Bill of materials
2x Spool Stand V4 (for 8mm bars)
http://www.thingiverse.com/thing:479993
Printed at 0.2mm layer height, 2 perimeters and 10% infill
(Remixed from: http://www.thingiverse.com/thing:320376)
1x My remix of: Faberdashery Spool Axe Extension
http://www.thingiverse.com/thing:343269
Printed at 0.2mm layer height, 2 perimeters and 10% infill
1x 8mm wood dowel (1 meter) but metal would also work, or you could even print a length to fit
Bought from Antics model shop for £1
2x 608 bearings
I used 2 bearings from my old skateboard
The build
The first stage was to print the stand legs. At 100% scale, the stands require a printer with a print bed capable of 19cm² or about 7.5inch². As standard, the Printrbot has a maximum print volume of 6inch³, so I scaled the object down to 0.76 in Repetier and printed a quick test to ensure the biggest version I could print would still be tall enough to hold the spool of a surface it would stand on.
As you can see, the print messed up quite a bit, but all I needed to know is that there is at least a small clearance between the bottom of the spool and the table, so I was able to continue with using this object. One mistake I made here is that I scaled the object 0.76 in all 3 axes meaning that the total thickness of the stands was also reduced. I should have left the scale of the Z axis at 1.
Next was working on the axle which would fit into the center of the spool. Firstly, I again did a quick test print to see if the size was correct to fit into the center of the spool and to hold the bearings in place. It seemed that the size was just about right for the bearings, but the diameter of the axle was way too big for my spool. The solution in most cases, as with the stands, is to scale down the object in Repetier before slicing and printing. However, as I needed the diameter of the inner circle of the axle to remain the same size, this required some remodelling of the object.
To start, I imported the stl which I downloaded for the axle into Maya, but as stl files holds the geometry as triangles, it was going to be hard to edit just the outer circle of the object, as the object is not too complex I decided that I would be best starting from scratch and model the axle again using the original as a guide for size. Also doing this enabled me to create a higher resolution model giving the final print smoother sides.
With the axle remodelled it was time to do a new test print. This required figuring out a workflow of getting the object from Maya into a .stl file, but unfortunately Maya doesn't have the capabilities for exporting .stl files. After a little research I found that 3Ds Max does have the capability of exporting .stl files, so it was a simple case of transferring the model by exporting from Maya as a .obj file and importing that into Max to, then export the final .stl file for printing.
While remodelling the axle I resized the outer circle to something which I thought was roughly the correct diameter for the inside of the spool. During my first test print I could tell that I was pretty close, and after a few iterations I was able to get the correct diameter. Rapid prototyping really is one of the beauties of 3D printing.
Before printing the final axle I made sure that the bearing fit into the center, and that the axle fit into the spool center. During one iteration, I must have resized the whole object which made the center circle for the bearing too small, so I am glad that I checked this before wasting a lot of time and filament printing at this point.
After checking the sizes were right (36.2mm outer diameter for the spool, and 21.4mm inner diameter for the bearing), I scale up the height of the axle in Maya to the total required and printed the final version of the axle. There was a problem with the print (which I now believe to be the hot end clogging with filament) about 80-90% of the way through, so the final height was not what I intended. My design was for there to be a little extra of the axle sticking at each side of the spool (in case other spools I have in the future are a little wider), but luckily the spool center has a small lip inside that the axle can sit on.
Total time and cost
- 2x Spool Stand ~ 3 hours (1.5 hour each) - cost of filament ~ £1.08 (£0.54 each)
- 1x Spool Axle ~5 hours print and 3 hours to remodel the spool and adjust to fit - cost of filament ~ £0.90
- 1x 8mm 1x 8mm wood dowel - £1
- 2x bearings - £2.50 (£10 for a box of 8 Abec 7 Fracture skateboard bearings - £1.25 each)
Total time spent: ~ 15 hours, but this includes print time and remodelling of the axe and adjusting to fit the spool and bearings.
Lessons learnt
- only scale objects in all 3 axes if totally necessary
- cleaning the bed before printing with isopropyl really does help with warping on the corners when printing larger objects
