS parts may be assembled using a variety of techniques each requiring certain design consi details are presented in other Ryton PPS literature derations Procedural Ryton PPS Design Guide Ultrasonic Welding Ryton PPS compounds are relatively easy to weld together Joint design is however critical to the finished part strength A shear joint is the best overall although the step joint has been used successfully with Ryton PPS R 4 The shear joint will generally be six times stronger than the step joint There are many types of joint designs Typical joint designs for the shear and step jo
24. mmended as various substances can clog them over long part runs Vacuum venting has been used successfully in areas where a blind pocket exists The vacuum is turned on after the mold closes and prior to the start of the injection cycle Vented runners are recommended Ryton PPS Design Guide Figure 17 Parting Line Vent Detail 0 06 0 09 in LAND 0 8 1 6 mm ra PARTING LINE SECTION Gate Geometries The illustration in Figure 18 points out some of the pitfalls of less than optimum gating methods and offers design solutions Part distortion is caused by differential shrinkage As the molded part shrinks internal stresses are developed which distort the part The greater the difference in part cross sections the greater the chance of distortion To avoid distortion the designer should strive to maintain uniformity throughout the part and minimize weld lines Since Ryton PPS compounds are filled compounds they behave anisotropically For typical Ryton PPS compounds this means parts will shrink about half as much in the flow direction as perpendicular to the direction of flow Figure 18 Gate Geometries WELD LINES QO a b EDGE GATES SPOKE GATE DIAPHRAGM GATE For larger parts direct gating into the top surface using multiple gates has shown to be effective in reducing warpage Mold Design Gates A variety of different gating methods is suitable for molding Ryton
25. pered hole is specified for the following reasons 1 Positioning of the insert is faster more accurate and ensures proper alignment every time 2 Places the insert in a partially installed position in the hole permitting more rapid installation because the volume of plastic which must be displaced is decreased 3 Provides the best release of the plastic part from the mold Table VI Specifications for Ultrasonic Inserts Figure 34 Design Recommendations for Ultrasonic Inserts Insert Size Length Max E Max No 0 amp No 2 0 115 0 121 0 126 0 188 0 110 0 126 No4 0435 0456 0162 1 0219 0144 0 162 el i No 6 0 150 0 202 0209 INSERT LENGTH 0250 0 188 0209 No 8 0 185 0 229 0 237 0 312 0 211 0 237 No 10 0 225 0 270 0 280 0 375 0 249 0 280 1 4 in 0 300 0 352 0 366 0 500 0 324 0 366 5 16 in 0 335 0 434 0 451 0 562 0 404 0 451 3 8 in 0 375 0 526 0 543 0 625 0 491 0 543 All dimensions in inches Ryton PPS Design Guide Molded In Threads Because of the excellent processability of Ryton PPS molded in threads can be designed into most parts This will eliminate the need for expensive secondary machining operations Molding in the threads should also provide superior performance as compared to machined threads due to the normal skin effect on injection molded parts Table VII has the pull out values for molded in threads Table VII Holding Power of Various Fastening Met
26. refore sharp corners should be avoided in part designs The optimum fillet radius for Ryton PPS compounds is 0 6T where T represents the wall thickness Figure 6 Figure 6 Design for Radii 3 0 6T 0 6T POOR BETTER BEST Abrupt changes in part geometry like sharp inside corners cause amplification of stress in the area of the abrupt change Quick geometry variations can promote additional problems as well such as flow impedance molded in stress and voids Figure 7 shows the relationship of stress concentration at a sharp corner as a function of the radius to wall thickness ratio Figure 7 Typical Stress Concentration Factor 3 5 FORCE M R 0 6T WALL gt THICKNESS 3 0 2 5 2 0 STRESS CONCENTRATION FACTOR R 0 6T di RECOMMENDED DESIGN STANDARD 0 0 25 0 5 0 75 1 0 1 25 1 5 RADIUS WALL THICKNESS RATIO R T Part Design 7 Ribs and Bosses Proper rib design can increase part strength significantly Ribs are most effective in a thin area which must bear a load perpendicular to its plane Figure 8 illustrates the optimum relationship between wall thickness rib thickness and radius In addition to allowing reduced wall thickness and cooling time ribbing can improve flow paths to make the part easier to fill However ribs that are too thick can cause sink marks warpage and cracking The part design must incorporate a sufficient radius at the base of the rib Boss design should fol
