Posted by Robert Kiser on Wed, Apr 01, 2009 @ 09:43 AM
Some rapid prototyping services offer "instant" quoting where you upload your 3D Stereolithography files and you receive an instant price quote. However, most Rapid Prototype, or 3D Printing service providers have an "online quoting" page on the website and "online quoting" should not to be confused with "instant" quoting. The "Online quoting" process takes your uploaded file and puts it directly in the hands of a person who accurately quotes your job per their standards then sends you a printed quote. "Instant" quoting takes your uploaded file, scans the volume that exists within a box that surrounds the entire part, then issues an instant quoted based on the volume inside the box. There may be empty space within the box that the 3D model doesn't occupy that you are paying for. If you used the instant quoting services before, you have probably noticed that when you upload larger, or complex parts, you don't get an instant quote right back. This is because the larger, or more complex parts require personal attention to perform an accurate quote. I am not a recommender of "instant" quoting because I don't see it as an accurate method to qualify a job and I have seen large differences in quoted prices from "instant" quoting services and they are always higher than a quote from the more accurate "online" quoting method. Instant quoting is more a marketing tool. Real hands on analysis of every job is needed to accurately quote a 3D Model. See example here:
"Online quoting" services for rapid prototyping and 3D Printing offer the accuracy needed because of the human factor involved. We take your rapid prototype project and place it into our rapid prototype OEM application software where the entire 3D model is scanned, the surrounding box empty space is ignored, and an accurate material usage and build time is displayed to the analyst performing your quote. Online quoting doesn't take much time, so just because a rapid prototype service doesn't have an "instant" quoting service, don't be alarmed, but rather be assured you will receive an accurate quote.
Posted by Robert Kiser on Fri, Mar 27, 2009 @ 12:14 PM
Kaiser3D recently produced a functional actuator gear assembly made from PolyJet Vero Blue at an extreme cost and time saving to a customer who needed 30 of the parts within 2 days. The rapid prototype part was cylindrical in shape and stood 2" tall and was 1.5" in diameter. The customer requested this 3D model as a totally functional replacement for a more expensive aluminum part. The aluminum part had to be polished after production in order to meet the same surface resolution of the PolyJet rapid prototype that came straight out of the 3D printer. This was needed in order to prevent jamming during movement of the actuator gear performing a mission critical function. Not only did the high resolution PolyJet Vero Blue part perform just as well as the more expensive aluminum part, Kaiser3D shaved 10 days off the customer's waiting period and saved the customer over $1,700.00. Because the PolyJet 3D functional model had the capability to withstand absorbtion of water, it performed excellently when exposed to weather conditions of high humidity, then a short time later, operating at high altitudes in extremely low humidities and severe cold.
This success story is only one of many where Rapid Prototyping, or 3D printing, is used as an alternative to Rapid Manufacturing.
Posted by Robert Kiser on Mon, Feb 16, 2009 @ 09:47 PM
Laser Scanning is a non-contact technology that digitally captures the shape of physical objects using laser light. A laser probe projects a line of laser light onto a surface while cameras continuously triangulate the changing distance and shape of the laser line as it sweeps along, digitizing the object in three dimensions (see below for more information about laser triangulation).
Laser triangulation is an active stereoscopic measurement technique that computes the distance of an object with a directional light source and a video camera. A laser beam is deflected from a mirror onto a scanning object. The object scatters the light, which is then collected by a video camera located at a known triangulation distance from the laser so that the 3D spatial coordinates of a surface point or line are calculated. The CCD camera’s 2D array captures the surface profile’s image and digitizes all data points along the laser and can be seen here:
Overview of 3D Laser Scanning, Dimensional Inspection & Long Range Scanning
Rapid prototyping steps in when the scanned output data is saved as a stereolithography file solid CAD file. This file can then be created into a physical 3D model for analysis via use of rapid prototype 3D printing technology.
Posted by Robert Kiser on Fri, Jan 30, 2009 @ 12:16 PM
There are two basic factors taken into account which define overall "build speed" of rapid prototype systems and 3D printers. One factor is "Total Build Time" and the other is "Post Processing Time". These two totalled together = Total part production time.
Total Build Time is an important consideration when studying the many rapid prototype systems on the market today. Many lay claim to being "the fastest", but you have to consider not only physical build speed that occurs on the machinery platform, but also post processing time (processes involved after the 3D model has finished building). If it takes 4 total hours to build a 3D model on a platform from one manufacturer, and 6 more hours after completion for cleanup, post curing, and other processes prior to shipment, the total build time is 10 hours. If the same 3D model takes 5 hours to build on another manufacturer's platform, but only takes 3 hours for post processing, the total build time is 8 hours. So overall, the rapid prototype system that gets the final 3D model into the shipping box sooner is overall faster and should be a strong consideration of yours.
A general rule of thumb is that a system that builds faster normally has poorer surface resolution than a slower building machine. This is because a faster rapid prototype system is building in thicker layers in the Z-axis (height), while slower systems generally build in thinner layers which allow a tighter compaction and finer surface quality. Slower, higher surface resolution rapid prototype systems make up for the tighter layering process by speeding an array of other processes that occur inside the system during build. Hence, a higher surface resolution system may only lag slightly behind a lower surface resolution system and advancements in technology now have these higher resolution systems building faster. But if post processing time of the faster system is greater than the post processing time of the slower system, end product completion is actually faster using the slower system.
