Low-Volume Layered Manufacturing (LVLM) is a design-thru-manufacturing method that is already known by many different names in the short time it 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 redefine 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.

Knowing how to design and manufacture parts using LVLM will help machine designers 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 uses 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 three RP technologies are available that can manufacture parts suitable for use as end-use parts: FDM® (Fused Deposition Modeling), SLS® (Selective Laser Sintering), and SLA® (Stereolithography).

Each production RP technology has its strengths and weaknesses. 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.

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's the good news -- with LVLM, these "old way" design rules are all thrown out the window. It's time to take off the handcuffs 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, as thoughts of delays and cost overruns fill his head!

Parts with tooling investment become locked in time and unchangeable, since the cost of reworking the tooling, or worse, making new tooling altogether, prohibits the weak part from being changed.

Parts designed for LVLM do not require expensive, long-lead-time tooling. With LVLM, redesign is 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 redesign as learning occurs -- what might be called "active evolution," since the part design, and therefore product performance, can improve with each unit shipped.  More important, active evolution enables you to be laser focused on the needs of your customer.

Focus on Part Consolidation

To take advantage of LVLM, designers must shift their design paradigm to take advantage of part consolidation -- 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 to far fewer parts, which can then only be made using LVLM.

Consider, for example, a robotic arm.  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. 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.

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 example,  this time 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, which meets the product requirements (fully functional, accurate, strong).

The benefits?  15 separate parts are reduced to 1 part (inventory reduction).  Unique tooling for each part 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.

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.

Limitations of LVLM

All manufacturing processes have limitations, and LVLM has its own unique set.  The most notable limitation in all layer-based manufacturing methods is 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 for end-use commercial applications.  LVLM parts are now available in ABS, medical and food grade ABS, polycarbonate, nylon, and epoxy, all with mechanical properties 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 not quite as good as CNC or molded parts.

What Can You Do Now?

This may be the first time you have heard of LVLM, as it is not widely known or understood as a tool in the machine designer's toolbox.  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, other than with LVLM.

You can now 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 subassembly.  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.  See how the financial picture looks for the manufacture of your LVLM parts.

To review a detailed financial analysis of a typical project, comparing the use of LVLM vs traditional manufacturing, email mmackie@quickparts.com.

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 as well as 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.