The engineering drawing for a custom cable is the written agreement between design and manufacture. It specifies precisely how the construction, dimensions, tolerances, materials and wiring will be constructed, inspected and accepted. This document is not a quick sketch, or a 3-D model, but the one and only source of truth for what is acceptable on the floor and in the field.

Reading it carefully before ordering/quoting or releasing production, avoids the most common and expensive errors of wrong revision, incorrect length, mismatched materials, or pinout errors which only arise during commissioning. 

Start with the Title Block and Revision Information

Open all of the custom cable engineering drawings at the title block. This little section provides you with information about what you’re viewing, who owns it, and what version it is. 

Part Number, Description, and Revision

The part number will be used to order, track in ERP, and be used to identify the cable on the finished assembly. Should be identical to the RFQ, the purchase order and any BOM line that may reference this drawing.

The description provides a readable summary, something like “Robot Servo Cable 4×2.5 + 2×2×0.5 mm², PUR, UL AWM”.

The revision letter or number is the most important individual field. When a drawing is revised from Rev A to Rev B, and the purchase order is still for Rev A, it’s a good example of scrap. Check revision on drawing against intended revision before proceeding with work. 

Units, Scale, and Default Tolerances

Look at the units first — metres or centimetres, or millimetres or inches. If a millimetre drawing is measured as inches, errors will be made immediately and it will be very costly.

Unless specifically required, a scale is usually not relevant to a cable assembly, and should never be used from a PDF or a printed plot.

All dimensions which are not individually specified have default tolerances, typically shown as “Unless otherwise specified ±0.5 mm for one decimal place”. Many length and OD callouts are at the edge between these general rules and explicit tolerances and should be read in conjunction. 

Notes, Standards, and Drawing System

General Notes in the area to the right of the title block or in a separate notes area may override the default settings. They can refer to an internal cable-drawing standard (ASME Y14.5), halogen-free requirements, specific UL AWM styles or packaging rules. The note always overrides the title block, as is usual on engineering drawings. 

Understand the Overall Cable Construction Views

Most cable drawings include 3 mutually complementary views, so that one has a full picture in his mind of the assembly. 

Side View — Length, End Connectors, and Orientation

The side view displays the total assembly length, connector positions, boots, breakouts and label locations. It also shows the orientation of the connectors: keying, clocking angle, right angle or straight body.

Length may be from end to end, from connector mating faces, or to the end of a strain relief boot. The drawing should identify which datum the measurement is made from—the common mistake in quoting and manufacturing is to measure from the wrong datum. 

Cross-Sectional View — Internal Cable Structure

The cross-section shows the cross-section composition: number and size of conductors, insulation colours, type of shielding (foil or braid or both), drain conductors, fillers and outermost jacket. A materials table and/or notes are typically provided on the cross-section that indicate the specific compound and rating of each section. 

Detail Views — Breakouts, Overmolds, and Special Features

Detail or section views provide clarity on complex areas: Multi-leg breakout lengths, Heat-shrink coverage, Overmold geometry, Potting, and Strain-relief geometry. These views should be carefully considered for any assembly other than a simple 2-ended cable. 

Reading Dimensions and Tolerances on a Cable Drawing

On a cable drawing, dimensions are grouped into length, outer diameter, breakout geometry, and interface feature dimensions that impact fit and function. 

Overall Length, Leg Lengths, and Length Tolerances

Overall length is important for the cable to reach its destination and in routing excess length. Long legs or short legs control strain, break out lengths control connector reach. It is essential that the tolerances within this range of ±10 mm to ±50 mm are not unrealistic for the production method and the installation environment. Check if the quoted length includes connectors and strain reliefs or just the jacketed cable. 

Outer Diameter and OD Tolerances

Fit with cable glands, energy-chain cavities, conduit and panel openings are defined by outer-diameter callouts and tolerances. When clearance is tight, the nominal OD is not enough, the complete tolerance range should be compared with the mating parts. 

Other Dimensional Callouts (Labels, Boots, Overmolds)

Other dimensions provide location of labels, determine boot or overmold length, and establish clearances around breakouts. The following features have an impact on readability of a finished machine and space for future service. 

Construction and Material Callouts — What the Cable Is Made Of

The material information is found in notes, materials table, cross section callouts or BOM lines. It must be checked with the application for each layer. 

Conductor Size, Material, and Stranding

It is important to include the conductor size (in either cross section or AWG), conductor material (bare or tinned copper), and conductor class of stranding. Current capacity, voltage drop, flexibility, and reliability in the connection to terminals or contacts are controlled by these details. 

