All procurement guides · By ZDPTFE
Use a controlled drawing with the model
A 3D model describes geometry, but the purchasing package also needs a clear statement of requirements. Provide a drawing number, revision, units and material specification. Add dimensions for the interfaces that determine whether the part fits. Identify the authoritative document if the PDF and model disagree, and resolve the discrepancy before approving manufacture.
Explain critical dimensions and measurement conditions
PTFE can be challenging to machine to narrow tolerances because of its low strength and high thermal expansion, as described in Ensinger's machining guidance. Review feasibility for the actual geometry and grade rather than adopting a blanket tolerance. In your RFQ, distinguish critical mating dimensions from general dimensions and ask how the critical features will be measured.
Describe the part in its assembly
For a bushing or sleeve, include the mating bore or shaft and identify which surfaces locate the part. For a valve seat, show the sealing profile and its relationship to the valve assembly. For an insulator, include the mounting arrangement. State whether the drawing describes the free part or an assembled condition. These details help the supplier identify questions that a standalone model may not answer.
Define inspection and sample acceptance
List the dimensions to appear on a report and specify any required inspection method or conditioning procedure. Identify visual requirements, edge treatment and marking locations. If a sample is needed, agree who approves it and what evidence constitutes acceptance. Keep approval of geometry separate from validation of the finished equipment's operating performance.
Manage revisions through the order
Send one current drawing package with a concise change list when updating a request. Ask for confirmation of the revision used in the quotation and production order. Keep the approved material and inspection requirements with the drawing so repeat orders do not rely on an old email attachment or a sample whose revision is unknown. Include quantity and delivery requirements when requesting the updated quotation.
Technical reference: Ensinger: PTFE machining. Supplier guidance is background information, not a statement of ZDPTFE manufacturing capability.
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