DMLS in Aluminum, Inconel or Titanium - Is it worth it?

DMLS in Aluminum, Inconel or Titanium - Is it worth it?

The million dollar question right...is it really worth prototyping the exotic metals using DMLS rather than machining them. I guess it is really going to depend on your time frame and geometry. The thing about DMLS is, its super fast, on top of that it can do some crazy geometries. Would it be worth a one off CNC of a titanium or aluminum part if you have to create work-holders and buy a lot of material to do just one part, probably not. Let me talk a little about each of the exotic materials.

DMLS TITANIUM

Since DMLS is an additive technology, it drastically reduces material waste in comparison with traditional processes. Investment casting of titanium, for example, is difficult and often has a high scrap rate. Currently, many titanium aerospace components are machined from solid stock, often cutting away 90% or more of the original material – a time-consuming, costly operation that is completely eliminated with DMLS titanium not to mention much lower labor costs.

Some of the characteristics that make titanium ideal for aerospace applications also make it difficult to machine. Its hardness and low heat conductivity reduce tool speeds and life, require a great deal of liquid cooling during machining, and limit the productivity of certain shapes, such as thin walls. Laser-sintered titanium, however, retains the beneficial properties of the metal and involves no tool-wear or coolant costs. In addition, nearly any geometry, including thin walls, can be created with laser-sintering. - Nextbigfuture.com

Typical Applications:
- Direct manufacture of functional prototypes, small series products, individualized products
- Spare parts
- Parts requiring a combination of high mechanical properties and low specific weight, e.g.structural and engine components for aerospace and motor racing applications, etc.
- Biomedical implants

DMLS ALUMINUM

EOS Aluminium AlSi10Mg is a master alloy aluminium- powder. AlSi10Mg is a typical casting alloy with good casting properties and is used for cast parts with thin walls and complex geometry. The alloy combination silicon/magnesium results in a significant increase in the strength and hardness. It also features good dynamic properties and is therefore used for parts subject to high loads.Standard building parameters completely melt the powder in the entire part.
Parts made of EOS Aluminium AlSi10Mg can be machined, wire eroded and electrical discharge machined,welded, micro-blasted, polished and coated. Unexposed powder can be re-used.

Typical applications:
- Direct manufacture of functional prototypes, small production runs, user-specific products or spare parts
- Parts that require a combination of good thermal properties with low weight, e. g. for motor-sport applications

DMLS INCONEL

Try machining Inconel 718 and see how many people start yelling about that. Its tough and nobody likes to do it. Well until now. The DMLS process allows you to produce Inconel parts quick while being affordable.

This material is ideal for many high temperature applications such as gas turbine parts, instrumentation parts, power and process industry parts etc. Material also possesses excellent cryogenic properties and potential for cryogenic applications.
Standard processing parameters use full melting of the entire geometry, typically with 20 μm layer thickness. Parts built from EOS NickelAlloy IN718 can be easily post-hardened to 40-47 HRC (370-450HB) by precipitation-hardening heat treatments. In both as-built and age hardened states the parts can be machined, spark-eroded, welded, micro shot-peened, polished and coated if required. Unexposed powder can be reused.

Typical applications:
- Aero and land based turbine engine parts
- Rocket and space application components
- Chemical and process industry parts
- Oil well, petroleum and natural gas industry parts

I look forward to your comments!

