QC-10® High Strength Aluminum Injection Mold
QC-10® Aluminum Molds for high-volume production are emerging as an attractive option for an increasing
number of applications because it can reduce cycle times dramatically, speed mold construction, and trim
tooling costs. A successful application utilizing a QC-10 Aluminum Injection Mold will typically run 20% to
40% faster than the same part running in a steel mold. This translates into a cost advantage for the molder and
customer that is difficult to match.
Rapid heating of the QC-10 Aluminum mold during injection facilitates molding at lower injection pressures
while the rapid cooling of the QC-10 Aluminum mold enables faster de-molding. If you monitored the actual
temperature of a steel mold during a molding cycle and compared it with a QC-10 aluminum mold, the
QC-10 mold would show a rapid spike in temperature during injection followed by an equally rapid reduction
in mold temperature. For a steel mold, the temperature profile would show a slower, more gradual rise in
temperature followed by a gradual decrease in temperature.

Studies have shown that the QC-10 LOW Interfacial heat resistance (High Conductivity) will remove
heat from the plastic melt even during Injecting and NOT only during the Cooling time of the part.

It is important to counter act this fast cooling phenomena of QC-10 by using slightly faster fill speeds
and slightly elevated mold temperatures to counteract surface blemishes caused by fast
Injection/melt/solidification.

However, even with slightly higher mold set temperatures (10 - 20 degrees) the plastics solidification
will occur at a faster rate than with steel molds, therefore result is faster melt solidification and shorter
cooling/ cycle times.
QC-10® High Strength Aluminum Injection Mold Design Tips
QC-10® molds can be designed with many features such as slides and lifters. These are general guidelines and do
not constitute limitations but help to plan more economical aluminum molds.
1. Filled Resins such as Glass Filled Nylon have been successful running in QC-10 Molds. For higher
volume requirements, surface coatings are recommended.
2. QC-10 Continuous Mold Temperature should not exceed 250°F
QC-10
Yield
Strengthvs
vs.
Exposure Time
Time
QC-10
Yield
Strength
Exposure
550
Yield Strength (MPa)
500
450
400
350
300
200
250
300
350
250
o
F
F
o
F
o
F
o
(93 oC)
(121 oC)
(180 oC)
(230 oC)
200
0.1
1
10
100
Exposure Time (hr)
3. QC-10 Mold surfaces can be Acid or Laser Etched for Texture
4. Shut-off angles - 5 degrees minimum is recommended, Preferred shut off angle is 7-8 degree for all
matching surfaces
5. Narrow, tall standing cores should be inserted with a more stable material, P-20 – MoldMAX®
6. Ejection pins should be located so that they will eject even short shots. This could help eliminate mold
damage that can occur when trying to remove a short shot.
7. Increase slide contact surface by 25% (un-treaded aluminum)
8. If an aluminum surface is to be treated with a hardened coating of 52RC, then the lifters and slides
would not need to be oversized, the same dimensions as a conventional steel mold should be suitable.
9. The area of shut off should be typically twice the surface area of the impression, with an inch added to
the W & L for each inch of depth of the impression.
Example: a 6.00” x 6.00” impression = 36.00 sq in. -- 36 x 2 = 72. The square root of 72 is 8.5,
2.00” depth of the impression add 2 inches 10.50” x 10.50” should be the block size.
10. If blind holes are created during the mold build that need to be plugged, QC-10 is recommended as the
material for this plug. Using a lesser grade alloy such as 6061 can be the cause of pre mature failure.
Two dissimilar metals in contact in a corrosive environment can result in galvanic corrosion. In the
QC-10 - 6061 galvanic couple, QC-10 is expected to act as the anode (more active) and 6061 as the
cathode (more noble).
11. Thermal Expansion should be taken into consideration when designing a QC-10® Injection Mold that
may incorporate inserts, slides, lifters or mounted plates that may be made with different alloys. The
Thermal Expansion differences between the different alloys could result in pre-mature failure.



Coefficient of linear thermal expansion for QC-10®:
Coefficient of linear thermal expansion for P20 Steel:
Coefficient of linear thermal expansion Beryllium Copper:



QC-10® Expansion: for every 25F = 0.0003425” :
P-20 Expansion: for every 25F = 0.0001775” :
Beryllium Copper Expansion 25F = 0.0002425” :
13.7 x 10-6 - (0.0000137) per F
7.1 x 10-6 - (0.0000071) per F
9.7 x 10-6 – (0.0000097) per F
100F expansion will be 0.00137”
100F expansion will be 0.00071”
100F expansion will be 0.00097”
Linear thermal expansion can be expressed as:
dl = L0 α (t1 - t0)
Where:
dl = change in length (inches)
L0 = initial length (inches)
α = linear expansion coefficient ( in/inoF)
t0 = initial temperature ( oF)
t1 = final temperature (oF)
12. Straight Thread O-Ring Type water fittings are recommended, less stress on threads, Stainless Steel or
Aluminum fittings preferred to avoid Galvanic Corrosion Issues.
