By Mark Mackie, Executive VP and Co-Founder of Quickparts.com, Inc.

Low-Volume Layered Manufacturing, LVLM for short, is a design-thru-manufacturing method that is already known by many different names in the short time is has been an option for engineers. Whether you call it 'Rapid Manufacturing' (RM) or the term coined by 
The Society of Manufacturing Engineers (SME), ‘Direct Digital Manufacturing’, LVLM has the potential to re-define the way machines 
and products are designed. This technique provides machine designers with a method to improve quality, decrease costs, and decrease lead times of products and machines.

In this article, I will explore the LVLM method as it applies to machine design and manufacture. I will look at the definition of LVLM, 
then explore the ways that LVLM can be deployed with positive results. Finally I will suggest what you can do right now to take 
advantage of this new technique.

If you are a machine designer you can’t afford to put this article down. Knowing how to design and manufacture parts using LVLM will help you gain easily measurable project benefits by designing parts without limits. LVLM allows you to reduce cost by eliminating 
tooling, and by reducing assembly part count via part consolidation. LVLM allows you to increase the efficiency of your development process, as you can manufacture new, slightly different parts in just a few days. The results of applying LVLM methods are clear: 
Better Machine Designs, Faster Machine Designs, Quicker Machine Deployment.

LVLM Defined

LVLM is the method of using Rapid Prototyping (RP) equipment to manufacture end-use parts. RP machines make parts using 
'additive' fabrication, meaning that the parts are made from the 'bottom up', by adding material to the build space. This 'layer-by-layer' process virtually eliminates all part design constraints, or design rules that exist with traditional manufacturing processes, such as 
CNC Machining and Injection Molding.

Currently there are 3 available RP technologies that can manufacture parts suitable for use as end-use parts: FDM® (Fused 
Deposition Modeling), SLS® (Selective Laser Sintering), and SLA® (Stereolithography). Figure 1 shows these machines.

Figure 1: Rapid Prototyping (RP) machines now use materials strong enough for use as production parts. 

Each production RP technology has its strengths and weaknesses, as described in Figure 2. In order to be viable as a replacement 
for traditionally manufactured parts, LVLM parts must meet the needs of the application: strong, functional, accurate, and appealing. 
All three current technologies, FDM®, SLS®, and SLA® meet those needs. Selecting the best technology for your application depends entirely on your needs.

Figure 2: This chart compares the functional properties of RP materials.

The 'Old Way'

Traditional methods of design require a good understanding of the constraints imposed by the manufacturing process that will be 
used to make the parts. In fact, training engineers in Design-For-Manufacturing (DFM) and Design-For-Assembly (DFA) has put more than a few bucks in the pockets of professional training firms.

For example, parts that will be made by CNC machines must be designed without narrow deep pockets, since the rotating cutter of 
the CNC machine cannot cut narrow deep pockets. Parts designed to be injection molded must be designed with drafted walls in the direction of the tool movement, to enable the part to release from the tool after molding. Injection molded parts must also be designed without 'undercut' or 'die-locked' features. These DFM and DFA rules exist to enforce the constraints of the part's manufacturing process.

A significant challenge to the broad adoption of LVLM techniques is the education of designers in how to design parts and 
assemblies that take advantage of the design freedoms provided by LVLM.

The Good News: Design Flexibility

Here is the good news...With LVLM, these ‘old way’ design rules are all thrown out the window. It's time to take off the hand-cuffs of design constraint! Since the part will be made from the bottom up, layer-by-layer, design constraints are completely eliminated. 
Narrow deep pocket in your part? No problem. Reverse draft in your part? No problem. How about a part with internal, hidden 
channels? Bring it on! LVLM can make that part.

The elimination of design constraints enables 'on demand' product flexibility, and real-time continuous improvement of products. 
Since parts made with LVLM have no tooling commitment, they can be improved on the fly, continuously, based on customer or performance feedback. This 'Continuous Product Improvement' leads to higher customer satisfaction and market responsiveness.

LVLM also enables 'on-demand inventory' of the improved design, since the improved units can be manufactured within a few days of conception. With the LVLM method, the days of obsolete inventory are gone, since existing designs are made just-in-time, and new, improved parts can be manufactured quickly.

More Good News: No Penalty For Changes

LVLM cleans up a product manager's dirtiest word...change. In fact, if you whisper 'design change' to a product manager after a manufacturing release, you are likely to cause a heart attack. Thoughts of delays and cost overruns will fill his head!

Parts with tooling investment become locked in time and un-changeable, since the cost of re-working the tooling, or worse making 
new tooling altogether, prohibits the 'weak' part from being changed.

When parts are designed for LVLM, they are NOT designed for a process that requires expensive, long-lead-time tooling. LVLM 
makes re-design possible, even encouraged. With no tooling investment, and newfound design freedom, part design can be 
improved in real-time, with new parts being manufactured in a few days.

LVLM encourages active re-design as learning occurs. Let's call it 'active evolution', since the part design, and therefore product performance, can improve with each and every unit shipped. More importantly, active evolution enables you to be laser focused on the needs of your customer.

