Undercut

Undercuts are a central design feature in technical engineering, purposefully used in cases, transport containers and foam inlays. In practice, they influence demouldability, stability, assembly workflows and the secure fixation of devices or samples. For KKC Koffer GmbH, based in Stemwede-Levern, proper handling of undercuts is essential to deliver functional solutions for professional applications in industry, medical technology, electrical engineering and the trades.

Definition: What is meant by an undercut?

An undercut is a geometry that opposes the demoulding direction or steps back behind an edge, so that a component cannot be removed straight from a tool without additional measures. Typical examples include negative drafts, latching tabs, T-slots, continuous beads, recesses and interlocks. In case and inlay manufacturing, undercuts are either a challenge (e.g., with injection-moulded or thermoformed parts) or a means to an end (e.g., with CNC-milled foam inlays for form-fit retention).

Technical significance in case construction and foam inlays

In professional case manufacturing, undercuts act in two ways: They shape the feasibility of case shells and profiles and they secure the hold of devices, tools and samples inside. When planned correctly, they increase operability, transport safety and service life.

Undercuts in plastic cases

In plastic cases (e.g., ABS or PP), undercuts arise from latch geometries, grip recesses, clip connections, hinge mounts, continuous stacking rims and embossed reliefs. Their implementation in injection moulding often requires slides, core pulls or collapsing cores. Design guidelines:

• Maintain draft angles; use negative draft only purposefully for latching and safety functions.
• Limit slide undercuts to a few clearly defined zones to control tool complexity and cycle times.
• Design radii and transitions softly to reduce stresses and notch effects.
• For thermoforming: avoid undercuts or compensate them with flexible demoulding concepts and adapted material thickness.

Undercuts in aluminium cases

Aluminium cases use profiles and folded edges that create functional undercuts: T-slots for fittings, underlapping folds to accommodate gaskets and panels, and recessed stacking rims. In sheet-metal processing, undercuts arise from hemming and beading operations; in profile technology from slots and chambers that hold panels with a form-fit. The goal is robust edge guidance with good repairability and ease of assembly.

Undercuts in transport containers

Transport containers benefit from undercut stacking edges, secured latch seats and integrated tie-down points. Undercuts improve stacking safety, prevent slipping and enable form-fit positioning in storage and vehicle systems.

Undercuts in foam inlays: form-fit, retention and ergonomics

In foam inlays (often PE, EVA or EPP), targeted undercuts create a defined clamping fit, protect surfaces and speed up handling. Relevant aspects:

• Retention: Under-gripping contours secure devices, gauges and samples against vibrations and shocks.
• Ergonomics: Finger recesses with gentle negative draft facilitate removal without weakening the hold.
• Manufacturing: CNC milling enables stepped depths and partial undercuts; waterjet and knife plotters create complex contours with clean edges. Strongly pronounced undercuts are often achieved through a multi-layer build-up.
• Material selection: Hardness and density define the required undercut depth. Softer foam needs less undercut than high-density foam.
• Durability: Ease edges with small radii; local reinforcements or laminated surfaces reduce abrasion.

Industry requirements

For cases for medical technology, undercut contours must be designed to be especially gentle on materials to protect sensitive surfaces. In cases for electrical engineering and cases for measuring equipment, undercut cable guides and connector channels support tidy routing. Professional cases for tradespeople and professional machinery cases use pronounced undercuts for robust mounts without making removal difficult.

Design guidelines: From concept to production-ready undercut geometry

A production-ready design balances function, demouldability and cost-efficiency:

1. Define the function: retention, guidance, sealing, latching or stacking?
2. Select the manufacturing process: injection moulding, thermoforming, sheet and profile technology, CNC milling, waterjet.
3. Ensure demoulding: set draft angles and parting lines, limit undercuts to zones with a clear function.
4. Check loads: drop, vibration and temperature behaviour; consider material fatigue at edges.
5. Plan assembly: access for assembly tools, ease of disassembly, tolerances and joining sequences.

Manufacturing of foam inlays

For pronounced undercut geometry, a layered build-up is proven: upper guiding contour, middle clamping layer, lower base support. This creates a defined form-fit without overstraining the material. For delicate areas, avoid sharp corners; use fine radii instead.

Applications: How undercuts increase the utility of professional cases

Demo cases and presentation cases benefit from form-fit undercuts that hold exhibits securely and align them precisely. Equipment cases, transport cases, industrial cases and special cases use undercuts for vibration-proof storage of sensitive assemblies. In cases for medical technology, gentle negative drafts enable easy-to-clean contours; in cases for electrical engineering, undercut cable channels route leads neatly; in cases for measuring equipment, stepped grooves ensure reproducible positioning.

Mobile work table in a case: undercuts for mobile processes

The Mobile Work Table in a Case (see mobile work table in a case) requires functional undercuts for folding mechanisms, panel supports and safety clips. Cable pass-throughs with a recess prevent tensile loads on connectors. Inlays with a slight negative draft hold measuring devices, IT components or tools without jamming. For testing companies, IT service providers, service technicians, mobile tradespeople, measurement technology manufacturers, HVAC, presenters, consultants, exhibition outfitters, electrical plant engineering, electrical installation and mechanical engineering, such contours improve speed and process reliability in mobile use.

X-PCK backpack case: undercuts for carrying comfort and modular interiors

In the X-PCK backpack case, undercut mounting rails and modular slots support individual interior configuration. Strap pass-throughs benefit from set-back edges that guide webbing and fittings with a form-fit. Foam inlays with a defined undercut secure portable measuring instruments or small devices against movement.

Branding and undercut: embossed logos, reliefs and surface quality

Branding can be implemented via embossed or recessed reliefs. In plastics, undercuts on logos and lettering must be sized carefully to preserve demoulding and surface quality. In aluminium case fronts, recessed fields can serve as protective frames for markings. In foam inlays, shallow relief undercuts enable clean integration of nameplates or colour inlays.

Quality and testing: implementing undercuts with functional reliability

For robust results, retention forces, edge durability and removal speed are tested. Relevant tests include vibration, drop and climatic exposure. If necessary, local undercuts are adjusted, radii increased or material densities changed until handling and protection are within the target window.

Typical mistakes and how to avoid them

• Excessive negative drafts without grip aids: removal becomes difficult; solution: pull tabs, finger channels, gentle transitions.
• Undercut without a demoulding concept: the tool jams; solution: slides or geometry adjustment with sufficient draft angles.
• Underestimated material creep: retention decreases; solution: adjust density/hardness, enlarge contact areas, optimize edge radii.
• Sharp edges: increased notch effect; solution: functional radii.
• Overengineering: too many undercuts increase manufacturing effort; solution: function prioritisation and standardisation.

Planning in the specialized manufactory

As a specialized manufactory for B2B cases, KKC Koffer GmbH develops undercut solutions that unite manufacturing, assembly and use. In coordinated steps, cases, aluminium cases, plastic cases, transport containers, precise foam inlays with undercuts and branding elements are combined so that protection, operability and repeat accuracy are ensured in professional day-to-day use.