13. Water Lines should be twice the diameter of the water line from the mold surface, 1.00” minimum is
recommended whenever possible.
14. The pitch (distance between cooling channel centers) should be three to five times the channel diameter.
15. The high thermal properties of QC-10 allow for flexibility in the placement of water lines.
16. Maintain neutral water pH levels to combat premature corrosion. Water systems must be maintained at
pH levels between 6.5 and 8.5.
17. Eliminate or maintain minimum levels of dispersed rust, dissolved metals, chlorinated biocides, heavy
metals, chlorides, and phosphates in water.
18. When using QC-10 as an insert in a steel mold base, clearance holes should be considered in the steel
mold base for water lines into the QC-10 insert. This will allow cooling water to go directly into the
QC-10 without passing thru the steel. This will help to reduce corrosion and eliminate the need for oring seals.
Pipe Nipple
Steel Mold Base
QC-10 Insert
Clearance Hole
19. When the need for Turbulent Flow Baffles is necessary, Plastic Flow Baffles should be considered.
Dissimilar materials such as QC-10 Aluminum and Brass can be the cause of Corrosion in the future.
Plastic Flow Baffles as shown in the picture do have a maximum coolant temperature of 212°F.
Photo Courtesy of DME
20. When Cutting Slots, Notches or Insert Pockets, Please refrain from cutting Sharp Corners, Use as Large
of a Radius as Allowable. Sharp Corners will create a weak point in the material, cracks begin at weak
points. A 45° edge should be cut on an insert to clear the radius.
45° Chamfer on Insert
Use as Large of a Radius as Allowable
21. Sharp angles must be avoided to reduce local stress concentrations that could lead to early failure of the
mold. Use as Large of a Radius as Allowable, the minimum should be 0.100” on the core and cavity,
parting line should use radii of at least 0.40”, more if possible.
22. Polishing of a QC-10 Aluminum mold is basically the same and with the same equipment as with steel
molds, but can be done in less time. Mirror or optical polish surfaces can be achieved, coating these
types of surfaces is recommended.
Mold Flow™
For Mold Flow™ simulations, the criterion for QC-10 is loaded into the Mold Flow software.
Density
2.85 g/cm3
Specific Heat
884 J/kg-C
Thermal Conductivity
160 W/m-K
Elasticity Modulus
70 MPA
V
0.33
Coefficient Thermal
Expansion
24.7 x 10-6 m/m/°C
Processing with Corrosive materials like POM (Acetal) or PVC (Polyvinylcloride) produces considerable wear
in Steel mold. However, the high corrosive resistant nature of QC-10 Mold Block will combat the corrosive
nature of the resins mentioned and therefore no surface treatment is needed processing corrosive resins
General Machining Guidelines
Traditional machining operations are easily performed on aluminum QC-10 alloys.
The thermal conductivity of QC-10 assists with heat dissipation.
Even though QC-10 Mold Plate has been stressed relieved, some minor degree of residual stress does
remain. To minimize distortion caused by these residual stresses, the following basic machine guidelines
should be followed :
1. Machine or Grind 0.040 to .060 inches from each side of the plate.
2. Rough machine the plate removing the majority of the material, leaving enough
material for further distortion.
3. Un-Clamp plate and let stand 8 - 12 hours
4. Re-clamp plate for final machining.
Note : Do Not Distort the plate when re-clamping, use shims where required
5. Clean up Top and Bottom for flatness
Always use a good grade of coolant with a neutral pH that is free of Chlorides
MILLING SPEEDS AND FEEDS
Machining
Process
Tool Description
Roughing
4” Carbide Insert
Face Cutter
1” Roughing
4 Flute End Mill
Roughing
Finishing
Cutting
Speed
(sfpm)
5,000
3,500
2 Flute Carbide
Ball-Mill
2,500
Feed Rate
(In /
Tooth)
0.012 –
0.025
0.01 –
0.020
0.005 –
0.010
Depth of
Cut (In.)
Tool Size
RPM
IPM
5,000
250 350
500 600
0.2 – 0.25
4” Cutter
0.2 - 0.25
1” End Mill
10,000
0.03 – 0.06
1/2” BallMill
10,000
350 400
Depth of
Cut (In.)
