General
Fabrication Guidelines
The following guidelines are
presented for those machinists not familiar with the machining
characteristics of plastics. They are intended as guidelines
only, and may not represent the most optimum conditions for all
parts. The troubleshooting quick reference in this section
should be used to correct undesirable surface finishes or
material responses during machining operations.
Most quality stock shape
materials are stress relieved to ensure the highest degree of
machinability and dimensional stability. However, the relative
softness of plastics (compared to metals) generally results in
greater difficulty maintaining tight tolerances during and after
machining. A good rule of thumb for tolerances of plastic parts
is +/- .001 per inch of dimension although tighter tolerances
are possible with very stable, reinforced materials.
When machining plastic
stock shapes, remember...
- Thermal expansion is up to
10 times greater with plastics than metals
- Plastics lose heat more
slowly than metals, so avoid localized overheating
- Softening (and melting)
temperatures of plastics are much lower than metals
- Plastics are much more
elastic than metals
Because of these differences, you
may wish to experiment with fixtures, tool materials, angles,
speeds and feed rates to obtain optimum results.
Getting Started
- Positive tool geometries
with ground peripheries are recommended
- Carbide tooling with
polished top surfaces is suggested for optimum tool life and
surface finish. Diamond coated or polycrystalline tooling
provides optimum surface finish when machining Duratron® XP
or Vespel®
PI or Celazole* PBI.
- Use adequate chip clearance
to prevent clogging
- Adequately support the
material to restrict deflection away from the cutting tool
Turning
Operations require inserts with positive geometries and
ground peripheries. Ground peripheries and polished top surfaces
generally reduce material build-up on the insert, improving the
attainable surface finish. A fine grained C-2 carbide is
generally best for turning operations.
Drilling
The insulating characteristics of plastics require
consideration during drilling operations, especially when hole
depths are greater than twice the diameter.
Small
diameter holes (232" or 1mm to 1.0 or 25mm)
High speed steel twist drills are generally sufficient for small
holes. To improve swarf removal, frequent pull-out (peck
drilling) is suggested. A slow spiral (low helix drill will
allow for better swarf removal.
Large
diameter holes (1.0” or 25mm and larger)
A slow spiral (low helix) drill or general purpose
drill bit ground to a 118° point angle with 9° to 15° lip
clearance is recommended. The lip rake should be ground (dubbed
off) and the web thinned.
It is generally
best to drill a pilot hole (maximum 1/2” diameter) using 600 to
1,000 rpm and a positive feed of 0.005” to 0.015” per
revolution. Avoid hand feeding because of the drill grabbing
which can result in microcracks forming. Secondary drilling at
400 to 500 rpm at 0.008 to 0.020” per revolution is required to
expand the hole to larger diameters.
A two step
process using both drilling and boring can be used on notch
sensitive materials such as Ertalyte® PET-P, Torlon* PAI,
Duratron® XP, Vespel® PI, Celazole* PBI and glass or carbon
reinforced products. This minimizes heat build-up and reduces
the risk of cracking.
- Drill a 1”
diameter hole using an insert drill at 500 to 800 rpm with a
feed rate of 0.005” to 0.015” per revolution.
- Bore the
hole to final dimensions using a boring bar with carbide
insert with 0.015” to 0.030” radii at 500 to 1,000 rpm and a
feed rate of 0.005 to 0.010” per revolution.
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Threading and Tapping
Threading should be done by single point using a
carbide insert and taking four to five 0.001” passes at the end.
Coolant usage is suggested. For tapping, use the specified drill
with a two flute tap. Remember to keep the tap clean of chip
build-up. Use of a coolant during tapping is also suggested.
Milling
Sufficient fixturing allows fast table travel and high
spindle speeds when end milling plastics. When face milling, use
either high positive or high shear geometry cutter bodies.
Sawing
Band sawing is versatile for straight, continuous
curves or irregular cuts. Table saws are convenient for straight
cuts and can be used to cut multiple thicknesses and thicker
cross sections up to 4” with adequate horsepower. Saw blades
should be selected based upon material thickness and surface
finish desired.