27. rers 100 140 180 220 260 300 340 380 37 60 82 104 127 149 171 193 MOLD TEMPERATURE F C Shrinkage Shrinkage is affected by part weight and thickness compound type fiber orientation mold temperature amount of coring in the mold and any post molding annealing Figure 11 shows the expected shrinkage for a highly cored part Figure 11 Flow and Transverse Shrinkage for Highly Cored Parts FLOW DIRECTION SHRINKAGE TRANSVERSE SHRINKAGE 0 006 0 007 E 9005 0006 0004 O 0 005 0 003 0 004 0 002 2 40 GLASS FILLED z f 0 003 0 001 o 65 GLASS MINERAL FILLED 0 000 0 002 0 05 0 07 0 09 0 11 0 13 0 05 0 07 0 09 0 11 0 13 1 27 1 78 2 29 2 79 3 30 1 27 1 78 2 29 2 79 3 30 WALL THICKNESS in mm Mold Design 9 For any given part mold shrinkage is less with increasing part weight i e fully packing out the part decreases shrinkage Thicker wall sections generally exhibit higher shrinkage than thinner ones since they hold heat longer Mold shrinkage increases somewhat with increasing mold temperature due to increased crystallization Parts restrained during molding by coring will exhibit lower shrinkage than unrestrained parts Annealing also affects shrinkage in Ryton PPS parts Cold molded parts will develop substantial crystallinity and shrink considerably if held above 400 F 204 C for extended periods
28. rface treatments are e Borofuse e SR 19 eNitride eDiamond Black Please consult trade publications such as the Thomas Register for Metal Treating Companies Figures 12 and 13 show tool wear of different steels and surface treatments Figure 12 Wear Resistance of Tool Steels Figure 13 Wear Resistance of Surface Treatments 0 20 0 18 9 8 0 16 d 0 14 0 12 5 0 10 4 0 08 3 0 06 2 0 04 0 20 2 D 2 0 00 m FERRO TIC BOROFUSE NITRIDE LSR 1 B corr B us Prototype tooling is often an excellent way to produce a short production run of parts and discover the unique facets of producing particular parts Prototype tools can be made from a variety of softer steels and aluminum The ease of machining the softer metals makes them economical to use during prototyping Care must be taken however with aluminum tools since they are more difficult to heat uniformly and cannot withstand high injection and clamping pressure as well as steel tools WEIGHT LOSS WEIGHT LOSS Ryton PPS Design Guide Sprue Design Standard sprue designs are quite acceptable with nominal values of 2 of draft and reverse taper or Z cut sprue puller systems Keep the runner as short and highly polished as possible to ease part removal from the stationary half of the mold Figure 14 is a standard sprue design Figure 14 Standard Sprue Design MACHINE
29. s More typical tolerances are 0 0010 in in with some large parts requiring tolerances as high as 0 002 in in Ryton PPS Design Guide Mold Design Mold design is as critical as part design The best mold designs optimize the performance properties of Ryton PPS For example to produce crystalline parts the mold must be designed to operate at 275 F 135 C or hotter It must compensate for material shrinkage within the required level of dimensional precision A well planned mold will control the effects of gate location and melt flow paths on shrinkage wargape and part strength The tool steel used is also a consideration since it will determine the length of time the mold will be in service Mold Temperature Mold temperature significantly affects crystallinity and thus the dimensional stability of the part when it is exposed to temperatures above the glass transition Tg temperature Figure 10 Figure 10 Effect of Mold Temperature on Cyrstallinity NOTE It is very important to keep the mold temperature either above 275 F 135 C or below 180 F 82 C To operate between these temperatures will produce varying resultant dimensions Parts that are used at high temperatures should be molded using a mold temperature at or above 275 F 135 C CRYSTALLINITY INDEX A o Please refer to the Processing Guide for specific information regarding mold heating cooling equipment and their manufactu
30. s 366 1628 0 190 in 4 83 mm 0 149 in 3 78 mm 0 380 in 9 65 mm 1133 5040 0 625 in 15 88 mm 1408 6263 10 32 Brass No 21 3 Turns 274 1219 0 190 in 4 83 mm 0 159 in 4 04 mm 0 318 in 8 08 mm 920 4092 0 625 in 15 88 mm 1370 6094 1 4 20 Mild Steel No 7 3 Turns 560 2491 0 250 in 6 35 mm 0 210 in 5 33 mm 0 550 in 13 97 mm 2460 10942 0 625 in 15 88 mm 2617 11640 Bolts Broke Stripped Threads Ryton PPS Design Guide Self Tapping Screws The excellent creep resistance of Ryton PPS makes it well suited for assembly with self tapping screws Due to the hardness of Ryton PPS compounds thread cutting types rather than thread forming types perform best The hole size recommended by the Machinery s Handbook for phenolformaldehyde thermosets should be used To demonstrate the holding power and torque retention of self tapping screws Tables Ill IV and V were assembled for Ryton PPS 40 glass filled and 65 glass mineral filled compounds This data indicates that Ryton PPS is an excellent choice for screw assembly techniques Table Self Tapping Thread Cutting Screw Holding Power in Ryton PPS 40 Glass Filled Compound Screw Type Thread Driving Undriving Stripping Avg Holding Suggested and Size Engagement Torque Torque Torque Load Tensile Drill Size Mild Steel mm inelbf Nm inelbf Nm inelbf Nm PoundseForce N mm Type F 4
