timslab

dedicated

08/02/2019 at 16:28

Test: Simple corner beam mould

Objective: Test mould concept / Find a replacement for corner joints

Process:
The mould was made by cutting a 50x50mm square tube at 45°, welding tabs at the join and adding a nozzle to the tube (image 3). From there it was a matter of gathering some plastic and pressing go. For most tests I ran the machine at 200 C @ 170rpm.

Findings:
-In this case, cold moulds performed far better than warm moulds. It seems as if a cold mould forces the plastic to cool as it enters the mould and then continues to “fountain”, thus allowing it to turn the corner as hot plastic is always at the front. When the mould is warm, the plastic doesn’t cool straight away and ends up “sliding” along the mould and being too rigid to turn the corner.
-In image 2 you can see how much the forms actually shrink during cooling. What’s interesting is that the angle didn’t change at all.
-Creating corners in this manner as opposed to a traditional joint creates a far stronger result (tests will come). One can then focus on connecting the straight edges as opposed to the corners.

This is a wide topic, so feel free to shoot your ideas and suggestions!

s2019

starter

08/02/2019 at 23:28

Great work.
A couple of questions. What does the “XX mins make” represent?
Also, are the section cuts in the background  from this experiment? Are you using multi color material? Have you done a longitudinal section cut?

Very interesting, thanks again.

timslab

dedicated

14/02/2019 at 12:52

Hey @s2019, thanks.

XX mins make is just stating how long the machine was running to make the part. XX minutes from time of start to time of stopping the machine.

Those sections in the background are from a beam from last months tests where I changed colours at regular intervals. I’m busy working on something to illustrate the process. Planning on doing a longitudinal cut too 🙂

cgoflyn

helper

14/02/2019 at 13:14

@timslab: so you’re using 3Kw at the end ? And are using the wood auger drill, and at which speed ? Thanks, we’ve some users asking to build extrusion machines for beams …

timslab

dedicated

14/02/2019 at 18:23

Hey @cgoflyn. From what I understand, we’ve got a 3kW motor and it puts out the same torque no matter the rpm. I’ve recently been running it at 170rpm, but I do sometimes ramp that up to 250 if we need to fill something quickly. We’re using the custom PP extrusion screw.

cgoflyn

helper

14/02/2019 at 18:42

@timslab, thanks! Same torque sounds weird too me. I’ve got good experience with 4 Kw, unstoppable and I can recommend this. It’s enough to power the shredder at the same time. However, 170 RPM is amazing fast, wasn’t even aware it needs that much speed.
By ‘custom PP screw’ you’re referring to a standard industrial chromoly based screw ? Whilst at, how long is the barrel then 🙂
g

s2019

starter

14/02/2019 at 20:33

@timslab In some of your other tests you used a plug to apply some resistance to the plastic front. I wonder if applying this technique to the second leg of the angle to maintain pressure in the mold will help reduce internal voids. Even maintaining pressure in the mold during the initial cooling may help as well.

It will be interesting to see some of the section cuts once you make them.