search

jes / 3d-metal-printing

Notes and information about 3d metal printing
1 stars 0 forks source link

Sinter 3: M10 bolt #3

Open jes opened 5 years ago

jes commented 5 years ago

So for this sinter I wanted to try something that would produce a "usable" part even if it was hollow at the top 50% or something. I made a M10 bolt with 17mm head, and sintered with the head at the bottom, with the idea that even if the top half of the thread is hollow, I can just cut that off and then I have a usable bolt that is only half as long.

It didn't work, but I did a few things differently this time.

  1. I only gave the plaster about 12 hours to set before starting the heating
  2. The "flask" was only half as tall as it needed to be, so the extra height was made up with gaffa tape, which was removed before heating
  3. I left the lid of the furnace open below 300 degrees C, to allow gases to escape more easily

I noticed boiling/sizzling noises in the furnace for the first few hours, so I think there was still liquid water being boiled out of the plaster. I'm not sure if this created cracks or something which allowed oxygen inside the plaster.

The final part was 100% hollow, and even the walls weren't completely filled in. It broke into two parts, and was nowhere near usable.

jes commented 5 years ago

image

jes commented 5 years ago

Initial mass: 13.6g Final mass 3.4g (-75%)

Comparing this with the -28% mass change of the first attempt shows that we definitely lost a lot of material here. Don't yet know whether it was oxidised or whether it remained in powder form and just got lost in the bottom of the bucket with the plaster powder.

jes commented 5 years ago

I just had a look inside the furnace and fount a bolt-head-shaped piece of bronze lying in the bottom, along with a puddle-shaped piece of bronze.

I'm going to say that the plaster had a crack in it, which allowed some of the plastic to run out while it was heating, and also allowed the plaster to break and the bolt head to fall out the bottom when I removed the plaster from the furnace.

So this bodes well for the theory that we can just add a head of material and let it all run downhill when the plastic becomes liquid.