Tim Ruffner
GPI Prototype & Manufacturing Services, Inc.
940 North Shore Drive
Lake Bluff, IL 60044
http://gpiprototype.com
Phone: 847.615.8900
Fax: 847.615.8920
Email: Timr@GPIprototype.com
GPI on Twitter
Tim Ruffner LinkedIn

Surface Finish & Finishing of DMLS - (Direct Metal Laser Sintering) Parts

FINISHING/POLISHING (SURFACE ROUGHNESS)
Parts “as built” off DMLS machines have a “raw” finish comparable to a fine investment cast, with a surface roughness of approximately 350 R a- μ inch or R a-μm 8.75, or a medium turned surface. This surface roughness can be improved all the way up to 1 R a- μ inch or R a-μm 0.025, qualifying as a super mirror finish. There are several processes available that can be used to achieve the desired surface roughness or finish. These processes include, but not limited to:

Abrasive Blast (Grit & Ceramic)
Abrasive blasting is the operation of forcibly propelling a stream of abrasive material (media) against a surface under high pressure to smooth a rough surface. Abrasive blasting services are included standard for all DMLS projects. If a “raw” DMLS part is desired, this should be noted at the time of the RFQ when addressing the desired surface roughness. Abrasive blasting with grit and ceramic media provides a satin, matte finish of approximately 150 R a- μ inch or R a-μm 24. This finish is largely uniform, but does not provide a 100% uniform finish.

Shot Peen
Shot peening is a process used to produce a compressive residual stress layer and modify mechanical properties of metals. It entails the use of media to impact a surface with sufficient force to create plastic deformation. It is similar to blasting, except that it operates by the mechanism of plasticity rather than abrasion. Peening a surface spreads it plastically, causing changes in the mechanical properties of the surface. Depending on the part geometry, part material, shot material, shot quality, shot intensity, and shot coverage, shot peening can increase fatigue life from 0–1000%. Shot peening is used primarily for foundries for deburring or descaling surfaces in preparation for additional post-processing.

Electrochemical Polishing
Electrochemical polishing also referred to as electro polishing, is an electrochemical process that removes material from metal parts through polishing, passivation, and deburring. It is often described as the reverse of electroplating; differing from anodizing in that the purpose of anodizing is to grow a thick, protective oxide layer on the surface of a material rather than polish. The process may be used in lieu of abrasive fine polishing in micro structural preparation, and is an inexpensive option for DMLS projects that are not tolerance dependent, creating a bright uniform finish. The extent to which electro polishing is successful depends upon the degree of preparation of the treated surfaces.

Abrasive Flow Machining (Extrude Hone) Polishing
Abrasive flow machining (AFM), also known as extrude honing is a method of smoothing and polishing internal surfaces and producing controlled radii. A one-way or two-way flow of an abrasive media is extruded through a workpiece, smoothing and finishing rough surfaces. One-way systems flow the media through the workpiece, then it exits from the part. In two-way flow, two vertically opposed cylinders flow the abrasive media back and forth. The process is particularly useful for difficult to reach internal passages, bends, cavities, and edges. This is an inexpensive option for DMLS projects that are not tolerance dependent, and a more uniform surface roughness. The extent to which AFM is successful depends upon the degree of preparation of the treated surfaces.

Electroplating
Electroplating is a process that uses electrical current to reduce ions of a desired material from a solution and coat a conductive object with a thin layer of the metal material. Electroplating is primarily used for depositing a layer of metal to bestow a desired property (e.g., abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.). Another application uses electroplating to build up thickness on undersized parts. Plating is also an inexpensive method of improving surface roughness, with the reduction in roughness once again hinging upon the degree to which surface are treated prior to plating. DMLS parts can also be plated in their raw state, and then finished in combination with another method.

Optical Polish (Hand Finishing)
When projects have geometries in low quantities that are not tolerance dependent, the best finishing option is an optical polish. Optical polishes are extremely cost effective, and the best way to achieve a brilliant finish. Due to surface porosity of DMLS metals, .003” to .010” of surface material is removed depending upon geometry. If this option is desired, it is imperative that designers or engineers consult with GPI prior to building, as specific surfaces may need to be offset with additional material to ensure part integrity after post-processing. Optical polishing is not ideal for large batches as it lends itself to an inconsistent finish from part to part.