31. ss money To meet that objective designers work to minimize the number of parts and incorporate features to streamline assembly etc As each design improvement is made however the demands on the performance characteristics of the material the part is made from also increases The most fundamental performance characteristics a designer must consider during the material selection phase include certain mechanical physical thermal and electrical properties As these facts are considered the materials that many designers specify to meet this combination of performance properties are polyphenylene sulfide resins manufactured by Chevron Phillips Chemical Company LP Chevron Phillips Chemical and its affiliates and sold under the registered trademark Ryton herein Ryton PPS The combination of unparalleled thermal mechanical physical and electrical properties of Ryton PPS together with its exceptional chemical and flame resistance means it performs over a broad range of demanding design requirements The design guidelines presented here are intended to provide application requirements and help designers maximize the versatility of Ryton PPS engineering thermoplastics in their products They are the result of direct experimentation performed at the Plastics Technical Center and our technical service staff s experiences in helping customers While some of the opinions information or any other technical advice contained herein may have worked for
32. ss must be increased to compensate for lower transverse strength Refer to Figure 4 for transverse versus flow direction strength information Figure 4 Tensile Strength vs Fiberglass Orientation E FLOW DIRECTION STRENGTH E TRANSVERSE DIRECTION STRENGTH 40 Glass Filled Glass Mineral Filled RELATIVE TENSILE STRENGTH Variable Wall Thickness Some areas of a part may require more strength than others However wall thickness should be as uniform as possible throughout the part Radical variations in wall thickness tend to concentrate stresses both molded in and externally applied The shrinkage differential between thick and thin sections causes molded in stress at the juncture A uniform wall section creates an even flow that has uniform shrinkage and minimal molded in stress If wall thickness changes are unavoidable they should be gradual in order to minimize stress concentration Figure 5 is an example of the preferred method for achieving a variable wall thickness Coring the part in thick sections is a good way to ensure uniform wall thickness Coring will also provide a means for cost savings in material usage For further information on coring refer to the Mold Design section Figure 5 Wall Thickness Transitions FLOW POOR FLOW BETTER FLOW BEST 3T Ryton PPS Design Guide Radii Ryton PPS compounds as is the case with other engineering thermoplastics are notch sensitive The
33. te Efficient works well on parts where concentricity is important or parts with dome shapes Figure 20 Pin Gate Used much like a sprue gate this gate can be used with multi cavity tooling and provides automatic separations of part from runner Figure 21 Fan Gate Good for uniform polymer flow front into a part similar to a flash gate Figure 22 Diaphragm Disk Gate Ideal for producing highly concentric cylindrical parts without weld lines Figure 23 Spoke Gate Can be used in parts which are too large for a diaphragm gate Odd number of spokes should be used so that gates are not opposite one another In addition gates should be positioned such that weld lines form in the areas of thickest cross section Figure 24 Flash Gate Good for parts with large flat surfaces requiring minimum warpage Figure 25 Edge Gate Most commonly used allows high degree of fiber orientation generally seen on multi cavity molds requiring moderate precision in tolerances Figure 26 Tunnel Submarine Gate Submarine gates have been used successfully with Ryton PPS compounds however special consideration must be given to the design The tunnel included angle should be 30 35 and the center line of the tunnel should be 25 30 from a line drawn perpendicular to the mold parting line Figure 27 presents a recommended submarine gate design The tunnel must be well polished with no undercuts Ryton PPS Design Guid
34. thod of joining like or dissimilar materials Holes rivets clamps and screws have a tendency to cause stress points in concentrated areas Adhesives tend to distribute the load over the entire area thus virtually eliminating localized stress areas There are many adhesives that will bond Ryton PPS compounds provided the surface is properly prepared to allow the adhesive to wet the surface The adhesive is selected to best meet the need for the application in which the product will ultimately be used Ryton PPS Design Guide In each adhesive application the following criteria must be considered Characteristics of the materials to be joined Surface preparation Joint design Adhesive selection and handling Application Cure of the adhesive adhered couple Ultimate strength and environmental performance of the adhesively joined fabricated part or structure zoo Or opor rs Surface preparation and adhesive selection is discussed in our Technical Service Manual TSM 283 Tapped Threads for Bolts It is often desirable to assemble plastic components to each other or to different materials using bolts In most applications where repeated assembly and disassembly is not required Ryton PPS moldings with tapped threads work very well To characterize the bolt holding strength of Ryton PPS compounds holes were drilled in injection molded 0 625 in 15 9 mm thick Ryton PPS R 4 and R 10 7006A slabs Three hole sizes were tappe
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