Internal 5-Axis CNC Factory Solution: How to Choose One That Holds Tolerance
A practical guide for engineers and sourcing teams comparing 5-axis suppliers. We cover the checks that decide whether a shop can actually hold ±0.005 mm, what machine travel limits to ask about, and where quotations usually hide risk.
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What matters before you send an RFQ
5-axis supplier checks: what to ask, what to accept
Use this as a scoring sheet. Mark each row pass or fail before you compare price.
| Check | Weak answer | Acceptable answer | Why it matters |
|---|---|---|---|
| Axis control | We have 5-axis machines | 16 simultaneous 5-axis centers | Indexed 3+2 cannot cut a true contoured surface |
| Tolerance | We hold tight tolerance | ±0.005 mm (±0.0002 in) | Sets the floor for bearing bores and seal faces |
| Max part size | Depends on the part | 4,000 mm maximum processing size | Large frames and housings may not fit |
| Rotary table | Standard table | Ø400 mm rotary table | Small tables limit swing and part rigidity |
| Finish range | Good surface finish | Ra 0.2–0.8 μm fine, Ra 1.6–3.2 μm as-machined | Sealing and mating faces need a stated Ra |
| Certifications | ISO certified | ISO 9001, IATF 16949, ISO 13485, ISO 27001 | Medical and automotive buyers need the right one |
| MOQ | Minimum 100 pieces | No minimum order quantity | Prototype runs should not be blocked by MOQ |
| Quote turnaround | We will get back to you | Quotation and free DFM within 12 hours | Slow quoting hides a slow engineering team |
How to tell a real internal 5-axis CNC factory solution from a 3+2 shop
Most suppliers claim five-axis capability. Fewer can run all five axes at once. The difference shows up the moment your part has a ruled surface, a blended fillet, or a port that must be machined without a witness line. On an indexed 3+2 machine the table tilts, locks, and cuts. The tool path is still a three-axis path. On a simultaneous machine the rotary axes move while the tool is in the cut, so the tool tip stays normal to the surface through the whole pass.
Ask one question and the answer is hard to fake: how many axes are interpolating during a finishing pass? If the answer is two rotary plus three linear, you have a simultaneous machine. If the answer is that the table indexes between operations, you do not. This matters for impellers, turbine blades, medical bone plates and any part with a continuous compound curve.
The second tell is the rotary table size. A Ø400 mm rotary table sets the swing you can hold rigidly. Parts that overhang the table vibrate, and vibration shows up as chatter in the finish. For a 5-axis CNC factory solution to be useful on real work, the table has to match the part family you are sending, not just the one-off sample.
Third, look at the spindle reach. Five-axis access is only useful if the tool can get to the feature without the holder hitting the wall. Deep cavities and undercuts need long, slim holders, and those deflect. A shop that quotes a five-axis cycle on a part with a 4:1 depth-to-diameter pocket should also tell you how it will control deflection.
- 1Ask for the axis countTwo rotary plus three linear, interpolating at the same time.
- 2Ask for the tableDiameter and load rating, in writing.
- 3Ask for a sample pathA short tool-path plot shows whether the rotaries move in the cut.
Tolerance, finish and the features that break a quotation
±0.005 mm is a real number, not a slogan. Holding it across a batch depends on thermal stability, tool wear compensation, and how the part is held. A thin wall will move when you unclamp it. A long bore will taper if the tool deflects. The shop has to plan for that before the first cut, not inspect it out afterward.
When you read a quotation, look for the features the shop flagged. A good 5-axis CNC factory solution will call out a thin web, a deep bore, or a tight true-position callout and explain how it will hold it. A quotation that lists only a price and a lead time has not been engineered yet.
Surface finish is the second place where quotations get vague. State the Ra you need on each face. Ra 0.2–0.8 μm is a fine finish and usually needs a separate finishing pass or a polishing step. Ra 0.8–1.6 μm is a typical high finish. Ra 1.6–3.2 μm is as-machined. If the drawing says only 'smooth', expect an argument at inspection.
Material choice also moves the tolerance window. Aluminium 6061 and 7075 cut cleanly and hold ±0.005 mm well in a temperature-controlled shop. Stainless 316L work-hardens, so light passes and sharp tools matter. Titanium Ti-6Al-4V and Inconel generate heat at the cutting edge and need lower surface speed and more coolant. Do not assume the same feeds apply across all three.
- 1State Ra per faceNot one number for the whole drawing.
- 2Flag thin walls earlyBelow 1 mm the clamping plan changes.
- 3Match material to processTitanium and Inconel need different parameters than aluminium.
Setup count, supply chain and what one vendor should cover
Every setup adds a datum. Move a part from one machine to another and you re-establish origin, and the stack-up grows. A single simultaneous 5-axis operation that reaches five faces removes those re-datums. That is the cost argument, and it is usually larger than the hourly rate difference between shops.
The second cost driver is the number of vendors in the chain. If the same shop can mill, turn, finish and inspect, you avoid shipping parts between suppliers and re-qualifying each one. GreatLight runs 127 high-precision CNC machines across 3 wholly-owned plants covering 7,600 m², with 150 technicians, so a part can move from 5-axis milling to finishing without leaving the group.
Certifications decide which industries you can serve. ISO 9001:2015 covers general quality management. IATF 16949:2016 is the automotive and EV requirement. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which matters when your drawings are confidential. Ask which certificate applies to the plant that will actually run your part.
Confidentiality is part of the buying decision, not an afterthought. Uploads should be secure, and an NDA should be available on request before you send detailed drawings. If a supplier hesitates on an NDA, that is a signal about how they treat customer data in general.
- 1Count the setupsFewer datums means less stack-up.
