Should a Drawing Requirement Change When a Supplier Says It Is Difficult to Manufacture?
For OEM equipment manufacturers and machine builders, a supplier may sometimes review a custom fastener drawing and suggest changing a tolerance, dimension, feature, material or other requirement because the part is difficult to manufacture.
That feedback can be useful, but it does not automatically mean the requirement itself needs to change.
Manufacturing difficulty is not necessarily a drawing problem. Before changing a requirement, it is useful to understand what is creating the difficulty and whether it comes from the requirement itself, the combination of requirements or the manufacturing approach being considered.
Why Might a Supplier Ask for a Drawing Change?
The Requirement May Create a Real Manufacturing Constraint
Some requirements can have a significant effect on how a part is manufactured or verified. A tight tolerance, geometric requirement, material condition, thread, surface requirement or local feature may introduce additional manufacturing or inspection constraints. In these situations, understanding why the requirement is difficult matters before deciding whether a change is appropriate.
Several Requirements May Become Difficult Together
A supplier's concern may not come from one requirement in isolation. Dimensions, tolerances, geometry, material, heat treatment and surface requirements may each be achievable individually while their interaction makes a particular manufacturing approach more difficult to control. The manufacturing question may therefore be about the combination of requirements rather than one specification being inherently unsuitable.
The Difficulty May Be Specific to a Manufacturing Approach
A requirement that is difficult under one manufacturing route may be more compatible with another. Different processes, equipment, production sequences or supplier setups can create different constraints around the same drawing. A request to change the drawing can therefore reflect the limits or fit of a proposed manufacturing approach—not necessarily a need to change the finished-part requirement.
Project Conditions May Influence the Recommendation
Quantity, production stage, inspection requirements and repeat-production expectations can also affect how a supplier evaluates a requirement. A manufacturing route that is reasonable for a prototype may create different constraints at repeat-production volume, while an approach designed around larger quantities may not fit a small initial batch. The reason behind a proposed drawing change should therefore be considered in the context of the project.
Does Manufacturing Difficulty Mean the Requirement Should Change?
Not automatically.
A drawing requirement exists to define something the customer needs from the finished part. A manufacturing concern identifies a difficulty in producing or verifying that requirement under a particular set of conditions.
These are related, but they are not the same decision.
Sometimes changing a requirement may be the appropriate project decision. In other cases, it may be worth reviewing the manufacturing approach before deciding whether the drawing needs to change.
When Is a Proposed Drawing Change Worth Reviewing?
A proposed drawing change may be worth reviewing from the manufacturing side when accepting the change would affect an engineering requirement or project decision.
Common situations include:
- A supplier asks to relax a critical tolerance before quoting or sampling.
- A feature that is important to the part's function is proposed for removal or modification.
- One supplier requests a drawing change while another considers the existing requirement manufacturable.
- The proposed change would require engineering approval, customer approval or revalidation.
- A supplier explains that the requirement is difficult for its current process or equipment.
- A requirement that was previously achieved becomes difficult under a new supplier, quantity or production stage.
These situations do not mean the proposed drawing change is unnecessary. They are signals that the manufacturing reason behind the requested change may be worth understanding before the project commits to a revised requirement.
What Should Be Reviewed Before Changing a Requirement?
When a supplier proposes changing a drawing requirement because of manufacturing difficulty, consider:
The purpose of this review is not to avoid drawing changes, but to understand what manufacturing problem the proposed change is intended to solve.
What Helps With a Manufacturing Review?
If a supplier has proposed changing a drawing requirement because of manufacturing difficulty, the drawing alone may not explain whether the requirement itself is the limitation. Reviewing the drawing together with the proposed change, the supplier's reason and the relevant project conditions can help clarify what manufacturing problem the change is intended to solve.
Useful information includes:
Technical drawing
Supplier's proposed change
Supplier's reason for requesting the change
Critical function or requirement affected by the proposed change
Expected quantity and production stage
Prototype, inspection or validation information, if relevant
Has a Supplier Asked You to Change a Drawing Requirement?
If a supplier has suggested changing a tolerance, feature, material or other drawing requirement because of manufacturing difficulty, send us the drawing together with the proposed change and the reason the supplier provided.
We can review the part from the manufacturing side and help identify whether the difficulty may be related to the requirement itself, the interaction between requirements, the proposed manufacturing approach, inspection or another project condition.
Send Drawing for Manufacturing Review