Precision Manufacturing Glossary
Twenty terms that decide whether a drawing gets quoted correctly. Each entry gives the definition first, then the practical consequence that the definition implies.
Most sourcing disputes trace back to a term being used with two meanings — a tolerance read as a one-sided value, a Cpk quoted without a sample size, a finish specified by colour instead of thickness. These definitions are written to remove that ambiguity: each one states what the term means and what it does not mean.
A
- Adhesive Backing
-
The double-sided tape on the reverse of an IP20 strip, used for fastening to a clean, flat surface.
3M 300LSE and Tesa 4965 hold well on aluminium and painted steel but fail on dusty melamine and on any surface above 40 °C. Above 1 kg per metre, or on a ceiling, mechanical clips are the reliable fixing.
B
- Bin Code
-
The label that records the chromaticity, flux and forward-voltage group a reel was sorted into during production.
A bin code is what makes a replacement reel match an installed one years later. Without it, the only match available is nominal CCT, and two 3000 K reels from different bins can be visibly different whites.
C
- COB (Chip on Board)
-
An LED strip construction in which bare LED dies are bonded directly onto the flexible PCB and covered by one continuous phosphor layer, instead of being packaged individually before assembly.
Bonding at 480 chips/m and coating the whole row removes the 8–16 mm dot pitch of an SMD strip. The trade-off is roughly 20–30% higher cost per metre and a cut length fixed by the die series, typically 25 mm.
- CRI (Colour Rendering Index)
-
A 0–100 score for how faithfully a light source renders eight reference colours compared with a daylight reference of the same colour temperature.
CRI 80 is the volume lighting standard, CRI 90 suits retail and hospitality, and CRI 95 is specified where merchandise colour is the product. CRI alone hides red rendering, so R9 is quoted separately — a CRI 90 strip with R9 below 20 makes red fabric look brown.
- Cut Length
-
The shortest repeat unit of a strip that can be cut without breaking the electrical series circuit, marked on the FPC.
Cut length is 3 LEDs per segment on most SMD strips and 25 mm at 480 chips/m on COB. Cutting between marks leaves the remaining segment dark, and this is the most common installation error in the field.
- Constant Voltage vs Constant Current
-
Two driver architectures: constant voltage holds a fixed output (12 V or 24 V) and each strip segment regulates its own current through resistors; constant current holds a fixed current and regulates voltage across a series string.
Constant voltage is simpler and allows cutting to length, but voltage drop limits run length. Constant current holds brightness over 20 m or more but requires fixed-length strings and a driver matched to the string.
D
- DMX512
-
A lighting control standard that carries up to 512 channels per universe over RS-485, widely used for architectural and stage lighting.
A DMX universe controls 170 RGB pixels or 128 RGBW pixels, so a 1,200-pixel facade needs 8 universes. Pixel strip therefore normally runs SPI from a DMX-to-SPI converter rather than DMX directly.
E
- Efficacy — luminous efficacy
-
The luminous flux produced per unit of electrical power, expressed in lumens per watt (lm/W) at a stated colour temperature and colour rendering index.
An SMD strip at 120 LEDs/m reaches 160–190 lm/W at CRI 80 and 4000 K, but the same strip at CRI 95 and 2700 K drops to 110–130 lm/W. Quoting efficacy without CCT and CRI is meaningless.
F
- FPC (Flexible Printed Circuit)
-
The flexible copper-clad substrate that carries the LEDs, conductors and cut marks in an LED strip.
Copper weight is quoted in ounces per square foot. A 1 oz FPC suits 5 m runs; 2 oz is standard for 10 m; 3 oz and 4 oz are used for 20–50 m runs where voltage drop would otherwise be visible.
I
- IP Rating — Ingress Protection
-
A two-digit classification (IEC 60529) for resistance to solid objects and water, where the first digit covers dust and the second covers water.
IP20 is bare strip; IP65 resists water jets; IP67 allows temporary immersion to 1 m; IP68 is continuous immersion by agreement. None of these ratings cover chemical attack, so a pool installation still degrades from chlorine whatever the second digit says.
J
- Junction Temperature (Tj)
-
The temperature of the LED semiconductor junction itself, which sets the rate of lumen depreciation and is always higher than the strip surface temperature.
A strip surface measured at 55 °C corresponds to a junction near 75–85 °C depending on package thermal resistance. Every 10 °C above 85 °C roughly halves the time to L70.
L
- LM-80
-
An IES test method that measures lumen maintenance of an LED package over at least 6,000 hours at controlled case temperatures.
LM-80 tests packages, not strips. The data is extrapolated with TM-21 to project L70 or L80 life, and the projection is only valid at or below the tested case temperature — a strip in a sealed profile runs 20 °C hotter than the test condition.
