VDG P690 Investmen castings, dimensional tolerances, surface

VDG-MerkblattBDG Reference Sheet

P690Status: September 2010Investment castingsDimensional tolerances, surface condition, machining allowanceCONTENTS 1 Standard references S.1 | 2 Definition and field of application S.2 | 3 Objective S.2

4 Dimensional accuracy S.3 | 5 Dimensional tolerances S.5 | 6 Surface quality S.9

7 Machining allowances S.9 | 8 Additional notes and data S.9 | 9 Further reading S.101 Standard referencesThe documents cited below are necessary to apply this document. In dated references, only the edition

referred to is valid. In dateless references the current edition of the document is authoritative (includ-ing all modifications).DIN 406-10

DIN 406-11

DIN 406-11

echnische Zeichnungen; Maßeintragungen; TBegriffe, allgemeine GrundlagenTechnische Zeichnungen; Maßeintragungen;

Grundlagen der AnwendungBeiblatt 1 – Technische Zeichnungen – Maßeintragungen –

Teil 11: Grund lagen und Anwendung; Ausgang

der Bearbeitung an RohteilenTechnische Zeichnungen; Maßeintragungen; Eintragung

von Toleran zen für Längen- und WinkelmaßeTeil 1 – 4 Schriften – Serifenlose Linear-AntiquaTechnical drawings – Geometrical tolerancing – Datums

and datum-systems for geometrical tolerancesGeometrical Product Specifications (GPS) – Geometrical tolerancing –

Tolerances of form, orientation, location and run-outGeometrical Product Specifications (GPS) – Indication of

surface texture in technical product documentationGeometrical Product Specifications (GPS) – Indication

of surface texture in technical product documentation,

Corrigendum to DIN EN ISO 1302:2002-06DIN 406-12

DIN 1451

ISO 5459

EN ISO 1101

EN ISO 1302

EN ISO 1302

Compiled by the BDG technical committee “Investment Casting”To be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

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P690Status: September 2010EN ISO 5459 raft standard – Geometrical product specifications (GPS) – DGeometrical tolerancing – atums and datum-systems

EN ISO 8062-2 Geometrical Product Specifications (GPS) – Dimensional and

geometrical tolerances for moulded parts – Part 2: RulesEN ISO 8062-3 Geometrical Product Specifications (GPS) – Dimensional and

geometrical tolerances for moulded parts – Part 3: General dimensional

and geometrical tolerances and machining allowances for castingsISO 19959 Visual examination of the surface condition of investment

castings – Steel, nickel alloys and cobalt alloysBDG-Reference Sheet P 510 M aßliche Erstbemusterung auf der Basis von 3D-CAD-DatenVDG-Reference Sheet P 701 K ennzeichnung von Gussteilen2 Definition and field of application2.1 DEfINITIONInvestment casting is an industrial precision casting process using in contrast to other moulding process-es a melt out pattern (lost pattern) to create an undivided ceramic mould (lost mould). In those metals

and alloys based on iron, aluminium, nickel, cobalt, titanium, copper and magnesium are cast. Castings

manufactured like this are distinguished by their dimensionally accuracy and their high surface quality.

The process is also known as “Lost Wax Moulding”, “Lost Wax Process” or “Fonte à Cire Perdue”.

2.2 fIElD Of aPPlICaTIONThis reference sheet does not apply to precious metals cast by means of the lost-wax process, products

of the jewellery industry, dental laboratories or artistic castings.2.3 RaPID PROTOTyPINGDimensional and surface tolerances of castings produced in rapid prototyping might vary. They must be

agreed upon separately between producer and user of investment castings.3 Objective3.1 TaRGETThe reference sheet defines dimensional tolerances, machining allowances and surface roughness which

represent the state of the art in investment casting. It is the basis to promote optimum co-operation be-tween producers and users of investment castings.3.2 SuRfaCESThe technical data given in this Reference sheet apply for the shot-blasted or pickled surfaces of castings.

The delivery state might vary, e. g. because of additional surface treatment. Exceptions must be agreed

on in advance when processes are involved which may alter the dimensional be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

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P690Status: September 20103.3 aGREEmENTUnless otherwise agreed, first-off samples will be supplied for the first order. These are intended to define

and coordinate product characteristics in the interests of both parties. The first-off samples must be test-ed by the user. After testing release for serial production must be given to the foundry in written form.

Any deviations, which are accepted by the release for serial production or the approval of the first-off

samples, are binding for the production process and must be included in the (casting) drawing.4 Dimensional accuracy4.1 ShRINkaGE, CONTRaCTIONWhen cast metals cool down and solidify, a contraction in volume takes place which causes shrinkage.

