ManufacturingStandards

These standards apply to parts made by PREMSA Industries by CNC machining (milling, turning and mill-turn), 3D printing and laser cutting, and to the finishes and special processes we manage with approved suppliers.

They do not apply to customer-supplied parts for secondary operations except for the operation PREMSA performs on them.

We manufacture from the CAD model you upload (STEP, STL, 3MF, DXF or DWG). The model defines the geometry; the drawing defines what the model cannot express: specific tolerances, finish, threads, treatments, marking, critical dimensions and key characteristics.

If the model and the drawing disagree, the drawing prevails in what it states and the model in everything else. If we spot a contradiction before manufacturing we flag it during quote review and nothing is made until it is resolved.

The drawing and model revision the lot is made against is frozen when the work order is generated and recorded in the lot file. A later revision change is quoted as an engineering change.

When the drawing shows no tolerances, we apply ISO 2768-1 class m (medium) to linear and angular dimensions and ISO 2768-2 class K to geometric tolerances.

Tighter tolerances are routinely achieved, but they must be on the drawing to be quoted, programmed and inspected. As a reference, in CNC machining we normally deliver:

• Linear dimensions: ±0.10 mm (±0.004") by default; down to ±0.025 mm (±0.001") on specified dimensions.
• Diameters and fits: to the fit class on the drawing (h7, H7, g6, etc.), measured with calibrated instruments.
• Geometric tolerances (GD&T per ASME Y14.5 or ISO 1101): as drawn, with their datums.
• Threads: class 6H/6g (metric) and 2B/2A (unified) unless otherwise stated.
• FDM 3D printing: ±0.20 mm or ±0.2 % of the dimension, whichever is greater, subject to geometry and material.
• Laser cutting: ±0.10 mm on the contour, with the process taper inherent to the thickness.

The default finish is as machined: surfaces show the tool marks of the process, without polishing or texturing. As a reference, Ra ≤ 3.2 µm (125 µin) for milling and Ra ≤ 1.6 µm (63 µin) for turning; a specific Ra is called out on the drawing.

Edges are deburred and lightly broken (0.1–0.5 mm or 0.005–0.020") unless the drawing calls for a chamfer, a radius or a sharp edge. Parts are delivered clean, free of burrs and chips.

There is no default cosmetic standard: fixturing marks, transition lines between operations and tone variations are acceptable while within tolerance. If the part has appearance surfaces, note it on the drawing and we verify against a reference sample.

Materials are supplied to the specification in the quote catalog (for example aluminum 6061-T6 per ASTM B221, stainless steel 304 per ASTM A276). A different designation or standard must be stated on the drawing or in the notes.

With a traceability requirement, each lot is made from an identified heat, with the mill certificate (EN 10204 3.1 or equivalent) filed in the lot record and available with the shipment. Without that requirement, material may be commercial grade without a certificate, and is declared as such.

Heat, lot and certificate are recorded on the work order from the moment material is reserved until the part ships, so any delivered part can be traced back to its origin.

Threads are machined to the class in section 3 and verified with go/no-go gauges. Holes are made to drawing size; without a stated tolerance, ISO 2768-m applies.

Threaded inserts (helical, press-in or molded) are installed only when the drawing or quote includes them, with the manufacturer reference stated. Insert holes are machined to the insert manufacturer's data sheet.

Anodizing, chem film, black oxide, paint, heat treatment, passivation and other special processes are performed by suppliers approved for that scope, against the specification on the drawing (for example MIL-A-8625 Type II, AMS 2700). The supplier certificate is filed in the lot record and delivered with the parts when the customer requires it.

Drawing dimensions are understood BEFORE finish unless the drawing states after finish. Coating thickness is accounted for at quoting when the drawing specifies it.

Areas that must remain free of coating (threads, electrical contact surfaces) are masked only when the drawing says so.

Every work order goes through three inspection points: first-piece approval of each setup before the lot runs, in-process inspection during the run per the control plan, and final inspection before the shipment is released. No part ships without a signed final inspection.

Measuring instruments carry current, traceable calibration; every measurement records which instrument was used. Inspections are performed against the ballooned drawing of the part's inspection plan.

Reports available, as agreed in the quote, are:

• Certificate of Conformance (CoC) for the lot, signed, referencing the order and the packing list.
• Dimensional report per part or per sample, with nominal, tolerances and measured values.
• First Article Inspection report (FAI) per AS9102 Rev C.
• PPAP package (AIAG, levels 1 to 5) with PSW, control plan and initial capability study.
• Material and special process certificates.
• Source inspection with the customer present, by appointment.

When the drawing or the order defines no sampling plan, final inspection is 100 % on dimensions marked critical and by sample on the rest, with an acceptance criterion of zero nonconforming in the sample. A different plan (AQL, first N pieces, 1 in N) is defined at quoting.

An out-of-tolerance part does not ship without the customer's written concession. It is reworked, replaced, or documented as a nonconformance with its disposition; the customer is notified when the disposition affects quantity or date.

Parts are made to order in the exact quantity quoted. There is no overrun by default; if your application allows a quantity tolerance (for example ±10 %), state it when quoting.

When a lot comes up short because of scrap and the customer authorizes it, it ships with the corresponding note and the shortfall is replaced or credited as agreed.

Parts are delivered clean and free of cutting oil, except steels, which are protected with a light oil against corrosion. Part marking (laser, engraving, label) is performed only when the quote includes it.

Standard packaging protects parts against impact and abrasion in transit: individual bag or divider when the geometry requires it, corrugated cardboard box and cushioning. Special packaging (individual, anti-static, ISPM-15 treated wood crates for export) is quoted separately.

Every shipment carries its packing list with the order, the customer's PO, quantity per package and weight.

A change to the model, drawing, material, finish or quantity after the quote is accepted is evaluated as an engineering change: it may modify price and delivery date and is confirmed in writing before it is applied. Work already done under the previous revision is agreed case by case.

Our management system operates to the requirements of ISO 9001:2015: document control, traceability, instrument calibration, control of nonconforming product, corrective actions and quality records retained for 7 years. The specific requirements of AS9100D or IATF 16949 are addressed when the customer specifies them in the quote.

The whole process, from material to shipment, is recorded in our platform, so any delivered part can be traced to its heat, its operator, its inspection and its reports.

To clarify any requirement before quoting or manufacturing, write to ventas@premsaindustries.com or call +52 81 2634 1113. PREMSA Industries S.A. de C.V., Monterrey, Nuevo León, Mexico.