Marketing Services for CNC Machine Shops: How to Read a Supplier's Claims

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  Five checks before you shortlist a shop
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  What each claim actually tells you
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  Tolerance claims: read the feature, not the number
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  DFM feedback is the best signal a shop gives you
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  Lead time math: separate quote, first cut and ship
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  MOQ, setup cost and what no minimum really means
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  Certification scope: the part family matters
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  How to run the five checks in one week

A tolerance figure on a homepage is almost always the tightest value the shop has ever held on one feature, on one material, on one machine. That is not a lie, but it is not a promise either. Before you treat ±0.005 mm as a working assumption, ask which features it applies to and how it is verified. On a turned shaft, diameter and roundness are easy to hold. On a milled pocket 180 mm deep in 7075, wall deflection and tool push-off will eat that budget fast.

The useful question is not what tolerance the shop can hit, but what tolerance it can hold across a 500-piece run without sorting. That number comes from process capability, not from a single good part. Ask for the inspection method: a CMM with a stated accuracy, a micrometer reading, or a go/no-go gauge. Each has a different error floor. A shop that names the instrument and the report format is usually telling the truth.

Also check the drawing side. If your print calls out ±0.005 mm on a non-critical clearance hole, a good shop will flag it as over-specified and suggest a looser callout. That saves you money and signals the shop is reading the print rather than quoting the quantity. A shop that quietly accepts everything is either very good or not looking closely.

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  Ask per featureCritical bore, mating face and cosmetic surface have different budgets.
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  Ask for the instrumentCMM, micrometer or gauge. The method sets the error floor.
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  Ask about the runOne good part is not capability. Ask about 500.

Send the same STEP file to four shops and compare the replies. One returns a price. Another returns a price plus three notes about a 0.8 mm wall, an internal corner with no tool radius and a thread that runs too close to a chamfer. The second reply is worth more than the first, even if the price is higher. It means someone opened the model in CAM and looked at it.

Good feedback is specific. It names the feature, the problem and a fix. A 1.5 mm deep 0.8 mm slot in 316L will chatter on a long tool; widening it to 1.2 mm or switching to EDM removes the risk. Vague comments like improve tolerances or simplify geometry are filler. Specific comments mean the shop has run parts like yours before.

Timing matters too. A DFM note that arrives with the quote is useful. One that arrives after the PO, when the material is already cut, is a change order. Ask when DFM is done in the process. At GreatLight, quotation and free DFM analysis come back within 12 hours, before any material is ordered.

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  Same file, four shopsCompare the notes, not just the totals.
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  Specific beats politeFeature, problem, fix. That is the pattern to look for.
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  Before the PODFM after material cutting becomes a change order.

Fast delivery is the most abused phrase in this industry. It hides three separate clocks. The first is quote and DFM. The second is material in and first cut. The third is inspection and packing. A shop can be fast on one and slow on another, and the customer only sees the total.

Ask for the three numbers on your specific part. For a simple aluminium bracket, material is often in stock and first cut can start the next day. For a 17-4PH medical housing, material lead time alone can dominate. If the shop quotes a four-day delivery on a grade it does not stock, either it has a mill cert on the shelf or the date will slip.

Then look at the inspection step. A shop cutting 3–5 day deliveries across a mixed order book has to schedule CMM time, not just spindle time. If inspection is the bottleneck, a shorter machining time does not shorten the order. Ask how many parts ship per week and how final inspection is scheduled. Historical late-delivery probability below 2% is a reasonable benchmark to ask about, but ask for it in writing.

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  Three clocksQuote, first cut, inspection. Ask for each.
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  Material dominatesExotic grades move the date more than spindle speed.
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  Inspection is a queueCMM time is scheduled separately from machining.

No minimum order quantity is a real advantage for prototypes, but it does not mean the first part is cheap. Every job has a setup: fixtures, tool offsets, first-article inspection. On a one-off part that setup is spread over one piece. On a 10,000-piece run it disappears into the unit price. The phrase tells you the shop will take the order, not that the price curve is flat.

Compare quotes at three quantities: 1, 100 and 1,000. If the unit price barely moves between 1 and 100, the shop has either automated setup or hidden the setup cost in both. If it drops sharply, the setup is real and you are paying it once. Neither is wrong. You just need to know which model you are buying into.

Watch for tooling and fixture charges listed separately. A soft jaw set or a vacuum plate is a one-time cost that should be itemized. If it is missing from the quote, it will appear later. Ask what is reusable and what stays with the shop between orders.

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  Three-point price checkQuote at 1, 100 and 1,000 pieces.
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  Itemize fixturesSoft jaws and plates are one-time costs.
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  Ask about re-useDoes the fixture stay for the next order?

A certificate badge on a footer means the management system was audited. It does not mean the audit covered your part family, your material or your process route. ISO 9001:2015 covers quality management. IATF 16949:2016 adds automotive-specific requirements such as traceability and change control. ISO 13485:2016 is the medical device equivalent. ISO 27001:2022 covers information security, which matters when you upload proprietary CAD.

For an automotive bracket, ask whether the shop holds IATF 16949:2016 and whether the certificate scope names machining. For a surgical instrument housing, ask about ISO 13485:2016 and the cleaning and packaging controls that come with it. For a defense or IP-sensitive program, the ISO 27001:2022 scope is the relevant one, because it governs how your files are stored and who can open them.

Check the certificate number, the issuing body and the expiry date. A certificate that expired eight months ago is a document, not a system. Ask for the current PDF and confirm the legal entity name matches the company you are contracting with. Plants in different countries may hold separate certificates.

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  Match the standardIATF for auto, 13485 for medical, 27001 for IP.
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  Check the scope lineIt should name machining, not just trading.
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  Verify the entityCertificate holder must match your contract.