Insulating film cutting refers to the precise cutting of electrical insulating films into defined geometries for use in electric motors, generators, transformers, and electrical assemblies. The goal is to provide insulating parts with an accurate fit, reproducibly and ready for assembly.
Simply put: a roll of insulating film is turned into a precisely formed part that ensures electrical safety, mechanical protection, and reliable assembly. In the electrical insulation industry, cutting is a critical step because dimensional deviations, burr formation, or material damage directly affect dielectric withstand strength and service life.
Tasks and functions of insulating film cutting
Insulating film cuttings perform several functions at the same time:
- Electrical separation between conductive components
- Ensuring creepage and clearance distances
- Mechanical protection of winding wires and edges
- Process support in winding, inserting, and assembly
- Reproducibility for series production and automation
Cutting is therefore not a purely mechanical step, but part of the electrical safety concept.
Materials for insulating film cuttings
Depending on the application, different films and composite materials are used:
- Polyester Film (PET): widely used, good electrical properties, cost-effective
- Polyimide film: high temperature and dielectric withstand strength
- Aramid paper: temperature stable, very good electrical insulation
- DMD and NMN laminates: combination of film and nonwoven for improved impregnability
- Polypropylene films: low dielectric losses, chemically stable
- Mica-based films: for high-voltage and high-temperature applications
Material selection depends on the thermal class of insulation, mechanical stress, and environmental conditions.
Cutting processes at a glance
Die cutting
- High cost-effectiveness at large quantities
- Very good repeatability
- Suitable for fixed contours and series products
Roll slitting
- Ideal for strips, reel material, and simple geometries
- High process speed
- Low tool costs
Kiss-Cut
- Partial cut through the film, the liner remains intact
- Especially suited for self-adhesive insulating parts
- Clean presentation on the liner
Laser cutting
- Non-contact, very high contour accuracy
- Ideal for prototypes, small series, and complex shapes
- Thermal influence on the material must be considered
Water jet or knife plotter
- Flexible when switching materials
- Short set-up times
- Used especially for small series
Requirements for quality and tolerances
A high-quality insulating film cutting meets the following criteria:
- Dimensional accuracy in line with drawing and application
- Burr-free edges without notches or melted sections
- Consistent material thickness without crushing
- Clean cut surfaces without fibre pull-out
- Compliance with minimum bending radii for subsequent assembly
Dimensional tolerances are frequently defined according to DIN ISO 2768, supplemented by application-specific requirements from motor or transformer engineering.
Integration into manufacturing processes
Insulating film cuttings are usually part of a larger process chain:
- Winding processes in motors and generators
- Assembly of slot and Layer Insulations
- Placement of phase and end insulations
- Impregnation with resin systems
- Automated assembly via pick-and-place
Consistent cut quality is a prerequisite for stable series processes and low scrap rates.
Typical applications
- Slot insulations in stator and rotor laminations
- Layer and phase insulations in windings
- Cover and interlayer sheets in transformers
- Form coil and field coil insulations
- High-voltage insulating parts in switchgear
- E-mobility: cuttings for hairpin and HV applications
Advantages and challenges
Advantages
- High reproducibility
- Reduced assembly times
- Improved electrical safety
- Adaptable to various materials
Challenges
- Material distortion with thin films
- Thermal effects in laser cutting
- Tool wear in die cutting
- Cleanliness and freedom from particles for high-voltage applications
GOBA Takeaway
Insulating film cutting is a decisive building block in the electrical insulation industry. Precise geometries, clean cut edges, and reproducible quality are prerequisites for electrical safety and efficient assembly processes. Whether die cutting, roll slitting, or laser cutting: the process must be matched to material, quantity, and application. A well-designed cutting process reduces failures, extends the service life of electrical machines, and enables stable series production.