Other important factors influencing the production of investment castings are the shrinkage of the lost

patterns and the expansion of moulds during heating. The sum of these factors is taken into account

by the manufacturer of the injection patterns in the contraction allowance. These are empirical values

which are dependent on the casting contours, the pattern material, the ceramic mould material and the

metal itself as well as on the specific production methods of individual foundries.4.2 DaTum PlaNES aND DaTum POINTS

For producing castings, it is necessary to enter datum planes and datum points (so-called locating points)

systematically in the drawings or CAD-data to ensure that dimensional inspection and subsequent ma-chining are properly matching. These datum points and planes must already be determined between

the designer and the investment-casting foundry. The zero position of the datum planes is defined pre-cisely by the dimensions of the datum 1 Datum plane – datum points©

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(BDG)The primary datum plane „A” is fixed by the three datum points A1, A2 and A3. lt should correspond to

the largest surface of the secondary datum plane „B” has the two datum points B1 and B2. If possible, these should be lo-cated on the lengthwise axis. The tertiary datum plane „C” has only one datum point C1, which should

be located in the centre of the casting or in the vicinity be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

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P690Status: September 2010figure 2 Reference system (Schematic example)The datum planes are laid through the symmetry axis of the casting. All datum points should be arranged

in such a way that they cannot be altered or removed by subsequent machining operations. The datum

points should be located on the outer surface of the investment casting. They may be either recessed or

raised in relation to the casting surface. In the case of castings with narrow tolerances of shape and po-sition, raised datum points are fixing the position of the datum points, it should be ensured that they are not in the vicinity

of a sprue/ ingate. Complex shapes of castings can be accurately positioned by (pre-) machining the lo-cating points.4.3 OVER-DEfINITION/REDuNDaNT DImENSIONINGIn accordance with DIN 406, over-definition/ redundant dimensioning should be avoided. Wall thick-nesses must always be stated.©

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(BDG)4.4 mOulD aND PaTTERN DRafTAs a rule, mould and pattern drafts are not required. Any exceptions due to technical requirements

must be agreed on between the supplier and the customer (cf. DIN EN ISO 8062-3, Amendment F) (Not

yet published at date of printing).To be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

D-40237 Düsseldorf, Phone: (0211) 68 71-252, Fax: -361, 4 of 10

VDG-MerkblattBDG Reference Sheet

P690Status: September 20105 Dimensional tolerances5.1 lINEaR TOlERaNCESThe dimensional tolerances achievable on investment castings are dependent on the following factors:

> casting material> casting dimensions and shape5.1.1 Casting materialsIn production, the tolerance range of dispersion is affected by the varying characteristics of the materi-als, For this reason, different tolerance series apply for different groups of casting materials (table 1):material-group D:

alloys based on iron nickel, cobalt and cooper

material-group a:alloys based on aluminium and magnesium

material-group T:alloys based on titanium

Accuracy gradeD1 to D3A1 to A3T1 to T35.1.2 Validity of accuracy grades

Three accuracy grades are stated for each of the material groups D, A and T.

accuracy grade 1 applies for all free sized dimensions. accuracy grade 2 applies for all dimensions to

be toleranced. accuracy grade 3 can only be met for certain dimensions and must be agreed with the

casting manufacturer, as additional production processes and costly tooling adjustments are e 1a: linear dimensional casting tolerances (DCT in mm) for dimensional

casting tolerance grades (DCTG) material group DNominaldimension range up to 6

over 6 up to 10

over 10 up to 18

over 18 up to 30

over 30 up to 50

over 50 up to 80

over 80 up to 120

over 120 up to 180

over 180 up to 250

over 250 up to 315

over 315 up to 400

over 400 up to 500

over 500 up to 630

over 630 up to 800

over 800 up to 1000

over 1000 up to 1250

D1DCTDCTGDCT0,240,280,340,40,626789105D2DCTG4DCTD3DCTG0,30,360,440,520,80,91,11,62,42,63,64,05,46,27,25678910110,20,220,280,340,50,60,71,01,51,687©

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(BDG)4560,740,881,31,92,22,83,24,45,0To be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

