Qu'est-ce que le matériau POM?

POM (Polyoxyméthylène), communément connu sous le nom d'acétal, est un thermoplastique d'ingénierie de haute performance largement utilisé pour les pièces usinées CNC de précision. Delrin® est une marque commerciale bien connue d'homopolymère acétal, tandis que POM comprend également des grades de copolymères d'autres fabricants. Le matériau combine une faible frottement, une bonne résistance à l'usure, une stabilité dimensionnelle, une raideur et une excellente usinabilité, ce qui le rend particulièrement précieux pour les engrenages, les douilles, les rouleaux, les dispositifs de précision, les composants de guidage et les pièces mécaniques.
Note sur la terminologie des matériaux: «POM» et «Delrin» ne devraient pas être considérés automatiquement comme des spécifications identiques. POM est la famille des polymères; Delrin® est un nom commercial enregistré associé aux produits d'homopolymère acétal. Les propriétés réelles dépendent du grade spécifique et de la fiche de données du fournisseur.

1. Informations matérielles de base

Dénomination du matériel et Classification

Le POM est généralement divisé en deux grandes familles de matériaux :

POM-H (acétal homopolymère) — typically higher stiffness, strength and dimensional stability.

POM-C (copolymère acétal) — generally offers improved resistance to thermal and chemical degradation and is widely used for engineering components.

La qualité réelle doit être spécifiée en fonction de la fiche de données du fournisseur, car les additifs, le renforcement et la formulation peuvent changer considérablement les performances.

Positionnement du noyau

Le POM est l’un des plastiques d’ingénierie les plus importants pourcomposants mécaniques de précision.

Par rapport à l'ABS, POM offre généralement:

• Meilleure résistance à l'usure

• Friction inférieure

• Une raideur plus élevée

• Meilleure stabilité dimensionnelle

• Meilleure usinabilité pour les composants mécaniques de précision

• Par rapport au PEEK, le POM offre généralement:

• Coût inférieur

• Un usinage plus facile

• Capacité de température inférieure

• Performances chimiques et mécaniques plus faibles à des températures élevées

Cela rend le POM particulièrement attrayant pourPièces en plastique CNC de précision où le mouvement mécanique et la précision dimensionnelle sont importants.

2. Propriétés physiques du POM

Les valeurs suivantes représententgammes typiques pour les grades POM commerciaux non remplisCe ne sont pas des limites de spécification universelles. Les qualités d'homopolymère et de copolymère peuvent différer considérablement.

Densité

Le POM a une densité d'environ1.40–1.43 g/cm³.

Il est considérablement plus léger que l'aluminium tout en étant considérablement plus dense et plus raide que de nombreux plastiques de base.

Cela offre une combinaison utile de:

• Construction légère

• Rigidité mécanique

• Bonne stabilité dimensionnelle

• Faible friction
  
  
  Résistance à la traction & Rigidité

POM non rempli typique fournit une résistance à la traction dans la plage approximative de60 à 75 MPaavec un module de traction communément autour2.5–3.5 GPa.

Cela rend le POM adapté aux composants chargés mécaniquement qui seraient trop exigeants pour les plastiques plus doux tels que le polyéthylène.

Cependant, le POM ne devrait pas être considéré comme un remplacement direct des métaux dans les applications fortement chargées ou à haute température.

Résistance aux chocs

Le POM a une bonne résistance et peut tolérer les charges mécaniques répétées mieux que de nombreux plastiques fragiles.

Son impact réel dépend de :

• Classe

• Température

• Géométrie de la partie

• Épaisseur de mur

• Historique du traitement

• Présence de renforcement

Résistance à l'usure

La résistance à l'usure est l'un des avantages d'ingénierie les plus importants du POM.

