Uploading a model and receiving a price is the visible part of an online machining service. The part that decides whether the order runs smoothly is the engineering work behind the quote: how the model was interpreted, what was assumed about tolerances, and who checks that the answer matches the drawing.
What an online quote should tell you
A price on its own is not a quotation. A usable reply names the material and condition priced, the finishing operation and where it applies, whether inspection is included, the revision the price refers to, and any feature the supplier believes cannot be produced as drawn. The last item is the most valuable, because it is the only part of the reply that can save a revision.
| In the quote | Why it matters |
|---|---|
| Material and condition | Determines machinability, finish and whether the prototype predicts production |
| Finish and its scope | Finishing is a separate operation with its own handling cost |
| Inspection included | Distinguishes a dimensional record from a visual check |
| Revision reference | Prevents a batch being made to a superseded drawing |
| Manufacturability notes | Flags features that will not hold, before the machine runs |
Which files and inputs prevent a second quote
A solid model plus a drawing that carries intent.
The model defines the geometry, and the drawing defines everything geometry cannot express: which dimensions carry the fit, what the surface condition is, which datum the measurements reference, and whether a limit applies before or after finishing. Sending one without the other forces the supplier to infer, and an inferred assumption is what a second quotation is usually correcting. 6CProto accepts STEP, STP, IGES, IGS, SLDPRT, 3DM, SAT and X_T, and returns manufacturability comments with the price.
Two details outside the files also change the number. Quantity tells the supplier how far the fixed block can spread, and a note on whether the order repeats changes how much fixture work is worth doing. Neither is obvious from the model, and both are cheap to state.
How the price is actually built
Online pricing looks like a single figure but behaves like two. Programming, fixturing and first-article inspection form a fixed block charged once per order; cycle time, material and secondary operations form a per-part block. Moving from one piece to ten lowers the unit price considerably, and moving from ten to a hundred lowers it again if the routing stays the same.
Where two online quotes differ sharply, the cause is usually routing rather than rate. One may assume a single setup and the other two, or one may include a finishing operation the other has not priced. Asking each supplier to state the setups and the operations included makes the comparison meaningful, and it is the same discipline that makes an in-house quote reviewable. Cost structure guidance for small manufacturers is published by the NIST Manufacturing Extension Partnership.
Where an online order usually stalls
Orders rarely stall in machining. They stall at four handoff points: an ambiguous drawing waiting to be queried, a finish callout arriving after production, a revision released while the machine is running, and a packing requirement nobody specified. Each is removed by information supplied at the start rather than by chasing later.
The revision case is the most common and the most avoidable. Releasing a small change mid-batch splits one delivery into two revisions under one inspection record, which makes the paperwork harder to defend than the change was worth. Booking it as its own release keeps the parts traceable and makes the cost of the change visible while the decision is still cheap.
What should come back with the parts
The baseline pack is material identification, the inspection record for the features the drawing controls, and a clear link between the parts in the box and the revision they were made to. Regulated industries need more, and the requirement is best established before production rather than reconstructed during an audit.
For repeat orders, ask for the inspection format to stay the same between batches. A consistent record makes drift visible: two reports describing the same dimensions the same way show a process moving before it produces a rejected part. Where a drawing needs modification to make that possible, the drawing conventions followed are those published by ASME, surface-condition terminology by ASTM Committee B08, material behaviour data by ASM International, and machining-waste handling obligations by the US EPA.
How to judge an online service before the first order
One test order answers most of the questions a capabilities page cannot. Send a part with one genuinely awkward feature, at the quantity you actually need, and compare three things: whether the quote mentioned that feature, whether the inspection report addressed it in a way you can check, and whether the person who answered the technical question was the person who had read the drawing. Those three signals predict the second order better than any certification list.
It is also worth checking how the service handles a change. A revision released before cutting should produce a new quote with an explanation, not a silent edit to the program; a revision released after cutting should produce a clear statement of what is already finished and what is scrap. Ask how that is handled while the first order is still small. Design and inspection conventions are described under precision machining and standards and tolerances.
Upload a model and drawing to receive a manufacturability review with the quotation instead of a price alone.
FAQ
How much does CNC machining cost per hour?
Hourly rates are quoted per job rather than published as a single figure, because machine type, tolerance and material all change the rate. What is comparable between suppliers is the split between the fixed block and the per-part block.
Where can I find online machining services?
Look for a service that accepts a solid model with a drawing, returns manufacturability comments before quoting, and states what inspection is included. 6CProto quotes from uploaded CAD files and returns the review with the price.
What should be in the file package for an online quote?
A STEP or IGES solid, a drawing carrying tolerances and finish, the quantity, and one line on what the part does. Together they remove the clarification round that otherwise arrives before machining starts.