D-40237 Düsseldorf, Phone: (0211) 68 71-252, Fax: -361, 5 of 10

VDG-MerkblattBDG Reference Sheet

P690Status: September 2010Table 1b: linear dimensional casting tolerances (DCT in mm) for dimensional casting

tolerance grades (DCTG) material group aNominaldimension rangeup to 6

over 6 up to 10

over 10 up to 18

over 18 up to 30

over 30 up to 50

over 50 up to 80

over 80 up to 120

over 120 up to 180

over 180 up to 250

over 250 up to 315

over 315 up to 400

over 400 up to 500

over 500 up to 630

over 630 up to 800

over 800 up to 1000

over 1000 up to 1250

A1DCTDCTGDCTA2DCTGDCTA3DCTG0,30,360,440,520,80,91,11,61,92,62,83,24,45,05,66,6567890,240,280,340,40,620,740,881,31,52,22,42,63,44,04,6450,20,220,280,340,556784678989100,60,71,01,21,61,71,910Table 1c: linear dimensional casting tolerances (DCT in mm) for dimensional casting

tolerance grades (DCTG) material group TNominaldimension rangeup to 6

over 6 up to 10

over 10 up to 18

over 18 up to 30

over 30 up to 50

over 50 up to 80

over 80 up to 120

over 120 up to 180

over 180 up to 250

over 250 up to 315

over 315 up to 400

over 400 up to 500

over 500 up to 630

over 630 up to 800

over 800 up to 1000

over 1000 up to 1250

T1DCTDCTGDCTT2DCTGDCTT3DCTG0,50,60,70,81,01,51,72,02,43,23,64,05,46,27,260,40,4670,50,70,81,20,40,40,440,520,620,981,11,31,5910©

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(BDG)768910111,41,61,92,62,83,24,45,0785.1.3 Position of tolerance zone

The position of the tolerance zone in relation to the nominal dimension can be freely selected. It is ad-visable to place the tolerance zone evenly on each side of the nominal dimension. In the case of surfac-es to be machined mechanically, the sum or difference of tolerance zone and machining allowance must

be taken into account (see item 7).To be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

D-40237 Düsseldorf, Phone: (0211) 68 71-252, Fax: -361, 6 of 10

VDG-MerkblattBDG Reference Sheet

P690Status: September 20105.2 TOlERaNCES Of ShaPE aND POSITIONTolerances of shape and position limit the deviations of the shape feature from its theoretically precise> shape or

> direction, or> from its exact – locationindependently from the actual dimension of the shaped element. Tolerances of shape and position re-quire that datum surfaces and datum points (see item 4.2) are fixed, based on DIN ISO 1101. If tolerances

of shape and position are fixed by the order, they must be stated individually and entered in the draw-ing in accordance with DIN EN 1101 .Three accuracy grades are available. The higher the degree of accuracy, the bigger the production

complexity. Accuracy grade 3 (according to table 1) can only be met for certain dimensions and must be

agreed on with the castings manufacturer, as additional production process steps and costly tooling ad-justments are necessary.5.3 aNGlE TOlERaNCES fOR maTERIal GROuPS D, a aND TAccuracy3)Nominal dimension

range 1)Angularminute1mm per 100

mmAngularminute2Allowed deviation of directionmm per 100

mmAngularminute3mm per 100

mmup to 30 mmover 30 up to 100 mmover 100 up to 200 mmover 200 mm302)3030302)2)2)0,870,870,870,58302)0,870,580,440,44202)152)102)102)0,580,440,290,29202)152)152)1) The nominal-dimension range is deter-mined by the length of the shorter side2) The angle may deviate in both directions

Tolerances of angle differing from those

given in table 3 must be agreed between

supplier and user, and entered in the

drawing in accordance with DIN ISO 1101.3) For investment castings based on Titanium

alloys accuracy grade 1 has to be appliedTable 2: angle tolerancesTolerances deviating from table 2 must be agreed on between supplier and user and entered in the draw-ing in accordance with DIN ISO 1101.5.4 RaDIuS Of CuRVaTuREThe tolerances stated apply for the material groups D, A and cy1)Nominal dimension range12Radius of curvature [mm]3©

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(BDG)up to 5 mmover 5 up to 10 mmover 10 up to 120 mmover 120 mm± 0,30± 0,45± 0,70 ± 0,20 ± 0,35 ± 0,50 ± 0,15 ± 0,25 ± 0,40linear (cf. table 1)1) For investment castings based on

Titanium alloys accuracy grade 1 is

generally validTable 3: Radius of curvature for material groups D, a and TRadii of curvature deviating from table 3 must be agreed on with the investment casting be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

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VDG-MerkblattBDG Reference Sheet

