Michigan CNC Services: What to Check Before You Order

• 1
  Key takeaways
• 2
  How Michigan CNC services compare by order type
• 3
  Tolerance: what Michigan CNC services can actually hold
• 4
  Machine travel and part size: when a shop says no
• 5
  Certifications: which one your industry actually needs
• 6
  Lead time and quoting: what a realistic schedule looks like
• 7
  Order size, setup cost and the MOQ trap
• 8
  Materials and finishing: where quotes quietly diverge
• 9
  7 steps to screen Michigan CNC services

A tolerance callout on a drawing is a request. Whether a shop holds it depends on the machine, the fixturing and the room the machine sits in. ±0.005 mm ( ±0.0002 in ) is achievable on a 5-axis center, but only when the shop controls thermal drift across a long cycle. Ask how they qualify a new machine and you will hear either a number or a story.

The practical question is where the tight tolerance sits. A ±0.005 mm bore on a 50 mm aluminum bracket is routine. The same callout on a 900 mm steel weldment is a different job, because a 5 °C swing over the length of the part moves the feature more than the tolerance allows. Good shops split the print into tight features and loose features and machine them in that order.

Surface finish and tolerance travel together. If your print calls Ra 0.8–1.6 μm and ±0.01 mm, a standard carbide insert will do it. If you also want Ra 0.2–0.8 μm on the same face, expect a second operation, a smaller stepover and a longer cycle. That cycle time is the real cost of the tighter callout.

One more check: does the shop measure what it machines, or does it ship on the operator's word? 100% inspection before shipment with raw material check, in-process monitoring and final inspection is the baseline. Ask for the report format before you place the order, not after.

• 1
  Ask for the machine, not the claimA tolerance number means nothing without the model and the fixture plan.
• 2
  Split the printTight features on a 5-axis center, loose features on a 3-axis mill.
• 3
  Budget the second opRa 0.2–0.8 μm usually means a separate finishing pass.

Most RFQs die on size, not on price. A shop with 500 × 500 × 450 mm travel cannot quote a 1,200 mm housing at any price, because the part will not fit the envelope. Ask for travel figures up front and you save a week of back-and-forth.

GreatLight runs three travel classes on the same floor: compact at 500 × 500 × 450 mm and 500 × 310 × 200 mm, medium at 750 × 1,150 × 550 mm and 600 × 600 × 600 mm, and large at 4,000 × 400 × 150 mm. A part that fits the medium class has more machine options, which usually means a shorter queue and a lower setup cost.

Rotary work is a separate question. A Ø400 mm rotary table handles most round features, but a part that is both long and has radial features may need a mill-turn center instead of a 3-axis mill with a fourth axis bolted on. Mill-turn removes one setup, and every setup you remove removes a stack-up error.

If a supplier says they can do a 4,000 mm part, ask which machine will run it and who owns that machine. Subcontracting the large work is common, and it adds a week to the schedule plus a second party to the tolerance stack.

• 1
  Ask for travel, not capacityMachine count says nothing; the envelope decides whether you can be quoted.
• 2
  Long plus radial means mill-turnOne setup beats two, and the concentricity callout gets easier.
• 3
  Check ownershipSubcontracted large parts add schedule risk you cannot see in the quote.

Certificates are not a score. They map to industries. If your part goes into a car or an EV, IATF 16949:2016 is the one that matters, because it covers traceability, PPAP discipline and change control. If your part touches a patient, ISO 13485:2016 covers the process controls and record keeping that a medical reviewer expects.

ISO 9001:2015 is the baseline quality system and most serious shops hold it. ISO 27001:2022 is different: it covers information security. It matters when you upload CAD, drawings and BOMs, because it says the shop has a documented process for handling your files, not just a promise to keep them private.

Ask for the certificate scope, not the logo. A certificate that covers machining at one site does not cover finishing at another. If the shop sends parts out for anodizing or plating, that supplier is inside your quality chain, and you should know whether they are audited.

