One of the questions we encounter a lot is “how should I paint my stereolithography parts?” That is a good question.  As you may be aware, a stereolithography part is created using a vat of liquid UV-curable photopolymer resin and a UV laser to build part one layer at a time. This creates a “stair-stepping” feature in the part.  Once the part is finished, it is wet sanded and bead blasted to remove stair-steps and to create a smooth appearance.  With this finish, the part looks very smooth and paint ready.  Unfortunately, this is the common mistake made by many.

As you can imagine, once you apply a coat of paint, a number of surface imperfections reveal themselves.  This is not good if you are planning to use this part to win a big order or if you want to impress the boss.  Instead, the boss will most likely ask you if your kid painted it…which is not a great feeling. Now the way you want to approach painting  your stereolithography part is to prime it first.  Then hand sand it and prime it again.  And then sand it again.  Yes, this is not a very efficient process but it will make the part look much  better when you finally do paint it.  The priming process helps fill in the pock marks and cover up any imperfections.  This is the crucial step in making your stereolithography part a big success.

So what is Design for Manufacturing? Why do I care? These are a couple questions we hear in the development phase of a new product.  The brief description according to wikipedia.com is that DFM is the general engineering art of designing products in such a way that they are easy to manufacture. The basic idea exists in almost all engineering disciplines, but of course the details differ widely depending on the manufacturing technology.DFM is intended to prevent:

  • Product designs that simplify assembly operations but require more complex and expensive components
  • Designs that simplify component manufacture while complicating the manufacture process
  • Designs that are simple and inexpensive but are difficult or expensive to service and support

I think that is a good overview of the general concept of what DFM is.  So the next question is “why is it a problem?”

There are a number of possible answers for this question.  First possible answer is that the manufacturing techologies are continuously changing so it is difficult to keep up with the new technologies available.  This could be true…I am not sold though.  The next answer could be that engineers are not trained properly coming out of college.  This is a possible answer but it seems like it blames the problem on someone else.  Last, the answer could be that engineering is no longer performed at the same facility as manufacturing….bingo! With manufacturing moving offshore to locations far away from engineering, the collaboration that existed in the past between design engineering and manufacturing no longer happens.  Designs are created and then passed to manufacturing to make parts.  Sounds great and very efficient…just not as flawless in practice.  How does an engineer learn about the hidden “gotcha’s” of injection molding? Well, unfortunately, they don’t.  Not until they design a part and have it manufactured do they see problems.

With that said, there are now services out there to help with the manufacturing process during the product development phase.  We are Quickparts provide a DFM of every part we review for injection molding.  We saw the void created in the industry and want to provide a free service that helps both our customers and us during the manufacturing process.  We have seen this as a huge success for customer wanting to proceed to injection molding.  This has helped product development companies reduce cost, lead time and ultimately FRUSTRATION.

To learn more about the service or see an example, give us a call or check Quickparts out at http://www.quickparts.com/ToolingProduction.aspx.

Here is an example of a DFM report: http://www.quickparts.com/UserFiles/File/Design_For_Manufacturing_analysis_report.pdf

Quickparts.com (www.quickparts.com) has launched a new video series starring Johnny Quickparts. He will be sharing his adventures in product development. Johnny is the star engineer in Better Be Running! Tools to Drive Design Success, an “almost” best selling book on product development and manufacturing.

A video series with a common character is a very unique approach to marketing in manufacturing. Most manufacturing information is very dull and boring. The video information that is available is typically shots of a machine doing something….great for 10 seconds, then dull after that….some may know the feeling.

There will be another 15 episodes this year and then the execs at NBC/CBS/ABC will decide if they cancel it (if they too busy, then we will decide the future).

Please check out the video and let us know what you think. http://www.youtube.com/user/JohnnyQuickparts

Recently there was a great piece wrote by David Maltz providing tips on selecting a rapid prototyping system.  The piece included some great information on the differences between the systems and benefits of each system.  I found the most useful information was the ilustration of the various finishes a user can expect from each machine.  The systems compared in the piece were the Dimension Elite, Fortus XXXX, ProJet HD 3000, Objet Alaris30, Objet Eden 260V and the Envisiontec Perfactory Mini Multi Lens. David’s final conclusion was to select the Perfactory machine because it ultimately provided the best fine feature control on the parts they used as test cases.  If you are interested in reading the full article, you can view it here at: http://www.makepartsfast.com/articles/2322/9/Tips-for-Selecting-a-Rapid-Prototyping-System.aspxIf you would like to know more about the rapid prototyping processes in general, check out www.quickparts.com.

