Laser scanning is accomplished by using a laser device that collects range data. The most common method for acquiring range data is active optical triangulation. Range data is produced by placing a depth value on a regular sampling lattice from the surface of the object. Then, by connecting triangular elements with the nearest neighbors, a range image is created. The image to the right illustrates the point-cloud generated after registration.
Beyond the scope of "how to make", the ability to collect and process large volumes of elevation data holds great interest to those who need highly accurate information in making critical decisions when time is of the essence. Technological advances in terrain mapping developed by NASA and commercialized by U.S. firms are now being utilized on a global basis. Just such a venture is resulting in export of U.S. technology and engineering experience to several points around the world.
A case in point is the Swiss Department of Agriculture who engaged SwissPhoto, Zurich, Switzerland and TerraPoint LLC, Houston, Texas to develop highly accurate elevation and surface terrain models for over 20,000 sq. km of Swiss countryside with the specific application of defining forest boundaries now encroaching on agricultural land (see images at the top-right).
Great tips from Nadav
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There are, in general, 3 ways to fabricate a 3D shape:
1. Send the model to the 3D printer
2. Turn the model into a tool path for subtractive cutting
3. Slice the model and send it to laser or vinyl cutter
STRATASYS
General Information:
The Stratasys uses ABS plastic (it extrudes a filament of plastic, like a glue gun). It has 2 nozzles:
one for he ABS plastic, and one for a water soluble support material. The Stratasys can make substantial structural parts--heavy and thick - which uses up a lot of material. So you need to remember to make your models hollow and support them internally with buttresses if needed. This machine builds very slowly-- hours and hours for larger objects. The modeling envelope is 10"X10"X10". It takes .stl files-- a simple, but bullet proof file format that all 3D printers use. As you build in the Stratasys environment, the machine provides a support structure. The machine
software defaults to adding a thin support base size (about 5 mils). You should increase this to about 20 mils to provide ample support, too thin a support base will cause your model to adhere to the Styrofoam base, too thick a support base can be unstable and possibly cause your job come off the base during fabrication. The Stratsys only prints monochrome objects. Its resolution each layer deposits .012 inch of material. When this machine is working, it works well. When it goes down it is a bear.
Software package to print is called "Insite". You will have to upload your files to the net and then download them on the computer dedicated to the Stratasys to print. Remember this machine takes the .stl file. (Tip-- don't use this computer or the ZCorp computer when another job is running --because if you run into problems and have to reboot the computer, it stops the current job printing, and that job has to be started all over again.
STEP 01 Click on the "2000" button to set parameters.
We use AVSP400 for modeling material and Soluble ABS P400SR for support material. If you choose the wrong support material the job will take much longer to print-- by hours and hours due to the fact that it will raster the base, not contour and fill it. T16 tip. (There are 3 sizes .016in,.012in, .010in-- .016 gives the best value for resolution and time.) Slice height .010
Click on the flag-- this generates/autowrites the model-- slices, curves, and writes a toolpath.
On the upper menu bar, click on the stack of lines-- this allows you to see all layers of the model. The red lines are the modeling material, the yellow and gray lines are support material.
Try to rotate your model such that the z axis is as low/short as possible. This will reduce your printing time.
You want to be sure that you have set the tip for both the modeling and the support to T16, depositing up to .012in thick layers.
STEP 02 Go to machine now. Little screen above should be set on Low Temperature. (Actually whenever you finish a job, you should leave the support material at the Low Temp setting --210 degrees F). To start you want to check that the modeling material is at 270 degrees and that the Support is at 210 degrees. Scroll through settings by using the right and left arrow keys. Once you have verified the appropriate temps for both nozzles, hit ENTER. The support material temp will increase up to 236 degrees. The support material tip has more
of a problem feeding than the support material head. Sometimes the support tip stops feeding-- as in when it stays at high temp too long and clogs the head. AS you set up,let this tip feed for about 30 seconds, then hit
"load" again.
STEP 03 Now go to the panel on the right side with the 3 led temp displays and buttons and arrows. Here the center button in the directional array allows you to move the heads around the x,y and z axes. Bring the head to the front.
Brush off the bottom of the heads with the wire brush that sits on the Stratasys table. Press the "Load" button- see material come out of the head. Feed the modeling material out for a bit, say 30 seconds to a minute until the
extruding filament is pure white. Then Hit "Load" again if you like the material. DON'T HIT UNLOAD-- as it will remove the filament from the tube entirely. Once satisfied, go to the Model Support button. Put the head in the down position (there is a slight offset between set and down-- I think you do this manually. )
STEP 04 Now go back to computer and hit the little computer "print "icon. On the screen you can now add files such that you print several at a time. The software will optimize the positioning of each file in the envelope. Once you are happy and loaded, hit OK.
STEP 05 Go back to machine. Pause button will be blinking.
STEP 06 Set the x,y, and z axis. This works much like the laser cutter. The orientation of the machine is that the upper left corner of computer file is zero/zero. As on the laser cutter we set our own origin.
Press z on the arrow/button array. Move x,y to be where you want them to be. Move the bed up or down until the tip just mushes into the styrofoam support-- by about .001in. The modeling tip establishes the Zero point of origin for your file.
Once x,y and z are set, hit the z button again to get out of orientation mode. Press Pause button again.
