In 140807 MMD I talked about 3-D printers and laser cutters
in manufacturing hard-to-find and low-quantity items we use in our
restoration activities.  I thought I would report on a recently
completed task, cutting valve gasket rings from blotter paper using
a laser cutter.

I was approached by an individual who needed valve ring gaskets for
an "Electrova" mechanism.  These are not particularly complicated in
design, having an outside diameter of 1.5", an inside diameter of 1"
and four screw holes spaced evenly around the mid-point of the ring
(1.25" diameter).  While I intend to submit a more detailed article
to the AMICA bulletin about making them, here is a short synopsis.

I "drew" the basic shape using Adobe Illustrator, although _many_
graphics programs would handle the task.  Once the master design was
finished, it was a simple matter to group all of the elements and
copy it multiple times for a single pass through the cutter.  This
cutter has a 60 cm x 90 cm cutting bed and the blotter paper came in
sheets that were (slightly smaller at) approximately 2 feet x 3 feet,
so I could cut the gaskets "100-up".

A nice thing about laser cutting is that you have complete control over
both the power of the cutting beam from zero, up to 100% of its maximum
power (for the cutter I used, that happens to be 80 watts) as well as
the linear speed of the cutting head.  Relatively high powers and slow
speeds are used to completely cut through material, but if you select
relatively low powers and correspondingly high speeds, you can achieve
"engraved" features only very slightly into the surface of the material.
This allowed me to "brand" each individual gasket with some production
information, such as an identifying origin and part number.

Since laser cutting is really a precisely controlled burning process,
blotter paper is an ideal material to process, and can be done so much
more economically than the traditional method of using steel-rule dies
to mechanically stamp the gaskets.  The entire process, engraving
first, then cutting, took about 20 minutes for a quantity of 100.  The
pictures shown of the material in the machine show a trial run in which
the "branding" was omitted.  The red dot is a spotting tool only, not
the actual cutting beam.

I am experimenting with materials other than paper, such as cork,
composition cork/rubber (Corkprene), leather and various sheet materials
such as rubber and silicone.  Pure cork is not a good candidate for
laser cutting as its internal voids tend to create fairly rough edges
as well as a pesky black residue, the well-known "burnt cork" effect
from vaudeville days.  Die-cutting is a better choice here.

Composition is cleaner but takes multiple low-power passes in order to
minimize charring and edge deformation.  I am currently working with a
gentleman who needs replacement gaskets for his "Power-Roll" interface.

If you need valve gaskets of a design not currently available from
other sources, please contact me for a quote.  I have 0.020" thick
blotter paper in stock but can work to your specifications.  I prefer
that you send me actual sample gasket removed from service but can also
work from accurately dimensioned sketches.

On the 3-D printing front, I have a few Ampico "B" curtain valve grids
(rectangular holes) executed in black ABS plastic, including the one
for the pump spill valve and the pedal regulator.  If my 3-D printer
ever gets delivered <grrr!> I will soon following have the round-hole
grids for the expression regulators, with more parts to follow.

John Grant

 [ Cutting in progress.
 [ http://www.mmdigest.com/Attachments/14/10/06/141006_115258_20140904_190555.jpg 

 [ Finished (unbranded) set of 100 gaskets.
 [ http://www.mmdigest.com/Attachments/14/10/06/141006_115258_20140904_190930.jpg 

 [ Finished gasket (detail).
 [ http://www.mmdigest.com/Attachments/14/10/06/141006_115258_Gasket%20G-002.JPG