MOLD ENGINEERING STANDARDS
1.0 GENERAL OVERVIEW
1.1 MOLD ENGINEERING / PLANNING WORKSHEET
A Mold Engineering / Planning Worksheet will be completed by Majors and supplied at the initial stages of planning and estimating (See Attachment ‘A’). It is to be used on all molds, whether constructed or used internally or externally.
1.2 MOLD DESIGN FORMAT
1.2.1 Print Sizes will be: Manual Drawings = ‘E’ size
CAD Drawings = ‘C’ size
Specific format exceptions will be listed on the ‘Mold Engineering / Planning Worksheet.’
1.2.2 Manual designs or CAD designs will be completely detailed and dimensioned. All designs will have all details called out on the main plan stack up views. A bill of material with complete component specifications will be included.
1.3 MOLD DESIGN APPROVAL
1.3.1 Preliminary mold designs must be approved by Majors prior to construction.
The Executive Vice President and Process Engineer will specify personnel authorized to approve mold designs.
1.3.2 Preliminary designs will include the following for approval;
a) Knock out pin locations.
b) Split up of cavity inserted sections.
c) Heater holes or water lines (flow pattern).
d) Knock out rod pattern.
e) Shut height and over all mold size.
f) Mounting holes.
g) Support pillars.
h) Stop blocks.
i) Gate, runner, and manifold locations.
j) Parting lines.
k) Special components, pinch pin stickups, etc.
1.3.3 Preliminary designs requiring revisions must repeat the approval process unless
waived by Majors.
1.3.4 Approval of preliminary design constitutes authorization to proceed with
purchasing mold materials and construction.
1.3.5 All changes to mold design after original design is complete should be updated to the 3d mold data and the 2d mold prints.
1.3.6 Tool prints shall have tie bar location drawn on preliminary and final designs.
1.3.7 Shrinkage allowance will be provided by Majors and noted on preliminary mold drawings.
1.4 MOLD TRYOUT
1.4.1 Mold tryout is to be provided by Majors unless agreed otherwise. Tryout should
simulate the final process as closely as possible.
1.4.2 Majors will keep a detailed process of parameters from each tryout.
1.4.3 Majors will provide processing guidelines to oversees vendors for each tool. ie. Cycle time, machine size.
1.4.4 Oversees vendor will provide detailed setup sheet for each tool after first shot samples to ensure tool will run within our quoted threshold.
1.5 FIRST PIECE ACCEPTANCE
1.5.1 A minimum three-piece initial sampling (per cavity) and 100% inspection will be
conducted. The actual number of samples required can vary, depending on customer requirements.
1.5.2 Majors will submit sample parts and inspection results to the customer for
approval. When corrective action to the mold is required, the ‘First Piece Acceptance’ process must be repeated.
1.5.3 Oversees vendor will provide part inspection report following first shot samples.
1.6 PROCESS CAPABILITY
1.6.1 Normally, a process study will be required after first piece approval. With
multiple cavity molds, each cavity will be studied independently. The study will be based on 30 parts identified in numerical order. The customer will specify frequency of samples. Capability will be based on critical dimensions identified by the customer.
1.7 MOLD CLASSIFICATION (SPI/SPE)
1.7.1 The following has been adopted from the Society of Plastics Engineers mold
classification system and is used here in reference to mold life and warranties. Actual mold construction details will be specified on the Mold Engineering / Planning Worksheet.
Cycles (Life of Mold)
Built for extremely high production.
Highest quality materials are to be used.
Medium to high production good abrasive
materials and/or close tolerance parts.
High quality mold, built to very close
Medium production mold. Most for low
to medium production needs.
Low production mold. Limited production
preferably for non-abrasive materials.
Prototype mold. Construction in an
inexpensive manner for producing a limited
number of prototype parts. Not intended
for actual production.
Majors will provide detailed mold specification worksheet for each tool upon submitting request for quote. Worksheet will dictate basic construction of the tool and any special conditions.
2.0 THERMOSET, THERMOPLASTIC MOLD STDS
2.1 MOLD FRAMES
2.1.1 DME bases and standard components are to be used unless approved by Majors.
2.1.2 All exterior edges are to be broken approximately 1/16 x 45°. Mold plates to be
doweled (No blind dowel.).
