Make: Geometry

tive is generally not

abrasive, but other

filament additives may

be. If you buy marble

PLA filament, check

to see if the manufac-

turer warns that it will

abrade your nozzle. If

so, be sure your printer

has a hardened nozzle

that can handle it.

TESTING YOUR ARCHES

Print and assemble

(with some putty) two

arches with all the vari-

ables the same, except

that one should be a

Gothic arch (gothic =

true), and one circular

(gothic = false).

Now, set your arches

up vertically (Figure

13-6).

Press your hand down

on the top of each arch.

What happens? (Figure

13-7) Most likely the

circular arch collapsed

with far less force

than the Gothic one.

The c ...