Tooling for Die Casting

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NADCA Product Specication Standards for Die Castings / 2015

s e c t i o n

Section Contents NADCA No. Format Page

Frequently Asked Questions (FAQ) 2-2

1 Introduction 2-3

2 Types of Die Casting Dies 2-4

2.1 Prototyping 2-4

2.2 Rapid Tooling Dies 2-4

2.3 Production Dies 2-5

2.4 Unit Dies 2-6

2.5 Trim Dies 2-6

3 Casting Features and Die Considerations 2-7

3.1 Core Slide Requirements 2-8

3.2 Parting Line: Cover & Ejector Die Halves 2-8

3.3 Ejector Pins 2-9

3.4 Cast-in Inserts 2-9

4 Die Materials 2-10

4.1 Die and Cavity Materials 2-10

4.2 Die Cavity Insert Materials 2-10

4.3 Die Steel Heat Treatment 2-11

5 Controlling Die Performance 2 -11

5.1 Porosity Control: Gating, Venting, Vacuum 2-11

5.2 Thermal Balancing 2-12

5.3 Oil Heating Lines 2-12

5.4 Alternate Surface Textures 2-12

5.5 Extended Die Life 2-12

6 Secondary Machining Preplanning 2-14

7 Gaging Considerations 2-14

8 Inherited Tooling 2-15

9 Engineering Consultation 2-15

10 Database Guidelines 2-16

11 New Die/Inherited Die Speciﬁcations 2-16

12 Die Life 2-16

13 Checklist for Die Casting Die Speciﬁcations T-2-1-12 Checklist 2-17

14 Guidelines to Increase Die Life T-2-2-12 Guideline 2-19

CLICK HERE TO RETURN TO A&B DIE CASTING HOME PAGE

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NADCA Product Specication Standards for Die Castings / 2015

Tooling for Die Casting

RUNNER

& GATE

MOVING/EJECTOR

MOLDBASE

RETAINER AND

EJECTOR PLATE

GUIDED EJECTION

ASSEMBLY

STATIONARY &

MOVING CAVITY

INSERTS

RUNNER

& GATE

COLD

CHAMBER

STATIONARY/COVER

MOLDBASE

RAIL

EJECTOR PIN

RETURN PIN

CORE

DIE CAVITY

SUPPORT

POST/PILLAR

STOP

BUSHING

RAIL

LEADER/GUIDE PIN

CLAMPING SLOTS

COOLING LINE

PARTING LINE

LEADER/GUIDE PIN BUSHING

SPRUE

HOLE

SPRUE

HOT CHAMBER DIE

COLD CHAMBER DIE

Figure2-1Shownaboveisamultiple-cavitycold

chamberdiecastingdie.Withthisprocessthemetal

entersthedierunners,gatesandcavitythroughthecold

chamber.eSpruereplacesthecoldchamberinthe

hotchamberprocesswhichisusedforzincandsmaller

magnesiumcomponents.

Frequently Asked Questions (FAQ)

1) What type of material should be used for die cavity inserts?

See page 2-10, Die Materials

2) What is the proper heat treatment procedure for dies?

See page 2-11, Die Steel Heat Treatment

3) What is the dierence between a Prototype Die and a Rapid Tooled Die?

See pages 2-4, Prototype Dies and 2-5, Rapid Tooled Dies.

4) Why are trim dies used?

See page 2-6, Trim Dies.

5) What is the dierence between a unit die and a self-contained die?

See pages 2-3 through 2-6, Types of Die Casting Dies.

6) What types of venting air are possible on a die?

See page 2-11.

A-PARTING LINE

Surface where two die halves

come together.

B-LEADER/GUIDE

PIN & BUSHING

Guides the two die halves

together and maintains die

alignment.

C-DIE CAVITY

Die recess in which casting is

formed.

D-STATIONARY &

MOVING CAVITY INSERT

Premium grade tool steel

containing the cavity details.

E-RUNNER & GATES

Precisely designed passage

thru which metal ﬂows from

sprue hole or cold chamber

into die cavity.

F-COLD CHAMBER

Passage thru which metal

enters runners and gates.

F1-SPRUE HOLE

& SPRUE PIN

Forms passage thru which

metal enters runners & gates

in a hot chamber die.

G-CORE

Usually a round tapered pin

used to cast various hole

details.

H-STATIONARY/COVER

MOLDBASE

Stationary holder that

contains and supports the

cover inserts.

I-RETURN PIN

Large ejector pin that resets

ejection system.

J-EJECTOR PIN

Pin which pushes casting from

die cavity.

K-MOVING/EJECTOR

MOLDBASE

Movable holder that contains

and supports the ejector

inserts.

L-RAILS

Supports the ejector side

moldbase and contains

clamp slots.

M-RETAINER AND

EJECTOR PLATE

Contains and pushes the

ejector pins.

N-SUPPORT POST/PILLAR

Additional support members

to resist die deﬂection.

O-GUIDED EJECTION ASSEMBLY

(STOP, PIN & BUSHING)

Supports and guides the

ejection system.

P-CLAMPING SLOTS

Opening for die clamps to

mount die halves to machine

platens.