2.1.3 Leader pin length to engage of minimum of ½” before force and cavity
engagement, and ¼” before angle pins.
2.1.4 Pry bar slots ¼” deep to be provides in all four corners of mold plates at split line.
2.1.5 Molds are to stamped on both halves (operator side of movable half, and top of
stationary half) with their assigned tool number, weight per half, and total weight using ½” high characters. In the event of exterior insulation, mold numbers should be etched on the insulation as well.
2.1.6 Leader pin bushings must be adequately vented through lower plate to allow air
and debris to escape as pin enter.
2.2 LIFT HOLES
2.2.1 All molds will be equipped with a set of 3/4 - 10 or 5/8 – 11 tapped holes (as plate
thickness allows) to facilitate lifting. These holes will be located on the edges (center) of the A and B plates. A minimum of eight per mold unless interference with the water lines.
2.3 CLAMP PLATES
2.3.1 Clamp plates are to be at least 7/8” thick.
2.4 RETAINER STRAPS
2.4.1 Retainer straps (opposite side) for safe storage and transport will be supplied with
all molds. Straps are to be a minimum of ½” thick x 1 ½” wide x appropriate length for tying the mold halves together. 3/4 - 10 SHCS are the preferred bolt size. 5/8 – 11 SHCS can be used on small molds.
2.4.2 Straps will be positioned to allow being pivoted on one bolt for storage on the
mold during production without obstructing the parting line.
2.4.3 Molds to be mounted in the molding press in a horizontal position will have a
special top lifting strap. This strap shall have a ¾” tapped eyebolt hole located between the mounting holes. The eyebolt is to be positioned to allow the mold to hang in a level position while mounting the mold in the press. The eyebolt is threaded into the plate and welded to prevent turning. A typical top strap would be 1x4x9” CRS with 3/4 –10 SHCS for fastening it to the mold halves.
2.5 SPRUE BUSHINGS
2.5.1 Bushings with runners in top surface will be fastened at the shoulder to prevent
2.5.2 Molds running Polyester Glass materials are to have carburized and hardened.
(.050-.060 deep) sprue bushings.
2.5.3 Sprue radius to be ½” nominal
2.5.4 ½” taper per foot unless otherwise specified
2.5.5 5/32 O diameter unless otherwise specified.
2.6 LOCATING RINGS
2.6.1 Standard DME #6524 locating rings are preferred on most 3.990 diameter
2.7 RUNNERS and GATES
2.7.1 Runner systems will be balanced for effective cavity fill.
2.7.2 Family molds will have shutoffs on runners. Shutoffs must be accessible from the
2.7.3 Full round runners are standard. Alternatives require approval from Majors. All
corners to be radiused.
2.7.4 Runner system is to be vented.
2.7.5 Cold wells must be provided at runner ends whenever making 90 turns.
2.7.6 Gates and runner sizes to be specified or approved by Majors.
2.7.7 Sub gate mold whenever possible.
2.8 SPRUE PULLER PINS
2.8.1 The standard methods of puling sprues is to use a hardened shoulder bushing with
a reverse taper. The pin is to be the same diameter as runner.
2.8.2 Sprue bushings are to have a ½” nozzle seat radius.
2.9 FORCES and CAVITIES
2.9.1 Forces and cavities should be split as necessary to facilitate machining and
polishing. Thin and wear prone inserts should be inserted separately to facilitate replacement.
2.9.2 Steel selection will depend on the class of mold and molding material specified.
This information will be provided to the vendor via the Mold Engineering / Planning Worksheet. Preferred hardness ranges are listed below.
H - 13
48 - 52
Preferred steel for Thermosets
52 - 56
Preferred steel for Thermoplastics
50 - 54
58 - 60
Gate inserts, etc.
P - 20
30 - 36 (Pre-hard)
Prototype & very low volume
2.9.3 Details will be stamped or etched with detail number, type of steel and cavity
number where size permits.
2.9.4 Bypass shut-offs are to be a minimum of 5° angle unless otherwise approved.
2.9.5 Bearing surfaces in ejector or core pins holes to be 3/8” or 1-½ times the pin
diameter, whichever is greater.