Le POM est souvent choisi pour les composants mobiles en raison de sa combinaison de:

• Faible friction

• Bonne résistance à l'abrasion

• Bonne résistance à la fatigue

• Bonne stabilité dimensionnelle

Il est couramment utilisé dans:

• Bushings

• rouleaux

• engrenages

• Blocs de guidage

• Components coulissants

• Cages à roulements

Pour des applications tribologiques extrêmement exigeantes, des grades POM spécialisés contenant du PTFE, de la silicone ou d'autres modifieurs lubrifiants peuvent être plus appropriés.

Résistance à la température

Le POM fonctionne généralement bien dans les applications mécaniques à température modérée.

A typical continuous operating range is approximately −40°C to +90/100°C, depending strongly on grade, load and environment.

Short-term exposure may be possible at higher temperatures, but continuous service conditions should be evaluated against the manufacturer's specification.

POM is therefore generally unsuitable for applications involving sustained temperatures approaching its melting range.

Absorption d'humidité

POM has relatively low moisture absorption compared with many polyamides.

This is an important advantage for precision components because dimensional changes caused by ambient humidity are generally smaller than with materials such as PA6.

Nevertheless, moisture and temperature still need to be considered when extremely tight tolerances are required.


3. POM Chemical Properties

Composition chimique

POM is based primarily on repeating oxymethylene (-CH₂-O-) units.

Unlike metallic materials, POM does not have an ASTM/UNS elemental alloy composition.

The exact formulation varies by manufacturer and grade.

Commercial POM may contain:

• Lubrifiants

• UV stabilizers

• Fibres de verre

• Mineral fillers

• PTFE

• Other performance modifiers

Therefore, the specific material datasheet should always be used when a component has critical chemical or mechanical requirements.

Résistance chimique

POM generally provides good resistance to many:

• Hydrocarbons

• Oils

• Combustibles

• Les alcools

• acides faibles

• Alcalines faibles

• Many organic solvents
  

This chemical resistance contributes to its use in mechanical and fluid-handling components.

However, POM has important chemical limitations.

Strong acids and strong oxidizing agents can cause degradation.

POM should be evaluated carefully when exposed to:

• Strong mineral acids

• Strong oxidizers

• Chlorine-containing environments

• High-temperature aggressive chemicals

Résistance à la corrosion

POM does not corrode or rust like metallic materials.

This makes it attractive for applications where metal corrosion would be problematic.

However, "corrosion-free" does not mean chemically inert. Chemical attack can still cause:

• Cracking

• Swelling

• Surface degradation

• Loss of mechanical strength

Résistance aux UV

Standard POM is not naturally optimized for long-term outdoor UV exposure.

Prolonged sunlight can cause:

• Surface degradation

• Color changes

• Reduced mechanical performance

For outdoor applications, a UV-stabilized grade should be considered.

Welding & Bonding Compatibility

POM is relatively difficult to bond using conventional adhesives compared with ABS.

This is largely related to its low surface energy and chemical resistance.

Possible joining methods include:

• Fixation mécanique

• Press fits

• Type à pression

• Ultrasonic welding under suitable conditions

• Specialized adhesive systems

For precision assemblies, mechanical joining is often preferred.|


4. POM CNC Machinability Analysis

Difficulté d'usinage: Facile

POM is one of the most machinable engineering plastics for CNC manufacturing.

Its excellent machinability is a major reason why POM is frequently selected for precision plastic components.

Compared with many softer thermoplastics, POM produces relatively predictable chips and can achieve good surface quality when properly machined.

Outils de coupe recommandés

Recommended tools include:

• Sharp carbide end mills

• Polished carbide cutters

• Single-flute/O-flute cutters for certain milling operations

• Sharp drills

• Sharp turning inserts

The most important factor is maintaining a sharp cutting edge.

Dull tools can create:

• Excessive heat

• Frottement de surface

• Drift dimensionnel

• Poor surface finish

• Burrs

Guidance générale des paramètres de coupe CNC

Typical starting ranges for unfilled POM can be approximately:

These are starting ranges rather than fixed production parameters. The optimum cutting conditions depend on tool diameter, flute count, machine spindle speed, workpiece geometry and grade.