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Tooling for Die Casting

Figure2-2A“unit”diecastingdie,liketheoneabove,allowsuseofreplaceablecavitiesinstandardizedmaindie

framesforlowerdiecosts.

1 Introduction

e die casting die, or mold, is a closed vessel into which molten metal is injected under high

pressure and temperature, then rapidly cooled until the solidied part is suciently rigid to

permit ejection from the mold.

For longevity of operation in this environment the die casting die must be built from high-quality tool

steel, heat-treated to the required hardness and structure, with dimensions of the die and cavity machined

to exacting specications. e two die halves run in a die casting machine that is operated at the required

temperatures and pressures to produce a quality part to net-shape or near-net-shape customer specications.

e customer’s product design requirements directly aect the size, type, features, and cost of

the required tooling. e items involved in the tooling decision include the number of cavities,

number of core or slide requirements, weight of the die, machining, nish requirements, polishing

and plating to name just a few. A convenient checklist of die construction considerations, intended

for use in discussion with your custom die caster, appears at the end of this section (page 2-17).

Explanation of the most important terms related to die design are given in the following sec-

tions of this chapter. A complete glossary of die casting terms appears at the end of this volume.

e discussion in this section provides a guide to aid the die casting specier in understanding

the requirements of the die caster that will be necessary to produce the optimum die casting, by

the most economical production methods.

e various alloys available for die casting, from aluminum to zinc, require unique and special

features in the die that produces them. Because of these dierences, the descriptions and param-

eters described in this text are generic. Where possible, options are listed but should be used only

as a general guide, with the nal decisions discussed between the customer and the die caster.

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Figure2-3issinglecavitydieusesthemoveablediecomponents(slides)toproducecomplexfeaturesin

thepartshown.

2 Types of Die Casting Dies

ere are various types of die casting dies and each serves a critical need for the customer. e

choice of which type of die casting die the customer requires is usually determined by the following:

•Sizeoftheparttobecast

•Volumeofpartsrequired

•Requirementsfor“ family”setsofparts

•Desirabilityofcoreslides

•Requirementsforcast-ininserts.

2.1 Prototyping

Prototypes are usually requested by the customer to produce a small number of castings under

production conditions. ey enable thorough product testing and market exposure before com-

mitting to full production dies.

Only production from an actual die casting die can yield a part with precise die cast character-

istics. However, there is a range of prototyping strategies that can be employed to approximate

a die cast part for eventual production die casting. Among them: gravity casting, including the

plaster mold process; machining from previously die cast parts or from wrought and sheet stock;

and rapid prototyping techniques such as stereolithography (See the NADCA design manual,

Product Design for Die Casting.)

2.2 Rapid Tooled Dies

Rapid tooling is a term that refers to dies and inserts produced by methods shorter in lead-time

than the conventional method of rough machining, heat treating, and nish machining. Rapid

tooling methods include processes such as LENS (Laser Engineered Net Shaping), EBM (Elec-

tron Beam Melting), RSP (Rapid Solidication Process), SLS (Selective Laser Sintering), DMD

(Direct Metal Deposition), and high speed machining of unhardened steel or pre-hardened tool

steel. Investment casting, and KTEL may also be used. Tools produced by these methods may

be utilized as prototype or production dies. Production volume requirements may dictate which

rapid tooling methods are most viable.

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NADCA Product Specication Standards for Die Castings / 2015

Tooling for Die Casting

Unit Holder + Cavity Block or Replaceable + Cavity

Cavity Unit` Insert

Customer Owned

Die Caster

Owned

Figure2-4Componentsofaunitdieillustrateeachpartoftheassemblyandthedieconstructionoptionofacavity

blockoraholderblockwithcavityinsert.

Single-CavityDie

Multiple-CavityDie

2.3 Production Dies

ese are the most common types of tools produced. ey range from a single-cavity die, with

no slides, to a mulitple-cavity die with any number of slides. e cavities are made from high-

quality tool steel, retained in a quality holder block.

Production dies are built to critical dimensions, coring the maximum amount of stock from

the casting, and allowing the agreed-upon amount of machining. A unit die is a special type of

production die.

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NADCA Product Specication Standards for Die Castings / 2015

Tooling for Die Casting

Figure2-5Photoonleftshowsuntrimmedzincdiecastingasitcomesfromthedie.Atright,thesamecasting

aftertrimming.

FamilyDie

2.4 Unit Dies

A unit die is a lower cost production tool that has a standardized main die frame and replaceable

cavity units. ese replaceable units are designed to be removed from the main die frame without

removing the standard frame from the die casting machine.

e most common commercial types of unit dies are single and double unit holders. ese

types of dies are generally used for smaller parts, or a family of parts, with no slides or a mini-

mum number of slides. Unit dies limit the use of core slides because of the conguration needed

for interchangeable unit inserts and the limited space available.

2.5 Trim Dies

e trim die is a tool that trims the runner, overows, and ash from the casting. e trim dies

are single or multiple cavity tools, made in the same conguration as the die casting die.

Depending on the shape of the casting, the trim die may be a simple open-and-close trim die

or it may include as many slides as the die casting tool. In some cases multiple station trim dies

will be used for successive trimming operations.