Micro Machining Process (MMP)
Micro Machining Process (MMP) is a mechanical-physical-chemical surface treatment applied to items placed inside a treatment tank, providing highly accurate selective surface finishes. The desired surface finish is obtained by using MMP only on those areas where that particular finish is required. MMP begins with a detailed analysis of the surface state of the item to be treated, establishing the processing parameters required to meet the customer’s objectives. MMP can finely distinguish and selectively apply different primary roughness, secondary roughness and waviness profiles to surfaces. MMP is a batch process that is quite expensive, with costs ranging from $500 to $1000 for sample finish testing. After acceptable samples have been provided, costs for batch runs start at approximately $3000. This process has selective application, and is ideal for projects requiring precision tolerance finishing to a large number of parts, as well as parts with internal passages that cannot be reached by an alternate method.

CNC Finishing/Machining
CNC finishing permits high quality contoured milling applications to achieve tight tolerances. Detail-oriented precision can be accomplished with 3-axis, 5-axis and 6-axis CNC lathes. Conventional fixed headstock and Swiss-style CNC lathes can be utilized to support complex operations such as cross drilling and cross tapping, cross milling and slotting, C-axis milling and off-center work. Proper fixturing can yield tolerances as tight as 1 micron or (.00004). Should this post processing option be desired, pre-build planning is required to add sufficient material to machined features and surfaces so that tolerances can be met.


Cobalt Chrome MP1, media tumbled.


Cobalt Chrome MP1, optical polish #2


Cobalt Chrome MP1, optical polish (mirror finish) #3.


The shell behind the finished part is a "raw" part. You can see the contrast with this finish. This finish is the "optical finish". Stainless Steel. PH1.


This is an insert which had supports removed and abrasive blasted. MS1.


Raw with supports. Stainless Steel.


Stainless Steel PH1, shot peened finish.


Stainless Steel PH1, raw with supports removed.

Tim Ruffner
Account Executive
GPI Prototype & Manufacturing Services, Inc.
940 North Shore Drive
Lake Bluff, IL 60044
http://gpiprototype.com
Phone: 847.615.8900
Fax: 847.615.8920
Email: Timr@GPIprototype.com
GPI on Twitter
Tim Ruffner LinkedIn
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Tim Ruffner
Account Executive
GPI Prototype & Manufacturing Services, Inc.
940 North Shore Drive
Lake Bluff, IL 60044
http://GPIprototype.com
Phone: 847.615.8900
Fax: 847.615.8920
Email: Timr@GPIprototype.com

3D Printing

Previous means of producing a prototype typically took person-hours, many tools, and skilled labor. For example, after a new street light luminaire was digitally designed, drawings were sent to skilled craftspeople where the design on paper was painstakingly followed and a three-dimensional prototype was produced in wood by utilizing an entire shop full of expensive wood working machinery and tools. This typically was not a speedy process and costs of the skilled labor were not cheap. Hence the need to develop a faster and cheaper process to produce prototypes. As an answer to this need, rapid prototyping was born.

One variation of 3D printing consists of an inkjet printing system. Layers of a fine powder (plaster, corn starch, or resins) are selectively bonded by "printing" an adhesive from the inkjet printhead in the shape of each cross-section as determined by a CAD file. This technology is the only one that allows for the printing of full colour prototypes. It is also recognized as the fastest method.

Alternately, these machines feed liquids, such as photopolymer, through an inkjet-type printhead to form each layer of the model. These Photopolymer Phase machines use an ultraviolet (UV) flood lamp mounted in the print head to cure each layer as it is deposited.

Fused deposition modeling (FDM), a technology also used in traditional rapid prototyping, uses a nozzle to deposit molten polymer onto a support structure, layer by layer.

Another approach is selective fusing of print media in a granular bed. In this variation, the unfused media serves to support overhangs and thin walls in the part being produced, reducing the need for auxiliary temporary supports for the workpiece. Typically a laser is used to sinter the media and form the solid. Examples of this are SLS (Selective Laser Sintering) and DMLS (Direct Metal Laser Sintering), using metals.