We recently launched a new alternate rapid prototyping process at Quickparts.  Machined Plastic Prototyping (MPP). What is Machined Plastic Prototyping?MPP is a subtractive rapid prototyping fabrication process for creating plastic prototypes. The plastic material is removed from a solid block by Computer Numerical Control (CNC) equipment that cuts away the unwanted material.The MPP process is offered for 3 production plastics – ABS – Natural, ABS – Black and Acrylic – Clear. Unlike traditional rapid prototyping processes, the MPP material is a production grade plastic that is durable enough for end-use applications.Why select MPP process for your prototypes?MPP offers a more functional prototype part than any of the rapid prototyping processes available. This is due to the process of removing material from a solid block of production grade plastic rather than creating the part through an additive manufacturing process.If you are interested in learning more, give us a ring at 770-901-3200 or check out our website at www.quickparts.com.

The Crittercam was envisioned and invented by marine biologist and filmmaker Greg Marshall. National Geographic introduced the first generation of the Crittercam back in 1987 and has continually been improving it. The Crittercam has been used in March of the Penguins, National Geographic’s Wild Chronicles and many other National Geographic DVDs.With this new version, Greg Marshall and his team wanted to make it smaller, lighter and incorporate the latest technology for both audio and video, thereby allowing it to be more robust. In order for this to occur, they needed to think outside the box. They decided that a custom SLS part would serve multiple purposes and allow them total design freedom.Click here to read the full story and find out how Quickparts was able to help National Geographic meet their needs.

Yesterday, we launched the new email instant quoting for custom designed parts and rapid prototypes.  Quickparts was the first to provide online instant quoting for rapid prototyping and that has always mainstay foundation for the company.  But we heard from our customers that we needed to make it easier for them to start the quoting process.  We took that feedback and developed a great technology now. So how it works is that our customers can now email files to an email address: instantquotes@quickparts.comand our system takes the files and uploads them to their account.  Then an automated email is sent back to our customer with a link.  Click on the link and now the quoting process is started.  So, longer does a person need to login and upload their files.  In some cases, this can save our customers 5-10 minutes of very valuable time. In the world of instant gratification, we have continued to push the envelope.  We are excited about this new technology and we are even more excited for our customers who will get an even better experience when they use Quickparts.  If you would like to try it, go to www.quickparts.com create an account and start quoting today!

A very important step in producing a high quality prototype is to design with the process tolerance in mind. Each rapid prototype process has build tolerances that will affect the accuracy of the CAD model provided. If tolerances are not designed into the model, parts will not fit together as intended, wasting time and money.The table below shows standard tolerances for each rapid prototyping process.

Process

Vertical

Horizontal

 

First Inch

Each   Additional inch

First Inch

Each Additional inch

SLA

+/- 0.010”

+/- 0.002”

+/- 0.005”

+/- 0.002”

SLS

+/- 0.010”

+/- 0.003”

+/- 0.005”

+/- 0.003”

FDM

+/- 0.010”

+/- 0.002”

+/- 0.005”

+/- 0.002”

*PolyJet

+/- 0.010”

+/- 0.002”

+/- 0.005”

+/- 0.002”

Based on this data, the tolerances can either cause a part to be slightly oversized or undersized. Keep in mind that tolerances are additive, meaning that as the part dimensions get larger, tolerances will have more of an effect on the overall part size.How much tolerance should I factor into my part dimensions?For parts fewer than a few cubic inches, you can design a0.010″ – 0.015″ clearance and receive prototypes that meet your needs. For parts close to the maximum process build space, a clearance of 0.025″ – 0.040″ is needed to accomplish the same success.tolerance1If you would to learn more, be sure to visit www.quickparts.com for all your rapid prototyping and injection molding questions.