The job should start now. Starts with the support material first.
If for some reason you need to stop briefly, to add or check on something, press Pause and it will stop. In this mode you can move the x and y axes and not looses your orientation. But if you change the z axis, all is lost and you have to start printing the file over again.
STEP 07 Finishing: Once your file is complete ( 5-10 hours to complete printing is typical) you need to take off the support material manually/mechanically. Go to the shop next door with the drills and band saws and stuff in it. Get as much of the support material off using hands, screwdrivers, etc. as possible. Then go to the Ultrasonic Cleaner. Take the top off pull out the wire basket and put your object into the basket. Resubmerge basket in liquid tank and put the cover back on it. Check the temperature settings... should be 125 Degrees F. How long to run it? Hours. Need to check on it every hour or two until the support material has dissovled away. The ABS can bend and deform is if the temp gets too high. So check on it hourly or so. Start the timer and leave it. This post process is most useful for objects that have moving parts. (If you are making an object with moving parts, best to give it .015in gaps for moveable sections.)
Z-CORP
The ZCorp uses plaster and can print in 4 colors. It is a faster printer, but the objects are more fragile, and can be water soluble unless waxed. For this printer it is best to leave your object drying overnight 10-12 hours and then try to mine out the powder and unwanted materials from the cracks and crevices. You can add color or textures to your model in Blender. Then export the model as a VRML2.0 file. ZCorp accepts VMRL for color. The resolution for Zcorp is 4 thousandths of an inch - each layer is .004in thick. This is a pretty good resolution.
STEP 01 Software package called "ZPrint". Open ZPrint
Open your file-- this machine too has a dedicated computer, so you'll have to download your file from elsewhere. (Another tip-- don't use this computer or the Stratasys computer when another job is running--because if you run into problems and have to reboot the computer, it stops the current job printing, and that job has to be started all over again. You will be an unpopular graduate student with your peers!)
Set the parameters: We use ZB56 Powder (check that the measring standard is correct-- inches, mm, etc.)
(Note: You actually can use a .stl file in Zcorp, you just add one color to your file and the object is printed entirely in that one color.)
Under "File" you can get the print time estimate -- for monochrome or multicoloured. Monochrome is always faster. The Model envelope size /bed is 14"X10"X8". "Justify" will help you position the object to side , center or bottom of grid. Also, rotation lets you change the orientation of the object. With the Zcorp, the z axis, or height of the object is in the critical time path. That is, z should be as low as possible, the higher the z the longer the
build. You can copy/paste copies on side or top of each other to make multiple files or copies in one run of the machines. Be sure to leave 1/2" between objects for safe clearance. Click on the 3D print icon. A check list will come up on screen.
STEP 02 Go to the machine. Open the top to check on the amount of plaster in the trays. Close it again. Look underneath in the machine's cabinet. there are two compartments there. One is for waste plaster, and one is for washer fluid.
The waste bin should be less than 1/2 full. The washer jug should be almost full. There is an extra washer jug, that one doesn't need to be full.
Now check the ink cartridges up top. There are 4: yellow, red, blue and clear. The ink is the binding material for the plaster. Be sure there is plenty of ink in each cartridge.
(All of these materials, ink, washer fluid and plaster is extremely expensive-- costing a few hundred dollars a gallon, so
please conserve them carefully.)
STEP 03 Once you've checked all this stuff, then hit the "spread" button on the machine. (machine has to be closed to do this)
This will take the head out of the way. Now take the bottle of DI (deionized) water and rub a bit of DI over the head cleaner
(black square object in the back right corner of bed. ) Now take the vacuum (hidden in the big gray box next to ZCorp machine-
the vacuum is below in the cabinet. Turn it on inside by flipping the toggle switch-- have to reach inside to do this) and clean up the sides around the base of working area. As John likes to say..."A clean machine is a happy machine!" Also note
that you should close the curtain as this is a messy process, and note that the plaster is abrasive--thus it is important to clean as much as you can.
STEP 04 Look at the plaster containers in the middle of the bed. The left side is the feed bed (feeds the plaster), the right side is the build bed. If the plaster seems low, or is unevenly loaded or disturbed, close the top of the ZCorp and hit spread
several times until the bed looks perfectly evenly distributed. Sometimes the plaster is just low, and requires that you raise the feed bed and spread more plaster/add material to get it just right. Keep repeating until the bed is smooth and
full again.
STEP 05 When you are satisfied, go back to the computer. Check off the check list items, skip the temperature setting question, and
hit "Go". This sends the print job to the ZCorp printer. At the machine, push the offline button to "online". The job should start --there is a startup series of things the machine does that takes a few minutes -- like cleaning the print heads. This shouldn't last more than a minute or two.
Occassionally the print heads get too hot. An alarm will go off and you'll have to change the print heads over. Takes about a half an hour to do so.
STEP 06 Finishing: First of all you need to leave the objects in the printer overnight or for 10-12 hours to dry well enough to handle without breaking them. When they are dry enough, lower the feed table-- lower it quite a bit-- a few inches. Then you become a Jr. Archaologist. Put on a face mask, take a brush and slowly, carefully brush off object, leaving as much of the loose plaster
behind in the bed. Then put object in the vacuum chamber (top part). Vacuum it-- get it as clean as possible.