What We Check Before Quoting a Rapid Prototyping Project

A practical RFQ checklist for engineers, designers, and purchasing teams

When a rapid prototyping inquiry arrives, the first question is rarely just, “How large is the part?”

Before preparing a quotation, a manufacturer needs to understand how the component will be used, which features matter most, and what the customer expects from the finished part. Two components that look similar on a computer screen may require very different processes, inspection methods, and production schedules.

A clear request for quotation, or RFQ, helps both sides. The customer receives a more reliable price and lead time, while the manufacturer can identify potential production problems before material is ordered or machining begins.

Disclosure: This article was prepared with AI assistance and reviewed by Dakings Rapid before publication.

1. Is the design information complete?

A 3D CAD file gives us the overall geometry, but it does not always contain everything required for an accurate quotation.

Whenever possible, an RFQ should include:

• A STEP, STP, IGES, or other suitable 3D file
• A 2D drawing for critical dimensions
• Material requirements
• Surface-finish requirements
• Required quantity
• Expected delivery date
• Inspection and reporting requirements

The 3D model shows the physical shape of the component. The 2D drawing communicates the details that should not be left to interpretation.

Threads, inserts, hole specifications, critical tolerances, surface texture, and cosmetic requirements are often easier to communicate on a drawing than in an email.

The file revision should also be clearly identified. Quoting one version and manufacturing another can create unnecessary delays, especially when several people are involved in the same project.

2. What will the prototype be used for?

Not every prototype serves the same purpose.

Some parts are produced only to check appearance, size, or assembly space. Others must carry a load, withstand heat, create a seal, or operate as part of a moving mechanism.

The intended application affects several manufacturing decisions:

• Process selection
• Material selection
• Dimensional tolerances
• Surface finishing
• Inspection requirements
• Whether the prototype must match the final production part

A visual prototype may not require the same material or dimensional control as a functional engineering prototype.

For example, if a component will only be used for a design presentation, appearance may be the main priority. If it will be installed in a working machine, material properties, fit, and dimensional stability may be more important.

Explaining the purpose of the part gives the manufacturer useful context. It can also reveal a more practical manufacturing option.

3. Has the material been specified clearly?

Descriptions such as “aluminum,” “plastic,” or “stainless steel” are often too broad.

Different grades can behave differently during machining, finishing, assembly, and testing. Material availability may also affect the price and delivery schedule.

If the exact grade is important, include it in the RFQ. If it is not fixed, explain how the part will be used.

Useful application information might include:

• Operating temperature
• Mechanical load
• Corrosion exposure
• Electrical requirements
• Weight restrictions
• Cosmetic expectations
• Contact with chemicals or fluids

It is also helpful to state whether an equivalent material is acceptable. A suitable alternative may be easier to source while still meeting the functional requirements of the prototype.

However, material substitutions should always be confirmed before production. A similar appearance does not necessarily mean similar mechanical or thermal performance.

4. Are all the requested tolerances necessary?

Tolerances can have a significant effect on manufacturing cost and lead time.

A common problem is applying tight tolerances to every dimension, even when only a few features affect assembly or performance. Tighter requirements may involve additional machining operations, specialized fixtures, temperature-controlled measurement, or more detailed inspection.

Engineering standards such as ASME Y14.5 provide a common language for communicating geometric dimensioning and tolerancing requirements.

Before submitting an RFQ, identify the features that are genuinely critical:

• Mating surfaces
• Bearing and shaft locations
• Hole positions
• Sealing areas
• Alignment features
• Datum surfaces
• Interfaces with other components

For dimensions without an individual tolerance, a drawing may use a suitable general-tolerance standard. One example is ISO 2768–1, which addresses general tolerances for linear and angular dimensions without individual tolerance indications.

The applicable standard and tolerance class should be stated on the drawing when they are part of the design requirements.

This is not about accepting lower quality. It is about applying precision where precision has a functional purpose.

5. Is the surface-finish requirement clear?

“Black finish” can mean several different things depending on the material and application.

