Prototyping services look interchangeable on a capabilities page and behave very differently on the third revision. The distinction that matters is not how many machines a supplier lists but how much engineering work happens between your upload and the first cut.
What to compare between two prototyping services
Compare the workflow, not the equipment list. Four points separate suppliers quickly: whether the quotation carries written manufacturability comments, whether the same process will still be available when the part moves to a pilot batch, whether inspection is defined before production, and who answers your questions once the order is placed. A supplier strong on all four removes a revision from the programme; one weak on any of them adds one.
| Comparison point | Weak signal | Strong signal |
|---|---|---|
| Quotation | Price only | Price with manufacturability notes |
| Process continuity | Prototype on one process, pilot on another | Same routing family from first article to repeat batch |
| Inspection | Report on request, format unknown | Agreed dimensions and datums before cutting |
| Communication | Contact changes each message | Named engineer for the programme |
RFQ inputs that prevent a second quotation
Most re-quotes happen because one of five facts was missing: material and condition, quantity and whether it repeats, finish and where it applies, the inspection expectation, and which features are allowed to move if the process cannot hold everything. Sending those five with the model removes the clarification loop, which is usually longer than the machining itself.
File format matters less than completeness. A STEP or IGES solid carries the geometry; the 2D drawing carries the intent that geometry cannot express, including threads, surface condition and datum references. 6CProto accepts STEP, STP, IGES, IGS, SLDPRT, 3DM, SAT and X_T, and reviews the model for manufacturability before quoting.
Keeping the prototype and the pilot batch consistent
A prototype that passes on one process and a pilot batch produced on another has validated a design, not a production route. Where the quantity is small enough, keeping machining as the production process avoids that re-qualification entirely; where the part will eventually be molded, the prototype is most useful when it reproduces the material and finish the mold will use. Deciding which of those two the prototype is for changes what should be specified. Related process detail sits on the CNC machining and rapid prototyping pages.
First article expectations on a service order
On a service order the first article is the only point where a mistake is still cheap, so it deserves its own decisions. Agree which dimensions will be reported, from which datum, and whether the report is a dimensional record or a comparison against the drawing. For assemblies, add the fit check that matters most, because a part can pass every dimensional callout and still not seat.
It is also worth saying explicitly what the prototype is for. A part that will be photographed needs cosmetic surfaces controlled; a part that will be tested to failure needs material and heat treatment fixed; a part that will be used to validate an assembly needs the interfaces controlled and the rest relaxed. One sentence of context usually changes the routing advice you receive.
Where the cost of a prototype actually sits
At prototype quantities, price is dominated by work that is performed once: programming, fixturing, tool selection and first-article verification. Material and cycle time matter, but they rarely explain why two quotes differ by a factor of two. When they do differ that much, the cause is usually a different assumed process, a different setup count, or a finish that one supplier planned and the other did not.
The consequence is that arguing about the unit price at five pieces is less useful than changing the inputs: consolidating revisions, relaxing non-functional callouts, or moving to a batch size that lets the fixed block spread. Suppliers who itemise the fixed block make that conversation possible; suppliers who quote a single number do not. Cost structure is discussed further in the quotation workflow.
How to keep a prototyping programme from slipping
Prototype schedules rarely slip during machining; they slip in the gaps. The three largest are the wait for a clarification, the queue for finishing after machining, and the rework that follows a first article nobody measured properly. Booking the finishing slot before the machining slot, and agreeing the inspection format before the first cut, removes two of the three without making anything faster.
The third gap is a communication habit rather than a technical problem. Designate one person on each side to answer technical questions, and record the answer in the order rather than in a chat thread. When a drawing is ambiguous, the supplier’s interpretation becomes part of the delivered part, so both parties should be working from the same written assumption. Supply-chain practice for small manufacturers is documented by the NIST Manufacturing Extension Partnership, material behaviour references are published by ASM International, and coating callouts follow ASTM Committee B08. Compare routes on the CNC milling and precision machining pages before fixing the process.
Write the assumption into the order rather than into a message thread, and confirm the revision the quotation refers to. Drawing conventions are standardised through ASME, and material condition definitions through ASM International.
Upload a model to request a prototyping quote and receive manufacturability comments with the price.
FAQ
How do I choose between two prototyping services with similar prices?
Compare the engineering content of each quote. Written manufacturability comments, an agreed inspection format and the same process route from prototype to pilot batch are worth more than a small price difference, because they remove a revision later.
Should a prototype be made on the process that will eventually produce the part?
Where the part will be machined in production, keeping the same process validates both the design and the route. Where the part will be molded, the prototype should reproduce the material and finish of the mold so the tests predict something useful.
How many prototypes should I order for a first article?
Order enough to inspect, assemble and test without relying on a single part, and no more. Extra pieces only reduce the unit price because the fixed block spreads, so the useful number is driven by how many tests the design has to survive.