Monthly Archives: March 2013

Use Filament to substitute bolts in your 3D designs, weld plastic with your extruder

Many designs I’ve found online seem to not take full advantage of the 3D printer. If you have a machine that can make anything, why are you resorting to using bolts in your design. I think if 3D printing is to become a common household tool, then more things should be designed to only use the products of 3D printing.

A while ago I realized that I could use a piece of filament as a substitute for a bolt in my designs. The way I seal the filament into the piece is by extruding extra plastic from the extruder manually. Extruding manually while moving the piece underneath works pretty well, but it won’t be as pretty as the rest of the print. I find that there are many trace hairs of plastic that get stuck to the print head. It’s probably a good idea to clean off the print head after using it to weld 2 pieces of plastic together.

Ok, so the real reason for doing this. This is secretly part 1 and 2 of 507 Mechanical Movements.

Getting PLA to stick to your Printrbot build platform with Hairspray or ABS juice

I was having a ton of trouble with PLA. It never wanted to stick to my build platform when I started working with it. I started searching online for solutions and I found a few.

The two best solutions I found were to use either hairspray or ABS juice. The recommended brand of hairspray is Aquanet Super Ultra Hold. You’ll know your brand of hairspray is working well if it makes the build bed tacky after you apply it. Here is some more information about hairspray :

The second best I found was to use ABS juice. ABS juice is a mixture of 9 parts acetone with 1 part ABS. Its not a problem if you add more ABS into the acetone, it’ll stay at the bottom and be mush. The acetone dissolves the ABS and stays in solution. When you apply that acetone it’ll leave a thin layer of ABS on the build platform for your material to stick to. It works, but the acetone will slowly eat away at your Kapton tape as you apply more and more. I’m not looking forward to replacing the Kapton tape, so I’ll stick with the hairspray.

Good luck with your PLA prints.

3D Printed Crossbow

I was given the challenge to make something that will shoot, and make it fully printable. I settled on making a printable crossbow. In the 3rd century to make a crossbow required a team of skilled artisans and weeks of time. I figured using 21st century technology I should be able to do about the same in about a day.

The bow design was basically designed by eye by what looked good. I choose the 2mm wall thickness for it after a few test prints of strips at different thicknesses. The 2mm wall thickeness gave me what looked to be the best flexibility and durability.

When printing this bow I set Slic3r to infill the material in a concentric pattern. What this did is made the flexible in the dimensions I needed it also helped with the trigger. The bow was printed with the handle side up and with support material. The part under the trigger needed support material.

The trigger design stumped me for a while. I was originally going to steal some design from google images. All of the designs I found had far too many moving parts. I wanted the bow to be simple and not have much assembly. After drawing every trigger out, I figured I can just use the plastic as a spring, which worked great.

You can download the model here :

Adjustable Focus 3D Printed Liquid Filled Lens

A while ago I saw a TED talk about adjustable glasses. I wanted to build my own. This could eventually be used for eye glasses that are printed out or for a telescope or a microscope.

The biggest problem with this is making a seal that doesn’t leak around a plastic film. There were several designs I went through to get to the hexagonal pattern that I eventually published. Using the circular mating plates for the film never gave me a good seal all the way around. It turned out that since the printer doesn’t print thin lines accurately all the way around the circle, that the grooves in the plates wouldn’t ever mate up properly.

With the hexagonal parts I found that the groves printed out more reliably and mated much better. Still not perfect since it leaks, but a little RTV or Weldit can solve that problem.


Experiments using Acetone Vapor to smooth 3d printed objects

I found a hackaday post on smoothing out the rough edges on 3D prints and thought I should experiment for myself.

I wanted to try out how the smoothing would effect different kinds of prints. I found a tall statue , a shotglass skull, and a twisting heart box.

I collected all of the items that I’d need according to the video. The items where

  1. Acetone
  2. Wire hanger
  3. Bottom of a soda can 
  4. Glass jar with lid
  5. Printrbot

I set my Printrbot to 110c through Pronterface. Every few minutes I monitored the temperature with an infrared temperature sensor to make sure the bed is at the right temperature. While waiting for the bed to get to temperature I poured out about one tablespoon of nail polish remover into the glass jar. When the heated bed was at the right temperature I put the jar on for it to heat up.

The jar I was using started to form condensation of acetone on the walls in about a minute. It took about 5 minutes for the condensation to be forming from the top of the jar. In hindsight, I should have waited for the vapor to fill the whole jar before I put in the first model.

The first model I used was the statue from thingiverse :

I took the model out every few minutes, you can see the progress in the gallery bellow.


I next experimented with a heart shape box from thingivers:

With the heartshape box I wanted to see how it would slide after being treated. My results were disappointing with this. It did not become glossy and smooth, it didn’t get the beautiful clear coat of abs as a shell. It basically only got a little shinier. I’m not sure why this model didn’t have any real results from the acetone. Even after this 15 minute trial, I went back later at night and left the box in the chamber for an hour, still no difference. I think there is something else going on here that makes a model be effected by the acetone treatment.


Finally I wanted to test out the skull shotglass:

The skull shotglass had good results from 15 minutes of treatment. The face and back of the skull became very shiny. There was no loss of detail that I can tell from the face. The entire exterior of the plastic feels completely smooth almost as if it was injection molded. The top side of the skull has  more of a shine then the bottom, which is telling me the acetone vapor is dropping from the top onto the skull. The whole skull somehow feels more solid, if you tap it, it gives you a satisfying thunk. The inside of the shotglass is a similar surface to the surface on the heart box, it also has the same results as the heartbox. The inside is basically the same, no real differences. I wonder what process is going on preventing these smooth curved surfaces from being effected. Here is the skull after 15 minutes.

The vapor treatment worked really well with 2 of my models. I’m still unsure as to why it didn’t work well on the heart box.

Acetone Vapor bath