Trim dies require as much attention to detail in design as the die casting tools and the use of

quality materials should be specied to extend their productive life.

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Tooling for Die Casting

Figure2-6Mostcrackingcanbeeliminatedwithlargerradii.

Figure2-7isejectordiehalfshowsthetwomoveablecone-shapedcoreslides,A,atleftwhichformthe

interiorofthediecastingsinthistwo-cavitydie.Oppositeslidesareattheright.



3 Casting Features and Die Considerations

e features that are required of a cast part determine the complexity of the die. e simpler the

part, the lower the cost of the die casting tool.

e customer should look at the casting in terms of total manufacturing cost. e die caster

will aid the customer in examining not only the part design’s castability, but also all of the

secondary operations that may be required.

Castability and die cost will be determined by answers to the following: Are the wall thick-

nesses as well as the ribs constant, or do they vary greatly? If bosses exist, do they vary widely in

diameter? Will any thin channels on the design create thin standing slivers of steel on the die? Is

the part number and other engraving recessed into, rather than raised out of, the casting, making

the die more dicult to machine? Are the cored holes that may be called for extremely small

in diameter and thus dicult to cast? Is the part designed with sharp corners, promoting stress

cracks or with generous radii? See the gure 2-6 and llet information on page 6-4.

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NADCA Product Specication Standards for Die Castings / 2015

Tooling for Die Casting

Parting

Line "A"

Parting

Line "B"

Parting

Line “B”

Line “A”

Figure2-8Steppartingline“A,”originallyplacedonthiscastingdrawingwouldnot

haveproducedthebestproductionresults.elocationofthepartingline“B”inthebottom

drawingwillallowbettercastingllandcleanercastingtrim,plusprovidelongerdielife

andalesscostlydietobuild.

For the proper design of production tooling, pressure tightness, secondary machining and

surface nishing specications must be understood in detail. Areas of the casting subject to

machining must be fully discussed at the outset, so that the die can be designed to reduce to an

absolute minimum the presence of porosity in those areas. Cosmetic surface requirements for the

casting will require specic steps in nishing the cavities of the die.

ese are among the types of questions that the customer should be prepared to discuss with

the die caster while reviewing the supplementary checklist at the end of this section.

e Engineering and Design sections provide detailed treatment of the tolerancing implications of

various casting design features, as well as guidelines which apply under diering casting conditions.

3.1 Core Slide Requirements

Fixed cores and core slides (or pulls) can be designed in the die to cast selected features in place,

eliminating the need for most – or all – secondary machining of the cast part.

Core slides, similar to collet or cam movements, can be activated by various sources of motion.

Two of the most common are angle pins and hydraulic cylinders.

e angle pin is a mechanical source of motion that is activated by the die opening and closing.

Its advantages are that it does not require hydraulics or limit switches, and is generally more

economical to manufacture. Its limitations are that it can be used only for short slide travel and

there is no control over the cycle of the slide pull. It is not recommended for use on top slides.

Although the use of springs can make this possible.

e hydraulic method of slide motion permits: a choice of cycles, the placement of slides on the top of

the die, and avoids interference when removing the casting from the die (as is the case with the angle pin).

Among the other methods of motion are rack and pinion, ejector lifter, and cam bars. e choice

of motion depends on factors such as production volume, size of die, length of travel of slide, size of

area being cored out and the conguration of the part. e die caster should be relied upon for the

optimum recommendations on core slides, also called moving die components or moving die parts.

3.2 Parting Line: Cover and Ejector Die Halves

e parting line is that perimeter on the casting which is the separation point of the two halves of the die

casting die. is line aects which half will be the “cover” die half and which will be the “ejector” half.

is line also inuences any tolerances that must be held in this area of the casting. Toler-

ancing standards specic to part characteristics at the parting line are presented in Engineer-

ing and Design, Section 4A.

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NADCA Product Specication Standards for Die Castings / 2015

Tooling for Die Casting

Ejector Die

Die Casting

Figure2-9Ejectorpins,showninblack,arerecessedasthemetalllsthediecavity(aboveleft);thenactuate

sequentiallytoreleasethecastingfromthedie(above,right).

It is not obvious where the parting line on a casting drawing should be placed. Where the

parting line is indicated by the part designer, it is necessary for the die caster to conrm the

designer’s determination. Agreement on the optimum parting line location is essential for the

casting to be produced to the desired specications.

In the case of a part that must have a cosmetic surface, the cover half will generally be used to produce

the cosmetic surface. is permits the ejector half to contain the ejector pins, inserts and any engraving.

If there is no cosmetic surface requirement, the casting can be oriented to suit the most

favorable casting conditions. On cosmetic parts, the customer must discuss with the die caster

where the gate, overows and vents will be, to be certain that there is no interference or

blemish on the important cosmetic surfaces.

Where there are cosmetic requirements, since normal, incremental die erosion is inherent in

the die casting production process, the customer will want to discuss special die maintenance

procedures to extend the ability of the die to produce parts with the required high-quality

surface nish. Secondary operations to the surface of the part, such as polishing or bung,

should also be discussed to maintain cast part specications.

