Heads Up ...

[Ian Petrie]

.. heads up in the chill out area.

I have put two head sculptures in the chill out area. They were made by my father forty years ago. They are lost polystyrene.

He cut them from polystyrene ceiling tiles - I can remember him sitting in his chair and spiralling round the shape with a narrow blade made out of an old hacksaw blade.

The polystyrene was then set in sand, some fine holes poked through the sand to let gasses escape, and poured in aluminium bronze  - copper with 5-11% aluminium

The process is quite safe - in a well ventilated area.

https://en.wikipedia.org/wiki/Aluminium_bronze

I've brought them in so members can see what could be possible with our casting set-up. The level of detail is high - the cells of the original polystyrene tile are well defined - and what sort of finish is possible - my father polished some surfaces.

The casting kit has not really been put to use as yet. Who would be interested in a casting weekend?

Ian

[Andy Noyes]

Yes, certainly is possible. Here's a video where I used the rlab kit for the same process (this was a couple of years ago). As you don't need to split the mould and remove the pattern, you can cast more complicated shapes (though the parts I made were very simple).

[Tom Allen]

I have a stack of ceiling tiles and other various off cuts of polystyrene and pir insulation in my yard if anyone wants some material to make casts from. Free to a good home :)

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[Alex Gibson]

Hi Ian

 

I’d like to do some lost PLA casting…  been interested for ages but not made it to previous full casting sessions, hard to carve out the time at weekends!

 

What are the realistic limits of detail, shrinkage, etc we can achieve at rLab?

 

Cheers

Alex

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[Ian Petrie]

PLA  casting has been mentioned a lot and some failed attempts made - but it is a different process akin to the lost wax process. I have a jeweller friend who uses lost wax and I'll see if she would be willing to come along and discuss that process and investigate how it would need to be modified for pla.

The lost polystyrene process is much simpler. When the Shapeko is commissioned I plan to experiment with routing polystyrene then casting the result

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[Malcolm Napier]

I am interested in casting activities but not often in Reading these days. However, with notice, I will try to attend any casting sessions.

TLDR for the following- PLA good for pattern based casting. Not good for "lost wax".

Several years ago, TVRRUG was invited to exhibit at the Sandown Model Engineer Exhibition. The brief included attempting kito collaborate with traditional model engineers. My interest in Stirling Engines is a result of the second time that we attended.

However, for the first attendance, Ian Bowden undertook a couple of collaborations in the field of casting - one of which was lost PLA. The other was making a "proper" pattern.

The feedback from the foundry was that the PLA did not burn out cleanly. This rules out its use for parts where structural integrity matters because an inclusion of PLA might form at location that is structurally significant. Similarly, artistic casts might have imperfections in visible locations.

However, the feedback from the pattern making was much more positive. Ian printed a wheel for a (sizeable) model steam engine and then passed it to a competent pattern maker for fettling. Print time + fettling time was about 1.25 - 1.5 days. The same pattern maker then made an identical pattern in the traditional way. That took him closer to 4 days. The resulting casts were pretty much identical. And at the same exhibition, the following year, I counted 3 stands where pattern makers were exhibiting 3d printers as part of their service.

I later partnered with a model engineer in West Berkshire, who was having problems with the design and manufacture of a particular part for the steam engine he was making. If anyone is interested, I have a set of the resulting bronze casts, which are very impressive.

[Andy Noyes]

Matt Daubney tried multiple times to get lost PLA to work at rLab. The hardest part was melting out the PLA, it requires much more heat than wax, and leaves behind ash deposits whereas wax just vaporises.

If you're planning to make accurate parts you'll almost certainly need to machine or clean up the raw casting. You can oversize the pattern by a few % to get you closer to finished size after shrinkage.

[Hugo Mills]

Just wondering out loud here... Is there a suitable hard/high-MP
wax that could be 3D printed sensibly and then used for casting? (I'm
thinking something like sealing wax, or the hard waxes that were used
by some high-end colour printers back in the '90s).

Having a wax, rather than PLA, might even help with the process of
cleaning/polishing/preparing the pattern, if it's a softer material
than PLA.

Hugo.

On Wed, Jan 03, 2018 at 03:26:39AM -0800, Andy Noyes wrote:
> Matt Daubney tried multiple times to get lost PLA to work at rLab. The
> hardest part was melting out the PLA, it requires much more heat than wax,
> and leaves behind ash deposits whereas wax just vaporises.
>
> If you're planning to make accurate parts you'll almost certainly need to
> machine or clean up the raw casting. You can oversize the pattern by a few
> % to get you closer to finished size after shrinkage.
>
> On Wednesday, 3 January 2018 00:43:57 UTC, Alex Gibson wrote:
> >
> > Hi Ian
> >
> >
> >
> > I’d like to do some lost PLA casting… been interested for ages but not
> > made it to previous full casting sessions, hard to carve out the time at
> > weekends!
> >
> >
> >
> > What are the realistic limits of detail, shrinkage, etc we can achieve at
> > rLab?
> >
> >
> >
> > Cheers
> >
> > Alex
> >
> >
> >

> > *From:* reading-...@googlegroups.com <javascript:> [mailto:
> > reading-...@googlegroups.com <javascript:>] *On Behalf Of *Tom Allen
> > *Sent:* 03 January 2018 00:36
> > *To:* reading-...@googlegroups.com <javascript:>
> > *Subject:* Re: [RDG-Hack] Re: Heads Up ...