CNC Milling POM

POM is highly suitable for:

• Pocket milling

• Contouring

• Slotting

• Perforage

• Threading

• 3D surface machining

• Precision profiling

For complex geometries, 3-axis, 4-axis and 5-axis CNC machining can all be used.

For high-quality surfaces, a dedicated finishing pass is generally preferable to relying entirely on the roughing toolpath.

CNC Turning POM

POM is particularly suitable for CNC turning.

Common turned components include:

• Bushings

• rouleaux

• Spacers

• Shafts

• Sleeves

• Sealing components

• Precision rings

Sharp turning tools and adequate chip clearance are important for maintaining dimensional accuracy.

Drilling POM

POM can be drilled efficiently.

Potential issues include:

• Heat accumulation in deep holes

• Chip packing

• Hole oversize

• Burrs

For deep holes, peck drilling or optimized chip evacuation can be beneficial.

Tapping & Threading

POM can be directly tapped and threaded.

For low-load applications, machined plastic threads can work well.

For frequent assembly/disassembly or higher loads, consider:

• Brass inserts

• Stainless-steel inserts

• Press-fit threaded inserts

The choice depends on load, assembly frequency and environmental conditions.

Common POM CNC Machining Problems

1. Dimensional Expansion or Contraction

POM can change dimension with temperature.

During machining, excessive heat can cause the component to measure differently immediately after machining than after it has thermally stabilized.

Solutions:

• Keep cutting heat under control

• Use sharp tools

• Avoid excessive rubbing

• Allow parts to thermally stabilize before final inspection

• Maintain controlled inspection temperature

2. Burrs

Burrs can occur around:

• Holes

• Slots

• Sharp external edges

• Intersecting features

Sharp tooling and optimized finishing passes can significantly reduce burr formation.

3. Déformation de la paroi mince

Although POM is relatively stiff for a thermoplastic, thin sections can still deform under clamping force.

Recommended approaches include:

• Soft jaws

• Vacuum fixtures

• Custom fixtures

• Reduced clamping pressure

• Multiple finishing passes

4. Heat Buildup

POM has relatively low thermal conductivity.

If cutting heat is not removed efficiently, localized temperature increases can affect:

• Précision dimensionnelle

• Finition de surface

• Tool life

• Edge quality

Air blast and efficient chip evacuation are often effective.

5. Stringy or Recut Chips

Improper cutting conditions can produce undesirable chips.

Solutions include:

• Optimizing feed rate

• Increasing chip evacuation

• Using suitable flute geometry

• Avoiding excessive rubbing

Capacité de tolérance CNC

POM is particularly suitable for precision machining.

Under controlled conditions, CNC machining can achieve approximately ±0.02–0.05 mm on selected features.

However, this should not be interpreted as a universal tolerance capability.

For very tight tolerances, engineers should account for:

Part dimensions

Thermal expansion

Material grade

Stock stress

Fixture method

Machining sequence

Inspection temperature

· 

For functional designs, GD&T should be used to identify which dimensions actually require tight control rather than applying unnecessarily tight tolerances across the entire drawing.

Finition de surface

CNC-machined POM can achieve good surface quality.

A typical machined surface may fall approximately within:

Ra 0.8–3.2 μm

depending on:

• Tool geometry

• Vitesse de coupe

• Feed

• Stratégie de finition

• Machine condition

• Géométrie de la partie

For functional sliding surfaces, consistency and dimensional control can be more important than simply minimizing Ra.


5. Typical POM Applications & Part Scenarios

 
Automatisation industrielle

POM is extensively used for:

• Blocs de guidage

• rouleaux

• Bushings

• Composants du convoyeur

• Positioning components

• Sliding plates

• Custom fixtures

Its low friction and wear resistance make it especially suitable for moving mechanisms.

robotique

CNC-machined POM can be used for:

• Bushings

• Spacers

• rouleaux

• Cable-routing components

• Low-load gears

• Guide components

• End-effector components

For high-load robot joints, metal or reinforced engineering plastics may be more appropriate.