3.3 Ejector Pins

Ejector pins are used to push the casting out of the die after the metal shot has been made and

casting solidied. e location and size of the ejector pins are dependent on the conguration,

size, and other requirements of the casting.

e die caster will always attempt to locate ejector pins in a nonfunctional area of the casting, such as

in an overow, on a boss, in the bottom of a deep pocket, or the bottom of a rib. His recommendations

are important as to the size, location and number of ejector pins required for successful part production.

Each ejector pin must be sized to suit the casting conguration in the selected area and will leave

a slight impression on the cast surface. For this reason, they are not placed against the cosmetic

surface side of the part.

Product standards related to ejector pin locations are discussed in Engineering and Design, Section 6.

3.4 Cast-in Inserts

In some castings, there may be a need for a bearing surface, internal thread, or some other

unique feature that could be accommodated by an insert molded into the casting. is require-

ment can often be met by the die caster within the normal operation of the casting process.

is “insert molding” oers the advantage of rmly setting an insert into the casting so that it

can be machined, drilled and tapped. is advantage, however, rarely osets the added costs of the

insert casting operation.

e added costs result from reduced machine cycle time, due to loading the insert into the die

and the heating procedure required to heat the inserts before they are placed into the die half. is

preheating is recommended to avoid putting moisture into the die, allowing metal to chill around

the insert and causing the insert to loosen.

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4 Die Materials

e grade of tooling materials to be used in the construction of a die casting die should be

specied as high quality, at a minimum, and preferable premium quality. ese requirements are

based on the extremely high temperatures and pressures used in die casting production.

Tooling grade requirements will vary depending on the tooling component, the alloy being die cast,

the critical character of the cast part design and the long-term production quantities desired. Every

aspect of the proposed product’s design and production specications must be discussed with the die

caster before tooling material can be selected. e following are typical tooling lowest requirements:

4.1 Die and Cavity Materials

• DieCastingDiesforZincAlloys:P-20,H-11,H13,PremiumGradeH13(PerNADCANo.229),

SuperiorGradeH13(PerNADCANo.229),orothergradesasdenedinNADCANo.229..

e zinc alloys, which cast at the lowest temperature in the nonferrous family, cause the least wear on

their tooling and thus permit the use of non-premium die material, such as P-20, in cases where part

designs are relatively simple. Purchasers are cautioned, however, to be aware of the unwise investment

in non-premium grade tooling for zinc parts if there is any possibility that production quantities may

reach higher levels than originally anticipated. At higher production levels, such tooling may expire

and the cost of replacement dies will far outweigh an original investment in premium material.

• DieCastingsDiesforAluminum,Magnesium&ZAAlloys

(Noncriticalpartdesigns,lowvolume):H-10,H-11,H13.

Aluminum, magnesium and ZA die casting dies require high quality tool steel, as above.

If part designs have very critical features or if high production runs are being contemplated,

however, premium grade tooling will always be the wisest investment.

• DieCastingDiesforAluminum,Magnesium,ZA-12&ZA-27Alloys

(Criticalpartdesigns,highervolume):PremiumGradeH13(PerNADCANo.229),Superior

GradeH13(PerNADCANo.229),orothergradesasdenedinNADCANo.229.

For Al, Mg, ZA-12, and ZA-27 die cast parts, H13 Premium or Superior Grade tool steel

is recommended whenever part design features are intricate and specications tight, and when

production volumes will be high. In such cases, non-premium grade tooling will nearly always

result in costly premature die failure.

• DieCastingDiesforBrassAlloys:H13

Since copper alloy die castings are cast at the highest temperatures of the nonferrous alloys,

only H13 high grade tool steel is recommended for brass die casting dies.

Metal certications for the material grades listed, provided by quality tooling material suppliers,

will be made available for inspection by the die caster. e H13 Premium or Superior Grade should

meet the NADCA No. 229 tool steel standard (Special Quality Die Steel and Heat Treatment

Acceptance Criteria for Die Casting Dies).

4.2 Die Cavity Insert Materials

e materials recommended for use as tool steel for die cavity inserts parallel the recommenda-

tions for die cavities, above, with some additions.

In addition to H13 Premium or Superior Grade, the maraging and speciality tool steels* are

used for die inserts needing higher hardness to improve their resistance to the heat checking

(thermal fatigue cracking) or crazing of the insert’s surface caused by thermal cycling of the

die from the high temperature molten alloy and die spray/die cooling. e ne cracks that may

result can produce corresponding veins on castings.

In high wear (erosion/washout) and temperature areas, especially if internal cooling and/or die

spray is dicult, small cores and inserts in aluminum die casting dies can eventually break or

wash away due to the velocity of the aluminum entering the cavity. Tungsten- and molybdenum-

based alloys are occasionally used successfully in these areas to resist these conditions. Although

these materials show superior physical properties compared to conventional steels at high

working temperatures, care must be used in machining them. Also, their increased cost must be

considered in the overall cost of the die and number of shots required (life of the die).

