In this week, I learned about 3D printing and scanning. I tested and tried different 3D printers. I found different characteristics of each printer. I also tried 3D scanning for the first time. 3D scanning required techniques and effort but at the end it came out very good result, close to the actual model.
Assignment
Test the design rules for your printer(s) (group project)
Design and 3D print an object (small, few cm) that could not be made subtractively
My initial idea of a object that cannot be made with subtract techniques was a dice which has a small dice inside.
I thought it is not possible to make a cube inside of a cube with subtract techniques. But after searching on the internet, I found many examples of people made this kind of objects with CNC milling machines or lathe. So I needed to change the idea. New idea came from a 3D printed object someone made in Fab Lab. There is a thin gap between the bigger outer circle and the smaller inner circles which allow each part to move.
My idea is:
an object which consists of cylinder shaped outer and inner part,
there are thin gap between the outer part and the inner part to allow them move individually
outer part has some kind of lid
Fab Lab logo is cut out on surface of the inner part
text “Fab Academy 2018” is cut out on the side surface of the outer part
I thought the gap between an outer object which is has a kind of lid and an inner object which is covered with the lid cannot be made with subtract techniques. Because CNC milling bits or lathe cutting tool cannot reach the gap.
Designing 3D object
I started designing the outer part in Fusion 360. To add wrap text around the cylinder surface, I used Unfold function in Sheet Metal Mode referring to this tutorial video. I found this video when I was working on 3D modelling of a globe for week 2 assignment. First I drew a outer circle which diameter is 50mm in xy plane in Sketch. I drew a line from the centre of the circle and selected Offset (Sketch> Offset) with 1mm distance.
I set two lines as construction line (Sketch Palette> Options> Construction).
I made 1mm slit between two construction lines by applying Trim on the line between the construction lines (Sketch> Trim)
I stopped sketching and changed mode to Sheet Metal. I selected the circle and applied Flange function (Create> Flange) to create a hollow cylinder from the circle. I can choose different materials, such as steel, aluminium etc., but thickness of all of them were less than 2.5mm. These materials are defined in Sheet Metal Rules. I wanted the side wall of outer part to be 5mm, so I added a new rule in Sheet Metal rules (Modify> Sheet Metal Rules). Later I realised 4mm thickness looks better, so I modified the rule. The thickness in the design was changed according to the modified rule.
I applied Flange again with the rule I added and set height as 15mm. I selected side 2 so that the diameter of the circle doesn’t change and the wall will be created inside of the circumference. 15mm height cylinder with a slit and 4mm thickness wall was made.
I went to Extrude (Create> Extrude), and selected one of the face of the slit, set distance as 0.5mm and chose operation type as Join to create a flat surface so that I can unfold this cylinder.
I went to Unfold (Modify> Unfold). I selected the thin flat surface of 0.5mm width that I created just now as Stationary Entity, and the cylinder wall as Bend.
The cylinder was unfolded and flat rectangle was appeared.
To cut out text, I needed to add a font which does not have “island” missing by cutting on the letters such as, A, b, d, e, 0, 8 etc. I searched on the internet with the word “stencil font”. No Island Sans was simple and good but this font doesn’t have small letters. Flamante Stencil has capital and small letters but doesn’t have numbers. It is also possible to create font, for example with FontForge. I chose Allerta Ster which has capital and small letters and numbers. I downloaded the font file as ttf format, opened file and selected Install and restarted the computer. I found the new font Allerta Ster added in Fusion 360, but when I selected it, the font of the text was not changed.. I found it worked in Inkscape so I decided to write text in Inkscape and import the SVG file in Fusion 360.
I wrote text in Inkscape, and saved the text as SVG format. I imported it in Fusion 360 (Insert> Insert SVG), but the font of text was changed to different one. I went back to Inkscape and changed text as path (Path> Object to paths).
I saved it as SVG format and imported in Fusion 360 (Insert> Insert SVG). It worked well and text was shown as Allerta Ster.
I extruded the text (Create> Extrude).
I folded the cylinder again and selected Extrude to fill the slit. I chose the face of the slit and selected To object as Extent and chose opposite face as Object. I selected Join and clicked Extend faces in Chain faces section to fill the slit.
Now perfect cylinder with wrap text around is here.