> >
> >
> >
> > I have a stack of ceiling tiles and other various off cuts of polystyrene
> > and pir insulation in my yard if anyone wants some material to make casts
> > from. Free to a good home :)
> >
> >
> >

> > On 2 Jan 2018 10:45 pm, "Andy Noyes" <andysm...@gmail.com <javascript:>>

> > wrote:
> >
> > Yes, certainly is possible. Here's

> > <https://www.youtube.com/watch?v=Dhs9fFg1K4U> a video where I used the

> > rlab kit for the same process (this was a couple of years ago). As you
> > don't need to split the mould and remove the pattern, you can cast more
> > complicated shapes (though the parts I made were very simple).
> >
> >
> >
> > On Tuesday, 2 January 2018 11:29:27 UTC, Ian Petrie wrote:
> >
> >
> > .. heads up in the chill out area.
> >
> > I have put two head sculptures in the chill out area. They were made by my
> > father forty years ago. They are lost polystyrene.
> >
> > He cut them from polystyrene ceiling tiles - I can remember him sitting in
> > his chair and spiralling round the shape with a narrow blade made out of an
> > old hacksaw blade.
> >
> > The polystyrene was then set in sand, some fine holes poked through the
> > sand to let gasses escape, and poured in aluminium bronze - copper with
> > 5-11% aluminium
> >
> > The process is quite safe - in a well ventilated area.
> >
> > https://en.wikipedia.org/wiki/Aluminium_bronze
> >
> > I've brought them in so members can see what could be possible with our
> > casting set-up. The level of detail is high - the cells of the original
> > polystyrene tile are well defined - and what sort of finish is possible -
> > my father polished some surfaces.
> >
> > The casting kit has not really been put to use as yet. Who would be
> > interested in a casting weekend?
> >
> > Ian
> >

--

Hugo Mills | You're never alone with a rubber duck...
hugo@... carfax.org.uk |
http://carfax.org.uk/ | Golgafrincham Captain
PGP: E2AB1DE4 | The Hitch-Hiker's Guide to the Galaxy

[Steve]

There are filaments especially designed for mould-making for lost-wax
type processes, for example

https://shop.3dfilaprint.com/moldlay-750gms-3mm-3d-printerfilament-by-kai-parthy-cc-products-11060-p.asp

Steve

[Toby Williams]

I was going to ask, could you use investment and then burn out the PLA instead relying on the heat of metal?

Would the themoformer oven be appropriate for this?

[Andy Noyes]

Yes, the PLA has to be melted/burnt out first (unlike with lost foam).  I don't think the Clarke oven is hot enough, at those temperatures (200-300°C?) the PLA is still a fairly thick liquid that sticks to the sides of the cavity.

[Tony Short]

I've done quite a bit of investment casting with PLA prints in silver with my aunt. They were impressed with the quality vs wax. Unfortunately we don't have the correct gear at rLab for investment casting.

T

On Tuesday, 2 January 2018 11:29:27 UTC, Ian Petrie wrote:

[Alex Gibson]

Brilliant ideas and suggestions - thanks all. I knew the Moldlay but had forgotten the name was American and was googling it wrong!

I had an idea about printing the part using just a single outer wall of PLA, and then ABS for the second outer wall and for infill - then dissolving out the ABS with acetone. In theory this could leave just a very thin, even PLA layer. Some sort of turning device might be needed to evenly distribute the acetone and flush out the ABS...

[Malcolm Napier]

@Tony,

Very nice!

Where did you get the casting done?

Presumably, as this was jewellery, it was jewellery casting rather than engineering casting?

In a similar period to when Matt was experimenting at rLab I approached a number of foundries but none responded - despite claims made on their websites.

I assume model engineers have better contacts with suitable foundries.

[Tony Short]

I was visiting a silversmith in Faversham, Kent. He runs regular casting weekends, but they are for silver rather than other metals.

If you want basic casting its probably easier to use www.shapeways.com as they do a range of metals.

T

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[Tara Martel]

I may need to make some metal signs in the next 6 months or so. I was going to cut the letters from MDF, mount on a board of the same then use this to make a single part sand mould and just pour the aliminium in. I assume that would work OK?

[Tara Martel]

Perhaps we could use this as an introduction to casting?