Note:

There are many die materi-

als available that vary in

both their chemical com-

positions and mechanical

properties. Developments

in high speed machining

and Wire EDM have led to

the use of a wide variety of

tool steels based on cavity

complexity and position

as the material relates to

the gate location. Specialty

tool steels have their own

specic properties but, if

used correctly, can increase

tool life by up to a factor

of two or more. It is also

important to note that they

usually are more costly as

noted in section 4.2. This

increased cost can be more

than offset by the increase

in die life achievable so it

is best to consult with the

die caster as to what some

of the options might be for

a given casting design. Spe-

cialty tool steels that do not

require heat treat or are pre-

heat treated before machin-

ing have been successfully

used in both Prototype and

Rapid Tooled Dies for early

production starts.

Some of the (but not limited

to) manufactures of these

specialty steels are Aubert

& Duval, Bohler, CMW,

Daido, Dunn Specialty

Steel, Elwood Specialty

Steel, Kind, Nippon

Koshuha, Schmolz & Bick-

enbach, and Uddeholm. It

is best to consult with the

die caster as to what some

of the tool steel options

are for individual casting

designs and die construc-

tion.

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Conventional

Vent

Vacuum

Valve

Figure2-10Conventionalventinginadiecastingdie,shownatleft,ventsairtotheatmosphere.With

avacuum-equippeddie,metalispulledintoaclosedsystem,withairdrawnbythevacuummechanism.

Asignicantreductioninairentrappedinthecastingresultsinlowerporosity.

4.3 Die Steel Heat Treatment

e quality of the heat treatment of the die steel is a very critical step in the tool building process. e

use of high quality rapid quenching heat treatment procedures is essential to normal die life. Care

must be exercised in the heat treatment procedure to balance the issues of distortion with metallurgial

properties that result from rapid quenching. e recommendations of the die caster should be respected.

Just as tool steel source certications are made available by the die caster, so are the heat treat

certications from the selected heat treatment sources. is documentation will certify that the

heat treat was properly carried out to achieve the correct hardness and microstructure.

Tool steel heat treatment should be expected to follow NADCA No. 229 heat treatment guidelines

(Recommended Procedures for H13 Tool Steel) and the recommendations of the tool steel manufacturer.

5 Controlling Die Performance

5.1 Porosity Control: Gating, Venting and Vacuum

Although die castings can be expected to exhibit high strength and integrity, some product require-

ments can call for additional steps in the part design, die design and on-line production stages.

Designers seeking to avoid porosity concerns will be alert to such techniques as eliminating

thick wall sections in their designs. (See Product Design for Die Casting for general guidelines).

For specic designs, the engineer should always consult with an experienced die caster before

design parameters are locked in.

Given the nal part design, the die caster will follow specied die design guidelines, and

ow simulation (if available), incorporating die gating, overow and venting congurations to

evacuate air properly from the die cavity and reduce porosity to an acceptable level. Where pres-

sure tightness is not a casting specication, the process can be designed so that residual porosity

enters only non-functional, internal areas of the casting. Porosity is acceptable in non-critical areas.

While not a substitute for sound product and die design, a vacuum system can also be used to

enhance die ll, reduce gas porosity, and improve mechanical properties. A vacuum system is

designed to evacuate ambient air from within the die cavity during casting and create a negative

pressure or a vacuum. e die must be specially built to accept a vacuum system, so discussions

of acceptable porosity levels should be held well in advance of die design.

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Tooling for Die Casting

Figure2-11Heatcheckingasseenonacasting.

Figure2-12Washoutasseenonacasting.

5.2 Thermal Balancing

To achieve maximum product quality, the dies are required to run at a precise, specied tem-

perature. is temperature will vary with such factors as the size of the casting, number of die

cavities, alloy being cast and machine cycle time.

e alloy is injected into the die at this exact temperature at high speeds and then rapidly

cooled for ejection. is extremely fast and repeated cooling requires careful engineering of a

complex network of internal die temperature lines. Infrared imaging and thermocouples placed

in the die can help measure and maintain correct die temperatures.

Proper thermal balancing through the strategic placement of these lines reduces die casting

cycle time, improves casting quality, and lengthens the life of the die.

Dierent areas of the die can be heated or cooled to dierent temperatures, i.e., dierent cover

half and ejector half temperatures can be used to aid control of part density or surface nish.

5.3 Oil Heating Lines

In some cases dierential heating of various areas of the die to produce specic casting design

features will be achieved by the use of hot oil lines in the die.

Hot oil systems heat a special oil to a given elevated temperature and pipe it through the die in

the same manner as water cooling lines. Both water cooling and hot oil heating lines may be used.

5.4 Alternate Surface Textures

Using photoengraving techniques in making the die cavities, a wide range of patterns, grainings

and textures can be selected for permanent die casting into the surface of a part. e die caster

can exhibit actual samples of the common die cast textures possible. (For illustrations of sample

textures, see the Surface Treatment chapter of Product Design for Die Castings.)

5.5 Extended Die Life

While optimum die life begins with high quality tool steel, several patented processes are available

which can be used to extend the life of a die casting die. ese processes involve shot peening tech-

niques, submersion in special baths, and chemical treatments of the die. e die caster can discuss the

projected eectiveness of such steps to reduce premature die wear in the case of specic part design.

A typical failure mode of dies is heat checking or thermal fatigue cracking.