Next I designed inner part. I went back to Sketch and selected xy plane. The outer circle’s diameter is 50mm (radius: 25mm) and the wall thickness is 4mm. So inner circumference of the outer part is 42mm. I decided inner part diameter as 40mm so that there is 1mm space around the inner part. According to our group assignment, all 3D printers we have in Fab Lab Oulu can make at least 0.7mm gap. So 1mm gap will be fine. I drew a 40mm diameter circle inside of the outer circle.
I wanted to have Fab Lab logo cut on the inner part. I searched Fab Lab logo on the internet and saved the image. I imported it in Inkscape and changed it to vector graphic (Path> Trace Bitmap). I deleted the original image and saved vector image as SVG format.
I imported the SVG file (Insert> Insert SVG). I placed the logo in the middle of the 40mm diameter circle.
I stopped sketching and changed to Model Mode. I selected the 40mm diameter circle and applied Extrude (Create> Extrude).
I set distance 14mm and selected New body as operation. I selected the bottom of the inner part and moved it 1mm up.
Now the inner part has 1mm space around in every direction.
Next I created the lid. I selected the top surface of outer cylinder and started sketching (Sketch> Create Sketch).
I drew two circles which diameter are 50mm and 36mm.
I stopped sketch and Extrude (Create> Extrude) the faces between 50mm diameter circle and 36mm diameter circle. I set distance as 2mm. I repeated the same sequence and created the lid also on the bottom of the outer part. Finally, I checked the distances of small parts and gaps of the design to make sure the 3D printer can make based on the test we conducted as group assignment (Inspect> Measure). The gap between outer and inner part is 1mm, all the printers can make 0.7mm distance, so it will be fine. The thin parts of Fab Lab logo were 1.3mm, all the printers can make at least 0.5mm wall so it will be also fine.
The thin parts of letters were 0.5mm. I decided to make the letters bigger so that the printer can make this wall for sure. I went back to the point when I inserted text in Timeline and imported SVG text file again and made it bigger. Now the gap is 0.55mm.
I extruded the text again.
It might be better to scale up before I print. I scaled up the object as 1.2 times (Modify> Scale). Now the thin parts of the letters are 0.7mm.
The design is ready for 3D printing.
3D printer operation
I printed with three different printers and compared the results.
Sindoh
Formlabs
Stratasys
Printing with Sindoh
I opened stl file in Sindoh 3DWOX.
I made tool paths for 3D printing. Each layer can be seen by scrolling the bar on the lower right corner.
Next I went to settings. The bottom surface of inner part is in the air, and there will be a space between printer bed and the bottom surface. I set Brim as Bed Adhesion. Brim makes one layer around the bottom layer of each part which touches on the bed. I thought it will help inner part be build, but I found out inner part did not touch the surface of bed, it did not work as I had expected. It is for small surfaces to be stable during filament is being layered.
I selected print. The camera in the printer showed the view of the bed. I made sure there was nothing left from previous printing and pressed print.
It started heating the nozzle and the bed, and printing was started. Printing time was about 3 hours.
After printing, I removed extra layer from the bottom. Since the printer doesn’t have support material, the inner part was not made properly. There was filament in the gap between inner and outer parts and I couldn’t move them separately. I manually removed filament as much as I can using cutter and thin hex key. After cleaning, it moves, but not smoothly. Also the thin gaps in the letters were not printed beautifully.
front
back
letters
filament inside
Printing with Formlabs
I opened stl file in PreForm.
I chose quick calculation which adjusts orientation of the object and adds supports for printing. If I want to add other object after I calculate orientation and supports, I need to use 1) orientation and 2) support button so that it will calculate only for the new object. But otherwise, I can use quick calculation.
Printability was shown as not good in the bottom. My 3D model needed additional supports where were shown as red. I added several supports until printability marked as good. I can change thickness of supports. I made additional supports thicker as 0.7-0.9mm so that I can remove easily.
I calculated time by clicking Printing Time button in the bottom. Printing time was about 4.5 hours. I clicked print and sent data to the printer.
Next I operated in the monitor on Formlabs. Formlabs uses resin to print 3D model. Resin is provided as liquid and gets hard when it is exposed to the ultraviolet light.
