When engineers design a custom plastic mechanical component, POM and nylon are often among the first materials considered.
Both are established engineering thermoplastics used for gears, bushings, rollers, guides, brackets, housings and many other industrial parts. However, they are not interchangeable. A component that performs well in POM may behave very differently when produced in nylon, especially when moisture, friction, dimensional accuracy or continuous mechanical load is involved.
For buyers, the correct question is therefore not simply "Which plastic is stronger?" or "Which material is cheaper?" The more useful question is: which material better matches the real operating conditions of this specific part?
In this guide, "nylon" refers mainly to PA66 unless otherwise noted. PA6 and other nylon grades have their own properties, so the exact resin grade should always be confirmed before tooling.
What Is the Main Difference Between POM and Nylon?
POM, also called acetal or polyoxymethylene, is commonly selected for precision mechanical components because it combines low friction, good wear behavior, useful stiffness and relatively stable dimensions.
Nylon, particularly PA66, is widely used where strength, toughness, fatigue resistance and structural performance are important. Glass-fiber-reinforced PA66 is also common when additional stiffness or heat resistance is required.
The biggest practical difference for many OEM projects is that nylon absorbs significantly more moisture from its environment than POM. Moisture can change nylon dimensions and mechanical behavior. POM is generally less affected by humidity, which is one reason it is frequently considered for precision gears, sliding guides and dimensional-critical bushings.
This does not mean POM is always better. Nylon can be the more suitable option for heavily loaded brackets, structural supports, pulleys, housings and other components where toughness and load-bearing capability are priorities.
How Do POM and PA66 Compare in Mechanical Performance?
POM and PA66 can both provide strong performance in industrial equipment, but they solve different engineering problems.
POM is often preferred for moving components. Its low friction characteristics and good wear resistance make it useful for sliding and rotating parts. It can also provide consistent dimensions for assemblies that require repeatable clearances.
PA66 is often considered when the part must carry more structural load or withstand repeated impact and fatigue. Reinforced nylon grades can provide substantially higher stiffness than unfilled nylon, although fiber reinforcement also changes molding shrinkage, surface appearance and warpage behavior.
For this reason, material comparison should always include the exact grade rather than only the family name. "POM" and "PA66" each include many grades designed for different requirements.
Which Material Has Lower Friction?
For applications involving sliding or rotating motion, POM is frequently the first material evaluated.
Its relatively low coefficient of friction can reduce resistance between moving surfaces, making it useful for gears, bushings, guides, rollers and other precision motion components. In suitable applications, POM may run against metal or another plastic with limited lubrication.
Nylon also has good wear performance and is widely used for gears, pulleys and bearings. However, friction behavior depends strongly on grade, load, speed, counterface material and lubrication. Some nylon grades include lubricating additives specifically to improve sliding performance.
If friction is critical, the buyer should tell the supplier what material the plastic part will contact, whether lubrication is present, the approximate movement speed and the expected operating life. Simply requesting a "low-friction plastic" is not enough for a reliable material recommendation.
Which Material Provides Better Dimensional Stability?
For many precision parts, POM generally offers an advantage in dimensional stability, especially when humidity changes during service.
Injection molded plastic parts change size as they cool after molding. In addition, some materials continue to respond to their environment after production. Nylon is hygroscopic, meaning it absorbs moisture. As moisture content changes, the dimensions and mechanical properties of a nylon component can also change.
This becomes important in assemblies with tight clearances. A nylon bushing, connector housing or precision guide may measure differently in a dry condition and after it has been exposed to a humid environment.
POM absorbs much less moisture and is generally more dimensionally stable under changing humidity. This is one reason it is often selected for precision gears, guides, valve components and mechanical parts where consistent dimensions matter.
How Does Moisture Affect Nylon Mechanical Parts?
Moisture is one of the most important factors to understand when specifying nylon.