5.5.1 Heat Checking. Die Casting tools show small cracks (network) as well as bigger (leading)

cracks after some time in use, due to thermal fatigue. Both are important to tool life.

e scale in gure 2-13 is designed to give you a combined grading using both network and

leading crack values.

Compare the scales with your tool. Give the tool a grading from both scales. Add the two

gradings. ese two combined readings give you the degree of heat checking.

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Figure2-13Photosofdiesurfacecrack

patternsreproducedapproximately70%of

actualsize.ediesteelheatcheckcondi-

tionsisreectedasraisedmaterialonthe

surfaceofthecasting.

CourtesyofUDDEHOLM

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Tooling for Die Casting

Determine at what point the die will no longer be useful. For critical surfaces, such as those to

be polished or chrome plated, you might stop using the die at a combined rating of six. For other

surfaces, especially those not seen by users of the nished product, the die might be used until

the rating is judged to be greater than 14. As the rating goes up, there is not only an aesthetic

loss but an economic loss in the production of the parts.

e scale also provides a concrete basis of comparison between dierent tools and number of shots.

6 Secondary Machining Preplanning

While most die castings are produced to near-net-shape, and many to net-shape, the close

tolerances possible with die casting and the repeatability of the process suits die cast parts to

economical high-precision secondary machining operations.

A die casting can be designed to accurately adapt to machining xtures by casting in locator

holes or casting a ush locating datum surface. Die castings can be drilled, tapped, reamed,

punched, or have nearly any type of machining operation performed on them.

Machining operations, including gaging and any other secondary operations that may be

required, can be performed by the die caster. Properly designing the part and the die for

optimum quality and economy in secondary machining will have an important impact on

reducing nal part costs. Detailed discussions should be held with die caster engineering

personnel to establish such machining parameters as the precise location, extent, and depth of

the machining required; the surface nish required; and any other specication necessary to

result in a quality component.

Decisions on special machining equipment ownership, maintenance and replacement must

also be discussed. Such matters are outlined in the Commercial Practices section of this manual

(page 8-1).

7 Gaging Considerations

What gages will be used in casting production and in secondary machining, and what they will

check, are important elements of the die casting program.

Gages may be used to check the casting in its as-cast state and again after machining. e gage may

be an attribute gauge, which is basically a “go” or “no-go” check and results in either a good or bad part.

A variable gage may also be employed which, used with a computer, can document variables,

collect data, and record Cpk’s.

More than one gage may be needed to check a casting: one to check it in its as-cast condition

and another to check the casting in a fully machined condition. ere may be a need for plug and

thread gages as well as nished gages or standards for painted surfaces.

e gaging should be considered by the customer as part of the tooling package. Gaging

requirements should be resolved early by the quality assurance managers of both the customer

and the die caster, so no questions remain on meeting the part print requirements.

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8 Inherited Tooling

In some instances a customer may transfer a die casting die from one die caster to another.

is generally will raise some operational questions for the receiving die caster of which the

customer should be aware.

e die may need to be put into a dierent type of die casting machine. is may require some

modications to the die’s ejector system as well as to the shot sleeve, i.e. the entry for molten metal.

e die’s gate and runner system may also need to be modied to suit the new machine

conditions. It may be necessary for any residual oil in the hydraulic system of the die to be sent

out for sampling to assure that it does not contain any contaminants.

e die must be evaluated by the customer and the die caster’s tool room superintendent to

assure that there are no visual problems with the die. ey should also determine whether the die

arrived with any required limit switches and hydraulic cylinders.

Upon this review an adaptation cost can be established and agreed upon before the receiving

die caster has invested a large amount of time and expense in preproduction work.

Checklist T-2-1, at the end of this section, will aid in addressing questions regarding trans-

ferred or “inherited” tooling.

Die or tooling ownership and replacement is often a point of discussion. Information regard-

ing this topic can be found in Section 8.

9 Engineering Consultation

e customer company, in the person of its engineering and quality assurance personnel, will usu-

ally be requested to meet with the custom die caster’s engineering and quality assurance personnel

as early as possible to discuss the design and function of the part design proposed for die casting.

ey will discuss the design’s function, t and precise assembly with other components.

e die casting process uniquely lends itself to parts consolidation, decreasing the number of

components in a product assembly.

Early involvement with the die caster is essential in avoiding expensive corrective steps in later die

construction. It can often simplify product assembly and signicantly reduce total product costs.

For example, an attached hinge bracket could be die cast as an integral part of the casting. A

slight design modication could assure clearance for a close assembly.

e die caster may be able to cast an integral bearing in the part that the customer was

planning to press in. Or the die caster may be able to perform a complete or partial assembly

operation more economically, such as installing a gasket after painting the casting, and shipping

the part ready for assembly. Many die casters have in-house capabilities for operations such as

pressure testing, impregnating, machining, surface nishing and subassembly.

e experienced die caster should be regarded as a invaluable source of expertise in the die

casting production and assembly process.

Depending on part conguration, very small high-volume zinc parts, weighing fractions of an

ounce, may be recommended for production on special hot-chamber zinc die casting machines.

Such parts, usually called “miniature” or “microminiature” die castings, can be cast ash-free,

with zero draft, to very close net-shape tolerances.