I checked the name of the file and selected Print Now. I opened the cartridge vent behind where resin is provided. I checked the build platform was set properly and confirmed. The printer started heating and printing was started.
file
check before start printing
heating
With Formlabs, objects are printed as they are hanged from the building platform. A object has large area to stick to the surface of the building platform, and it takes time to make that layer which is attached on the platform.
After printing, I needed to clean the object. Always make sure to wear gloves when I clean after printing! First I opened the orange cover and took the building platform off from the machine. I carefully removed the object from the building platform with small spatula kind of tool.
There are two boxes filled with alcohol to soak the objects after printing. I put my object in the basket in the left box. I moved the basket up and down in the liquid for 30 seconds. Then I left the object in the box for 10 minutes. After 10 minutes, I moved the object to the right box for another 10 minutes.
Meanwhile I cleaned building platform and spatula with paper and isopropanol.
Next I cleaned the tank filled with resin. I need to clean it because if there are something left in the tank, it affects the ultraviolet light and next object will not be printed properly. I pulled the bar in the tank which cleans the tank during printing and carefully slid and placed in the edge of the tank. I held spatula and placed it 45 degrees to the bottom surface of the tank. I carefully slid the spatula forward without spilling resin. I cleaned all area of the tank. I closed the orange cover and closed the cartridge vent.
After 10 minutes soaking in the alcohol, I washed the object in the water and dried it.
After it dried, I cut supports with nipper and used soft sandpaper to smooth the surface. The supports were attached with thin surface on the object, and easily removed.
after cleaning
removing supports
smoothing
The object was almost perfect. All the small gaps and thin parts were mede perfectly. Inner part and outer part move separately and smoothly. However, the surface has friction probably because of the material, resin.
Printing with Stratasys
I opened stl file in Insight. I selected Part interior style. There are three options sparse, double sparse and solid. Sparse is faster and printed objects are lighter. I wanted my object to be not too light so I chose double sparse.
I pressed the green frag and made each layer and supports visible. Estimated time was about 3 hours. I pressed Tool paths and Build.
Control Centre was opened. I selected Build. I wore gloves and opened the printer. I placed clear sheet on the surface of the printer bed at the marks on the back corners. I closed the door for a while to wait the sheet was heated and flattened. I waited until the cross on the vending sign disappeared. I selected the file I sent. On the screen I can see the bed and the object. I moved and placed the object where I wanted to build. I pressed the go button and printing was started.
At the end of the printing, the printer ran out of the material. So I changed the cartridge. I opened the lower doors. There were two cartridge, filament and support material. I pulled the bar above of the filament cartridge and moved upper and moved backward. I removed the cartridge from the machine. I used the cartridge which was leftover. I cut the edge of the filament with nipper to 1 cm to the cartridge. I held the wheel which sends filament to the printer so that filament wouldn’t go inside of the cartridge. I put the cartridge back to the printer. I moved the wheel downward to provide filament from cartridge to the printer till the green light above the cartridge turned on. I took the orange stopper away and put in the bottom of the cartridge. I pressed Up sign next to the material and material was provided. The printing was continued and completed. After printing, I took it from the printer and removed it from the clear sheet with spatula. There were a lot of support material inside and outside of the object. I removed it as much as I could and put in sodium hydroxide solution bath to dissolve the support material. I wore the gloves and soaked it in the bath. In the next morning, I picked it up and washed it in the water. I held it in paper for a while because the liquid is soaked in the material. All the support material was dissolved. All the small gaps and thin parts were perfectly made and movement was very smooth. Because of the material there is not much friction and it spins very quick.
Here is the comparison of objects made by three different printers.
Sindoh
Formlabs
Stratasys
3D scanning
Antti Mäntyniemi, Fab Lab Oulu manager introduced sensor scanning and photogrammetry. I tired to scan 20 cm cactus shaped object and a sculpture with these different scanning techniques. I used turntable to turn the objects to capture them from 360 degrees with camera or scanner in a fixed position.
To detect the angles of the object, we need to place something that software can easily understand the different orientation and angles, like this.
Sensor scanning
One of the ways to scan a 3D object is using depth sensor to detect the object. We have Sense 3D scanner in Fab Lab Oulu.
It allows us to make 3D model of an object by scanning the object from 360 degrees. The infrared depth sensor detects the shape of the object and camera captures the colour of the object. Sense has software where we can see the scanned objects and edit them. Software works only on Windows 8/10. I placed the cactus on the turntable. I connected Sense scanner to USB port of Windows computer which has Sense software. There I can choose a type of the object to scan from different options: person/ small object/ medium object/ large object.