P690Status: September 20105.5 DImENSIONal TOlERaNCE fOR wall ThICkNESSESThe tolerances of wall thickness are dependent on:> the size of the ceramic shell mould> its uninterrupted surface> its possible thermal deformation> its possible thermal deformationTolerances for wall thickness are therefore not dependent on the degree of accuracy. They are limit-ed (or reduced) by thicker edge areas, openings (holes, webs) ribs etc., all of which relieve stress on the

wall the applicable tolerance range, refer to table 4. This contains the lengths of the smallest side of

a surface (with reference to material group) on which the wall-thickness tolerance depends. The toler-ances apply for unmachined surfaces 3: Example for wall-thickness toleranceCase a: The surface formed by dimensions a and b is not interrupted. Dimension b is smaller than di-mension a. Dimension b determines the tolerance of wall thickness. Case B: The area formed by dimen-sions a and b is interrupted by a hole in the centre. The uninterrupted surface is therefore formed by di-mensions b and c. Dimension c is smaller than dimension b. The wall-thickness tolerance is therefore de-termined by dimension 4: wall-thickness tolerancesTo be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

D-40237 Düsseldorf, Phone: (0211) 68 71-252, Fax: -361, 8 of 10©

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P690Status: September 20105.6 DImENSIONal TOlERaNCES fOR PRE-faBRICaTED INSERTS aND CaST-ON PaRTSDiese sind mit der Gießerei zu vereinbaren.6 Surface qualityFor cast surfaces, Ra (CLA) shall be applied in accordance with table estandardsN 7N 8N 9Material group DCLA[µinch]Material group ACLA[µinch]Material group TCLA[µinch]Ra[µm]Ra[µm]Ra[µm]631252501,63,26,31252503,26,32506,3Table 5: Surface roughnessZone N7, N8 and special surface treatment must be agreed separately and entered in the drawing in accordance

with DIN ISO 1302. Unless otherwise agreed, N9 in shot-blasted state is the standard delivery condition.7 Machining allowancesFit sizes on surfaces or low surface roughness, which cannot be achieved by investment casting, receive ma-chining allowances. The allowance must take account of the specific material characteristics and the mathemat-ically least favourable position within the tolerance zone including the tolerances of shape and dimension.8 Additional notes and data8.1 INNER RaDIIRadii at inner corners and edges (concave fillets) prevent casting defects and reduce the notch tension

in the casting during use. The minimum radius should be about 20% of the biggest wall thickness, but

not less than 0.5 mm. It is recommended to select an inner radius which is at least equivalent to the low-est wall thickness.©

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(BDG)8.2 OuTER RaDII aND OuTER ChamfERS8.2.1 material Groups D and a

Unmachined investment castings do not have sharp edges with R=O. For this reason, outer radii and out-er chamfers are always stated as maximum radii, e.g. R< 0.5 max8.2.2 material Group TInvestment castings based on a titanium alloy might have sharp edges due to manufacturing reasons. Cham-fering those edges must be agreed upon between supplier and be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

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P690Status: September 20108.3 hOlES, BlIND hOlES, ChaNNElS, SlOTS aND GROOVESIn order to cast through holes, blind holes, channels, slots and grooves as economically as possible, i.e. with-out preformed ceramic cores, the figures given in tables 6 and 7 should be taken into 6: Dimensions for holes, blind holes and channelsWidth b[mm]Biggest depth belowopen ( l )≈ 1 x b≈ 2 x b≈ 3 x b≈ 4 x bclosed ( t )≈ 1,0 x b≈ 1,0 x b≈ 1,6 x b≈ 2,0 x b2 up to 4over 4 up to 6over 6 up to 10over 10Table 7: Dimensions for slots and grooves8.4 IDENTIfICaTION Of CaSTINGSlf the castings are to be labelled, the letter size (to DIN 1451 „medium”) and the location on the casting

must be agreed on. The VDG reference sheet no. P 701 „ldentification of Castings” should be used as guid-ance. The label may be either cast raised or recessed. Raised letters in a recessed field are preferred. If

the drawing does not contain any instructions, the kind of labelling should be fixed by the supplier.9 Further readingThe entire casting process is described in detail in a brochure entitled „Feingießen Herstellung – Eigen-schaften – Anwendung”, special print of the series „konstruieren + giessen” , No. 1, published by the

BDG, Düsseldorf. It contains practical notes on materials, design and numerous examples of the econo-my of the investment casting process. Company brochures and material data sheets of the German in-vestment-casting foundries in the BDG are available for more information on the products manufactured

by individual be obtained by: BDG-Informationszentrum Giesserei, Sohnstraße 70,

D-40237 Düsseldorf, Phone: (0211) 68 71-252, Fax: -361, 10 of 10©

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