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10 Database Guidelines

When databases are utilized, quotations for castings are often based on the assumption that any

CAD databases provided to build tooling and produce parts are complete, usable and are without

need of updating.

Databases may be deemed incomplete and unusable if:

1. egeometryofthepartisnotphysicallymoldable.

2. enecessarydraftandradiiarenotincorporated.

3. Lineandsurfacegeometryarenotconnectedwithin0.001”.

4.Partinglineisnotfullydeveloped.

Note: e database le format may not be compatible with existing capabilities and may

require a translator. STL les are usually only used for creation of prototype parts.

Any necessary database manipulation that is caused by incompleteness as described above

could add cost and extended lead-time to tooling.

If databases are designed only to nominal dimensions, tool life and casting tolerances may be

adversely impacted.

If solid model databases are used for tool construction, they should be accompanied by a

limited dimension part print (either paper or database) that contains all tolerancing information

and information pertaining to any secondary machining that is to be performed to the part.

e revision control for databases should be as agreed upon between the die caster and customer.

11 New Die/Inherited Die Specifications

Checklist T-2-1, which follows, will aid in discussions between the customer and the die caster

regarding the important considerations in the design of a new die casting die or in the produc-

tion of parts from “inherited” tooling.

12 Die Life

Die casters are frequently asked the question, “How many shots will I get from the die before

it needs to be replaced?” or “How many shots will you guarantee the die for?” A better question

might be, “What can we do to maximize die life and to minimize replacement costs?”

Aluminum and Copper die casting dies wear out due to the aggressive nature and high

melting temperatures of the materials being die cast.

Die life is a consideration of part design, part function, internal part requirements and part

cosmetics. In general, cosmetic areas of the part do not last as long as functional areas.

e following is a suggested approach to be used by the customer and die caster at the time of

part design. e intent is to dene critical areas of the die casting before the start of tool design.

is allows areas to be inserted to maximize die life and minimize the replacement costs.

First, is to develop a rating scale by which this information can be used to relate part considerations

to estimated tool life. A guideline (T-2-2) has been developed and includes; a Die Life Checklist,

sample part, example of tool steel inserting and identication matrix starting on page 2-19

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13 Checklist for Die Casting Die Specifications (To be used in consultation with your Die Caster)

Part 1 — New Die Casting Dies: Items to be Addressed

In the case of new die casting dies, all of the items in Part 1, below, should be reviewed. Note, in

the case of tooling to be transferred to, or “inherited” by a die caster, the items asterisked (*) in

Part 1 should be addressed, plus the items noted in Part 2 on the next page.

Type of

New Die

 Prototype Die Casting Die

 Production Die Casting Die

Cavity Steel*

 H13

 Premium Grade H13

 Superior Grade H13

 Othe r To ol S t eel: __________________________________________________

NADCA No. 229 Certiﬁcation Required: Yes No Grade Class

Cavity Steel

Heat Treat*

 Hardness Required:

 T ou ghn e s s R equ ir e d: ______ f t.- lbs

NADCA No. 229 Certiﬁcation Required:  Yes  No

Cored Holes*

 All Holes Cored

 Cored Holes As Noted On Print

 No Cored Holes

Die Operation

for Part

Features*

 Mechanical Movement

 Hydraulic Movement

 Features To Be Achieved By Secondary Operations

Estimated

Part Volume

Mon thly : _______________________________________________________________

Ann ual: ________________________________________________________________

E xpec t e d P rod uct L ife: _________________________________________________

Casting Alloy*

 Aluminum

 Copper

 Magnesium

 Zinc

 ZA

Alloy

_____________________

Casting Weight

Est i mate d Ca s ting We ight : _____________________________________________

As-cast Part

Finish*

 Mechanical Grade (Functional Finish) (Ref. 125 Ra)

 Painting Grade (Ref 63 Ra)

 Highest Quality (Cosmetic Finish) For Plating, Etc. (Ref. 32 Ra)

*Die wear can affect surface finish over the life of the die.

Class of Die

 Unit Die

 Conventional Die

 Single Cavity

 Multiple Cavity

 Multiple Cavity - Family Die

Cast-In Date

Insert*

 In Die Cavity

 Othe r Require ment s : ______________________________________________

 Not Required

Cast-In Part

Number*

 In Die Cavity

 Othe r Require ment s : ______________________________________________

 Not Required

Other

Write in any other special requirements (ie. tolerances, leak testing, x-rays):

____________________________________________________________________________________

NADCA

T-2-1-15

Checklist

This two-part speciﬁcation

checklist is intended for

use in consultation with

your die caster prior to

estimation of new die

design and construction,

or prior to die casting

production using “inher-

ited” tooling. It should be

used in combination with

checklists C-8-1 and C-8-2

in Commercial Practices,

Section 8.

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Part 2 — New Die Casting Dies: Items to be Addressed (Continued)

Cast-In Logo,

Lettering*

 In Die Cavity  Other

Inc lude: ________________________________________________________________

 Customer Logo  Cavity No.

 Supplier Logo  Revision No.

