History continues: " A small success"

One of the best things about having a 3d printer is the possibility of creating objects that would be difficult to get in a shop.
When we moved to a new place, we brought from the old apartment a shower-shelf that you hang on the door. We had no idea what to do with it- you can’t hang it on the wall, and now we do not have the shower door to put it on.
A bit later we got ourselves a plastic drawer box. The shelf would fit on its back quite nicely, providing additional space for whatever you want. Yet it was not mounted, so I always felt that I might drop it off. To feel more comfortable while moving around the bathroom, I designed the following small piece:

It took 10 min to heat up the printer’s bed, 7 min of printing, 2 minutes of polishing, 5 min of painting, 3 minutes for drilling and 3 minutes of mounting. In half an hour I managed to secure the shelf onto the drawer box with two nice holders. A nice, small success :)

Neurological box

After some time, here is a next chapter of the "historical" projects.

As one of the first “serious” projects I decided to help my wife by printing a box for glass plates washing. It appears that during some neurobiological experiments you put samples on a small glass plates (around 70x25x1 mm) and then need to put them in some solution for a while. The tricky part is that the solution is quite expensive, and you try to pack several of them together in a vertical position. Of course there are commercial boxes like that, but getting those in a government funded institution is a real pain in the ass. That’s where the 3d-hero enters!

I used FreeCad to design the object. It was nothing extremely complicated, but due to my lack of experience I used quite a long time to make the freakin’ drawing. Here is one of the first models. The thing was supposed to consist of the box and the led.

For some reason I decided that the walls are supposed to be 3mm thick. Not a good idea, but it occurred only during printing.

I also printed the led first and due to scaling mistake I made it too big… I re-designed the top part of the box just to be able to use the led.

Initially I wanted to make the box in one piece, yet I met the height limitation of my printer. For that reason I split the print in 2 parts. Then glue was supposed to fix the problem.

This is when I encountered the next issue. As you might already know, making a 3d object takes several phases: design, meshing, “slicing”, printing, finishing. Design is design. During meshing you create a standardized file that corresponds to the surfaces (STL). The slicing is the process of creating the orders for the printer using the meshed shells. It is like describing how to make an omelet to a machine- move right 3mm, extrude 0.1mm, move forth 2mm while extruding 0.2mm, and so on. You can do this part automatically using for example an open-source program called Slic3r. From what I gathered, in general it always creates commends as follows: print an outer shell (following the geometry), and then print the “inner” part. The infill is some generic pattern- like lines of 45 deg lying opposite to each other on each layer. Unfortunately for me, my object consisted of only small walls. Because of that, the infill was taking forever to print- imagine drawing a straight line when you have to move in space of 2mm and you can only move in 45 deg to the wall… I tried changing angle, but since the lines are always perpendicular to each other on succeeding layers, it ended up printing one layer nicely, and other by making 2mm lines lying next to each other on a distance of 3cm… terrible. In the end I tried to play with the GCode itself, to force the printer move as I like. I also changed the design a bit- made the walls thinner to save plastic. Here is the second design.

After a real torment I managed to make the first models. They were looking OK, the glasses fit, the led closed- success you would say. Well, there was one more test to make- they were supposed to hold liquid. As it appeared- they did not…

In order to save the prints I started to experiment with the finish. I decided to apply acetone on the surface hoping to melt it a bit and close the micro-holes in the plastic. I found in the net that people use acetone vapor to do that. Unfortunately I do not have the space for this kind of play in the house, so I just applied the substance- first with a cloth (bad idea- molten ABS is quite sticky) and then by shortly dipping the part in it. That was even worse idea… The concentrated acetone entered into the pores and cavities in one of the models and started to dissolve it- at least at the bottom of the box. After it changed the plastic into “plastic” pulp, it was clear that dipping any ABS part in a solvent is not the best way to proceed.

The last resort was to cover the surface with glue. It has worked just to some extent, still leaving several leakages.

There were also other tests- with and without acetone applied. In the end, none gave satisfactory results.

One full print of the box sould take around 5h (due to trouble with the infill and because of the small diameter of my extruder). I made at least 4 prints. Then few hours of fine grinding, acetone/glue treatment, and the result was still not satisfactory. At certain point my wife gave an act of mercy releasing me from the promise of delivering the box, and so the project ended… or did it? :)