In all over the world there are two methodes for digital fabrication the first on is by subtractive and the second one is by additive so the 3D printers are used to produce a part by add a new material.
In our fablab we have two type of printers:
1.SLA (stereolithography) In Stereolithography, UV light pattern is used to cure full layer of resin. The photo polymers are cured layer by layer to create the final object. SLA produces higher resolution objects and is more accurate than FDM as the resolution is primarily determined from the optical spot size which is very small. Also, much less force is applied in SLA than in FDM during layer formation and so the surface finish is much smoother and objects printed using SLA look much more professional than FDM printed objects, it has good surface finish for the printed parts and the cost of sla machines is high.
2.FDM (fused deposition modeling) In FDM technology, material is deposited in layers to create a 3D printed object. A plastic filament is fed through hot extrusion head. In the extrusion head, the filament gets melted. This melted filament will be deposited by drawing plastic lines on top of previous layers. FDM printing is one of the most widely used forms of 3D printing as of date, and the pros it has Low cost, easy availability, low cost maintenance, and the cons are the Mechanical Strength and Surface Finish.
In this week I designed a model that cannot produced by the subtractive methode and I printed it useing the additive method.
I start the design using autodesk fusion 360.
I drew two circle of diffrent diameters then I made extrude to them.
Then I made another circle extruded perpendicularly to the first one and I made some fillets.
Final step in the design is to make the edges flat to ensure good finish in the printing process.
In order to 3D print a part, a CAD model must be converted into a format that a 3D printer is able to interpret. The extension must be STL or OBJ files (The OBJ files used for the printers with full colors). After that it must be converted to G code as it is the language understood by the machine. The most famous slicer is CURA also another one is simplify3D which can you control more but it is not an open source.
I sent the design as STL format to cure software,and I entered the variabls.
The parameters are:
1.Material Used: PLA
3.Layer Height: 0.2mm, the layer hight should be half of the nozzle diameter or any divisible number so if we have a nozzle of 0.8 we can make the wall thickness 0.4,0.2 and 0.1.
4.Wall Thickness: 0.8mm usually I used 1mm or 0.8 to give a good surface finish
5.Top/Bottom Thickness: 0.8mm
7.The speed and cooling are change by defult when change the material
After one houre of printing I got this.
The scanner that we have in our fablab is 3D Sense Scanner
so we can make a 3D model by scan any object in this device, In this assignment I scaned my friend Osama, in the scaning process the object should remain static and I should move in a circular motion around it keeping the same distance the center point which is the object.
After I finished scaninig I saved the model as stl format.
and because Osama is atractive to problelems the filament gets tanggled
I printed osama again with a nother color.
Now I want to use diffrent machine in order to manufacture another model so I decided to use ultimaker 3 extended
I started the design with solid works so I made a sketch for 3 gears two of them have inner diameter of 8mm and one hase inner diameter of 5mm as shown
After I had made the sketch I made extrude from features by 12mm
Then I saved it as STL file in orded to lunch it in cure software
after I saved the file as stl I opened it in cura and the firs thing I did is to add the new printer
For the shell I have entered the wall thickness and bottom thickness as 1 mm also I have chosen 20% infill to save materials also as I wanted the print to be not that solid.
and this is the final setting, so the diffrence in this job is the wall/button thicknesses of 1mm and the previous job was 0.8.
Also its important to say that the pre-heating for PLA nozzel temprature is between 190-210 c and the
bed temprature is 60 c.
In ultimaker 3 extended there is two nozzelz so you can also print diffrent types of material, so i used the extruder number1 as shown.
finally I got this
Now I want to use diffrent material like felaflix material which is a Flexible Filament material, in our fablab we have flexible materials like TPU90 and 95 I used TPU90, in order to print filaflix material the auto pre-heating for the nozzel temprature shoud be 260 c and there is no temprature for the bed.
and the machine that used for the felaflix in our fablab is Witbox2
I will made a strap to but it in my hand, I start the design using solid works.
Here I opened CURA 3D printing software
and then I added a new printer which is WITBOX2
now I put the printing variables in order to get the model that I want
After half hour of printing I got this flixable strap
Problems and Conclusion
After I printed the gears with the PLA material I couldn't put the gear inside the motor shaft and the inner diameter of the gear equal to shaft diameter and that happened because the shrinkage of the plastic material, in my design the hole diameter is 5mm and after printing the hole aproximately 4 mm so 1mm of diameter reduced thats mean every edge hase redused by 0.5 mm and the best solution for this is to make the hole diameter 6 mm instade of 5mm.
Its important to talk about the surface finish, the felaflix materials has not a good surface finish and if we focuse on the printed layers we will notice a separate layers-spaces between then with comparing PLA material has a better surface finish also it hase a better strength.
Finally I want to talk about the advantages of 3d printing or the additive manufacturing over the milling cnc or subtractive manufacuring.
1. anyone can handle with the 3d printing because its easy to learn and to use also its more safty than CNC machines.
3. setup time, in 3d printing you just determine the nozzel and some variables and then you give tha machine the printing order, but cnc machine needs alot of time for setup time.
4. the finishing of CNC machines is better than the 3D printing and mora acurate because there is a shrinkage value for the plastic materials.
5. to make 3d model in CNC machines you need a diffrent settings and more time than the 2d cut but in 3d printing its all the same.
6. In cnc machines you need to use fixtures to make the work piece fixed and this need a lot of thinking how to make the right adjusting but in 3D printing you just need to put the right support in the software and thats it.
7.printing process taks too much time specially with large part it will take several hours
Download the files:
1. Joint stl file
and fusion file
2.Osama 3D scaned model stl file
5. strap stl
and strap sld