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Investment Casting & CNC Machining FAQs

Answers for Your Custom Manufacturing Project

Find practical answers to common questions about investment casting, materials, tooling, CNC machining, tolerances, quality inspection, samples and project preparation.

If your question is specific to a drawing or application, send us your project information for an engineering review.

Find Answers by Project Stage

Browse common questions by topic, from initial RFQ preparation and material selection to machining, inspection and delivery.

Project & RFQ

Drawing, quotation, samples and project preparation

Casting & Materials

Materials, size, tolerances, tooling and part design

Machining & Secondary Processes

CNC machining, heat treatment and surface finishing

Quality & Inspection

Material verification, dimensional inspection and reports

Production & Delivery

Lead time, progress updates, packing and shipping
Project & RFQ Questions
  • Q1. What information should I provide for a quotation?

    For an accurate quotation, please provide as much project information as possible, including 2D drawings and/or 3D models, material grade, estimated order quantity, critical dimensions and tolerances, heat treatment requirements, surface finishing requirements, and any specific inspection or testing requirements.


    If some details have not yet been finalized, you can still send us the available drawings or models. Our team can review the project and identify any additional information needed before quotation.

  • Q2. Can Zeren review my drawing before tooling begins?

    Yes. Before tooling and production, we can review your drawings from a manufacturing perspective, including casting feasibility, wall thickness, fillets, holes, machining allowances, datum selection, tolerances, and areas that may require secondary machining.


    Where appropriate, we may provide manufacturing suggestions for your review. Any design changes will only be implemented after confirmation with the customer.


  • Q3. What drawing and CAD file formats can I send?

    We can review commonly used engineering file formats such as STEP/STP, IGES, DWG, DXF, PDF, SLDPRT, and other standard 2D or 3D formats.


    STEP or STP files are generally preferred for evaluating 3D geometry, while dimensioned PDF or DWG drawings are useful for confirming tolerances, machining requirements, materials, and technical notes.


    If a complete drawing is not available, you may also provide an existing sample, photographs, sketches, or application information for preliminary evaluation.

  • Q4. Can you produce samples before batch production?

    Yes. Sample production is commonly used for new custom projects before mass production.


    Depending on the project, the typical process may include tooling preparation, sample casting, CNC machining, heat treatment or surface finishing, dimensional inspection, and customer approval.


    Batch production can then proceed based on the approved drawing, sample, and confirmed manufacturing requirements.

Investment Casting & Material Questions
  • Q5. What materials can you investment cast?

    Our main investment casting materials include:

    --Stainless steel
    --Carbon steel
    --Alloy steel
    --Duplex stainless steel
    --Heat-resistant steel
    --Wear-resistant steel

    Material selection should be based on the required strength, corrosion resistance, wear resistance, temperature resistance, machinability, and service conditions of the component.
     

    If you are unsure which grade is suitable, send us the drawing, application, and required mechanical or environmental performance for evaluation.
     

  • Q6. What part sizes and weights can you produce?

    Suitable casting size and weight depend on several factors, including material, geometry, wall thickness, dimensional requirements, tooling design, and subsequent machining or heat treatment.


    Rather than applying one fixed size or weight range to every project, we evaluate each component individually.


    Please send us the drawing or 3D model so we can confirm whether the part is suitable for our investment casting process and production equipment.

  • Q7. What tolerances can investment casting achieve?

    Achievable casting tolerances depend on part size, geometry, material, wall thickness, tooling design, heat treatment, and the location of critical features.


    Investment casting can provide good dimensional consistency for many features, but dimensions requiring tighter control are often finished by CNC machining.


    For critical dimensions, fits, sealing surfaces, bearing locations, threads, or assembly interfaces, we recommend clearly identifying the required tolerances on the drawing so that the appropriate casting and machining process can be evaluated.

  • Q8. Can logos, part numbers, or identification marks be added?

    Yes. Depending on the component design and identification requirements, logos, part numbers, batch numbers, or other markings may be produced by methods such as cast-in marking, laser marking, engraving, or machining.


    The most suitable method depends on the size of the marking, required appearance, production quantity, and whether the marking needs to remain visible after machining or surface treatment.


    Please indicate the required marking position and content on the drawing where possible.

  • Q9. Can you help evaluate whether my part is suitable for investment casting?

    Yes. We can review the component geometry and manufacturing requirements to determine whether investment casting is an appropriate production method.


    Typical evaluation points include wall thickness, draft and access conditions, internal cavities, holes, ribs, fillets, dimensional requirements, machining allowances, and potential deformation or shrinkage risks.


    If certain features may be difficult or costly to produce directly by casting, we can identify them during the engineering review and discuss possible manufacturing alternatives.

CNC Machining & Secondary Process Questions​​​​​​​
  • Q10. Can you provide CNC machining after casting?

    Yes. We provide CNC machining for cast components when tighter tolerances, functional surfaces, or assembly features are required.


    Typical machined features include:
    --Mounting faces
    --Sealing faces
    --Bores
    --Threads
    --Holes
    --Slots
    --Grooves
    --Keyways
    --Chamfers
    --Datum and positioning surfaces


    Combining casting and machining within one project can simplify supplier coordination and help maintain consistency between the casting datum, machining process, and final inspection requirements.

  • Q11. Can you provide heat treatment?

    Yes. Heat treatment can be arranged according to the material grade and required mechanical properties of the component.


    Depending on the application, heat treatment may be used to improve properties such as hardness, strength, toughness, wear resistance, dimensional stability, or overall material performance.


    The specific heat treatment process should be determined based on the material specification, drawing requirements, and intended service conditions.

