investment 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 patternsproduced byinjection
moulding are heat disposable and are melted outaftermanufacture of the ceramic moulds. The ceramic moulds aredestroyedafter casting. For this reason, both the pattern and themoulds aredesignated lost using this method. Casting usually takesplace into hotmoulds.

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

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

2. Purpose

2.1Thistechnicalmemorandum defines dimensional tolerances, specifiesmachiningallowances and surface roughness corresponding to the start ofthe art inthe field of investment casting. It serves as a basis foroptimumeconomic cooperation between investment casting suppliers andbuyers.

2.2Thespecifications mentionedhererefer to sand blasted preserved or pickledsurfaces in theirdelivered condition. Exception must be agreedwhere work processes areinvolved
which alter the dimensional tolerances.

2.3Unlessotherwiseagreed,initial samples are supplied for first-timeorders.These are usedto permit concrete mutual agreement betweensupplier andpurchaser.Initial samples must be appraised by thebuyer,followed by awritten release to the foundry for seriesproduction.Deviationacknowledged by the releaseor with positiveappraisal of theinitialsamples are binding for the production processand must beenteredintothe (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 of mouldsduringheating. The sum of these influencing factors istakenintoconsideration in the shrinkage
allowance during themanufacture ofinjection moulds. The shrinkage allowance is based onexperiencevalues,depending on the contour of the casting, the ceramicshell andthe casting materials, as well as the casting techniques usedin theindividual foundries.

3.2 Reference planes and reference points
Drawingusedin the manufacture 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, attention should be paid to ensuring that they do notfall inthe area of asprue. In case of complex shaping,it is possible inthisway to position the 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.Exceptionstothis for reason of mould making or casting necessity must beagreedbetween the investment 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 greatest dimension 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 accuracy level (greatest tolerancefield). Deviation outside theaccuracy level must be agreed between thesupplier and thebuyer.

Note: The technical info above are incomplete. Please contact us for more information.

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 of materials

Almost unlimited scope for the shaping of castings

The investment casting technique is characterized by

Summary

Generallyspeaking,theinvestment casting technique is used for small pieceweights of between1g and 10 kg. Largerwork-pieces up to 150 kg are alsopossible.

Piece weights

Thecastingare produced without any trace of flash, and with an excellentsurfacefinish.In many cases-expect for producing the required seatdimensionsthere isno need for a follow-on machining process.

Surface quality

Allcastablematerials can be processed using this method. Investmentcasting isparticularly suitable for use with materials unsuited tomachining.

Material selection

Fullservice manufacturing of investment castings, including machining,heattreating, passivation, plating, polishing,and painting.

We offer stainless steel, carbon or alloy steel casting made by investment casting in accordance with customer's design.

Investment casting

Investment casting made according to customer's drawing(OEM)
Material: Stainless steel, carbon steel, alloy steel