Reducing Cost and Material Usage for Large Parts
How to design low-cost
replacement frames for substantial cost savings now on existing products
and/or base next generation products on these low-cost parts..
Case Study #1 example: Low-cost Backhoe Boom
Replacement for Weldment (Case study #2 below)
The low-cost assembly (upper CAD model) replaces the heavy welded boom (lower
The assembled replacement is a truss, which is the lightest structure for
a needed strength, so it uses a fraction of the steel, and material cost,
compared to a structure made of heavy plate. The truss is built automatically on
ordinary CNC machine tools and assembled by non-skilled labor, as discussed
below. Note that the heavy load exerted by the boom piston is connected
to the thick "elbow" structure with the load supported at the ends of two
tetrahedrons. This CAD model and more machine frames below were drawn
by Dr. David M. Anderson, copyright © 2016. He
also has to-scale CAD models for other layouts, like front and rear wheel
loader frames, which he will work exclusive with the first mover to
The conventional design in the photo is made by welding many large heavy plates,
which has high skill demands and weakens the steel in the heat-affected-zone..
In order to provide accurate mounting holes and surfaces, which is essential for
industrial machinery frames, the warped weldment must be machined on an
expensive mega-machine with very high hourly costs for positioning,
machining, repositioning, and inspections, not to mention transportation and
Low-cost manufacturable replacements can be designed to be
back-ward compatible with expensive versions thus offering the following
Providing near-term cost reduction without spending the
cost, resources, and calendar time for a new product development cycle.
Becoming the basis for a next-generation development.
This one-day workshop applies very effective DFM principles to
large, heavy, or hard-to-build parts for major reduction in cost, material usage, and
build time. These improved designs could then be retrofitted onto current
products or used as a basis for new designs.
The workshop will show how to develop backward-compatible substitutes that will
replace expensive weldments, castings, or unnecessarily heavy machined parts with
more steel-efficient parts comprised of assemblies of CNC-machined parts that are rigidly
and precisely assembled by various DFM techniques.
Such a manufacturable structure could be based on assembled
plates or, for larger structures, look like this illustration, which will be
described below in the discussion of trusses that follow the load paths for the
highest strength per weight ratio.
Major Cost Reduction for Welded
The most applicable large welded assemblies should be analyzed for
opportunities at the conceptual level with the goal of avoiding the following
high-skill labor cost to weld plus other labor to position,
fixture, straighten warpage, and grind. Skilled labor shortages raise
costs and can delay production and lower quality. Note that welding acute angles (e.g. in welded trusses or diagonal bracing) requires extra
skill to get enough heat between diverging members. For military and
mission-critical applications, these kind of welds require a special
high steel usage and cost at a time when steel prices
are rising and will continue to rise for raw material and transportation
costs both for incoming materials and outgoing products.
cost and delays for annealing the weldments
or the risk of fractures from residual stresses.
and labor intensive practice of mounting parts in slots or large holes and
then aligning them manually, or
machining large parts after welding, which may
require large machine tools and furnaces to anneal them, which:
loss of strength in the heat affected zone from welding and
annealing, thus requiring more steel compared to steel used at its full
strategy would be to
proven parts with backwards compatible replacements with the same
functionality and strength (possibly enhanced) with much less total cost and
would provide cost reduction now on existing products. This would also encourage
a leap-frog strategy where these low-cost parts could then become the
basis for new generation products.
The specific strategy to eliminate the abovementioned costs would be to
create an optimized concept/architecture for constant-stress trusses and
structures (which, by definition, use the least material) with the following
The approach would be based on the following premises:
Fabrication. All machined parts would be small enough to be set up
and made quickly on readily-available CNC machine tools in a single setup
(Guideline P14 in the
DFM book, which states that all operations should be
done in one setup on versatile CNC machine tools).
parts would be limited to those that are small enough to be machined after welding by the typical in-house machine tools. This
may be appropriate for bearing blocks and other junction parts if not feasible
to machine from a single block.
Assembly. Precise alignment of
these assembled pieces would be assured by the programmable part manufacture.
Steps for Reducing Cost on Large
Parts and Assemblies:
Identifying existing loads,
directions, and attachment points, which would then be graphically represented.
In a workshop setting, these could be projected from a active CAD screen or printed on several sheets of large paper
with dark lines for the next step.
Brainstorming on various ways to
support these loads, with many ideas sketched on many printouts.
optimize the design of these parts for manufacturability and currently
engineered manufacturing strategies for trusses, assembling plates and bar
stock, and "space frames."
