FILENAMES:

roof_roller1.jpg
roof_roller2.jpg
roof_roller3.jpg

DESCRIPTION:

These are pictures of a modeler's accessory for moulding clay.
Posted by Eric Topp <topp@rrd.stanford.edu>. Eric provided the 
following description:

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Greetings.  I thought I'd share with you a little "extra credit" project I 
worked on this Spring.  Fourth graders in California schools are required 
to study the history of Spanish missions.  The kids often visit a mission 
and then build a model.  My son had to build a model this year and was 
gracious enough to let me help ;^).  To me the most challenging aspect of 
making such a model is coming up with realistic clay tiles for the roof.

I decided to build a roller that would leave an impression of clay tiles.
I made it wide enough to span the pitches of roof that the model needed
and tried to get the scale about right.  The roller is made of a stack delrin
disks one-quarter inch thick and about 3 inches in diameter.  They stack 
on a half-inch shaft and are aligned with steel dowel pins.

See roof_roller1.jpg

The disks were cut with a Dekel Mako DMU 70V 5-axis milling machine.  There 
are 36 lobes on each disk.  The shape of the lobes leaves an impression of 
alternating tapers and curvatures, as well as a saw tooth effect of 
overlapping roof tiles.  I wrote the program with some software tools that 
I've written to get a handle on 5-axis programming.  I used a 1/8 inch end 
mill and held circular blanks on a spud with an indexing dowel.  The 
program was fun to watch: each lobe sent the C-axis (the one normal to the 
table) through two big sweeps of nearly 180 degrees.  Simultaneously the 
B-axis (trunnion at 45 degrees to the table) gyrates, though less 
dramatically.  X, Y and Z axes change at each step. About 36,000 lines of code. 

See roof_roller2.jpg

At the ends of the roller I put slightly larger diameter wheels 
that govern the thickness of the clay.  We bought lots of terra
cotta-colered Sculpey, a clay that hardens when baked.  We prepared 
the clay with a rolling pin riding on strips of material on either 
side of the clay so that the thickness is uniformand correct.  
I had a little trouble with the clay sticking to the roller but I 
found that the clay likes to stick to a warm pan more than it 
does to the roller.  The "tiles" looked pretty good, and the mission
did too.

See roof_roller3.jpg

Eric Topp
topp@rrd.stanford.edu
June 2001