- L70 / L80
-
The operating hours at which a light source reaches 70% or 80% of its initial luminous flux, used as the practical definition of end of life for LED.
A strip rated L70 at 50,000 hours at 45 °C may reach L70 in 20,000 hours inside a sealed aluminium profile at 65 °C. The rating is only meaningful with its ambient and case-temperature conditions stated.
- Luminous Flux
-
The total light output of a source in lumens, weighted to the sensitivity of the human eye.
Flux per metre is the number that determines illuminance on a surface, but it falls 8–15% behind a diffuser and 3–6% behind a silicone tube. Quoting bare-strip flux for an installed product overstates delivered light.
N
- Neon Flex
-
A linear LED light enclosed in a solid silicone or PVC profile that diffuses the source into an even line and provides an IP67 seal.
Platinum-cured silicone is specified for exterior work because it does not yellow under UV, while PVC becomes brittle below −10 °C. The minimum bend radius is roughly three times the profile width, and bending tighter cracks the phosphor.
P
- Pixel Pitch
-
The spacing between individually controllable LEDs on an addressable strip, usually expressed as pixels per metre.
At 60 pixels/m the individual points are visible from about 2 m; at 144 pixels/m they merge at 1 m. Media facades viewed from 30 m are usually specified at 30 pixels/m, because resolution beyond viewing distance is cost without benefit.
- PWM Dimming
-
Brightness control by switching the LED on and off rapidly, where the duty cycle sets perceived brightness and the switching frequency sets flicker visibility.
Below about 1.5 kHz, PWM is visible as banding on a phone camera and can cause stroboscopic effects on video. Architectural and broadcast work specifies ≥ 1.5 kHz and often 3 kHz.
R
- R9
-
The ninth test colour in the CRI set, a saturated red, reported separately because it is excluded from the general CRI average.
Most phosphor-converted white LEDs score poorly on R9 unless the phosphor recipe is tuned for it. Retail and hospitality specifications increasingly call for R9 ≥ 50, and achieving it costs 8–12% more per metre.
S
- SDCM (Standard Deviation of Colour Matching) — MacAdam ellipse step
-
A measure of how far a light source sits from a nominal colour point, expressed in steps of the MacAdam ellipse where 1 step is the threshold of a just-noticeable difference.
SDCM 3 means adjacent reels are indistinguishable when installed side by side; SDCM 5 shows as a visible tint step on a continuous run; SDCM 7 reads as two different whites. Most architectural specifications call for SDCM ≤ 3.
- SPI — Serial Peripheral Interface
-
A synchronous serial protocol used by addressable LED strips, in which a data line and a clock-free timing scheme carry colour values to each pixel in sequence.
WS2812B and WS2811 are SPI variants. Timing tolerance is the practical constraint: a data line longer than about 5 m without a resistor or repeater produces random colour corruption at the end of the run.
T
- TM-21
-
The IES method for projecting LED lumen maintenance beyond the duration of an LM-80 test, using measured data to extrapolate a decay curve.
TM-21 caps extrapolation at six times the test duration, so 6,000 hours of LM-80 supports a 36,000-hour projection at most. A supplier quoting 100,000 hours from a 6,000-hour test is extrapolating beyond what the method allows.
- Thermal Derating
-
The reduction of drive current or rated power as ambient or case temperature rises, applied to keep the LED junction within its rated temperature.
Running a strip at full rated current inside a closed profile at 60 °C can raise the junction above 100 °C and halve the life. Derating to 70% current typically recovers most of the lost life at a 30% flux cost.
U
- Uniformity
-
The ratio of minimum to maximum luminance across an illuminated surface, usually quoted as edge-to-centre percentage for a lightbox.
The practical target for signage is ≥ 85% edge-to-centre. Uniformity is set by module pitch relative to box depth, not by module brightness — adding modules in the centre of a box makes the ratio worse, not better.
V
- Voltage Drop
-
The reduction in voltage along a strip caused by the resistance of the copper conductors, which produces a visible brightness gradient toward the far end of a long run.
A 24 V strip at 12 W/m loses about 1.6 V over 5 m on a 3 oz FPC and about 4.8 V on a 1 oz FPC. Doubling the voltage quarters the loss, which is why 24 V is specified for runs above 5 m.
Definitions follow ASME Y14.5, ISO 1101, ISO 4287 and AIAG terminology where those standards apply. Where industry usage differs from the standard, the practical usage is noted in the detail paragraph.
Send a specification, get a quotation in 24 hours
Tell us the product type, run length, wattage, CCT, CRI and IP rating. You will receive a fixed price, a lead time, and the feed and driver arrangement in writing — no obligation, and no sales call unless you ask for one.