I read a white paper once that listed build comparisons of rapid prototype technologies. I was amazed to find that technologies I knew were slower than others were listed as faster. The test had each rapid prototype system build the same part at the same layer thickness (in this case .012" thickness), started at the same time, then a winner was picked. Problem I found is the fact that all rapid prototype systems don't build at the same layer thicknesses. So of course, the results were skewed. Also, average post processing times were not taken into account. I then did my own notes and found that systems that actually built slower, but had a faster post processing time associated with them, produced the end product faster, much faster in many instances.
So when you look at purchasing a rapid prototype system, ask for fair comparisons of technologies against others. Ask in detail about the post processing procedures. Ask yourself if you can sacrifice surface quality to gain speed. Every person who I have spoken with that purchased a low resolution rapid prototype system has said: "if I had to do it all over again, I would spend the money on a high surface resolution machine".
Posted by Robert Kiser on Sun, Jan 25, 2009 @ 11:55 AM
Yes, and let me explain why.
When most people think of a printer, the image that comes to mind is a device you print a computer generated document to. I asked some very bright associates of mine what came to mind when I asked them what a 3D Printer is. They all stated it was a device that printed blueprints from 2-Dimensional drawings. I told them they were very warm.
All rapid prototyping systems use a concept to place a 2-Dimensional image on top of another. These processes differ in method per system manufacturer, but the end result is the same. This is an additive process to "grow" a shape that takes up more and more space. It is a physical process that requires that each 2-Dimensional image be somehow "fused" together to create the final solid shape. You might then think that this 2-Dimensional image really isn't 2-D after all, because if you could held it in your hand, it would actually be a 3-Dimensional solid mass. The 2-Dimensional images that rapid prototype systems use to create 3D models are in fact a large (or small) series of 2-Dimensional images, like the images you see on a computer screen. The are referred to as "bitmap" images, and their appearance to the naked eye is controlled by what is termed "resolution". The higher the resolution, the easier it is to see the image. There are software programs in existence that can design an image that is 3-Dimensional in appearance on a computer monitor. This 3-Dimensional image is what is called a "Solid Model". This is where the rapid prototyping process begins.
Once the 3-Dimensional image is complete and ready to be created into a hand held object, some neat things occur. The 3-Dimensional image is saved as a Stereolithography file which is a big series of triangular shapes put together to form the image. This file is then imported into the rapid prototype system's application software and maneuvered around for fastest creation time. When ready, the operator starts the process and the 3-Dimensional image file is sliced up into many of those 2-Dimensional bitmap images I mentioned. So now, our software is acting like a printer at this point. How do we take these images and "fuse" them together into a 3-Dimensional physical objet we can hold in our hand? This is where the rapid prototype system comes in.
The PolyJet is a true 3-Dimensional printer. Think of the PolyJet rapid prototype technology as an overgrown inkjet printer. It holds a liquid inside the jetting heads and jets out each individual 2-D bitmap image, on on top of another. Each 2-D bitmap image is jetted out at a certain mechanical thickness, fused together via ultraviolet light, then machined down to a certain height. This is the point at which a 2-Dimensional bitmap image becomes a 3-Dimensional physical objet.
So, are 3D printers and 3D printing technology rapid prototype systems? Yes, indeed, and the classification is called the "PolyJet" technology and is part of the rapid prototype technologies that exist today.
Posted by Robert Kiser on Fri, Jan 16, 2009 @ 03:15 PM
Rapid prototype system manufacturers normally state one specific tolerance the part measurements should never exceed across the surface of a 3D model. From experience, a critical dimension on a part may measure +/- .002" off dimension on one side of part, while on the other side, a dimension may measure +/-.003", .001", or .000" etc. The overall reason for this is what is termed "repeatability".
System repeatability speaks to the mechanics and software programs of automated manufacturing equipment and critical subsystems within whole systems. Some manufacturing systems have better critical dimensional accuracy capabilities than others. For example, I'll use a laser traveling across a build area of one foot in the X plane (left to right, or right to left). That laser energy beam looks nice and smooth as seen by the human eye as it draws a bitmap image of a certain depth (layer height in the Z axis) into the medium (powder in this case). What we can't see is that the laser is not actually traveling smoothly, but it is most likely traveling within acceptable parameters specified by the manufacturer and meets the manufacturer's definition for repeatability. It stops and starts (shutters) a little in it's travel and deviates off a straight line a little here and there. The key to good quality of 3D models being produced on a rapid prototype system is to have performance of critical subsystems meeting repeatable performance standards throughout production.
There are deviations in all axes on all manufacturing systems, some systems with better repeatability than others, even though the system may be the same model and manufacturer. For this reason, it is CRITICAL to have good and knowledgeable Field Support Engineers supporting your systems. In the Field, I have never seen a PolyJet part measure more than .005" off actual dimensions in all axes and normally measures no more than +/-.001" to .0025". A maximum dimensional tolerance number is issued by manufacturers as a baseline tool for Field Engineering and Applications of what to expect and target. State of the art software applications have increased repeatability excellently over the last 10 years in Rapid Prototyping and other manufacturing systems. In reality, a manufacturer states a maximum tolerance value average that is normally very high and all systems can be tuned to degrees of calibration for tolerance values of normally +/- .005" and less. Again, it is a baseline number. But in general, the PolyJet 3D printer system produces impressive dimensional accuracy and is the most "repeatable" rapid prototype system I have encountered because it is a 3D printer system.