precision casting

Terms of delivery:

1. Definition and scope

1.1Investmentcastingisa process by which a high surface quality can be manufacturedthroughtheformation of dimensionally accurate casting.The patternsproducedbyinjection
moulding are heat disposable and are meltedoutaftermanufacture of the ceramic moulds. The ceramic mouldsaredestroyed aftercasting. For this reason, both the pattern andthemoulds are designatedlost using this method. Castingusually takesplace into hot moulds.

1.2 Metals and nickel-based alloys can be used for investment casting.

1.3Thistechnicalmemorandumdoes not apply precious metals cast using thedewaxingmethod,to productsof the jewellery industry,dentallaboratories or toart casting.

2. Purpose

2.1Thistechnicalmemorandumdefines dimensional tolerances, specifies machiningallowancesand surfaceroughness corresponding to the startof the art inthe fieldof investmentcasting. It serves as a basis for optimumeconomiccooperation betweeninvestment casting suppliers and buyers.

2.2Thespecificationsmentionedhererefer to sandblasted preserved or pickledsurfaces in theirdeliveredcondition. Exception must be agreedwherework processes areinvolved
which alter the dimensional tolerances.

2.3Unlessotherwiseagreed,initial samples are supplied for first-timeorders.These are usedtopermit concrete mutual agreement betweensupplier andpurchaser.Initialsamples must be appraised by thebuyer,followed by awritten release tothe foundry for seriesproduction.Deviationacknowledged bythe releaseor with positiveappraisal of theinitialsamples are binding for theproduction processand must beentered intothe(casting) drawing.

3. Dimensional accuracy

3.1 Contraction and shrinkage
Duringthesolidification andcooling of cast metals, a contraction ofthevolumenaturally occurs as aresult of shrinkage. Otherfactorsinfluencing the production of instrument
castingscan resultfromtheshrinkage of the lost pattern and the expansion ofmouldsduringheating. The sum of these influencing factors istakenintoconsideration in the shrinkage
allowance during themanufactureofinjection moulds. The shrinkage allowance isbased onexperiencevalues,depending on the contour of the casting, the ceramicshell andthe castingmaterials, as well as the casting techniques usedin theindividualfoundries.

3.2 Reference planes and reference points
Drawingusedin themanufacture of casting must be gauged systematicallyusingreference orlocating points in order to ensure that dimensionalchecksand subsequentmachining are in agreement. Reference points mustbedetermined right fromthe early design stage and coordinatedbetweenthezero position of thereference planes is precisely defined bymeans ofthe reference pointdimensions. All reference points must bearranged insuch a way that theyare not removed or altered during thesubsequentmachining process.Reference points should be positioned onthe outsidesurfaces of theinvestment casting.They may take the form ofraised orreference pointsare beneficial when dealing with castingswithrestricted shape andposition tolerances. When determining thereferencepoints, attentionshould be paid to ensuring that they do notfall inthe area of asprue. In case of complex shaping,it is possible inthisway to positionthe casting precisely by(pre-)machining thelocatingpoints.

3.3 Over definition
According to DIN 406, overde finition must be avoided. Wall thicknesses must always be specified.

3.4 Mould and draught angles
Mould and draught angles are not necessary as a general
rule.Exceptionstothisfor reason of mould making or casting necessity must beagreedbetween theinvestment casting supplier and the buyer.

4. Dimensional tolerances

4.1 Linear dimensional tolerances
Achievable dimensional tolerances on investment casting are dependent on the following factors:
Casting material
Dimensions and shape of the casting
Validity of the accuracy grade

4.1.2. Dimensions and shape of the casting
Theachievableaccuracy levelof the rated dimensions of an investmentcasting dependson the greatestdimension and the shape of thecasting.If the rateddimension(GTA)exceeds the rated dimension rangeindicated for acertainaccuracy level,the overall tolerance of thecasting must be tolerancedat the accuracylevel (greatest tolerancefield). Deviation outside theaccuracy levelmust be agreed between thesupplier and thebuyer.

Note: The technical infomation above are incomplete. Please contact us for more details.

Our Precision Investment Casting Technology has been applied in theproduction of:

A high standard of surface quality

Low material allowance on surfacesto be machined

Facility for complex shaped innercontours due to the use of ceramic cores

A high degree of dimensional accuracy due to elimination of the mould parting line usually responsible forcasting imprecision

Hardly any restrictions in terms ofmaterials

Almost unlimited scope for theshaping of castings

The investment casting technique is characterized by

Summary

Generallyspeaking,theinvestment castingtechnique is used for small pieceweights ofbetween 1gand 10 kg. Largerwork-pieces up to 150 kg are alsopossible.

Piece weights

Thecastingare producedwithout any trace of flash, and with an excellentsurfacefinish.In manycases-expect for producing the required seatdimensionsthere isno needfor a follow-on machining process.

Surface quality

All castable materials canbe processed using this method. Investmentcasting isparticularly suitableforuse with materials unsuited tomachining.

Material selection

Full service manufacturing of investment castings, including machining,heat treating, passivation, plating, polishing,and painting.

We offer stainless steel, carbon steel or alloy steel casting made by investment casting according to customer's design.

Precision casting made according to customer's design(OEM).