Stock Size
RPM
IPM
0.05 – 0.10
3” Dia. Rod
5,000
50 150
Drill Size
RPM
IPM
½” Drill
12,000
60 120
Drill Size
RPM
IPM
¾” Drill
2,000
5
TURNING SPEEDS AND FEEDS
Machining
Process
Tool
Description
Single Point
Turning
Single Point
Carbide Insert
Cutting
Speed
(sfpm)
6,000
Feed Rate
(In / Tooth)
0.010 –
0.030
STANDARD DRILLING SPEEDS AND FEEDS
Machining
Process
Tool
Description
Cutting Speed
Feed Rate
(sfpm)
(In / Rev)
Standard 2 Flute
Drilling
Carbide Drill
2,000 – 2,500
0.005 - 0.010
GUN DRILLING SPEEDS AND FEEDS
Machining
Process
Tool Description
Gun Drilling
Carbide Inserted Hallow
Point Spade Gun Drill
Cutting Speed
Feed Rate
(sfpm)
(In / Rev)
300 – 400
0.005
Lubricant / Coolant
Direct coolant flooding at the point of cutting operation contact is recommended for optimal machining of
aluminum
Appropriate PH levels of lubricant/coolant are PH6.5 ~ PH8.5
(If lubricants/coolants with PH Levels greater than 8.5 or less than 6.5, black spots could form on the surface.)
No corrosion on non-machined area or finishing machined area when proper PH Level are maintained
The Impact of Water Acidity / Alkalinity on QC-10
Although aluminum has significant advantages when compared to other metals, it is not always completely
impervious to corrosion. QC-10 develops a self-healing, stable protective oxide layer when exposed to various
atmospheric conditions. This protective oxide layer can become unstable when exposed to water with extreme
pH levels or high acidity. As a result, the protective layer of QC-10 can break down, and its ability to
automatically renew itself may not be fast enough to prevent corrosion. This prolonged condition could result in
exfoliation corrosion within cooling lines. In addition, dispersed rust, dissolved metals, high chlorinated
biocides, heavy metals, chlorides, and phosphates in the water system can also corrode QC-10.
To avoid the possibility of corrosion, the following actions are critical:




Maintain neutral water pH levels to combat premature corrosion.
Water systems should be maintained at pH levels between 6.5 and 8.5.
Eliminate or maintain minimum levels of dispersed rust, dissolved metals, chlorinated biocides, heavy
metals, chlorides, and phosphates in water.
Neutral water ph levels are best practice to combat premature corrosion of QC-10.
QC-10 Material after 48 hr test – EXCO Rating EA
7075 Material after 48 hr test – EXCO Rating EC - ED
Hot Runner Use in QC-10® Injection Molds
1. Thermal insulation of the hot runner is crucial, without this, the Hot Runner will not function properly
- A hot half is ideal
2. Cooling lines should not be in close proximity to the hot runner
3. Hardened steel inserts and sleeves should be used in all hot runner contact areas for thermal isolation
and to prevent damage to the aluminum block during maintenance
4. All inserts must be properly designed and engineered to support the loads of thermal expansion and
preload of the hot runner components
5. Gate inserts are required for some hot runner tip designs
QC-10® Mold Cleaning and Oxidation Preventative
It is very important that the QC-10 mold surfaces be free of all finger prints and plastics residues, especially
molds with a SPI-A1 or A 2 Finish. Any Mold Cleaners and Release Agents used on the Mold Surface need to
formulated for Aluminum. It is recommended to use a dry spray “oxidation preventative” which does not
penetrate the ejector bushings and moveable parts of the mold.
It is not recommended to use rust preventative or mold cleaner spray’s that have been designed for
“Steel Molds”. These types of products generally contain trichloroethylene and ethylene chlorides that react
with the aluminum alloy resulting in quantities of corrosive hydrochloric acids which lead to corrosion by
degrading the natural oxide protective film.
QC-10® High Strength Aluminum Injection Mold Operating Tips
All molds can be abused by excessive clamp pressures, high injection pressures, over packing, flashing the part,
jerking the mold open and closed, lack of lubrication on the appropriate components, multiple ejection,
crashing the mold closed or closing up on partially ejected parts. These types of abuse are hard on steel molds
and even harder on aluminum molds.
Proper processing and maintaining an injection mold will help to eliminate these situations.
Always avoid hard closing (slamming) of the QC-10 mold, or any mold, clamp closing speeds should be setup
for rapid closing to within .250” of mold touch with the last .250” set at a much slower rate as to not slam the
mold surfaces together. Always avoid excessive clamp pressures, high injection pressures, and overpacking/flashing the mold. Always make certain the Mold Protect Feature is used and properly setup, you
should be able to close up on a piece of Solder without damaging the Solder.
