Acetal Plastic Machining

Your guide to Acetal Plastic Machining

__________

Amongst the strongest and stiffest of all thermoplastics

Two general types of Acetal resins: Acetal Homopolymer and Acetal Copolymer

Both have very good machinability

Acetal, also known as POM, has excellent machinability. It is an engineering plastic known for being amongst the strongest and stiffest of all thermoplastics.

This guide will take you through the main attributes, common applications, notes for designers and suitable finishing and treatments, as well as UK stock sizes and property tables. Don't forget to bookmark the page so you can refer back later.

If you are interested in Acetal machined parts, please scroll to the bottom of the page for more information about our service and to request a quote.

Acetal Guide: Properties, Applications and Design Considerations

__________

What is Acetal?

Acetal or POM (Polyoxymethylene) is an engineering plastic known for being amongst the strongest and stiffest of all thermoplastics.

There are two general types of Acetal resins available: Acetal Homopolymer and Acetal Copolymer.

Acetal homopolymer resins are made by the DuPont Company under the trade name Delrin®. Homopolymers are typically used in highly regulated industries.

Acetal copolymers are made by several companies. Slightly softer than Acetal homopolymers, the Acetal copolymers have a lower coefficient of friction.

You may also see Acetal referred to as:

Polyoxymethylene (POM)
POM-C (Acetal Copolymer)
POM-H (Acetal Homopolymer)
Ultraform® - Copolymer brand name
Celcon® - Copolymer brand name
Tecaform® - Copolymer brand name
Delrin® - Homopolymer trade name
Polyacetal
Polyformaldehyde

Unlike other engineering plastics that produce a long swarf thread when machined, Acetal chips in the machining process. It is therefore recommended to use very sharp cutting tools.

Industry Examples:

Copolymer: Food & packaging | Medical & pharmaceutical | Automative | Electrical/Electronic | Agriculture

Homopolymers: Aerospace | Nuclear | Pharmaceutical

Typical Components & Applications: Electrical insulation | Medical applications | Food contact components (FDA compliant) | Gears | Bearings | Housings | Fasteners | Bushings | Handles | Seals | Valves | Tooling

Main Attributes:

Acetal Copolymer:

Absorbs very little moisture
High mechanical strength and rigidity
Improved dimensional stability over comparable homopolymer formulations due to the lower level of crystallinity
Low coefficient of friction
Good compressive strength
Good shock resistance
Better chemical resistance with high pH solutions
Lower centerline porosity than homopolymer in extruded shapes
Excellent machinability

Acetal Homopolymer:

Stiffer
Wide operating temperature range (-40°C to 120°C)
Higher flexural modulus at room temperature
Higher impact strengths at room temperatures and low temperatures
Tensile strength is approximately 10-15% higher than comparable copolymers
Slightly higher continuous use temperature than copolymer (95°C vs. 90°C)
Good compressive strength
Good shock resistance
Lower thermal expansion rate
Better wear resistance
Easy to machine

Note For Designers:

When machined, Acetal produces very few post machining burrs, meaning the process of de-burring can be avoided, saving precious time in manufacturing.

Acetal Copolymer has a slightly lower cost than Homopolymer (Delrin®).

Acetal Copolymers are available in a wide range of colours.

Some disadvantages of Acetal which are worth noting for material selection:

Flammable
Subject to UV degradation
Difficult to bond
Poor resistance to acids

Can we meet your acetal machining needs? Contact us now

UK Stock Sizes

Acetal UK Stock Sizes

Please note we do not supply stock material, the information provided is purely for design and research purposes.

Stock sizes have a +/+ tolerance as the extrusion process is not as accurate as precision machining.

Stock finishes are often scratched and dented, some sheet plastics come with a protective coating, however because of long suppy chains these can still be scratched underneath.

Example Acetal Stock Sizes

Stock sizes will vary depending on supplier. Please get in contact to discuss further.