Precision Machinery

POM is frequently used in:

• Roulements

• Bushings

• engrenages

• Cam followers

• Guide rails

• rouleaux

• Mechanical couplings

Its combination of machinability and dimensional stability makes it a strong candidate for precision mechanical components.

Automobile

Potential applications include:

• Fuel-system components

• Bushings

• Gear components

• Clips

• rouleaux

• Guide components

• Interior mechanisms

The exact grade must be selected according to temperature, fuel and chemical exposure.

Électrique & électronique

POM can be used for:

• Insulating components

• Connector components

• Precision spacers

• Switch mechanisms

• Mechanical supports

However, electrical applications requiring flame-retardant certification should use an appropriately certified grade rather than generic POM.

Medical & Laboratory Equipment

Suitable applications may include:

• Instrument components

• rouleaux

• Guide components

• Mechanical fixtures

• Laboratory equipment components

Medical applications require appropriate material certification and consideration of cleaning, sterilization and regulatory requirements.

Semiconductor & Automation Equipment

POM can be used for selected:

Mechanical guides

Positioning fixtures

Handling components

Insulating mechanical parts

Low-friction mechanisms

For environments requiring exceptionally low outgassing, high-temperature resistance or specific chemical compatibility, specialized materials may be preferable.

6. Our POM CNC Machining Advantages

Material Selection Support

We can help select between:

POM-H

POM-C

Standard acetal

Modified/lubricated POM

Glass-filled POM

Other engineering plastic alternatives

Material selection can be based on:

• Load

• Friction

• Wear

• Température

• Chemical exposure

• Dimensional requirements

• Production volume

Mature CNC Process Control

POM is highly machinable, but precision results still depend on process engineering.

Our process planning considers:

• Tool geometry

• Cutting parameters

• Workholding

• Roughing/finishing sequence

• Thermal stabilization

• Burr control

• Inspection strategy

This is particularly important for precision gears, bushings and thin-wall components.

High-Precision CNC Machining

For critical POM components, we can control:

• Bore diameter

• Shaft diameter

• Concentricité

• Planitude

• Parallelism

• Position

• Profile

• Thread dimensions

GD&T requirements can be incorporated directly into the manufacturing and inspection process.

Prototype à production en lots

POM CNC machining can support:

• One-off engineering parts

• Prototype components

• Low-volume production

• Pilot runs

• Repeated batch production

• Higher-volume CNC manufacturing

For larger quantities, machining strategy and nesting can be optimized to improve material utilization and reduce cycle time.

Surface & Post-Machining Services

Depending on application requirements, post-processing can include:

• Precision deburring

• Edge breaking

• Polissage

• Nettoyage

• Laser marking

• Part identification

• Assemblée

Because POM has low surface energy and good chemical resistance, finishing processes should be selected specifically for the material.

Inspection et qualité Documentation matérielle

Inspection can include:

• Dimensional inspection

• GD&T verification

• Bore and thread inspection

• Surface-finish inspection

• Visual inspection

• Critical-feature inspection

• Material documentation where available

For production orders, inspection requirements can be established according to the customer's drawing and quality specifications.

POM CNC Machining Material Selection Summary

POM vs. ABS for CNC Machining

Recommandation d'ingénierie finale

POM/Delrin is one of the strongest choices for CNC machined plastic components that require precision, low friction, wear resistance and dimensional stability. It is particularly well suited to gears, bushings, rollers, spacers, guide components and other moving mechanical parts.

For procurement engineers and designers, the most important specification is not simply "Delrin." The drawing or purchase specification should identify the required POM grade, mechanical requirements, operating temperature, chemical environment, dimensional tolerances and any applicable certifications.

Contact us for a CNC machining quote and DFM consultation for POM/Delrin parts, including material-grade selection, precision machining, tolerance review and batch-production planning.

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