Trusses consist of struts and nodes:
Struts. Purely tension members could be made of rods; compression struts
must be wide and axisymmetric with the load path to resist buckling. This favors
tubing with threaded holes at the end to bolt to the node blocks. Thick wall
tubing could be plugged with threaded disks that could be joined to the tubing
with a low-heat axisymmetric weld. For smaller wall thickness, a clean,
inexpensive strut could be made by swaging down the ends to just past the tap
diameter for tapping threads that could then be bolted to the node blocks.
Swaged tubes are shown in the illustration (in grey), which can be inexpensively
procured from a swaging shop. In one application, a swaged tube cost $40
for a 25 inch long tube, 2.5" OD, with an 1/8" wall that that included
drilling-and-taping and facing off for a precision length (wall thickness can go
up to 1/4" and higher). The swagged struts can be made quite large
and strong, as was pursued in workshops for Caterpillar's underground coal
mining front loaders
four-axle trailers and other workshops indicated by the blue hyperlinks
on the client page. In workshop exercises, Dr. Anderson leads a
company team to brainstorm on many concepts for struts-and-nodes to support all
the hardware in a frame or structure.
The nodes would have bolt holes for
the struts and all hardware that bolts to the structure.
Node Blocks. Each node block would be designed and dimensioned so that
all operations for node attachments would be made in one setup (Guideline P14)
on an ordinary CNC machine tool. Families of similar parts could be
flexible fixtures that would be able to make all parts in the family
without setup delays and extra cost. The illustrations show spherical
nodes (in red) for clarity. Actual nodes would each be milled out of bar
stock using various design techniques to attach the struts and all the
hardware that needs to be supported. Dr.
Anderson helps companies design these through on-site consulting after the
workshop and through remote consulting and design studies.
Case Study Example # 2: Low-Cost
machine frame can be bolted together rigidly and precisely from parts
fabricated on ordinary machine tools. The two nodes shown can be
solid steel spheres with threaded holes, into which their struts thread in to
along with the machine feet.
The other nodes (not
shown) would be the fabricated blocks through which bolts connect their struts
and all machinery components that need to be anchored in that area.
The outer edges of a
rectangle frame are shown, to which covers could be attached to.
Interior components and
sub-frames would be supported by struts coming from the he main frame nodes
discussed above and triangulated to other existing nodes.
Machinery components that
are mounted to any outer wall could be anchored at a node anywhere between two
struts, which would then be triangulated to another existing node.
It is important to note
that such a frame replaces both the existing frame and all the
existing brackets to support components and sub-frames,
Case Study Example # 3: Low-Cost Machine
Frame to Support an Object or Machine
The low-cost machine frame concept shown bolts to
the existing framework of the supported object or machinery either directly
through adapter blocks, shown on each corner of the grey framework.
The truss are built as specified above and
the trusswork is a fully triangulated space frame that mounts to the
floor on three points to install and align quickly and avoid the
overconstraints common in all four-point frame mounts. If the truss frame
needs to be backward compatible with an existing four-point mounting
arrangement, that is also possible. If the supported object can be
supported by three mounts, then the frame would be the simpler
octahedron, as illustrated on the left below.
The load paths align with the struts from each corner of the
supported framework down and diagonally to the anchoring feet.
Case Study Example # 4: For big trucks and
These techniques provide the least costly way to achieve major
weight, steel, and cost reduction for big trucks and construction equipment. For
semis and road trucks, this may be necessary to meet new mileage standards.
This approach would be to replace the
usual heavy channel or welded frames with a truss, consisting of
struts and nodes, as described above. The truss would provide
the lightest possible frame for a given strength because its struts would align
with all the load paths between axle mounts, engine/transmission mounts, fifth
wheel mounts, cab/body/bed mounts, piston pivots, tank mounts, and everything
else that mounts to a truck frame. The nodes would correspond with all these
mounting locations, thus eliminating all the separate brackets now needed to do
this. CNC machine tools would fabricate all the nodes from bar stock blocks with
all the holes needed for struts and truck parts.
truss frame would be backward compatible with your current vehicles, thus
providing cost, steel, and weight reduction now and then be the foundation for
next generation designs.
truss would follow the load paths, it would be the lightest possible structure
for a given strength. Most of the workshops I have done on this have been big
structures with big loads, like the underground mining front-loaders for
Caterpillar, four-axle missile trailers for Finmeccanicas DRS division, and
many large machine frames, like the last CAD model on my web page. Clients that
held these workshops, or the consulting equivalent, are indicated by blue
hyperlinks at the client list page.