Acetal Plate*

Available in Natural (Off White) and Black. Selected Sizes available in Blue.

5 x 500	+0.20/+0.70
6 x 500	+0.20/+0.70
8 x 500	+0.20/+1.10
10 x 500/620/1000	+0.20/+1.10
12 x 500/1000	+0.30/+1.50
16 x 500/1000	+0.30/+1.50
20 x 500/620/1000	+0.30/+1.50
25 x 500/620/1000	+0.30/+1.50
30 x 500/620/1000	+0.50/+5.00
35 x 620/1000	+0.50/+5.00
40 x 500/620/1000	+0.50/+5.00
50 x 500/620/1000	+0.50/+5.00
60 x 500/620/1000	+0.50/+3.50
70 x 500	+0.50/+3.50
80 x 500/1000	+0.50/+5.00
100 x 500/1000	+0.50/+5.00
120 x 620	+0.50/+6.00
150 x 620	+0.50/+7.00
12.7 x 610	+0.00/+0.64
25.4 x 610	+0.00/+0.64
38.1 x 610	+0.00/+0.64
44.4 x 610	+0.00/+0.64
50.8 x 610	+0.00/+0.64

*Plate stock lengths may vary between 2,000mm and 3,000mm

Acetal Tube

Inside Diameter (mm)	Outside Diameter (mm)	Tolerance Outside (mm)	Tolerance Inside (mm)
10	20	+0.40/+1.10	-1.10/-0.4
15	25	+0.40/+1.10	-1.10/-0.4
15	30	+0.40/+1.10	-1.10/-0.4
18	25	+0.40/+1.10	-1.10/-0.4
20	30	+0.40/+1.10	-1.10/-0.4
15	32	+0.60/+2.00	-2.00/0.60
20	36	+0.60/+2.00	-2.00/0.60
20	50	+0.60/+2.00	-2.00/0.60
25	36	+0.60/+2.00	-2.00/0.60
25	40	+0.60/+2.00	-2.00/0.60
25	45	+0.60/+2.00	-2.00/0.60
30	40	+0.60/+2.00	-2.00/0.60
30	50	+0.60/+2.00	-2.00/0.60
36	45	+0.60/+2.00	-2.00/0.60
40	50	+0.60/+2.00	-2.00/0.60
30	56	+0.80/+2.50	-2.80/0.80
30	60	+0.80/+2.50	-2.80/0.80
40	56	+0.80/+2.50	-2.80/0.80
40	60	+0.80/+2.50	-2.80/0.80
36	70	+0.80/3.00	-3.00/0.80
40	80	+0.80/3.00	-3.00/0.80
50	70	+0.80/3.00	-3.00/0.80
50	75	+0.80/3.00	-3.00/0.80
50	80	+0.80/3.00	-3.00/0.80
60	80	+0.80/3.00	-3.00/0.80
50	90	+1.20/+3.60	-5.00/-1.60
50	100	+1.20/+3.60	-5.00/-1.60
50	110	+1.20/+3.60	-5.00/-1.60
70	90	+1.20/+3.60	-5.00/-1.60
70	100	+1.20/+3.60	-5.00/-1.60
80	100	+1.20/+3.60	-5.00/-1.60
50	125	+1.50/+4.50	-6.50/-2.00
80	125	+1.50/+4.50	-6.50/-2.00
100	125	+1.50/+4.50	-6.50/-2.00
100	150	+1.50/+4.50	-6.50/-2.00
125	150	+1.50/+4.50	-6.50/-2.00
100	165	+1.80/+5.40	-7.50/-2.20
125	180	+1.80/+5.40	-7.50/-2.20
150	180	+1.80/+5.40	-7.50/-2.20
100	200	+2.00/+6.00	-8.50/-2.50
150	200	+2.00/+6.00	-8.50/-2.50
200	230	+3.00/+9.00	-12.00/-3.00
200	250	+3.00/+9.00	-12.00/-3.00
200	300	+3.00/+10.00	-13.00/-3.50

Acetal is also available in red, yellow, green and grey colour options, however these are generally less readily available and may incur minimum order charges.

