On Thu, 21 Sep 2017 11:24:25 -0400, Ed Huntress
wrote:

On Thu, 21 Sep 2017 08:06:07 -0700 (PDT), "Dave, I can't do that"
wrote:

Guys,

I hate to mention the topic of wood, but I want to mount a 3D-printer on a flat stable base so I can move it around without disturbing the delicate (poor design) setup.

I cannot afford a 24" square piece of 1/2" aluminum and cannot lift a 24" square piece of 1/2" mild steel.

So, I am looking at 3/4" MDF, OSB and plywood, but open to other helpful suggestions, but low cost is the operative.

Which of those options is likely to be the most stable? The machine has many brackets for attaching to a base, so flexing and stability is at the pointy end.

Thanks

None is really stable if you have a big load on it, but thickness
makes up for it, if you don't mind gluing together a couple of sheets.

If the situation will handle 1-1/2" of thickness, I'd use two sheets
of 3/4"melamine-covered MDF, glued back-to-back. The melamine on BOTH
sides of the sandwich will give you a lot of stability from humidity
changes; the 1-1/2" thickness is stiff, and it looks nice.
What Ed said except that I would add that the stiffness can also be
increased quite a bit without adding as much weight if strips of MDF
that are 3/4" thick but 2" or 3" wide were glued edge on to the
underside of a piece of 3/4" thick MDF. You could glue the strips to
the underside around the perimeter and wherever the machine is
fastened to the top side, which I imagine is probably a square or
rectangular shape. This would leave much more area exposed to humidity
though and the changes that can cause. If humidity changing is
problem though you could seal the base with some sort of sealer made
for the purpose. You could probably find a can of sealer for free on
Freecycle, if it's available in your area. Maybe even find a base for
free.
Eric