For most sourcing decisions in Michigan, the useful question is: which certificate does my customer require me to pass down? Start there and the list gets short fast.

• 1
  Automotive: IATF 16949:2016Traceability, PPAP and change control are the deliverables.
• 2
  Medical: ISO 13485:2016Process records must survive an audit years later.
• 3
  Shared CAD: ISO 27001:2022Documented handling of your files, not a verbal NDA.

A quote that arrives in three days tells you the shop is busy. A quote with DFM notes in 12 hours tells you an engineer looked at the model, not a salesperson. The second is worth more, because DFM feedback before cutting metal is where most cost is removed.

On timing, the useful benchmarks are these. Quotation and free DFM analysis within 12 hours, production start within 24 hours once the order is released, and parts shipping in 3–5 days for standard work. Those numbers assume the material is in stock and the print is frozen. If either changes, the clock restarts.

Be skeptical of a schedule that is faster than the setup allows. A 5-axis job with two fixtures and a finishing pass takes what it takes. Ask how many operations are in the router and you can build your own schedule estimate.

Late delivery is a real risk, and every shop has some. What you want to see is whether the shop tracks it. Historical late-delivery probability below 2% is a number a shop can only quote if it measures on-time shipment, which means it has a schedule system worth trusting.

• 1
  DFM before priceFeedback in 12 hours is a better signal than a fast number.
• 2
  Freeze the printA revision after release resets the 3–5 day clock.
• 3
  Ask for the routerOperation count is the honest schedule estimate.

A minimum order quantity is really a setup cost in disguise. If a shop needs eight hours of programming and fixturing to run your part, they have to spread that over the order. A 1,000-piece minimum is often a way of saying the setup is expensive, not that the shop dislikes small runs.

Shops that quote from one prototype to 10,000+ part runs have a different cost structure. They program once, keep the fixture on the shelf and reuse it on the next revision. For a hardware team in Michigan running three builds before launch, that matters more than the piece price on the first order.

The trap is a low piece price with a high minimum. You buy inventory to reach the price break, then the design changes and the inventory is scrap. For anything still in test, buy to the build, not to the price break.

Also ask what happens to the fixture between orders. If it is scrapped after the run, every reorder pays the setup again. If it is stored, reorders are fast and cheap, and that is worth a small premium on the first batch.

• 1
  MOQ equals setupAsk what the minimum is paying for.
• 2
  Buy to the buildPrice breaks on inventory become scrap when the design moves.
• 3
  Ask about fixture storageStored tooling makes reorders fast and cheap.

Two quotes for the same aluminum part can differ by 40% because one shop buys 6061-T6 from a certified mill and the other buys generic stock. For structural parts, the temper matters. 6061-T6 behaves differently from 6061 in the annealed state, and the difference shows up in the chip, the finish and the strength.

Specialty alloys are where the real gap sits. Inconel and Ti-6Al-4V (TC4) cut slowly, wear tools and need high-pressure coolant. A shop that quotes them at aluminum rates has either not run them or plans to learn on your part. Ask for a tool life plan and a scrap allowance before you commit.

Finishing is a second sourcing decision. Anodizing, electroless nickel, zinc, silver and gold plating, powder coating and black oxide all have their own turnaround and their own tolerances. Hardcoat anodizing adds thickness and can move a tight bore. Masking decisions belong in the drawing, not in a phone call after the parts are made.

Laser marking is worth checking early. Minimum character height is 1.5 mm on most systems, and a 0.8 mm font on the drawing will not survive the marking setup. Print the mark at the size you will accept before the run.

• 1
  Temper is part of the spec6061-T6 is not interchangeable with generic 6061 stock.
• 2
  Exotics need a tool life planInconel and Ti-6Al-4V cut slowly and wear inserts fast.
• 3
  Hardcoat moves dimensionsSpecify masking and thickness allowance on the drawing.