The monitor showed the view of the scanner. It did not detect the cactus well, perhaps the object was too small. I put the cactus on the box to make the height higher.
To detect the object, there should be 0.8 - 3m distance between scanner and the object. It was difficult to do it by myself and I needed help to hold scanner, control software and turn the table. When the scanner detect the object, green rectangle appeared around the object. I pressed Start and scan started. I scanned the object from 360 degrees and changed the angle to higher position and scanned it 360 degrees.
Sometimes it lost the track and I needed to restart scanning. After several times practice, I managed to scan the cactus from 360 degrees from 2 different angles.
I stopped scanning and clicked Next. There I can edit the object.
I removed the unnecessary parts by Crop and Erase.
Solidify is to make the inside solid. Next I can change colour, brightness and contrast, of the object.
By using Trim, I cut the bottom the the cactus straight. Here is the result.
Photogrammetry
Another way of 3D scanning is using normal photos and software. Autodesk ReCap is reality capture and 3D scanning software which creates a 3D model from photos. It is Windows application and does not support Mac OSX. I searched alternative software, such as them. But ReCap looked the best option, compare to others, as it is simple, easy to use and free. So I installed it to one of the computer in Fab Lab. I went to Autodesk website and searched ReCap. I downloaded ReCap Pro, which is free for students. With only ReCap Pro, I couldn’t marge photos to create 3D model. I also downloaded Autodesk ReCap Photos Update. I placed the cactus on the turntable.
I used iPhone SE to take photos. I took 24 photos from different orientation of the object. I changed angle and took 24 photos again. I went to ReCap application, and imported the photos.
Photos were uploaded and proceeded to make 3D model. After a while, it was ready to download.
The result was failed.
3D model was not made. I also took photos of the sculpture but it was also failed.
I searched information of how to take good photos for photogrammetry, such as this. My assumption of the failure is:
There was not enough light.
Many things were in the photos behind of the object, so application did not recognise well which one to focus.
I gave another try under the light with the same strategy, turned the object, fixed camera. But this time also failed. So the problem was not the light.
I changed the strategy and moved myself and camera to take object in fixed position. I moved around the object and took 24 photos in the same angle and changed the angle and took another 24 photos.
This time it worked! ReCap built 3D model from the photos. 3D model was large area around the object.
I edited the 3D model in ReCap. I selected unnecessary parts in the 3D model and deleted (Edit> Delete).
After I deleted most fo the extra parts around the object, I cut the bottom straight with Slice and Fill (Edit>Slice and Fill). I can choose to make inside hollow or solid. I chose solid.
I edited one arm of the cactus where ReCap merged the extra part. I deleted the extra part and filled the hall (Edit> Hall).
I ran Analysis to check if there is no hall or error (Analysis> Diagnostics). It found one small hall. I selected Fix and hall disappeared.
I changed the scale, exported it as stl and printed with Formlabs.
Reflection
In this week, I tried three different 3D printers. From the testing and printing object I designed I found advantages and limitations between the printers. Formlabs has the best quality of printing details since each layer can be very thin. But it takes time and cleaning after printing requires effort. Also resin tank need to be clean, otherwise the quality gets lower. Stratasys is easy to operate and result is very good quality. The supports allow to print the objects which cannot be made easily with subtractive techniques, such as an object in an object. It takes effort and time to dissolve supports. Sindoh was easy to operate and doesn’t require much effort after printing. The quality of printing is less than other two printers but it can make thin gaps, small parts and bridges in a smiler level to Stratasys. Another topic was 3D scanning. I found sensor scanning is easier but the result of photogrammetry can be better. The key of photogrammetry is how to take pictures which software can easily recognise and build 3D model from it. The background needs to be changed so that software can calculate the orientation and angles. If the object is small and focus of the photos are only the object, it is possible to take good photos from fixed position with some background which software can recognise.
Files
The following zip file contains:
3D model designed with Fusion 360 (f3d/ stl format)
3D model scanned by phtogrammetry (obj/ stl format)
I opened the lower doors. There were two cartridge, filament and support material. I pulled the bar above of the filament cartridge and moved upper and moved backward. I removed the cartridge from the machine.
