Custom Car Door Handle Using SLM
Tom Shupe, Reid Archibald, Erik Ostler
This aesthetically pleasing, custom door handle is especially suited to production by
direct digital manufacturing (DDM) methods. Like most custom products this door handle will
have a small production run, normally consisting of 2-4 parts. To acquire hard tooling for this
type of application run would be extremely expensive and would result in an increased lead time.
This would delay the production of these handles for several months, and would require the cost
of each item to be very high to cover tool costs. In addition to this, producing these complex
handles by traditional subtractive methods would be difficult and time consuming.
The function of this door handle is relatively simple, so it will not require accuracy
beyond .001”, which Selective Laser Melting (SLM) is capable of producing. This is helpful,
because many rapid manufactured products require extensive finishing. This door handle will
require very little, just some shot peening to improve the surface finish.
One unique benefit of using SLM is the ability to produce a functional moving product
that does not require assembly. A similar door handle would have multiple components, but by
utilizing RP technology it can be built as a finished product. This not only simplifies
manufacture, but will increase savings by reducing labor costs.
A key feature of using SLM is the flexibility to offer new options than are currently
available in the market. Any customized geometry can be made including: words, designs, or
shapes. Internal geometries are also possible for wiring, making led displays an option. A key
hold illuminating LED can be seen in the figure above.
A combination of all the above mentioned aspects makes these custom door handles a
unique product, because it is not possible to achieve the same benefits by traditional means.
Build Volume 10.7 in3
Design for Direct Digital Manufacturing 2008 Competition:
Aftermarket Car Door Handles
Reid Archibald
Erik Ostler
Thomas Shupe
The aftermarket automotive peripheral selected for production for the direct digital manufacturing design
competition is a customized door handle. These customized door handles will be manufactured using selective
laser melting (SLM) from stainless steel. Currently many aftermarket products are available to customize the
exterior of your car. However, choices for aftermarket door handles are limited to a few existing designs. The
customized door handle will not only expand the market by enabling production of unique custom designs, but
also succeeds in differentiating a car from any other. This opportunity is made available by going to a website
and turning your creative idea into a custom design.
Innovative aesthetics via DDM
A handle with virtually any three dimensional geometry is possible using the SLM process. For instance, a
customer could buy a customized handle including names, pictures, or unique designs as seen below in Figure
1.
These
parts
can
also
have
coatings
added, for
example
chrome, to
give
the
desired
texture and
Figure 1 Depiction of two custom handles, made possible by SLM. Two of the infinite options.
finish.
options include lighting displays, created by embedded LED’s that can highlight the door handle.
Other
As an added feature, the door handle offers the option of a key-hole illuminating LED that will activate when a
sensor on the key ring is within range of proximity sensory on the back of the door handle housing. This system
provides easy access to the lock when lighting conditions are poor.
Innovative geometrical features via DDM
When building these handles as a finished assembly, it is necessary to leave space for un-sintered powder
between the handle and the housing to enable movement. However, any lateral sliding of the handle during
rotation will give the handle a sloppy feeling. Therefore, the handles are designed to be built in a tightly folded
orientation that is outside of the working range as shown in Figure 2. An
alignment ridge can now be built that will interface with the walls of the
housing as it is brought into the functioning range, allowing only the
expected motion. Other geometrical features include the LED channel,
the sensor housing, and a functioning one piece hinge.
Degree of Customization/Personalization
The handle shown is customized to fit a Ford Taurus, but a
handle/housing assembly could be made to fit any automobile. Neither
are Customers limited to handle that must be lifted, handles that pullout
could also be made. Both the housing and the handle can be made to
exact specifications from the customer for design, texture and finish. The
design of the handle can include logos, names, or any 3-D shape, and the
Figure 2 Picture illustrates the gap
housing can be made into different shapes and have different borders.
necessitating the ridge feature to control
Such requests could be given over the internet.
lateral motion
Parts Consolidation
A similar door handle made by
traditional methods would require a
housing, two pins for the hinge, and a 510 part welded assembly for the handle.
Our design condenses these numerous
parts to a single movable part that
requires no assembly, yet retains full
functionality.
0.17”
Justification of DDM Process
The SLM process will build fully dense
parts from a variety of metals, these parts
will have the same properties as the
intrinsic metal. SLM can hold tolerances
of .001” and produces parts that have a
surface roughness of less than 10 µm. In
addition, as a powder bed process SLM is
capable of producing complex geometry,
and it is independent of dissimilar
support material, the removal of which
would require increased finishing.
Justification of DDM Material
In general car door handles need to be
made of materials that will allow for Figure 3 Displays of build orientation, and working range of handle with ridges.
durability in a large range of conditions; (Top left- blow up of ridge clearance, Top right- build orientation, Bottom leftthese include: extreme temperatures, mild Lower range of motion, Bottom right-upper range of motion)
impact, and regular tension. Stainless
steel has an impact strength of 95.1 ft-lb, a tensile strength of 34.8 ksi, and a melting temperature of 1370 ºC.
Stainless steel has more than sufficient strength for all conditions this door handle will be placed under, and will
have a sturdy feeling when it is being used.
Cost/Benefit Analysis
The following cost analysis includes: initial investments (capital), machine wear, engineering cost, material
cost, finishing cost, and overhead. Analysis can be seen below in Table 1 and 2 below.
It is estimated that there will be an initial cost of $500,000 to purchase and set up the SLS machine. This
machine will be in operation for approximately 5,000 hours per year. Assuming the capability of fitting four
handles per build, the cost of wear on the machinery per part is $4.26. At this rate the SLM machine would pay
for a replacement in 10 years. Assuming that an average order would be for 2 car door handles, the engineering
cost per order would be approximately $150. Other costs per part are as follows: material costs are $95.84,
finishing costs are $30 per part (surface finishing, optional chrome plating, etc.), and overhead cost are $40. The
total cost to the customer is $483 per order of two handles. At this rate, if the company produces 5,000 parts per
year, it will receive a net profit of about $88,000 per year.
In comparison, a part produced by CNC machining would cost $3,000-$4,000 per handle according to Central
Valley Machine of Logan Utah. This is approximately 15 times more expensive than using the SLM process. In
addition, traditional production methods would have a cost of assembly.
Cost Estimate
Capital Cost Replacement
of Machine
Cost
10
yr(7%)
$500,000.00
$850,000.00
Replacement
Parts
Per
Cost
per
order
order
2
$8.51
Assume
Average
Parts
per
build
time machine run
(hr)
$85,000.00
4992
$17.03
4
4
Engineering Material
Finishing
General
cost
per Cost
per Cost
per Overhead
order
Part
part
Cost/ order
$150.00
$95.84
$30.00
$40.00
Yearly
Working
Savings for
Hrs/ year
new machine
Machine
cost/hour
Table 1 Cost analysis for production of door handles.
SUMMARY AND PROFITS
Orders per year
Profit per
before loans
year Profit per
after loans
2426
$157,320.49
$87,655.45
Business cost per order
$420.19
Profit: 15% of cost
0.15
Average Customer Cost Per Order
$483.22
Table 2 Price and profit summary for handle production
year Loan Repayment
Cost per year
per year
$69,665.04
$1,048,803.28
Conclusion
These door handles have more options, and more degrees of customization than existing door handles.
Producing these by SLM will effectively cut costs, consolidate parts, and maximize personalization in
producing aesthetically pleasing door handles. All of this can be done without sacrificing the structural integrity
of the part.