Nylon can absorb moisture from the surrounding environment. This can influence dimensions, stiffness and toughness. The magnitude of the effect depends on nylon type, grade, reinforcement, part geometry and environmental conditions.
For tight-tolerance nylon parts, the drawing and inspection plan should clearly define the condition in which the component is measured. A part measured immediately after molding may not represent the same dimensions it will have after conditioning or long-term use in a humid environment.
This does not make nylon unsuitable for precision components. It means the product design, tolerance and inspection method need to reflect the actual operating environment.
Which Material Is Stronger?
The answer depends on what "stronger" means for the application.
PA66 is well known for its mechanical strength, toughness and fatigue resistance. It is widely used for brackets, structural supports, pulleys, housings and components exposed to repeated mechanical loading.
Glass-filled PA66 can provide even greater stiffness and strength. This makes reinforced nylon attractive for structural plastic components that might otherwise be produced from metal.
POM also provides good stiffness and mechanical strength, but it is often selected because of its balance of precision, low friction and wear behavior rather than maximum structural performance.
When choosing between them, engineers should consider whether the part primarily needs to move accurately or primarily needs to carry load.
How Do POM and Nylon Perform at Higher Temperatures?
Both POM and PA66 are engineering plastics, but their temperature capability depends on the exact resin grade and operating conditions.
PA66 is frequently selected for applications requiring useful mechanical performance at elevated temperatures, particularly when reinforced or heat-stabilized grades are used. POM can also perform well across a broad industrial temperature range, but the correct grade should be confirmed for the actual service temperature.
Engineers should provide both the normal operating temperature and any short-term temperature peaks. Continuous exposure at a certain temperature is very different from a brief peak during cleaning, processing or equipment startup.
Do not select a material based only on a single "maximum temperature" number from a general datasheet. Mechanical load, duration, environment and safety factor all matter.
Which Material Is Better for Gears, Bushings and Sliding Guides?
POM is particularly common in precision motion components.
Gears benefit from its low friction, good wear performance and dimensional stability. Bushings and sliding guides can also benefit when consistent clearances and low resistance are required.
Nylon is also widely used for gears, rollers and pulleys, especially where toughness and impact resistance are more important than very tight dimensional control. Larger industrial pulleys and load-bearing components may benefit from nylon's structural performance.
The final decision should account for load, speed, lubrication, noise, counterface material and service life rather than relying on part name alone.
Which Applications Usually Suit POM and Which Suit Nylon?
There is significant overlap between the two materials, but certain patterns are common in industrial design.
POM is frequently considered for precision gears, small mechanical gears, bushings, sliding guides, valve components, rollers, spacers and other parts where friction and dimensional consistency are important.
PA66 is often evaluated for structural brackets, housings, pulleys, load-bearing supports, cable and connector parts and reinforced mechanical components.
These examples are not strict rules. A gear can be produced from nylon, and a structural component can be produced from POM. Application conditions should always control the decision.
What About Glass-Filled Nylon?
Glass-filled nylon deserves separate consideration because it behaves differently from unfilled PA66.
Adding glass fiber can substantially increase stiffness and improve dimensional performance in certain directions. It can also improve structural capability at elevated temperatures.
However, reinforcement changes how the material flows and shrinks during molding. Fiber orientation can create directional shrinkage and warpage. Glass-filled materials can also increase mold wear and usually produce a different surface appearance from unfilled resin.
Changing from standard PA66 to PA66 GF30 after the mold has been manufactured should therefore not be treated as a simple substitution. The part geometry, gate design and expected dimensions should be reviewed.
Which Material Is Easier to Machine or Finish?
POM is well known for good machinability and is frequently used for CNC-machined prototypes and low-volume precision plastic parts as well as injection molded components.
Nylon can also be machined, but moisture condition can affect dimensional measurement. This is important when a machined nylon prototype is being used to validate dimensions for a future molded part.
