Case Study – Missile Flight Control Surfaces Application Comparison - Game Changing Study - implies possibility of some army contracts..$$$$. I have downloaded it from LQMT website.
Missile Flight is Highly Sensitive to the Exact Geometry of Control Surfaces
Today’s modern missiles are capable of incredible targeting precision, thanks to highly sophisticated guidance and flight control systems. In most cases, flight is controlled by
pivoting fins attached to the body of the missile such as the typical canard shown in Figure 1 above. Missile flight is highly sensitive to the exact surface geometry of control
surfaces, especially at supersonic speed. Even slight deviations from specifications can add turbulence that affects speed and trajectory.
Manufactured by CNC (Computer Numerical Control) Machining
Missile flight control surfaces are typically manufactured by CNC Machines that use small cutting tools guided by computer programs to generate shapes within very close tolerances. However, no two machined parts are exactly the same because of variations
in the cutting process and continuous wear of the cutting tools. As a result, machined parts must be individually inspected. Exacting tolerances and intricate, time-consuming
geometries make these parts very expensive to manufacture. Liquidmetal Technologies, Inc., Copyright 2013 Page 2
MIM (Metal Injection Molding)
At first blush, missile parts appear to be an excellent application for MIM, which can be much less costly than machining for complex parts. The challenge for MIM is to meet
dimensional tolerances. The best MIM manufacturers can maintain tolerances of less than ± .005” inches in very high volumes, which is impressive. However, it is very difficult to consistently meet these tolerances in all three dimensions (XYZ planes) of a
complex part. MIM suffers variation in each of its three processing stages.
• During casting, molds must be designed such that each cavity has nearly identical flow pressure. Flow pressure can affect the ratio of powdered metal to binder in finished parts, creating distortion during de-binding and localized porosity that affects strength and weight. Density variation also increases with part size.
• During sintering, the final size and shape of the part can vary based on where in the oven each part is placed and the exact heating parameters of each batch or production run.
• And finally, parts must be supported by various fixtures to offset the effects of gravity while shrinking in the de-binding and sintering stages. Secondary processing can true-up a MIM part in critical dimensions; however the geometry of missile fins is far too complex to reshape by bending or removing material
which adds significant cost to the final part. Liquidmetal Injection Molding is Ideally Suited for Volume Production
Liquidmetal injection molding is ideally suited for volume production of missile fins. Liquidmetal parts are formed in a single step: injected and released from a mold where
each part is precisely the same as each and every part made from the same mold. With solidification shrinkage typically less than 0.2%, tolerances within ±0.002 inch can be achieved and parts need only be sampled to ensure conformance to specifications.
In addition customers often chose to utilize the as-molded finish of the Liquidmetal parts. This allows us to do a minimal amount of extra processing on the surface and leaves the customer with a beautiful finish that matches the surface roughness of the
mold. If a polished mold is specified, it is typical to see Liquidmetal parts come out of the tool with a surface roughness of 0.025-0.050µm (1-2µin) as seen in Figure 2 below: Liquidmetal Technologies, Inc., Copyright 2013 Page 3
Figure 2 - As-Molded Surface of a Liquidmetal part (measured at 2 Ra Finish)
Due to its unique amorphous atomic structure, Liquidmetal fins are extremely strong and will not bend out of shape due to mishandling. Part weights are also more consistent in Liquidmetal alloy than MIM parts, which can be critical for supersonic
flight.
Comparing Costs – Example Missile Fin Case Study
In the case of a missile fin, there are significant differences in performance between machining, MIM, and Liquidmetal injection molding. CNC Machining is often considered the gold standard for precision parts, but as we mentioned, it can be a challenge to
consistently maintain tolerances in high volume production. While MIM is less costly, it struggles to maintain tolerances in several dimensions and parts are not as strong as
their machined equivalents. Liquidmetal provides significantly lower cost than machining without compromising precision and strength.
For this case study, we are comparing the manufacturing costs for a hypothetical fin designed for a supersonic missile. Here is a simple sketch in Figure 3 below:
Figure 3 - Example Wing Design (hypothetical) Liquidmetal Technologies, Inc., Copyright 2013 Page 4
This part is smaller than 3” by 5” and a small hole is drilled in the shaft. The front and back surfaces of the fin conform to a precise geometric form optimized for supersonic flight. For simplicity, expected yields and inspection sample sizes are built-in to these cost estimates below:
Cost Comparison
CNC Machined MIM* Liquidmetal
Mold and fixtures - 55k 50k
Machine or Mold part $125 $25 $50
De-gate and drill - $3 $3
True-up - $10 -
Finishing $5 $5 -
Quality inspection $5 $5 $1
Total Part Cost $135 $48 $54
Total Amortized Cost
(20,000 parts) $135 $50.75 $56.50
*(MIM parts may not meet specifications in critical dimensions for this application)
Scaling Production
In addition to performance and cost, customers are concerned with ability to scale production and meet demand spikes. Machining is very time-consuming, requiring additional machines to meet high demand. MIM is well suited to volume production,
however, maintaining consistency can be very challenging due to the number of production steps required and variation from one production run to another.
Liquidmetal Technologies’ elegant process produces parts with remarkable consistency from the first part to the last.
Conclusion
Liquidmetal is the best option for precision parts in volume, especially when consistency, high strength and cosmetic finish are required. Missile fins are an excellent example. For a small number of precision parts, it’s hard to beat CNC machining. When
cost is the primary driver, MIM can deliver significant cost savings, especially in very high volume and for parts that require close tolerances only for limited features. When quality and performance are crucial, Liquidmetal alloy is in a class of its own.