Machining
Tips
- Rip and
combination blades with a 0° tooth rake and 3°
to 10° tooth set are best for general sawing in
order to reduce frictional heat.
- Hollow ground
circular saw blades without set will yield
smooth cuts up to 3/4” thickness.
- Tungsten carbide
blades wear well and provide optimize surface
finishes.
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Coolant Recommendations
Coolants are
generally not required for most plastic machining operations
(not including drilling and parting off). However, for optimum
surface finishes and close tolerances, non-aromatic, water
soluble coolants are suggested. Spray mists and pressurized air
are very effective means of cooling the cutting interface.
General purpose petroleum based cutting fluids although suitable
for metals and some plastics, may contribute to stress cracking
of amorphous plastics such as Acrylic, Polycarbonate,
Polysulfone, Ultem® PEI, and Radel® R PPSU.
Coolants Tips
- Coolants are
strongly suggested during drilling operations,
especially with notch sensitive materials such as
Ertalyte® PET-P, Torlon® PAI, Duratron® XP, Vespel®
PI, Celazole® PBI and glass or carbon reinforced
products.
- In addition to
minimizing localized part heat- up, coolants prolong
tool life. Example (flood) coolants suitable for
most plastics include:
A generally suitable
mist coolant is Astro-Mist 2001A (Monroe
Fluid Technology, Hilton, NY).
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FABRICATION GUIDELINES - TURNING AND DRILLING |
|
MATERIALS |
REL.
MACHIN-
ABILITY
(1 to 10
1=easiest) |
TURNING |
DRILLING** |
|
Depth of cut |
Speed
Feet/Min. |
Feed,
In./Rev. |
Nominal Hole Dia. |
Feed,
In./Rev. |
Acetal copolymer
Delrin®, Delrin® AF
Delrin® AF Blend
Nylon 101
Nylatron® GS, GSM
Nylatron® GSM Blue
Nylatron® NSM
MC® 901, MC® 907 Nylon
Polycarbonate
Polysulfone
Ultem® 1000 & 2300 PEI |
1
1
1
1
1
1
1
1
3
3
7 |
.150”
.025” |
500-600
600-700 |
.010-.015
.004-.007 |
1/16"
1/8"
1/4"
1/2"
3/4"
1"
1 1/2"
2" or > |
.007-.015
"
"
.015-.025
"
.020-.050
"
" |
Fluorosint® 500
Fluorosint® 207 |
1
1 |
.150”
.025” |
350-500
500-600 |
.010-.015
.003-.008 |
1/16"
1/8"
1/4"
1/2"
3/4"
1"
1 1/2"
2" or > |
.007-.015
"
"
.015-.025
"
.020-.050
"
" |
PEEK™, unfilled
PEEK 30% GF
PEEK 30% CF |
5
7
7 |
.150”
.025” |
600-1000
600-700 |
.010-.016
.004-.007 |
1/16"
1/8"
1/4"
1/2"
3/4"
1"
1 1/2"
2" or > |
.002-.005
"
"
.004-.008
"
.008-.012
"
" |
Ertalyte® PET-P
Ertalyte® TX
Hydex® 4101 PBT-P |
|
.150”
.025” |
500-600
600-700 |
.010-.015
.004-.007 |
1/16"
1/8"
1/4"
1/2"
3/4"
1"
1 1/2"
2" or > |
.002-.005
"
"
.015-.025
"
.020-.050
"
" |
Techtron® PPS
Ryton® PPS
Ryton® BG PPS |
|
.150”
.025” |
100-300
250-500 |
.010-.020
.005-.010 |
1/16"
1/8"
1/4"
1/2"
3/4"
1"
1 1/2"
2" or > |
.007-.015
"
"
.015-.025
"
.020-.050
"
" |
Torlon® 4203 PAI
Torlon® 4301 PAI
Torlon® 4501 PAI
Torlon® 4503 PAI
Torlon® 4540 PAI
Torlon® 5530 PAI
Duratron® XP
Vespel® PI |
|
.025” |
300-800 |
.004-.025
|
1/16"
1/8"
1/4"
1/2"
3/4"
1"
1 1/2"
2" or > |
.007-.015
"
"
.015-.025
"
.020-.050
"
" |
|
Celazole® PBI |
|
.150”
.025” |
100-150
150-225 |
.005-.010
