What is POM material?

POM (Polyoxymethylene), commonly known as acetal, is a high-performance engineering thermoplastic widely used for precision CNC machined parts. Delrin® is a well-known commercial brand of acetal homopolymer, while POM also includes copolymer grades from other manufacturers. The material combines low friction, good wear resistance, dimensional stability, stiffness, and excellent machinability, making it particularly valuable for gears, bushings, rollers, precision fixtures, guide components, and mechanical parts.
Material terminology note: “POM” and “Delrin” should not automatically be treated as identical specifications. POM is the polymer family; Delrin® is a registered trade name associated with acetal homopolymer products. Actual properties depend on the specific grade and supplier datasheet.

1. Basic Material Information

Material Designation & Classification

POM is generally divided into two major material families:

POM-H (homopolymer acetal) — typically higher stiffness, strength and dimensional stability.

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

The actual grade should be specified according to the supplier's datasheet because additives, reinforcement and formulation can substantially change performance.

Core Positioning

POM is one of the most important engineering plastics for precision mechanical components.

Compared with ABS, POM generally offers:

• Better wear resistance

• Lower friction

• Higher stiffness

• Better dimensional stability

• Better machinability for precision mechanical components

• Compared with PEEK, POM generally offers:

• Lower cost

• Easier machining

• Lower temperature capability

• Lower chemical and mechanical performance at elevated temperatures

This makes POM particularly attractive for precision CNC plastic parts where mechanical movement and dimensional accuracy are important.

2. POM Physical Properties

The following values represent typical ranges for unfilled commercial POM grades. They are not universal specification limits. Homopolymer and copolymer grades can differ significantly.

Density

POM has a density of approximately 1.40–1.43 g/cm³.

It is considerably lighter than aluminum while being significantly denser and stiffer than many commodity plastics.

This provides a useful combination of:

• Lightweight construction

• Mechanical stiffness

• Good dimensional stability

• Low friction
  
  
  Tensile Strength & Stiffness

Typical unfilled POM provides tensile strength in the approximate range of 60–75 MPa, with tensile modulus commonly around 2.5–3.5 GPa.

This makes POM suitable for mechanically loaded components that would be too demanding for softer plastics such as polyethylene.

However, POM should not be considered a direct replacement for metals in heavily loaded or high-temperature applications.

Impact Resistance

POM has good toughness and can tolerate repeated mechanical loading better than many brittle plastics.

Its actual impact performance depends on:

• Grade

• Temperature

• Part geometry

• Wall thickness

• Processing history

• Presence of reinforcement

Wear Resistance

Wear resistance is one of POM's most important engineering advantages.

POM is frequently selected for moving components because of its combination of:

• Low friction

• Good abrasion resistance

• Good fatigue resistance

• Good dimensional stability

It is commonly used in:

• Bushings

• Rollers

• Gears

• Guide blocks

• Sliding components

• Bearing cages

For extremely demanding tribological applications, specialized POM grades containing PTFE, silicone or other lubricating modifiers may be more appropriate.

Temperature Resistance

POM generally performs well in moderate-temperature mechanical applications.

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.

Moisture Absorption

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

Chemical Composition

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:

• Lubricants

• UV stabilizers

• Glass fibers

• Mineral fillers

• PTFE

• Other performance modifiers

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

Chemical Resistance

POM generally provides good resistance to many:

• Hydrocarbons

• Oils

• Fuels

• Alcohols

• Weak acids

• Weak alkalis

• 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

Corrosion Resistance

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

UV Resistance

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:

• Mechanical fastening

• Press fits

• Snap fits

• Ultrasonic welding under suitable conditions

• Specialized adhesive systems

For precision assemblies, mechanical joining is often preferred.|


4. POM CNC Machinability Analysis

Machining Difficulty: Easy

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.

Recommended Cutting Tools

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

• Surface smearing

• Dimensional drift

• Poor surface finish

• Burrs

General CNC Cutting Parameter Guidance

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

• Drilling

• 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

• Rollers

• 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. Thin-Wall Deformation

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:

• Dimensional accuracy

• Surface finish

• 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

CNC Tolerance Capability

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.

Surface Finish

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

• Cutting speed

• Feed

• Finishing strategy

• Machine condition

• Part geometry

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


5. Typical POM Applications & Part Scenarios

 
Industrial Automation

POM is extensively used for:

• Guide blocks

• Rollers

• Bushings

• Conveyor components

• Positioning components

• Sliding plates

• Custom fixtures

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

Robotics

CNC-machined POM can be used for:

• Bushings

• Spacers

• Rollers

• 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:

• Bearings

• Bushings

• Gears

• Cam followers

• Guide rails

• Rollers

• Mechanical couplings

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

Automotive

Potential applications include:

• Fuel-system components

• Bushings

• Gear components

• Clips

• Rollers

• Guide components

• Interior mechanisms

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

Electrical & Electronics

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

• Rollers

• 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

• Temperature

• 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

• Concentricity

• Flatness

• Parallelism

• Position

• Profile

• Thread dimensions

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

Prototype to Batch Production

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

• Polishing

• Cleaning

• Laser marking

• Part identification

• Assembly

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

Quality Inspection & Material Documentation

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

Final Engineering Recommendation

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.

Get an Instant Quotefor your custom POM-C parts today.