2.9.6 Bypass shut-offs within the part geometry should be inserted from both sides if possible
2.9.7 Complex sealing surfaces, parting lines should be CNC machined. NO HAND FITTING.
2.10 CAVITY IDENTIFICATION
2.10.1 Each cavity will have a number assignment to allow capability analysis,
2.11 SPECIAL SIDE CORE PULLS
2.11.1 Side pulls are to be mechanically activated if possible. Standard safety features
should be incorporated. Spring load cores in retract position. Slides to have angle locks in forward position. No ejector pins to be in the core paths. In the event of hydraulic cores, enclosed limit switches are to be used to indicate slide position.
2.11.2 If limit switches are to be used, they are to enclose in housings. 120 volt AC
electricity is to be used. (NEMA type 2 or better)
2.11.3 If ejector pins have to be used in core paths, the mold must have an exterior
positive ejector return (DME Toggle-lok) or a limit switch on the ejector plate to ensure the ejectors has returned.
2.11.4 Bronze plates wear plates to be used under slides. Grease grooves are to be
provided on slide bearing surfaces.
2.11.5 If cylinders are required, hydraulic cylinders should have a minimum pressure
rating of 3000 psi, and air cylinders a minimum rating of 300 psi.
2.11.6 Slide wear surfaces shall be hardened to 46-48RC
2.11.7 Tool shall be designed so that slides can be removed without removing tool from press.
2.11.8 Hydraulic core pull shall not be used with written approval from Majors.
2.11.9 Slides are to run horizontally in the tool as it hangs in the press.
2.12.1 Wires are to be buried in a covered channel with a single disconnect plug (DME
PIC – 12-G or DME PIC – 8 - G) for each mold half unless otherwise approved.
2.13.1 Standard thermocouples to be .188 diameter bayonet style, with J leads (iron / constantan). DME ‘TC’ series or equivalent.
2.13.2 Wire to be buried in a channel, and use DME MTC – 12-G or DME MTC –8-G multi-pin connector
unless otherwise approved.
2.14.1 Thermoplastic hot runner molds will have an insulator sheet mounted to the
stationary side clamp surface with a metal strap surrounding the edge for protection.
2.14.2 All insulating material is to be a non-asbestos variety such as DME’s ‘HTIS’
series. Standard thickness for sheets is ½” thick, parallel within + .002.
2.15 EJECTOR PINS
2.15.1 Ejector pins are to be DME type ‘EX’ unless approved by Majors.
2.15.2 Ejector pin holes are to be sized to the nominal of the selected pin; i.e. a ½”
diameter pin hole would be wire EDM to .5000.
2.15.3 All ejector pins are to be vented to atmosphere.
2.15.4 Special pins, blades, or pins smaller then 3/32” diameter much be approved by
2.15.5 Keyed ejector pins should be formed with mating flats on the ejector pin head and
a “D” shaped counterbore in the ejector retainer plate.
2.15.6 Alignment of ejector pin holes through the mold base is critical. Ejector pin should move freely through all plates and into the counterbore for ejector head without binding.
2.15.7 Ejector pin holes should be relieved to 1/32 over nominal pin diameter. Land from molded surface back should be 1-1/2 x Dia or 3/8”, whichever is greater.
2.15.8 All tools using subgate or banana gate shall be designed with ejector pin in the runner close to the gate. The distance from the edge of the pin to the opening of the subgate should equal the length of the subgate to allow for deflection during ejection.
2.16 RETURN PINS
2.16.1 Return pins are to be DME 5/8 or 3/4 diameter series or equivalent.
2.16.2 Pin holes to be reamed .005 oversize.
2.17 EJECTOR BARS
2.17.1 Ejector bars must have sufficient rigidity to resist deflection during ejection cycle.
Use at least two knock outs to punch the ejector bar, utilizing SPI pattern.
2.17.2 All molds to have guided ejection using DME standard leader pins and ‘GEB’
serious bronze plated bushings.
2.17.3 Do not install knockout extensions/flush plugs in Majors tools. Our knockout
bars are threaded directly into the ejector backup plate.
2.17.4 Knockout patterns for molds:
A) 1. Ejector support plate is to be drilled and tapped for 1/2 – 13.