It might refer to anodizing, painting, powder coating, black oxide, electroplating, or another finishing process. These options do not produce identical results. They can differ in appearance, coating thickness, wear resistance, corrosion protection, and cost.

When appearance or surface performance matters, provide:

• The required finishing process
• A color reference
• Gloss or matte preference
• The surfaces considered cosmetic
• Areas that must remain uncoated
• Masking requirements
• Surface-roughness requirements
• Whether minor machining marks are acceptable

Reference photographs can help communicate the desired appearance. However, they should support a written specification rather than replace it. Lighting conditions, camera settings, and different screens can all affect how a color appears.

Finishing can also affect dimensions. Threads, press-fit features, sealing surfaces, and close-tolerance holes may need masking or additional planning.

6. How many parts are required?

Quantity influences more than the total amount of material.

A single prototype may be produced with a simple setup. A larger batch may justify dedicated fixtures, different tooling, or a different production method.

When possible, provide both the immediate requirement and the expected future volume.

For example:

• Initial prototypes for dimensional evaluation
• A small batch for functional testing
• A larger quantity for field trials
• Possible production demand after design validation

This information helps the manufacturer determine whether the proposed process is suitable only for the current prototype or can also support the next stage of the project.

It also reduces the risk of selecting a process that works well for one part but becomes inefficient when the quantity increases.

7. Are there features that may be difficult to manufacture?

A CAD model can contain geometry that is technically possible to design but difficult, expensive, or impractical to manufacture.

For machined components, features that deserve closer review may include:

• Deep, narrow cavities
• Very thin walls
• Small internal corner radii
• Long, slender features
• Difficult tool-access areas
• Deep threaded holes
• Multiple setups with tight positional relationships
• Tight tolerances on flexible sections

These features do not automatically mean the design is unsuitable. They simply require additional evaluation.

A design-for-manufacturability review can help identify whether a small design adjustment might simplify production. More information about this process is available on our CNC machining services page.

The final design decision remains with the customer. The manufacturer’s role is to explain the production implications clearly enough for the customer to make an informed choice.

8. What inspection documentation is required?

“Inspect the parts” can mean different things to different companies.

Some projects require only standard in-process and final inspection. Others may require:

• A dimensional inspection report
• First Article Inspection
• Material certificates
• Surface-finish records
• Certificates of Conformance
• Photographs before shipping
• Measurement of specific critical features
• Project-specific quality documentation

These requirements should be stated during the quotation stage, not after the parts have been completed.

Early confirmation allows the manufacturer to plan the appropriate inspection method and maintain the necessary production records.

9. What does “urgent” mean for this project?

A specific required date is more useful than writing “ASAP.”

The project schedule may include:

• Design review
• Material purchasing
• Programming
• Fixture preparation
• Manufacturing
• Surface finishing
• Inspection
• Packaging
• International shipping

It is important to distinguish between the manufacturing completion date, shipping date, and required arrival date.

The destination country and preferred shipping method should also be included when delivery timing is critical.

If some components are more urgent than others, identify them clearly. Partial delivery may sometimes be possible, but it should be discussed before production begins.

A practical RFQ checklist

Before sending a rapid prototyping or manufacturing inquiry, check whether it includes:

• Current 3D CAD file
• Current 2D drawing
• Material grade
• Acceptable material alternatives
• Required quantity
• Expected future quantity
• Critical dimensions and tolerances
• Applicable drawing standard
• Surface finish and color
• Part application
• Inspection requirements
• Delivery destination
• Required arrival date
• Correct contact information

A complete RFQ does not need to be long. It simply needs to remove the uncertainties that affect manufacturing.

Clear information leads to a more useful technical review and reduces the number of questions exchanged before quotation. It also gives engineering and purchasing teams a better basis for comparing manufacturing proposals.

At Dakings Rapid, we view the quotation stage as part of the manufacturing process. The right questions at the beginning help turn a digital design into a physical part that performs as intended.

If you are preparing a new prototype or precision machining project, you can visit the Dakings Rapid website to explore our manufacturing capabilities and request a project review. This link takes you outside Medium.