CNC Plastic Machining | Metal One Slovakia

01 — machining

Material properties

Professional CNC machining of engineering plastics for industry

Engineering plastics are a fully-fledged alternative to traditional metal alloys in modern engineering, offering their own distinct mechanical and chemical properties. Metal One, based in Ladce in the Ilava district of Slovakia, carries out precision CNC machining of plastics for demanding applications. We focus on polymers that require strict control of cutting conditions to avoid thermal degradation of the workpiece.

In processes such as CNC milling and CNC turning of plastic blanks we use tools with sharp geometry and polished cutting edges. This approach minimises burr formation and delivers surface roughness of Ra 0.8 μm. Manufacturing parts to drawing takes place in climate-controlled premises, which is critical with plastics of higher thermal expansion in order to achieve ±0.01 mm tolerances.

We supply finished components to customers in Slovakia and across international markets. Our location provides direct access to the motorway network, letting us respond promptly to requirements from automotive and aerospace customers.

Specific challenges in milling and turning polymers

Every type of engineering plastic requires an individual approach to toolpath programming and coolant selection. Our production covers materials such as POM-C, which stands out for excellent machinability and dimensional stability. With this material we apply higher cutting speeds while reducing feed rates, eliminating the risk of material tear-out at edges.

High-performance plastics such as PEEK or PTFE call for dedicated clamping fixtures. PEEK is exceptionally strong and resistant to temperatures up to 260 °C, which predestines it for aerospace applications. We mill components from this polymer using solid carbide cutters with a DLC coating, which reduces friction and prevents chips from melting onto the cutting edge.

The engineering plastics we machine most frequently include:

POM-C (Polyoxymethylene): Ideal for gears, plain bearings and precision structural parts.
PEEK (Polyetheretherketone): A high-performance plastic for extreme thermal and chemical loads.
PTFE (Polytetrafluoroethylene): A material with outstanding sliding properties and chemical inertness.
PA6 (Polyamide): A tough material with good resistance to wear and impact.

Process routes and achievable parameters

Heat removal from the cutting zone is the critical factor when machining plastics. Because plastics are thermal insulators, the heat generated by the cut does not disperse into the workpiece but remains at the surface or passes into the tool. We therefore cool with compressed air or with special emulsions that do not chemically degrade the polymer.

Clamping plastic blanks presents a further technological challenge. Given their lower modulus of elasticity compared with metals, standard vices risk deforming the part. We therefore use vacuum clamping tables and shaped soft jaws that distribute clamping force over a larger area. This is essential above all for thin-walled components.

Our equipment delivers excellent geometric accuracy. When turning PTFE seals or milling polyamide guide rails we guarantee compliance with the tolerance bands of ISO 2768-m. For specific applications we also relieve internal stresses in the material by annealing before final machining.

Industrial applications of machined plastic components

Machined plastic parts are used wherever weight reduction, electrical insulation or resistance to aggressive chemicals is required. In the automotive industry we supply precision components for fuel systems and interior mechanisms, where absolute reliability and long service life without lubrication are essential.

In automation technology and robotics, grippers, sliding guides and insulators are in particular demand. Manufacturing parts to drawing from materials such as PET-GL allows design engineers to create maintenance-free assemblies with a minimal coefficient of friction. Every part produced passes strict final inspection on 3D coordinate measuring machines.

Density (POM-C) 1.41g/cm³

Tensile yield strength 65MPa

Tensile modulus 2800MPa

Hardness 82Shore D

Thermal conductivity 0.31W/(m·K)

Coefficient of thermal expansion 11010⁻⁶/K

Melting point 165°C

Water absorption (24h) 0.2%

02 — Process

How CNC machining works for Plastics

01

Blank preparation and clamping

We use soft jaws, shaped supports or vacuum clamping to prevent plastic deformation. Clamping forces must be precisely dosed to hold the ±0.01 mm tolerance without damaging the surface.

02

Cutting tool selection

We fit extremely sharp carbide cutters with polished flutes (designed specifically for plastics) and a large clearance angle. This prevents material melting and unwanted chip adhesion to the tool.

03

Setting cutting parameters

We select high cutting speeds and an appropriate feed per tooth. The key is to minimise heat generation in the cut, which would cause thermal expansion of the plastic and loss of dimensional accuracy.

04

Cooling and chip evacuation

We apply intensive compressed-air cooling (or a special emulsion where the material permits). Chips are continuously evacuated so they cannot re-melt onto the workpiece.

05

Finishing and final inspection

Machining is followed by a technological pause for parts to acclimatise. Final measurement on a 3D CMM takes place in a climate-controlled room (20 °C) to fully guarantee the ±0.01 mm tolerance.

03 — FAQ

Frequently asked questions about CNC machining Plastics

Can you genuinely guarantee ±0.01 mm tolerance on plastics such as POM-C or PEEK?

Yes. At Metal One in Ladce we achieve this accuracy through strict temperature control during machining, the use of special tooling and mandatory acclimatisation of the material before final measurement.

Which engineering plastics do you machine most often?

We specialise in POM-C, PEEK, PTFE (Teflon), PA6 (Nylon), PET-G and PC. For each of these materials we have proven cutting conditions and CAM strategies.

How do you achieve high surface quality without scratches or tool marks?

We use sharp single-flute or two-flute cutters with polished flutes and optimise toolpaths so that no rubbing or local melting of the surface occurs.

How do you deal with internal stress that causes distortion after machining?

For critical parts we buy stress-relieved (annealed) blanks and split the process into roughing and finishing cycles with an intermediate release of the clamping.

Is there a contamination risk when machining plastics for the food or medical industry?

For these specific applications we machine plastics entirely dry with intensive clean compressed-air cooling, which guarantees zero contamination of parts by cutting fluid.

What is your capacity for series production of plastic components?

At our facility we handle everything from prototypes to medium and large batches (tens to thousands of pieces), using automated CNC centres with bar feeders for maximum efficiency.

More materials