For injection molding projects, secondary operations may include drilling, machining, threaded inserts, assembly, laser marking or printing. The need for these operations should be identified during quotation because they affect both cost and process control.
How Do Chemical Resistance and Environment Affect the Choice?
POM and nylon both have useful chemical resistance, but neither should be selected using a generic statement such as "chemical resistant."
The actual chemical, concentration, temperature and exposure duration matter. A component that experiences occasional contact with lubricant has a different requirement from one continuously immersed in process fluid.
Outdoor exposure, UV radiation and humidity should also be considered. If the material will be used outdoors, the buyer should specify this so that a suitable stabilized grade can be evaluated.
For industrial equipment, the material should be reviewed together with the complete service environment rather than only the mechanical drawing.
Which Material Is Better for Tight Tolerances?
POM is often easier to specify for tight dimensional control because of its relatively low moisture absorption and stable dimensions.
However, tolerance capability still depends on part size, wall thickness, mold design, gate position, cooling and processing conditions. A poorly designed POM part can still warp or vary dimensionally.
Nylon can also be used for precision assemblies, but the engineer should account for moisture conditioning and clearly define the measurement state.
The best drawing does not simply assign the tightest possible tolerance to every dimension. It identifies the dimensions that actually affect function and allows practical molding tolerances elsewhere.
How Does Material Choice Affect Mold Design?
Material selection should ideally be finalized before mold manufacturing because resin behavior affects shrinkage, flow, cooling and warpage.
Changing from POM to PA66, or from unfilled nylon to glass-filled nylon, can change final part dimensions. The mold engineer may need different shrinkage compensation, gate strategy or cooling considerations.
This is why material should not be treated as an afterthought. If the customer is still deciding between POM and nylon, that discussion should happen during DFM review before steel is cut.
How Do You Choose Between POM and Nylon?
A practical material decision should begin with the application, not the material name.
If the part slides or rotates, friction and wear should receive high priority. If the component must maintain precise dimensions across changing humidity, POM may deserve closer consideration.
If the component carries structural load, experiences impact or requires reinforced grades for higher stiffness, PA66 may be a stronger candidate.
Moisture exposure, temperature, chemicals, assembly method and expected service life should all be evaluated.
Annual production volume also matters because the material choice can affect tooling design, cycle stability and total manufacturing cost.
What Information Should You Send for a POM or Nylon Parts Quote?
The most useful RFQ includes both geometry and application information.
For a custom mechanical plastic part, send the 3D STEP or STP file together with a 2D drawing showing critical dimensions and tolerances.
Also provide the required material grade if it is already defined. If the material has not been selected, explain the function of the component instead.
Useful information includes the initial order quantity, estimated annual volume, operating temperature, mechanical load, contact materials, lubrication, chemical exposure, humidity conditions and any special inspection requirements.
The more clearly the supplier understands how the part works, the more useful the material recommendation and quotation will be.
Should You Specify "Nylon" or an Exact Grade?
For serious OEM projects, "nylon" alone is often too broad.
PA6, PA66 and reinforced nylon grades can have significantly different mechanical, thermal and dimensional behavior. Even within PA66, there are unfilled, glass-filled, heat-stabilized, impact-modified and other specialized grades.
Where performance is critical, the exact manufacturer and resin grade should be specified on the drawing or approved material list.
If equivalent materials are acceptable, define which properties must be matched and require approval before substitution. This helps prevent production inconsistency across repeat orders.
POM or Nylon: Which One Should You Use?
Neither material is universally better.
POM is often an excellent choice for precision moving parts that need low friction, wear resistance and stable dimensions. Nylon PA66 is often a strong choice for structural or load-bearing components that benefit from toughness, fatigue resistance and reinforced grades.
The correct decision depends on load, motion, moisture, temperature, tolerance, chemical environment and cost targets.
SWKS supports custom injection molded POM and nylon components for industrial and OEM applications, including gears, bushings, guides, rollers, brackets, housings and other mechanical parts.