2. Ejector housing is to be clearanced with 1” hole.
B) 1. 7” positive – 7” between centers; 3-1/2” off center of sprue bushing 16-4
positive – This pattern has 4 holes 16” between centers and 4 between centers, 8” off center of sprue bushing, then 2” off center in both directions.
C) 1. Molds measuring 18” in the length of ejector plate must have positive 7”
2. Molds measuring over 18” in the length of ejector plate must have positive
7” and 16-4 knockouts.
2.17.5 Ejector plate assembly must move freely. A tight ejector system means guided ejection system is out of alignment and will wear prematurely.
2.18 PARTING LINE INTERLOCKS
2.18.1 Female side locks should be embedded in the movable half of the mold. The
preferred type locks are DME straight side PLM/PLF series. Majors will not except custom make interlocks. They must be a purchased DME or equivalent that can be purchased in the United States.
2.19 HOT RUNNERS
2.19.1 All hot runner manifolds are to be full flow (no hang-up areas) and externally
heated with balanced flow to each drop. All manifold zones and drops should have separate thermocouple temperature control capability.
2.19.2 Cold slug wells required directly opposing gate.
2.19.3 Hot runner connections are to multi-pin connectors unless otherwise approved.
Preferably DME PIC-12-G for Power, and DME MTC-12-G for thermocouple. They are to be mounted in boxes to the top of mold and have all wiring buried below mold surface and covered with plates. Wiring diagrams must be furnished by mold builder.
2.19.4 Gate areas should be inserted with water on insert wherever possible.
2.19.5 Hot runner/Hot sprue brand will be specified or approved by Majors.
2.19.6 All Hot Runner molds should be designed to allow for separation of the cavity plate and the manifold plate. Cavity plate should unbolt from front and pull over to the B half with straps giving access to the tips.
2.20.1 Vents will have a relief .030 deep extending .100 - .125 from the edge of the
cavity to the out side of the mold. Vent widths to be 1/8” – 1/2" wide depending on part size and material to be molded. The distance from the end of the relief to the cavity will be the effective vent depth. See vent depth development specification ranges below.
2.20.2 Thermoplastic vent depths
MATERIAL DEPTH MATERIAL DEPTH MATERIAL DEPTH
Acetal .0010-.0013 Polystyrene .0010-.00015 Acrylic .0010-.0015
Acetal-glass fill .0010-.0013 SAN .0010-.0015 PVC Flexible .0010-.0013
Nylon .0005-.0007 ABS .0010-.0015 PVC rigid .0010-.0020
Nylon glass fill .0005-.0008 Polycarbonate .001-.0020 PBT (Valox) .0007-.0010
Polyethylene .0007-.0010 Polycarbonate glass fill .0015-.0020 PET .0020-.0030
Polypropylene .0007-.0010 PPO (Noryl) .0010-.0015 Polyester sulfone .0010-.0015
Polyurethane .0025-.0005 Teflon FEP .0002-.0005 Polyetherimide .0010-.0015
2.20.4 All vents are to be draw stoned to ensure self cleaning.
2.20.5 Provide ejector pins or inserts in deep pockets and rib areas for venting purposes as necessary.
2.20.6 Location of parting line vents should be detailed on preliminary mold layout and reflect any results from mold flow showing air trap if applicable
2.21.1 Water connections including the male water fittings should be installed below the mold base surface where possible.
2.21.2 Maximum cooling is required on core and cavity.
2.21.3 Water ‘In’ and ‘Out’ to be stamped on mold. Use format: In 1 out 1, In 2 out 2, etc.
2.21.4 Baffles preferred over bubblers. Do not use plastic baffles or heat pipes in any case. When using a bubbler to cool a core, fabricate from Ampco material for improved cooler transfer.
2.21.5 DME 200 Series ‘Jiffy’ fittings are to be used as standard components.
2.21.6 Cool stripper plates and/or runner plates in 3 plate molds.
2.21.7 Standard water lines to be 7/16” diameter where possible.
2.22 MOLD MAKERS RESPONSIBLITIES
2.22.1 The mold maker is responsible for:
a) Insuring the mold conforms to specifications supplies by Majors.
b) Utilizing sound tool making practices in the construction of the mold.
c) See prior approval for non-desirable practices. (shims, wells, etc)
d) Meeting promised completion dates.