CNC Processing Services Sao Paulo: A Buyer Checklist

• 1
  Key takeaways
• 2
  How to compare CNC processing services Sao Paulo suppliers
• 3
  Tolerance, geometry, and what the drawing really asks for
• 4
  Lead time: separate the quote from the queue
• 5
  Match the process to the material and the part shape
• 6
  Certifications, inspection, and confidentiality
• 7
  How to read a quote and spot a lowball price
• 8
  Step by step: qualifying a supplier before you send a PO

A ±0.005 mm callout is not a shop-wide setting. It applies to specific features: a bearing bore, a mating face, a pin hole. When you send an RFQ for CNC processing services Sao Paulo buyers often paste a blanket tolerance block on the title sheet. That forces every dimension into the tight band and raises cost without improving function.

The practical question is which features control fit and which only control clearance. Mark the critical ones. Let the rest run at ±0.05 mm or the general block. A good supplier will push back on a tight callout that has no functional reason, and that pushback is a positive signal.

Geometry matters as much as the number. A deep pocket with a 4:1 depth-to-diameter ratio is harder than a shallow one at the same tolerance. Thin walls below 1 mm deflect under cutting force. If your part has either, say so in the RFQ so the shop can plan tool reach and workholding.

Surface finish follows the same logic. Ra 0.8–1.6 μm is a normal machined finish. Ra 0.2–0.8 μm needs a finer pass, a different tool, or a secondary operation. Specify finish only on the surfaces that seal, slide, or take a coating.

• 1
  Mark critical featuresTolerance the bore, not the whole part.
• 2
  Watch depth-to-diameter ratioAbove 4:1, tool deflection starts to show.
• 3
  Name the finishRa 1.6–3.2 μm as-machined is the default baseline.

Two suppliers can quote in an hour and ship three weeks apart. Ask what happens after the PO. A useful answer names the machine, the fixture build, the first-article check, and the shipping method. GreatLight quotes and returns free DFM analysis within 12 hours, can start production within 24 hours, and ships parts in 3–5 days for standard work.

For Sao Paulo buyers, transit is part of the schedule. Air freight from Dongguan is fast but priced by weight and volume. Sea freight is cheaper and slower. Decide which one your project can absorb before you compare quotes, because a low unit price with the wrong freight mode is not a low landed cost.

Batch size changes the plan. A single prototype may need one setup and a manual check. A 10,000-part run needs dedicated fixtures, a sampling plan, and a defined inspection frequency. Ask the supplier to describe both, even if you only need one right now.

Keep a late-delivery number in the file. Historical late-delivery probability below 2% is a figure worth asking for. If a supplier cannot state any on-time record, treat the promised date as an estimate.

Aluminum 6061-T6 is the default for prototypes and fixtures. It machines fast, holds tolerance, and anodizes cleanly. 7075 is stronger and more expensive, and it is worth it only when the part sees real load. 2024 has better fatigue behavior but poorer corrosion resistance without a coating.

Stainless 303 and 304 cover most general work. 316L and 17-4PH appear in medical and marine parts. Titanium Ti-6Al-4V and Inconel cut slowly, wear tools, and cost more per hour, so use them only when the service temperature or weight target demands it. Plastics such as POM, PEEK, and PC behave differently: PEEK holds dimension at high temperature, POM is stable and easy to cut, PC can craze if cooled badly.

Part shape decides the machine. A part with features on five faces, or one that needs a single setup for position accuracy, belongs on a simultaneous 5-axis center. A shaft with cross holes fits a mill-turn center. A simple plate belongs on a 3-axis mill, where the hourly rate is lower.

GreatLight runs 127 high-precision CNC machines, including 16 simultaneous 5-axis centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers. Maximum processing size is 4,000 mm. That range means the shop can route your part to the machine that fits it instead of forcing it onto one platform.

Certificates are only useful if the scope matches your part. ISO 9001:2015 covers a general quality system. IATF 16949:2016 applies to automotive production. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which matters if you are sending proprietary CAD. Ask for the current certificate and read the scope line.

Inspection is where claims get tested. A written plan should list raw material check, in-process monitoring, and final inspection, with 100% inspection before shipment and reports on request. A 99.99% qualification rate is a useful number only if the inspection method behind it is defined.

Confidentiality should be a process, not a promise. Secure uploads and an NDA on request are the baseline. If a supplier asks you to attach CAD files to a plain email with no agreement in place, that tells you how the rest of the project will be handled.

Ask who signs the first article. A named engineer with authority to hold shipment is worth more than a generic quality email address. On tight-tolerance work, that person is your real contact.

A usable quote breaks out material, machining time, setup, finishing, and freight. A single lump sum hides where the cost sits, so you cannot negotiate or compare. Ask for the material grade and the finish spec in writing. Aluminum 6061 and 7075 look the same on a line item and differ sharply in price.

Watch for missing operations. Anodizing, black oxide, bead blasting, and laser marking are separate steps. If the quote does not list them, the price is incomplete. The same applies to inspection reports and any special packaging you need.

Lowball quotes usually cut one of four things: material grade, tolerance compliance, inspection, or freight mode. Each one shows up later as a rejected lot or a surprise invoice. Compare landed cost and stated scope, not unit price alone.

Finally, ask what happens if parts fail inspection. A supplier that remakes or credits without an argument is cheaper over a year than one with a lower unit price and no clear remedy.