In the beginning before Rapid Prototyping….there was the evolution of 3D CAD.CAD was first developed over 20 years ago with the development of personal computers. The first company to become a leader in the CAD world was Autodesk with a product called AutoCAD. This was the first software product that allowed the user to produce 2-dimensional drawings on the computer and take advantage of the efficiencies that software can provide (copy, templates, etc.).  It is important to note that at this time in the product development world, all products were designed and developed from 2-dimensional drawings. These 2D drawings fully represented all appropriate views of the part or product. While this was a standard method of product design, it did require the learned ability to “visualize” what the part would look like in 3-dimensions (or in the “real” world). Since this was a subjective requirement, communication regarding the part was subject to misinterpretation. This also required parts to be designed much simpler than our products today. With 2D design, it was very difficult and expensive to develop parts that were highly contoured or with complex surfaces. This is the reason products of this era were more “blocky” and simple. Think of the cars of the 60′s and 70′s. It was not until the late 1980′s that software began evolving to render solid models and true 3-dimensional representations of the parts or products. Software was finally developed that could completely represent the part in 3-dimensional space so the designer did not have to imagine how the part would look.Once the 3D CAD became available, this lead to the development of rapid prototyping and 3D printing.  Now additive fabrication is becoming mainstream. It has been great to see over the past 20+ years.

Standard Tessellation Language (STL) is a file format native to the Stereolithography software created by 3D Systems. This file format is supported by many CAD software packages and is widely used for rapid prototyping and computer-aided manufacturing (CAM).STL is a facet-based representation that approximates surface and solid entities only with triangles (i.e., STL files describe only the surface geometry of a three dimensional object). Entities such as points, lines, curves, and attributes such as layer and color, in the CAD systems will be ignored during the output process.An STL file consists of a list of facet data. Each facet is uniquely identified by a unit normal (a line perpendicular to the triangle and with a length of 1.0) and by three vertices (corners). The normal and each vertex are specified by three coordinates each, so there is a total of 12 numbers stored for each facet. This data is used by a slicing algorithm to determine the cross sections of the three-dimensional shape to be built. This format approximates the surfaces of a solid model with triangles. With creating STL files, there are some common errors that will lead to poor part build or delayed leadtimes because the files are unusable.  Some of the errors are:

Manifold (Leaks)

Although it is not explicitly specified in the STL data standard, all facets in a STL data file should construct one or more closed volume entities. If a file is not ‘water-tight’, it is said to contain ‘leaks’. When a ‘leaky’ STL file is processed by slicing algorithms, the algorithms may not correctly detect the error, and as a result produce slice boundaries that are not fully closed. When the erroneous slices are used in the rapid prototyping process, the laser beam, cutter or whatever tools that generate the slice will ‘escape’ from the openings of the boundaries. Some recent pre-processing software such as 3D LightYear by 3DSystems, will try to correct the error by adding extra segments to link up broken boundaries.Degenerated Triangles Degenerated triangles are very thin triangular facets in the tessellated solid whose three defining vertices almost lie in a single line. The sides of degenerated triangles could create extra vectors in a given layer. These are usually the result of the design application’s attempt to tessellate a complex geometry.

Narrow or Wide Gaps

Violations of the Gapless Exterior Rule, narrow or wide gaps are empty spaces between defined triangular facets in the tessellated solid. These are also typically the result of the design application’s attempt to tessellate a complex geometry.

Inverted Triangles (Incorrect Normals)

Inverted triangles are a violation of the Right-Hand Rule for the formation of valid STL files. These are triangular facets in the tessellated solid whose normal vector (based on the order in which the vertices of the triangle are listed in the STL file) appears to be oriented in the opposite direction of the normal vectors of adjacent triangles. In other words, when examining the continuity of a region’s exterior surface, these triangles (based on the respective directions of their normals) appear to be oriented such that their exterior surfaces are facing inward.

Unmatched Triangle Sides

Unmatched triangle sides are a violation of the Vertex-to-Vertex Rule for the formation of valid STL files. These are triangles whose vertices touch the edges rather than the vertices of adjacent triangles.These are just some of the issues that arise from the creation of STL files.  In the end, it is best to consult an expert during the file creation process if you experience any issues.  Most issues can be solved pretty quickly…you just need to know what to look for.