Insulation and Jacket Material Specifications

Check insulation type and temperature rating (PVC, XLPE, PE, etc.) and jacket compound, including its key properties: PUR (Oil and Abrasion resistant), TPE (Flexible), Halogen-free (where applicable). The approval path is explicitly referenced with UL AWM styles, IEC or CSA. 

Shielding and EMC-Related Information

The protection is indicated by foil or braid or spiral or a combination of these and sometimes has a percentage coverage. The size and material of the drain-wire and whether or not the entire cable or individual pairs are shielded need to be specified. Typically, the termination technique at each connector (360° bond, pigtail, etc.) will be indicated on the drawing or in the pinout table. 

Special Properties and Compliance Notes

Flame ratings (VW-1, FT4, IEC 60332), RoHS/REACH compliance, oil resistance ratings, or cleanroom/LSZH requirements may be requested for notes. These are not discretionary, but required to gain access to the market and long-term suitability. 

BOM, Wiring Table, and Pinout — How Everything Connects

A drawing should contain a bill of materials and wiring/pinout table for any cable assembly. These sections turn the geometric and material information into a functional product. 

Bill of Materials (BOM)

All components are listed on the BOM including type of cable, connectors, boots, labels, heat shrink and any special hardware. The quantity, description, item number, and manufacturer part number (if applicable) are included on each line. The BOM should be consistent with the construction illustrated in the views and all discrepancies should be ironed out prior to quoting and production. 

Wiring / Pinout Table

The pinout table specifies where each cable core (colour, number, or duo) goes to from the origin connector and where it connects at the destination connector, including shield and drain-wire connections. One of the most frequent reasons for an assembly to fail is due to misreading one row. Systematically verify: core identification, origin pin, destination pin, shield continuity. 

Core Color Coding and Numbering

Colour or number coding helps to connect the drawing to the physical cable. If the cable has ring-marked or numbered cores, the drawing should specify the identification pattern, in order to avoid ambiguity in applying the wiring table. 

Tolerances, Notes, and “Unless Otherwise Specified” Requirements

Tolerances and notes describe what is allowed and the necessary process requirements. 

Length, OD, and Assembly Tolerances

There are dimensions that contain a tolerance value, and others that take the general tolerance block. Realistic tolerances must be allowed for mating-face length, OD at a gland entry, etc., functional dimensions which must be manufactured and installed. 

Electrical and Test Requirements in Notes

Continuity or insulation resistance testing, hi-pot or shield continuity testing, and visual criteria like “no nicks on conductors” and “no jacket damage” are common notes required for notes. These are not add on’s but an engineering requirement. 

Assembly Instructions and Process Notes

Process notes can include strip lengths, 360° shield bonding, overmold or potting parameters, exact label text and location, serial numbers, or date codes. Ensure any special process is both viable and budgeted in the quote. 

A Step-by-Step Checklist for Reviewing a Custom Cable Engineering Drawing

Follow this sequence prior to accepting a drawing for quotation or production. 

Step 1 — Confirm Identity and Scope

• Check part number, description and revision with project.
• Verify units and general tolerances.
• Make sure that the drawing is part of the machine/customer system. 

Step 2 — Understand the Geometry

• Check lengths overall and breakout, and orientations of connectors.
• Discuss cross sections and detail views, understand how to visualize complete constructions.
• Verify OD and bend radius applications with routing hardware. 

Step 3 — Verify Construction and Materials

• Verify conductor size, material and stranding.
• Inspect and verify the types and temperature rating of insulation and jacket materials.
• Checkshield type, coverage and termination.
• Record any special characteristics (flame, oil resistant, halogen free). 

Step 4 — Verify BOM and Pinout

• Verify all of the BOM lines with the views.
• Walk through wiring table of all cores, pairs and shields.
• Verify label location, text and identifying information. 

Step 5 — Verify Tolerances and Notes

• Verify length and OD tolerances are feasible for both manufacture and fit.
• Pass through all the general & specific notes for tests, packaging and approvals.
• Note any discrepancy or inconsistency between notes and title block for clarification. 

Reading the Drawing Is the First Engineering Test

To be able to read and ask questions to a custom cable engineering drawing is part of engineering good practice. An ambiguous or misunderstood drawing is more often the cause of many field failures and late stage change orders than simply a manufacturing mistake.

The thorough review of a drawing minimizes RFIs, misquotes, wrong builds, and commissioning delays. If a new custom design is needed, Hulk’s cable engineering team is ready to guide you through construction, tolerances, materials and wiring, to ensure that the drawing is clear and is a first-cut to a buildable contract.