Focus on Part Consolidation

To take advantage of LVLM effectively, designers must shift their design paradigm to take advantage of part consolidation. Simply put, part consolidation is the act of combining several parts in an assembly into a single part that can easily be manufactured using LVLM. Multiple parts currently only exist because of the constraints imposed by the process used to manufacture those parts.

Since LVLM removes those constraints, the designer can consolidate the parts into far fewer parts, which can then only be made 
using LVLM. For example, consider the robotic arm shown in Figure 3. Notice that the original design for the wrist consists of 3 
plates, 3 standoff posts, and 2 adapters, for a total of 8 parts, not including the screws.

Figure 3: The original robotic wrist is ‘consolidated’ into a single part, manufactured using the SLA® process
in High-Impact ABS-like material.

With LVLM, that assembly is combined into a single part, easily made with LVLM, but impossible to make with CNC or Molding 
methods. The benefit? Eight unique parts are reduced to 1. Tooling for those 8 parts is eliminated. The bill-of-materials is reduced 
by 7 parts. This illustration effectively shows one of the benefits in using LVLM for part consolidation.

Assemblies As A Single Part

LVLM excels when parts are designed to be manufactured together. This is certainly a new way to think about Design-For-Assembly. Again consider the robotic arm of Figure 4, this time look at the hand. Its original design requires separate parts for each finger, palm pads, joint pins, and washers. The LVLM version results in a complete single hand part, designed for LVLM, manufactured using 
LVLM, and which meets the product requirements (fully functional, accurate, strong).

Figure 4: With LVLM, the robotic hand is designed to be manufactured in the RP machine as a single assembly, with the movable 
parts designed with clearance and ‘grown’ together. This assembly is manufactured with the SLS® process in Glass-Filled Nylon.

And the benefits? 15 separate parts are reduced to 1 part (inventory reduction). Unique tooling for each of the parts is eliminated 
(cost reduction, lead time reduction). Changing the hand on-the-fly to suit customer needs is simple (small hand version, large hand 
version). This illustration effectively shows the benefits in using LVLM to design assemblies as a single part.

LVLM - Geometry Without Limits

Let's go ahead and take a closer look at the ability for layer-based manufacturing to produce previously unthinkable geometry. Since a part is being manufactured from the bottom up, nearly all design constraints are removed. In nearly all cases, if you can design the 
part in a 3D CAD software, then you can manufacture the part in an RP machine.

LVLM - The Limitations

All manufacturing processes have limitations, and LVLM has its own unique set as well. The most notable limitation in all Layer-based manufacturing methods are the capabilities of the materials used to make parts.

Rapid Prototyping machines have been making parts for over 15 years, but only recently have the materials been strong enough to be used in end-use commercial applications. LVLM parts are now available in ABS, Medical and Food Grade ABS, Polycarbonate, Nylon, and Epoxy, all with mechanical properties that are on par with production injection molded plastics. Surface finish is in second place
in the limitation race. LVLM parts cannot produce a smooth surface finish comparable to CNC machined or molded parts. LVLM 
processes also have well established tolerances, based on part size, which are good, but not quite as good as CNC or molded parts. Go ahead and review Figure 2 again for a chart of each technology’s strengths and weaknesses.

LVLM Education is Required

This article may be the first you have heard of LVLM, as it is not widely known or understood as a tool in the machine designer’s 
toolbox. There is a new set of rules, which are actually no rules at all, to design parts to be manufactured using LVLM. Taking 
advantage of LVLM is easy: clear your mind of design constraints. Imagine parts with obscure organic shapes. Imagine parts with internal volumes. Imagine parts that can't be made any other way, but with LVLM. Review Figure 5, which shows the process from Concept to CAD Design to Real Parts manufactured on RP machines.

Figure 5: LVLM enables you to go from Design Concept to 3D CAD to Production Parts, without design
constraint or tooling investment, but with the freedom to consolidate parts and design for one-build assemblies.

What Can You Do Now?

I have now equipped you with the know-how to begin applying the LVLM method to your designs. Consider your past design approach. Ask yourself how you have designed equipment based on the constraints of the process used to make the parts. Ask yourself what 
parts can be consolidated into one.

Your next step is to identify a candidate project, such as a current sub-assembly. Apply the LVLM method to create a design free from constraints. With 'new' designs in-hand, get a quote for the manufacture of the new part in the quantities you need (Register here).

Conclusion

Low-Volume Layered Manufacturing has become a useful tool for machine designers. LVLM enables designers to make dramatic improvements in quality, efficiency, and cost by designing ‘parts without limits’. LVLM enables part consolidation, and enables 
freedom from the design constraints that have historically been imposed by subtractive (CNC Machining) and formative (injection molded) manufacturing processes.

If you are faced with increased competition and are continually challenged to deliver better, faster and cheaper, then you should 
consider the use of LVLM methods to provide you with the competitive advantage you need.

Mark Mackie is the Executive VP and Co-founder of Quickparts.com Inc.