  • Q12. What surface finishing options can you provide?

    A range of surface finishing options can be provided depending on the material, application, and appearance requirements.


    Common options may include:

    --Bead blasting
    --Polishing
    --Passivation
    --Black oxide
    --Powder coating
    --Plating
    --Other project-specific finishing processes


    The achievable surface condition depends on the original casting surface, machining requirements, geometry, and finishing process.


    If the appearance or surface performance is critical, please provide the relevant specification, reference sample, photograph, or required surface standard during quotation.

     

     

  • Q13. Can you supply finished parts instead of raw castings?

    Yes. We can support projects ranging from raw investment castings to more complete finished components.


    Depending on the project, supplied parts may include casting, CNC machining, heat treatment, surface finishing, marking, dimensional inspection, and final packing.


    This allows customers to receive components closer to their final assembly condition rather than coordinating multiple manufacturing suppliers separately.

     

     

Quality & Inspection Questions​​​​​​​
  • Q14. How do you control quality during production?

    Quality control begins before production with drawing and technical requirement review.


    Depending on the project, quality control may include:

    --Incoming material verification
    --Tooling and sample confirmation
    --In-process dimensional checks
    --Casting visual inspection
    --Machining inspection
    --Material and hardness testing
    --Final dimensional inspection
    --Pre-shipment verification


    Critical dimensions and inspection requirements are reviewed according to the drawing and agreed project specifications.


    For new or complex components, sample or first-article approval may be completed before full batch production.

  • Q15. What inspection equipment do you use?

    Inspection equipment is selected according to the component geometry, tolerance, material, and customer requirements.


    Our inspection capabilities include equipment such as:

    --Coordinate Measuring Machine (CMM)
    --Optical or 3D scanning equipment
    --Spectrometers
    --Hardness testers
    --Height gauges
    --Micrometers
    --Vernier calipers
    --Gauges and inspection fixtures
    --Microscopic inspection equipment


    For complex dimensions or critical geometric features, suitable inspection methods can be confirmed during project review.

  • Q16. What inspection reports can you provide?

    Inspection documentation can be provided according to project requirements.


    Typical reports may include:

    --Dimensional inspection reports
    --Material or chemical composition reports
    --Hardness test results
    --First Article Inspection reports
    --Inspection photographs
    --Pre-shipment photographs or videos


    Additional testing or third-party inspection can also be discussed when required by the customer or application.


    Required reports should preferably be identified during quotation so they can be included in the inspection plan and project cost evaluation.

     

     

  • Q17. Can critical dimensions be inspected before shipment?

    Yes. Critical dimensions can be identified on the drawing and included in the inspection requirements before shipment.


    These may include dimensions related to: 


    --Assembly interfaces
    --Datum surfaces
    --Bores
    --Threads
    --Hole positions
    --Mounting surfaces
    --Sealing surfaces
    --Critical fits and clearances


    For dimensions requiring special gauges, CMM inspection, fixtures, or additional measurement procedures, the inspection method can be confirmed before production.

Production, Lead Time & Delivery Questions
  • Q18. What is the typical lead time for a custom casting project?

    Lead time varies according to the specific project.


    Factors that may affect the schedule include tooling requirements, component complexity, material, order quantity, CNC machining, heat treatment, surface finishing, inspection requirements, and sample approval.


    For new projects, the schedule normally includes separate stages for tooling, sampling, customer approval, and batch production.


    An estimated project schedule will be provided during quotation after the drawing and manufacturing requirements have been reviewed.

  • Q19. Will I receive production updates?

    Yes. For custom manufacturing projects, we can provide progress updates at key production stages when required.


    Depending on the project, updates may cover stages such as:

    --Tooling
    --Sample production
    --Investment casting
    --CNC machining
    --Heat treatment
    --Surface finishing
    --Inspection
    --Packing and shipment preparation


    For long-production-cycle or technically complex projects, keeping the customer informed at important manufacturing milestones can help identify questions earlier and improve project coordination.

  • Q20. What shipping options are available?

    Shipping can be arranged according to the order size, destination, delivery requirement, and agreed Incoterms.


    Common options include:

    --Express courier
    --Air freight
    --Sea freight


    Packing and transportation methods can also be selected according to part size, weight, surface condition, corrosion protection requirements, and the risk of damage during transportation.


    For larger or heavier shipments, suitable cartons, wooden cases, pallets, or other protective packaging can be discussed before shipment.

  • Q21. What happens if a quality issue is found after delivery?

    If a quality issue is reported after delivery, we will first review the affected parts together with the relevant drawing, approved sample, inspection requirements, photographs, measurement data, and production records.


    The purpose is to identify the actual cause and determine whether the issue is related to casting, machining, heat treatment, finishing, inspection, packing, or another stage of production.


    Where appropriate, corrective actions can then be discussed based on the confirmed cause and affected quantity.


    Providing clear photographs, measurement results, part numbers, batch information, and a description of the issue can help us review the case more efficiently.

Need More Detailed Technical Information?

Explore detailed resources for engineering review, supplier evaluation and project preparation.

Technical Downloads

Design guidelines, tolerance references and RFQ preparation resources.

Quality Assurance

Inspection equipment, quality processes and available reports.

Manufacturing Capabilities

Investment casting, CNC machining, heat treatment and surface finishing.

Have a Project-Specific Question?

Send Us Your Drawing for a Manufacturing Review
 
Every custom casting project is different. Send us your drawing, 3D model, material requirements, quantity and critical specifications, and our team can review the casting, machining and inspection requirements for your project.
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