the small cnc is out of order

[ada]

until a new sacrificial bed is obtained. the old bed has had it.

also some magical computery things might need to happen, but that
probably requires someone who understands Windows.

[Tim]

Can we just use MDF for the bed?

Tim

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[thejollygrimreaper]

you should be able to use a mdf sheet for it and mill it flat with a large pocket in cabam

[Kris]

Cabam?

I have a large sheet of 5mm ply, not sure if that's any good for the machine but if yes let me know the size and I'll drop out into the space Tuesday.

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[ada]

On May 19, 12:08 pm, Tim <cool...@gmail.com> wrote:
> Can we just use MDF for the bed?

mdf is yuck. plastic is yum.

I wonder how well the styrene sheets that SRW use would work.

[Tim]

Cheap chopping board?

[and...@arcadius.com.au]

There is a 90%+ chance that I will be picking up some sheets of rigid PVC foam in the next couple of days.  I am pretty sure this is the same material that is on the bed of my (commercial) CNC router.

The sheets I am picking up are 3mm thick.  If thicker is needed, it could be laminated.  The foam is available in 6mm, but I am not sure I could justify a sheet of this.

The PVC foam would be an awesome robot-building material for CNC routing.

Andrew

-------- Original Message --------
Subject: [RnD] the small cnc is out of order
From: ada <a...@panda2.net>
Date: Sun, May 19, 2013 11:23 am
To: "Robots & Dinosaurs" <sydney-h...@googlegroups.com>

until a new sacrificial bed is obtained. the old bed has had it.

also some magical computery things might need to happen, but that
probably requires someone who understands Windows.

[ada]

On May 19, 2:54 pm, <andr...@arcadius.com.au> wrote:
> There is a 90%+ chance that I will be picking up some sheets of rigid PVC foam in the next couple of days.  I am pretty sure this is the same material that is on the bed of my (commercial) CNC router.

What does PVC do to cutters, especially when run at high enough speeds
that it starts to melt? I've had bad results with both HDPE and PVC
caked onto cutters in the past.

The nice thing about HIPS is that it's gentle on cutters, and machines
like butter. Apparently ABS is quite similar in its machining
properties (I've never tried machining any, but maybe we could try
melting all our ABS offcuts into blocks for machining).

[Andrew]

I'll be able to tell you more about the PVC machining soon.

This, by the way, is a extremely dense foam rather than solid PVC.

If I am right in that the PVC foam is used on the bed of my current CNC
router, then the machining is great - produces a dust which is easy to
vacuum. This is at 24000 RPM with a 16mm 2-flute cutter.

The only time I machine the bed of my CNC is to level it after a move. I
use a separate sacrificial sheet (usually MDF) for actual cutting.

Like all plastics, feeds and speeds are important. I have done a lot of
HDPE and, when it is cutting right, I get snowstorms of statically-charged
chips that sticks to almost everything.

If you prefer HIPS, I know the supplier has that too. 3mm black or white
HIPS is approx $40 for a sheet 1270x760. 3mm is the thickest they carry.
This is much more expensive than the PVC foam. ABS in 3mm is a little more
expensive than HIPS (and possibly subject to cut sheet surcharge). HDPE is
also available as is rigid PVC.

Anyway, the offer is there is you want it.

Andrew

[Tom Davies]

Is the PVC foam like that sold as Sintra? http://www.solarbotics.net/starting/200207_sintra/200207_sintra.html

[Andrew]

Seems very similar.

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