For large trucks, there are so much weight saving opportunities because the
thickness of channel frames is determined by the loads around the bolt
holes, but since the channel plate must have constant thickness, most of this
steel is "loafing" and thus much heavier than necessary.
Comparisons with welded cubes. The usual orthogonal
welded frame (like the one on the right) needs much skilled labor to weld, which
results in a warped structure that must have holes drilled after welding
on an expensive mega-machine for large structures. Plus all 8 corners
would have to be ground for appearance or sanitation. And this is
diagonal bracing, which would require 6 more braces and 12 more welds, all of
which will induce residual stresses that will reduce the load capacity or
require more material.
By contrast, the truss (on the left) has all
parts machined automatically on ordinary CNC machine tools. The
struts are assembled to 6 nodes precisely and rigidly by unskilled labor.
The simplest truss, the octahedron, is shown, although trusses can be
designed to accept any geometries of mating attachments, like existing
For mounting loads, orthogonal frames, like
the one shown on the right, usually need many extra brackets to attach hardware
to the frame. This is so common that one long-term engineer at a commercial
truck company described it as a bracket company!
With trusses, the nodes also
all the mounts for all the mounted hardware, since all the struts and
nodes can be uniquely fabricated (this is called
mass customization) so
that a node is next to every
hardware mount. Trusses have inherent diagonal bracing and can support loads
without any warpage, overconstraints, or residual stresses.
Truss Frame with Bearing Mounts for Shaft.
© 2016 by Dr. David M. Anderson.
Two "tripods" can be bolted to any truss (in
this case, the above octahedron) to mount other structures like mount bearing
blocks to rigidly support machine shafts, axles, pivots, or any rotating
members. The bearing blocks have bearing mount surfaces bored and reamed
and also tapped holes on the outer surface on which to bolt the struts.
The tripod mounts result in fully triangulated
rigidity and is much stronger per weight than the usual techniques us using
heavy plates or weldments to mount bearings
If a single structural mount was needed, one tripod could be
utilized with an appropriate mounting surface.
Any subassembly could be bolted to any side
or multiple sides of any basic truss frame for functionality, for instance,
bearing blocks, in any plane.
Catenary Truss. Structurally,
the catenary truss is the ideal beam because the catenary shape matches
the load curve for beams that are supported at the ends, thus providing the
greatest strength for the least material, the lightest weight, and the lowest
cost. This type of truss is utilized in the most advanced bridges
The inverse of this is a suspension bridge in which the catenary
is a long cable with smaller cables connected to the bridge surface.
Catenary trusses, as shown below, can be utilized as cost-efficient frame work
that need to support weights (loads) over challenging distances, especially for
sub-frames that need to be light for accelerations. This may be the best design
approach for long beams like large machinery or frames for railroad
engines and passenger cars.
Like all trusses discussed above, all the parts can be built automatically on
ordinary CNC machine tools. assembled by non-skilled labor, and retain
neat treatments or cold-rolled strength of the raw materials.
This illustration shows a physical model, which can produce many ideas
quickly and can be passed around in meetings.. These model parts are made
by ZomeTool, which was designed by PhD mathematicians for molecular
biologists and structural engineers in addition to being widely available as
In this model, the red spheres (like in the above CAD models) represent the nodes that
connect the struts and are also the mounting blocks for objects. The black
spheres support the ends of the beam and anchor it.
Next Example: The Zig-Zag Truss for Long Structures. Similar
techniques can be used to create a
"zig-zag (Warren) truss for booms, masts or
Additional truss members in a perpendicular plane can provide
lateral stiffness. Similarly, three strut columns could provide lateral and torsional stiffness. These will be the lightest and strongest structures
possible without the cost, excess steel, and difficult machining of long
channels/bar-stock and without the warpage, distortion, imprecise hole
locations, and skill demands of welded trusses.
The results would
be much lower cost from:
quick machining on readily-available CNC machine tools
setup concurrently engineered for whole part families to
further reduce machine time
quick assembly with accuracy assured by
programmably machined features
higher strength per weight (meaning
higher strength per material cost) because of:
more structurally efficient designs (lower stresses to
support a given applied load)
all material would remain at
cold-rolled strength and heat-treated strengths could be preserved
These truss structures
would provide the absolute lowest weight for a needed strength.
For fabricated parts now made of excessively thick steel, the workshop group
would start by identifying the loads and load paths. Then we conceive of
structural shapes that match the load paths, which is will probably not be a constant
cross-section slab that has a lot of understressed material that leads to
unnecessary cost and weight. Then we brainstorm on optimal assemblies of
CNC-machined parts whose cross-sections are matched to the load, thus
approaching constant-stress parts, which have the highest strength per
weight. This would be accurately and rigidly assembled by various DFM techniques
in which the precision is entirely determined automatically by the CNC machines.