.002-.006 |
1/16" to 1/4"
1/2" or > |
.005-.015
.015-.025 |
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FABRICATION GUIDELINES - MILLING |
|
MATERIALS |
End Milling /
Slotting |
Face Milling
(C-2) Carbide Tool |
high speed
steel (m2,M7) |
Depth
of cut |
Speed,
ft./min. |
Feet,
in./tooth |
Depth
of cut |
Speed,
ft./min. |
Feet,
in./tooth |
Acetal
copolymer
Delrin 150, Delrin AF
Delrin AF Blend
Nylon 101
Nylatron® GS Nylon
Nylatron® GSM,
Nylatron® GSM Blue,
Nylatron® NSM
MC® 901 Nylon,
MC® 907 Nylon |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.150
0.060 |
1300-1500
1500-2000 |
0.020
0.005 |
Polycarbonate
Polysulfone
Ultem® 1000 PEI
Ultem® 2300 PEI |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.150
0.060 |
1300-1500
1500-2000 |
0.020
0.005 |
|
PEEK™ |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.150
0.060 |
500-750
" |
0.020
0.005 |
Fluorosint® 500
Fluorosint® 207 |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.150
0.060 |
500-700
550-750 |
0.010
0.005 |
Techtron® PPS
Ryton® PPS |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.150
0.060 |
1300-1500
1500-2000 |
0.020
0.005 |
|
Torlon® PAI |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.035 |
500-800 |
.006-.035 |
Ertalyte® PET-P
Ertalyte® TX
Hydex® 4101 PBT-P |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.250
"
"
"
.050
"
" |
270-450
"
"
"
300-500
"
" |
0.002
0.003
0.005
0.008
0.001
0.002
0.004 |
0.150
0.060 |
1300-1500
1500-2000 |
0.020
0.005 |
Duratron® XP
Vespel® PI
Celazole® PBI |
1/4"
1/2"
3/4"
1", 2"
1/4"
1/2"
3/4" |
.50
.015 |
450-650
"
"
"
250-350
"
" |
0.005
0.002 |
0.050
0.015 |
450-650
250-350 |
0.005-.010
.002-.006 |
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FABRICATION GUIDELINES - SAWING |
|
MATERIALS |
Sawing |
Material
thickness |
Tooth
form |
Pitch
teeth/in. |
Band Speeds
ft./min. |
Acetal copolymer
Delrin 150,
Delrin AF
Delrin AF Blend
Nylon 101
Nylatron® GS Nylon
Nylatron® GSM,
Nylatron® GSM Blue,
MC® 901 Nylon,
MC® 907 Nylon |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
10-14
6
3
" |
3,000
2,500
2,000
1,500 |
Polycarbonate
Polysulfone
Ultem® 1000 PEI
Ultem® 2300 PEI |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
10-14
6
3
" |
4,000
3,500
3,000
2,500 |
|
PEEK™ |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
8-14
6-8
3
" |
4,000
3,500
3,000
2,500 |
Fluorosint® 500
Fluorosint® 207 |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
8-14
6-8
3
" |
3,000
2,500
2,000
1,500 |
Techtron® PPS
Ryton® PPS |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
8-14
6-8
3
" |
5,000
4,300
3,500
3,000 |
|
Torlon® PAI |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
8-14
6-8
3
" |
5,000
4,300
3,500
3,000 |
Ertalyte® PET-P
Ertalyte® TX
Hydex® 4101 PBT-P |
<1/2"
1/2"-1"
1"-3"
3" |
Precision
"
Butress
" |
10-14
6
3
" |
5,000
4,300
3,500
3,000 |
Duratron®
XP
Vespel® PI
Celazole® PBI |
3/8"-1"
1"-2" |
Precision
"
Butress
" |
10
10 |
3,000
1,500 |
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TROUBLESHOOTING QUICK REFERENCE |
|
Drilling |
|
Difficulty |
Common Cause |
| Tapered
hole |
1.