- 2One vendor, several processesMilling, turning, finishing and inspection under one roof.
- 3Match the certificate to the plantThe certificate must cover the site doing the work.
Volume, lead time and the MOQ trap
A 5-axis CNC factory solution should scale from one piece to a production run without changing suppliers. Minimum order quantity is the usual blocker. If a shop needs 100 pieces before it will quote, you cannot prototype there. GreatLight sets no minimum order quantity, so a single prototype and a 10,000+ part run go through the same quoting process.
Lead time has two halves and buyers often only hear one. The first half is quotation and DFM feedback. The second is production. Ask for both. A fast shipping date on top of a two-week quoting delay is not fast. Quotation and free DFM analysis within 12 hours, with production able to start within 24 hours, keeps the front half short.
For finished parts, a 3–5 day shipping window is the working range once production starts. That number depends on material availability and the finishing step, so treat it as a planning input rather than a promise. A shop that tracks its own late-delivery rate is more useful than one that guarantees a date it cannot control.
Where the real risk sits is at the interface. If the shop quotes the machining but excludes heat treatment, anodizing, or inspection reports, your total lead time includes those outside steps. Ask what is included and what is passed through to a subcontractor.
- 1No MOQOne prototype to 10,000+ parts on the same process.
- 2Quote in 12 hoursWith free DFM feedback on the drawing.
- 3Ask what is excludedHeat treatment, finishing and reports are common exclusions.
Inspection reports and the questions that expose weak quality control
Inspection is where a low quote usually hides. The machining price is visible; the metrology behind it is not. Ask what is measured, on what machine, and how often. Raw material check, in-process monitoring, and final inspection are the three stages that catch different failures. Final inspection alone catches the wrong things late.
A CMM report should show the datum scheme, the nominal, the actual, and the deviation. If a supplier sends a single pass or fail sheet with no numbers, you cannot tell whether the part is close to the limit or comfortably inside it. For a first article on a 5-axis job, ask for the full dimensional report.
Sampling plans matter on production runs. A 100% inspection before shipment is the baseline for tight-tolerance work. For high-volume parts, a documented sampling plan with a defined AQL is normal, but the sampling rate has to be stated in the purchase order, not assumed.
The last check is traceability. Can the shop tie a finished part back to a material lot and a machine? On automotive and medical work that traceability is a requirement, not a nice-to-have. Ask how long records are kept before you place the first order.
- 1Three inspection stagesIncoming material, in-process, final.
- 2Numbers, not pass or failNominal, actual and deviation on the report.
- 3Trace the lotMaterial certificate tied to the finished part.
How to run the supplier selection in 6 steps
Run these in order. Do not skip to price.
- 1Sort parts by feature typeSplit your list into parts with compound curves or undercuts, and parts that are prismatic. Only the first group needs simultaneous 5-axis. Sending a simple bracket to a 5-axis cell wastes money.
- 2Match part size to machine travelList the largest envelope for each part. Compare against travel ranges such as 4,000 × 400 × 150 mm, 750 × 1,150 × 550 mm, and 500 × 500 × 450 mm. Parts outside the envelope need a different plan.
- 3Write the tolerance and Ra per facePut ±0.005 mm only on the features that need it. Mark Ra 0.8–1.6 μm on sealing faces and leave the rest as-machined at Ra 1.6–3.2 μm. Over-specifying drives cost with no benefit.
- 4Request DFM feedback with the quoteAsk for a written DFM note, not just a price. A useful note calls out thin walls, deep pockets, and any feature that needs a second setup.
- 5Confirm certification and inspection scopeName the certificate the project needs and the inspection report format you expect. Confirm both cover the plant that will run the job.
- 6Place a first-article order before the production runRun one piece and inspect it fully. Compare the report against the drawing, then release the batch. This catches datum and finishing issues while they are still cheap to fix.
Questions buyers ask before choosing a 5-axis supplier
What is an internal 5-axis CNC factory solution?
It means one factory group holds the 5-axis machining, turning, finishing and inspection steps instead of passing the part between separate vendors. The part stays inside one quality system and one scheduling queue.
For the buyer, the practical effect is fewer setups, fewer shipping handoffs, and one point of contact when something needs rework.
Do all my parts need simultaneous 5-axis machining?
No. Prismatic parts with features on three or four faces can often run on a 3-axis or 4-axis machine at a lower rate. Simultaneous 5-axis earns its cost on compound curves, contoured pockets, deep undercuts, and parts that would otherwise need four or five re-fixtures.
A good supplier will tell you when a part does not need 5-axis. If every part gets quoted on the most expensive machine, ask why.
What tolerance can I realistically expect?
±0.005 mm (±0.0002 in) is achievable on well-supported features in a temperature-controlled shop, with the right material and a stable setup. Thin walls, long bores, and unsupported overhangs will widen that window.
Give the tolerance only where the function requires it. A drawing with ±0.005 mm everywhere raises cost and inspection time without improving the part.
How do I compare quotations that use different scope?
Normalize the scope first. Check whether each quote includes material certification, heat treatment, surface finishing, inspection reports, and packaging. Then compare the machining line.
A lower price that excludes finishing is not a lower price. It is a smaller scope.
Is there a minimum order quantity?
At GreatLight there is no minimum order quantity, so a single prototype and a 10,000+ part run both go through the same quoting process. That lets you validate a design on the same process that will produce the volume.
Some shops quote prototypes on a different process than production. Ask whether the prototype and the production part come off the same machine type.
How is my design data protected?
Uploads are treated as secure and confidential, and an NDA is available on request before you send drawings. ISO 27001:2022 covers the information security side of the operation.
Ask for the NDA before the RFQ, not after the order. The answer tells you how the shop handles customer data.
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