Preventative maintenance required for a QC-10 aluminum mold should not be any more than for steel, but there
are different things to look for. For example, with the rapid cycle times typically achieved by aluminum molds,
more gases will be released and parting line build up may occur faster. In some cases there has been a buildup
of a Gray Powder type substance on the parting lines caused by “Micro-Fretting”. Micro Fretting is not harmful
to the mold itself but as a result, parting lines should be cleaned more often than with steel molds, all mold
surfaces and vents should be cleaned once per shift. Because of this same scenario, textured aluminum mold
surfaces will require more frequent cleaning than the steel mold.
The 1st kind of mold maintenance you can perform is aimed at reducing in-house tool abuse.
Have a clean operation using well-maintained machines and have the right tools. Pay close attention to machine
parallelism and alignment as part of its maintenance activities. A modest investment into
preventative maintenance now can save a lot of money later if a tool needs major repair.
Recommended Tools for QC-10® High Strength Aluminum Injection Mold
Parts stick at times, especially at startup, proper handling of these situations in an aluminum mold is critical.
Pictured below is a variety of Plastic and Cast Aluminum tools found on the internet that could be useful with a
QC-10 Aluminum Injection Mold.
Never use hard tools (screw drivers, hammers, punches, knives on any molding surface, parting line or shutoff
surface. Always use "soft" tooling like rubber mallets, punches and pliers made from plastic, soft aluminum,
copper, or brass on hand to avoid damaging the mold. If possible, check the hardness of the tools prior to using
them. QC-10 hardness is 150 – 180 HB, tools should be softer,
Repair of QC-10®Aluminum Mold Surfaces
Welding
In the back of every molder’s mind is this question; “If we have a crash, can I repair this new QC-10 mold?”
Production environments are tough places. Today’s injection molds are subject to hundreds of thousands of
cycles, stuck ejector pins, and the occasional hung up part. All can lead to damage to the surface finish of an
injection mold.
With Alcoa’s commitment to the injection mold industry, welding experts at the Alcoa Technical Center have
developed weld wire for surface repairs of smooth and textured molds made from QC-10. A near perfect match
of alloy allows the weld repair expert to perfectly match the material in order to achieve near perfect color
match and textured characteristics.
With easy training and “shop floor” techniques, QC-10 Weld Wire allows a manufacturer to quickly and
confidently repair his QC-10 mold and get it back into production.
Alcoa has demonstrated the ability to weld repair surface anomalies and wash outs of up to ½ inch in depth. It
must be noted that at this time, weld techniques on any high strength aluminum alloy is not recommended for
structural welds, weldment build-ups, or depths greater than ½”. However, such mechanical joining techniques
such as freeze-plugs are technically feasible and work very well in QC-10 tooling.
Following the instructions in the Alcoa QC-10 Weld Guideline, Alcoa has demonstrated that a weld repair can
be adequately employed in surface repair methods up to ½” in depth and re-machined and / or retextured in
order to repair surface anomalies.
Freeze Plug
A viable alternative to weld repair is the use of a Freeze Plug. The use of Freeze Plugs is not possible with steel
due to material phase changes at low temperatures.
Advantages of a Freeze Plug:
 Allows “exact” matching between materials
 Can be machined to correct dimensions and finish
 No heat affected zone
Damaged Area
Machined Hole
Machined Freeze Plug
Finish Machine
Cold Spray
Cold Spray Technologies is a process that was developed in the Soviet Union in the mid 80’s. A Team at the
Alcoa Technical Center has been experimenting with Cold Spray Technologies for several years with success
in many areas. Cold spray is a materials deposition process in which relatively small particles (ranging in size
from approximately 5 to 100 micrometers (μm) in diameter) in the solid state are accelerated to high velocities
(typically 300 to 1200 meters/second), and subsequently develop a coating or deposit by impacting an
appropriate substrate. Various terms—including “kinetic energy metallization,” “kinetic metallization,”
“kinetic spraying,” “high-velocity powder deposition,” and “cold gas-dynamic spray method”—have been used
to refer to this technique. In most instances, deformable powder particles in a gas carrier are brought to high
velocities through introduction into a nozzle, designed to accelerate the gas. The subsequent high-velocity
impact of the particles onto the substrate disrupts the oxide films on the particle and substrate surfaces,
pressing their atomic structures into intimate contact with one another under momentarily high interfacial
pressures and temperatures.
The Alcoa Technical Center is currently performing a number of tests to determine if Cold Spray Technology
would be a viable process for the repair and / or changes to a QC-10 Injection and Blow Mold. We have seen
some very promising results to date with limited run time on an injection mold, high volume injection molds
will be use soon. Pictures on the next page show a sample of repairs that have been studied.
Machined Simulated Repairs
Edge Repair
Hole Repair
After Cold Spray Repair
Acid Etched Texture
Surface
Note: The information presented in this document is presented as guidelines and does not incur the liability
of Alcoa.