Technical Properties

Acetal Technical Properties

Acetal Mechanical Properties

Mechanical Properties	Type of Acetal	Value	Parameter	Norm	Comments
Modulus of Elasticity (Tensile Strength) (MPa)	Homopolyer	3400	1mm/min	DIN EN ISO 527-2	For tensile test: specimen type 1b
Modulus of Elasticity (Tensile Strength) (MPa)	Copolymer	2800	1mm/min	DIN EN ISO 527-2	For tensile test: specimen type 1b
Tensile Strength (MPa)	Homopolyer	79	50mm/min	DIN EN ISO 527-2
Tensile Strength (MPa)	Copolymer	67	50mm/min	DIN EN ISO 527-2
Tensile Strength at Yield (MPa)	Homopolyer	79	50mm/min	DIN EN ISO 527-2
Tensile Strength at Yield (MPa)	Copolymer	67	50mm/min	DIN EN ISO 527-2
Elongation at Yield (%)	Homopolyer	37	50mm/min	DIN EN ISO 527-2
Elongation at Yield (%)	Copolymer	9	50mm/min	DIN EN ISO 527-2
Elongation at Break (%)	Homopolyer	45	50mm/min	DIN EN ISO 527-2
Elongation at Break (%)	Copolymer	32	50mm/min	DIN EN ISO 527-2
Flexural Strength (MPa)	Homopolyer	106	2mm/min	DIN EN ISO 178	For flexural test:supoort span 64mm, norm specimen
Flexural Strength (MPa)	Copolymer	91	2mm/min	DIN EN ISO 178	For flexural test:supoort span 64mm, norm specimen
Modulus of Elasticity (Flexural Test)	Homopolyer	3600	-	DIN EN ISO 178
Modulus of Elasticity (Flexural Test)	Copolymer	2600	-	DIN EN ISO 178
Compression Strength (MPa)	Homopolyer	19/33	1% / 2%, 5mm/min, 10N	EN ISO 604	Specimen 10x10x10mm
Compression Strength (MPa)	Copolymer	20/35	1% / 2%, 5mm/min, 10N	EN ISO 604	Specimen 10x10x10mm
Compression Modulus (MPa)	Homopolyer	2700	5mm/min, 10N	EN ISO 604	Specimen 10x10x50mm, modulus range between 0.5 and 1% compression
Compression Modulus (MPa)	Copolymer	2300	5mm/min, 10N	EN ISO 604
Impact Strength (Charpy) (KJ/m^2)	Homopolyer	n.b.	Max 7,5J	DIN EN ISO 179-1EU	For charpy test: support span 64mm, norm specimen. nb = not broken
Impact Strength (Charpy) (KJ/m^2)	Copolymer	n.b.	Max 7,5J	DIN EN ISO 179-1EU
Notched Impact Strength (Charpy) (KJ/m^2)	Homopolyer	15	Max 7,5J	DIN EN ISO 179-1eA
Notched Impact Strength (Charpy) (KJ/m^2)	Copolymer	8	Max 7,5J	DIN EN ISO 179-1eA
Ball Indentation Hardness (MPa)	Homopolyer	185	-	ISO 2039-1
Ball Indentation Hardness (MPa)	Copolymer	165	-	ISO 2039-1