These techniques include DFM
Guideline A3, in which mating parts would be aligned to sub-mill
tolerances by inexpensive pairs of round and diamond dowel pins in reamed
holes. Parts could be designed to be self-fixturing or simple fixtures could
be concurrently engineered to hold parts during alignment and clamp together
for fastening. Aligned parts would
then be bolted/riveted together with appropriate bolt strength, torque settings,
and retention strategies.
Reduction for Large Cast Parts
Cast parts require expensive tooling and lengthy and costly setups, which
usual force the OEM to order a large batch to amortize the setup costs,
but this violates lean production principles and makes it hard to do build to
large or complex castings, there may be a limited supplier base who can cast
them, thus causing transportation costs, shipping delays, and possibly queues
for busy suppliers. For example, for a certain size of large Diesel engine
blocks, there are only two suppliers in the world who can make them.
Further, castings all require machining, which may require an expensive
mega-machines for large castings, which may also incur lengthy setups,
queues, and delays to ship large castings to shops with mega-machines.
The workshop group
would start by identifying the loads and load paths. Then we conceive of
structural shapes that match the load paths. Then we brainstorm on optimal
assemblies of CNC-machined plates whose cross-sections are matched to the load, thus
approaching constant-stress parts, which have the highest strength per
weight. This would be accurately and rigidly assembled by various DFM techniques,
like Guideline A3 mentioned above.
The above techniques could replace many
hard-to-make large parts and fasten multi-part assemblies.
The group would explore some of the most promising
opportunities in the workshop to the point where they look feasible and it is
clear how to proceed at which point responsibility could be assigned to pursue
The group would also identify future opportunities to
be explored later based on pre-workshop research that will have identified some
opportunities. Opportunities will be summarized and then the workshop group will
vote on them for a baseline prioritization of opportunities.
Pre-workshop company research would also plot steel cost from the time current
products were designed and extrapolate price trends into the future.
Audience. Product development team with all designated and potential
members, with at least one person representing each function and one person
knowledgeable about each proposed candidate structure. The workshop would
benefit from close proximity to the physical structures being analyzed.
Prerequisite: workshop attendees should attend the
two-day DFM seminar first. Work could
proceed immediately with design studies (next point), which could be followed by
an in-house seminar or webinar.
Alternative: Consulting Design Studies
An alternative would be ask Dr.
Anderson to do the above as a
on a consulting basis, working with relevant design engineers. The
joint effort would present the most promising approaches for the company to
evaluate, select, and implement. Dr. Anderson is particularly effective for
complex parts that could benefit from more manufacturable design concepts and
concurrently engineered low-cost tooling and processing. He is in a unique
position to do machining/welding tradeoffs, since he once had his own machine
shop and has done welding since his college years.
He also has to-scale
CAD models for other layouts, like front and rear wheel loader frames, on
which he will work exclusive with the first mover to
contact him. Because of his
ethics code (from the Institute of Management Consultants) he will avoid
conflicts-of-interest by not working with direct competitors, so that means
first-come-first-serve for enlisting his considerable experience on these
techniques that he originated. See client engagements that included this
Steel/Cost Reduction workshop, as indicated by blue hyperlinks on his
Workshops Done and Proposed:
Dr. Anderson has already done workshops for low-cost
frames for: underground coal mining vehicles; four-axle trailers for heavy
loads; large paper converting machinery; 12' high box-makers; dock-scale natural
gas compressors; nuclear plant worst-case scenario filters.
Dr. Anderson has personally done both
welding and owned his own machine shop, and, thus, is a good position to advise
on tradeoffs between welding and machining. See sixth paragraph of his
He has proposed this workshop or consulting
studies for: low-cost frame and structures for industrial machinery; for the
largest dump-trucks, Diesel engine blocks, semi-truck chasses, molding machinery
foundations, large medical equipment gimbals, framework for farm machinery,
light-weight long-span structures for high-speed motion, and long-span
structures that support heavy loads, like railroad cars and locomotive chasses.
If your company makes any of
the products proposed above, contact Dr. Anderson for your own proposal for
workshops or design studies that will show you how greatly lower the cost of
your hardest-to-design parts. As a Certified Management Consultant (CMC),
Dr. Anderson's high ethical standards
prevent him from doing this for direct competitors, which means the first
to bring him in gets a unique competitive advantage.
To discuss this further, contact:
Dr. David M. Anderson, P.E.; CMC; Fellow, ASME
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