 Recycling Logo  Part Number

Die Layout

 Customer to Approve Layout

 Approval by Die Caster

First-Piece

Approval

 Customer Approval Before Production Run Required

 Run on Die Caster Approval  PPAP

Gages*

 Customer to Supply Special Gages

 Die Caster to Supply Special Gages

Trim Die

 Mechanical Movement

 Hydraulic Movement

 Features To Be Achieved By Secondary Operations

Machining

Fixtures

 No Secondary machining required

 Machining reguired, no special ﬁxtures

 Special machining ﬁxtures required, customer to supply

 Special machining ﬁxtures required, die caster to supply

Special Items

Special Items to be included in the tooling package:

_________________________________________________________________________

Part 3 — Inherited Die Casting Dies: Additional Items to be Addressed

In the case of inherited tooling, not the asterisked items (*) in Part 1, plus the items below.

Note that with transferred, or “inherited,” tooling for die casting production the existing die casting

die, the trim die, and, if required, the secondary machining xtures, must be available for review and

evaluation to determine whether the dies and xtures are capable of producing to specications and the

extent of maintenance and/or rework required before the onset of production. is would include any

adaptations of the die caster’s equipment to accommodate production using the inherited dies. Final

production estimates will be based on this review.

Inherited Die

 Die Casting Die Available for Evaluation

 Die to be Availa ble for E va luat ion (d ate): __________________________

Inherited

Trim Die

 Trim Die Not Required

 Trim Die Available for Evaluation

 Trim Di e to be Avail able for Eva lua t ion (date): _____________________

Inherited

Machining

Fixtures

 Special Machining Fixtures Not Required

 Machining Fixtures Available for Evaluation

 Mac hining Fixtures to b e Ava ila ble f or E val uati on (d a te): __________

Actual Casting

Weight

Wei ght of Actua l Ca stin g: ______________________________________________

Size of Die

Siz e of Ca s ting Die (for equ ipme nt limi tatio ns): _________________________

Weight of Die

Wei ght of Cas t ing Die (f or c ran e li mit a t ion s): ___________________________

Availability

of Die Design

 Yes

 No

PublishergrantspermissiontoreproducethischecklistaspartofadiecastingRequestforQuotationorProductionSpecication.

NADCA

T-2-1-15

Checklist

This two-part speciﬁcation

checklist is intended for

use in consultation with

your die caster prior to

estimation of new die

design and construction,

or prior to die casting

production using “inher-

ited” tooling. It should be

used in combination with

checklists C-8-1 and C-8-2

in Commercial Practices,

Section 8.

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14 Guidelines to Increase Die Life

Before the start of tooling

1)Redesignofparttoreduceoreliminatesharpinternalscornersorfea-

turesthatwillpromoteearlycrackingofthetoolsteel.

2)Useofspecialtoolsteelsinareaswherehighwearisexpected(increases

toolcosts).

3)Insertarea’sofcavityblocksformoreeconomicalreplacement(may

increasetoolcosts)aftertoolwearhasoccurred.

4)Doasurfacetreatment(shotblasting)tothetoolsteeltohelpreduce

heatcheckingandcracking(addstotoolcost).Note:iswilladda

surfacetexturetothediecastpart.

5)Addavibratory,shotblastordeburringoperationtotheparttohelp

extendtoollife(addedpartcost).

6)Addamachiningoperationtoremoveheatcheckingand/orcrackingin

areasthatarecriticalonthepart(addstopartcost).

7)Reclaimthesurfacehardness,ifpossible,whenitdropsfromthe40’s

HRCtothehigh30’sHRC.

8)Coatingscanbeappliedtothediesurfacetoreducewearandsoldering.

9)Useinternalcoolinginsteadofdiespraytocoolthedie.Sprayisonlyto

beusedasareleaseagent.

Die Life Checklist

Class

Part

Consideration

Critical to

Function &

Cosmetic

Cosmetic,

No Function

Critical to

Function

Not Critical

but Functional

No Function

Class

Estimated

Die Life/Shots

Less than

10,000

10,000 to

25,000

25,000 to

50,000

50,000 to

100,000

More than

100,000

Using the above will

develop and itemize the

areas of concern of a

sample part.

NADCA

T-2-2-15

Guideline

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Tooling for Die Casting

Sample Part

Sharp Corners

Non-Functional

Functional

Cosmetic

Non-Functional

Sealing Surface

Mounting Surface

O-ring Surface

Tool Steel Insert Construction

Insert #

Part Consideration

Estimated Die Life

Radius

Using the sample, the next step is to develop an inserting plan for the tool steel construction.

Last is to develop the matrix for communication of tool steel replacement needs and to develop

history on each insert. (e information shown in this example represents only what can be

done. e actual information to be included should be determined by the customer and the die

caster). Two examples of this type of matrix are shown, at the start of a new project and the other

as it may appear after the rst year of production.

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Tooling for Die Casting

As mentioned earlier this is just a suggested approach to improving die life and reducing replace-

ment costs. Die casting dies do wear out. It is an advantage to both the customer and the die

casters benet to layout a plan at the start of the project. is allows inserts to be replaced before

any actual failure thus preventing any possible loss of production. e examples shown are only

one of many possible methods to achieve this. If the customer and die caster choose to use this

type of approach, it should be on a part by part basis. e information in the matrix should be

relevant to the actual tool construction and the actual annual usage.

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