Acetal Thermal Properties

Thermal Properties	Type of Acetal	Value	Parameter	Norm	Comments
Glass Transition Temperature (°C)	Homopolyer	-60	-	DIN 53765	Found in public sources
Glass Transition Temperature (°C)	Copolymer	-60	-	DIN 53765	Found in public sources
Melting Temperature (°C)	Homopolyer	182	-	DIN 53765
Melting Temperature (°C)	Copolymer	166	-	DIN 53765
Service Temperature (Short Term) (°C)	Homopolyer	150	-	-	Found in public sources. Individual testing regarding application conditions is mandatory
Service Temperature (Short Term) (°C)	Copolymer	140	-	-
Service Temperature (Long Term) (°C)	Homopolyer	110	-	-
Service Temperature (Long Term) (°C)	Copolymer	100	-	-
Thermal Expansion (CLTE) (10-5 K-1)	Homopolyer	12	23-60°C, long	DIN EN ISO 11359-1;2
Thermal Expansion (CLTE) (10-5 K-1)	Copolymer	13	23-60°C, long	DIN EN ISO 11359-1;2
Thermal Expansion (CLTE) (10-5 K-1)	Homopolyer	13	23-100°C, long	DIN EN ISO 11359-1;2
Thermal Expansion (CLTE) (10-5 K-1)	Copolymer	14	23-100°C, long	DIN EN ISO 11359-1;2
Specific Heat (J/g*K)	Homopolyer	1.3	-	ISO 22007-4:2008
Specific Heat (J/g*K)	Copolymer	1.4	-	ISO 22007-4:2008
Thermal Conductivity W/(K*m)	Homopolyer	0.43	-	ISO 22007-4:2008
Thermal Conductivity W/(K*m)	Copolymer	0.39	-	ISO 22007-4:2008

Acetal Electrical Properties

Electrical Properties	Type of Acetal	Value	Parameter	Norm
Specific Surface Resistance (Ω)	Homopolyer	10₁₄	-	DIN IEC 60093
Specific Surface Resistance (Ω)	Copolymer	10₁₄	-	DIN IEC 60093

Other Acetal Properties

Other Properties	Type of Acetal	Value	Parameter	Norm	Comments
Water Absorption (%)	Homopolyer	0.05/0.1	24h/96h (23°C)	DIN EN ISO 62	Øca, 50mm, h=13mm
Water Absorption (%)	Copolymer	0.05/0.1	24h/96h (23°C)	DIN EN ISO 62	Øca, 50mm, h=13mm
Flammability	Homopolyer	HB	Corresponding to	DIN IEC 60695-11-10	Corresponding mean no listing at UL (yellow card). the information might be taken from resin, stock shape or estimation. Individual testing regarding application conditions is mandatory.
Flammability	Copolymer	HB	Corresponding to	DIN IEC 60695-11-10

Acetal Plastic Machined Parts

__________

Penta Precision provides the following plastic Acetal machining services:

CNC milling
CNC turning
Prototypes and batch runs
Insert installation
Part marking

Manual milling
Manual turning
Machining design advice
Design for manufacture service

Want to know more?

__________

Find out how we can help you

PLASTIC

Plastic Machining

EXPLORE

Industry Sectors

EXPLORE

Commitment To Quality

EXPLORE

Get A Quote

__________

Acetal Plastic Machining

Your guide to Acetal Plastic Machining

__________

Acetal Guide: Properties, Applications and Design Considerations

What is Acetal?

Acetal or POM (Polyoxymethylene) is an engineering plastic known for being amongst the strongest and stiffest of all thermoplastics.

Industry Examples:

Typical Components & Applications: Electrical insulation | Medical applications | Food contact components (FDA compliant) | Gears | Bearings | Housings | Fasteners | Bushings | Handles | Seals | Valves | Tooling

Main Attributes:

Acetal Copolymer:

Acetal Homopolymer:

Note For Designers:

Can we meet your acetal machining needs? Contact us now

Acetal UK Stock Sizes

Example Acetal Stock Sizes

Acetal Plate*

Acetal Tube

Acetal Technical Properties

Acetal Mechanical Properties

Acetal Thermal Properties

Acetal Electrical Properties

Other Acetal Properties

Further Reading & Resources

Acetal Plastic Machined Parts

Penta Precision provides the following plastic Acetal machining services:

Want to know more?

__________

Find out how we can help you

Plastic Machining

Industry Sectors

Commitment To Quality

Get A Quote