Incorrectly sharpened drill
2. Insufficient clearance
3. Feed too heavy |
| Burnt or
melted surface |
1. Wrong
type drill
2. Incorrectly sharpened drill
3. Feed too light
4. Dull drill
5. Web too thick |
| Chipping of
surfaces |
1. Feed too
heavy
2. Clearance too great
3. Too much rake (thin web as described) |
| Chatter |
1. Too much
clearance
2. Feed too light
3. Drill overhang too great
4. Too much rake (thin web as described) |
| Feed marks
or spiral lines on inside diameter |
1. Feed too
heavy
2. Drill not centered
3. Drill ground off-center |
| Oversize
holes |
1. Web too
thick
2. Insufficient clearance
3. Feed rate too heavy
4. Point angle too great |
| Undersize
holes |
1. Dull
drill
2. Too much clearance
3. Point angle too small |
| Holes not
concentric |
1. Feed too
heavy
2. Spindle speed too slow
3. Drill enters next piece too far
4. Cut-off tool leaves nib, which deflects drill
5. Web too thick
6. Drill speed too heavy at start
7. Drill not mounted on center
8. Drill not sharpened correctly |
| Burr at
cut-off |
1. Dull
cut-off tool
2. Drill does not pass completely through piece |
| Rapid
dulling of drill |
1. Feed too
light
2. Spindle speed too fast
3. Insufficient lubrication from coolant |
|
Cutting Off |
| Melted
surface |
1. Dull
tool
2. Insufficient side clearance
3. Insufficient coolant supply |
| Rough
finish |
1. Feed too
heavy
2. Tool improperly sharpened
3. Cutting edge not honed |
| Spiral
marks |
1. Tool
rubs during its retreat
2. Burr on point of tool |
| Concave or
convex surfaces |
1. Point
angle too great
2. Tool not perpendicular to spindle
3. Tool deflecting (use negative rake)
4. Feed too heavy
5. Tool mounted above or below center |
| Nibs or
burrs at cut-off point |
1. Point
angle not great enough
2. Tool dull or not honed
3. Feed too heavy |
| Burrs on
outside diameter |
1. No
chamfer before cut-off
2. Dull tool |
|
Turning & Boring |
| Melted
surface |
1. Tool
dull or heel rubbing
2. Insufficient side clearance
3. Feed rate too slow
4. Spindle speed too fast |
| Rough
finish |
1. Feed too
heavy
2. Incorrect clearance angles
3. Sharp point on tool (slight nose radius required)
4. Tool not mounted on center |
| Burrs at
edge of cut |
1. No
chamfer provided at sharp corners
2. Dull tool
3. Insufficient side clearance
4. Lead angle not provided on tool
(tool should ease out of cut gradually, not suddenly) |
| Cracking or
chipping of corners |
1. Too much
positive rake on tool
2. Tool not eased into cut (tool suddenly hits work)
3. Dull tool
4. Tool mounted below center
5. Sharp point on tool (slight nose radius required) |
| Chatter |
1. Too much
nose radius on tool
2. Tool not mounted solidly
3. Material not supported properly
4. Width of cut too wide (use 2 cuts) |
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| Also see:
Guidelines for Machining Ensinger Engineering Plastics
Trademark Acknowledgments:
RADEL and TORLON are registered trademarks of Solvay Advanced
Polymers.
RYTON is a registered trademark of Chevron Phillips Chemical
Company.
DELRIN and VESPEL are registered trademarks of DuPont.
ULTEM is a registered trademark of General Electric Company.
CELAZOLE is a registered trademark of Celanese Advanced
Materials, Inc.
HYDEX is a registered trademark of A.L. Hyde Company.
DURATRON, ERTALYTE, NYLATRON, and TECHTRON are registered
trademarks of Quadrant DSM Engineering Plastic Products.
PEEK is a trademark of Victrex plc.
The information on this page originally provided by Quadrant DSM
Engineering Plastics.
Other stock shape manufacturers have also provided relevant
information. |
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