ACMSO ACMS cheat sheet

Subtractive processes remove material (milling, turning, drilling); additive processes build by deposition; forming processes reshape without removing material.

Turning rotates the workpiece against a single-point tool; milling rotates the tool against a translating workpiece.

Cutting speed (surface feet per minute) relates to spindle RPM by SFM = π × D × RPM / 12, where D is diameter in inches.

Feed rate in milling equals feed per tooth × number of teeth × RPM.

Five-axis machining adds two rotational axes to the three linear axes, allowing undercut and compound-angle features in one setup.

Sheet metal bend allowance = (π/180) × bend angle × (inside radius + K-factor × thickness); K-factor is typically 0.3–0.5.

Laser and waterjet are thermal and mechanical blanking methods respectively; waterjet avoids heat-affected zones.

Casting processes (sand, investment, die) are chosen by tolerance, volume, and surface finish: die casting gives the tightest as-cast tolerances at high volume.

Design for manufacturability (DFM) rules reduce part count, standardize features, and align tolerances with process capability.

GD&T position tolerance controls location; profile controls form; runout controls rotation about a datum axis.

Maximum material condition (MMC) bonus tolerance is the difference between the actual mating size and the MMC size.

A datum reference frame establishes three mutually perpendicular planes: primary (3 points), secondary (2 points), tertiary (1 point).

Clearance hole diameter for a fastener is nominally bolt diameter plus 1/16 in (1.6 mm) for general fits.

Minimum bend radius for sheet metal is commonly 1× material thickness for mild steel and 1–2× for aluminum alloys.

Thread callouts follow diameter–threads per inch–class, e.g., 1/4-20 UNC 2B, where 2B denotes internal class of fit.

Design reviews should occur at concept, preliminary, and critical design phases before release to production.

Cp = (USL − LSL) / (6σ) measures potential capability; Cpk = min[(USL − μ), (μ − LSL)] / (3σ) measures actual capability.

A Cpk of 1.33 corresponds to roughly 63 defects per million; 1.67 corresponds to roughly 0.6 defects per million.

Control charts distinguish common-cause variation (within limits) from special-cause variation (outside limits or nonrandom patterns).

Gauge R&R below 10% of tolerance is generally acceptable; 10–30% is marginal and requires justification.

AQL sampling per ANSI/ASQ Z1.4 uses lot size and inspection level to determine sample size and acceptance number.

First article inspection verifies the first production part against all drawing requirements before full production.

Coordinate measuring machines report deviation from nominal; attribute gauges (go/no-go) report only pass/fail.

Tolerance stack-up can be worst-case (arithmetic sum) or statistical (root-sum-square), which assumes independent distributions.

Thermal expansion changes length by ΔL = α × L × ΔT; steel α ≈ 6.5 × 10⁻⁶ /°F (11.7 × 10⁻⁶ /°C).

IT grade numbers in ISO 286 increase with tolerance magnitude; IT7 is typical for precision machined fits.

A clearance fit has the hole always larger than the shaft; an interference fit has the shaft always larger than the hole.

Surface finish Ra is the arithmetic average roughness; a 63 µin Ra is typical for general machining, 16 µin for fine grinding.

Hardness scales (Rockwell C, Brinell) are empirical and not directly interchangeable without conversion tables.

Austenitic stainless steels (300 series) are generally non-magnetic and not hardenable by heat treatment.

Material certification (mill test report) documents chemistry and mechanical properties for traceability.

Economic order quantity EOQ = √(2DS / H), where D is annual demand, S is order cost, and H is holding cost per unit per year.

Little's Law: work-in-process equals throughput rate multiplied by flow time (WIP = TH × FT).

Takt time = available production time / customer demand rate.

Critical path method identifies the longest-duration path through dependent tasks; its length sets the project minimum duration.

Finite capacity scheduling limits work assigned to a resource to its available hours; infinite capacity ignores that limit.

MRP explodes a bill of materials using lead times and lot-sizing rules to generate planned orders.

Setup reduction (SMED) separates internal setups (machine stopped) from external setups (machine running).

OEE = availability × performance × quality, expressed as a percentage.

OSHA machine guarding (29 CFR 1910.212) requires guarding at the point of operation, power transmission, and other moving parts.

Lockout/tagout (29 CFR 1910.147) applies to servicing and maintenance where unexpected energization could cause injury.

Permissible exposure limit for noise is 90 dBA as an 8-hour time-weighted average; hearing conservation triggers at 85 dBA.

Hazard communication (29 CFR 1910.1200) requires safety data sheets and labeling consistent with the GHS.

ITAR and EAR control export of defense and dual-use items; EAR99 items generally need no license.

Personal protective equipment is the last line of defense in the hierarchy of controls: elimination, substitution, engineering, administrative, then PPE.

A confined space permit is required where entry hazards exist and the space is not designed for continuous occupancy.

Total part cost = material + labor + machine burden + tooling + overhead + margin.

Machine hour rate includes depreciation, power, maintenance, floor space, and indirect labor.

Material cost per part = (blank weight × material price per pound) / (1 − scrap rate).

Break-even quantity = fixed cost / (unit price − variable cost per unit).

Learning curve: unit time decreases by a fixed percentage each time cumulative production doubles (typically 80–90%).

Setup cost per part = total setup cost / lot size; larger lots reduce per-part setup but raise inventory carrying cost.

Quoted price should recover nonrecurring engineering (NRE) and tooling either up front or amortized across the expected volume.