Page 34 - MetalForming-Nov-2018-issue
P. 34
Fabrication: Waterjet Cutting
the easiest and least-intrusive method for adjusting taper without using acces- sories. Slow down the cutting head by raising the cut quality in areas that must exhibit zero taper. Keep in mind that slowing the cutting head will lead to slower cutting times and increased abrasive usage.
Since thinner materials tend to exhibit the greatest amount of taper, try stacking. Taper usually is most pro-
nounced in material thicknesses of less than 0.125 in. If available, use a stack- height calculator in the machine’s con- trol software to determine the optimum number of sheets to stack in order to produce the most parts in the least amount of time.
Note that standoff matters. The jet stream will flair once it exits the nozzle. To mitigate this, maintain a recom- mended distance between the nozzle
and the material being cut. Usually, standoff measures between 0.03 and 0.08 in. depending on the diameter of the nozzle. The closer the nozzle to the material, the less the jet stream will spread, and the less taper it will produce.
Use the highest-quality abrasive available. If experiencing taper with an 80-mesh abrasive, experiment with a 120- or 150-mesh. Lower-quality abrasives tend to have less-consistent particle sizes. In the end, this comes down to purchasing abrasive from a reputable distributor.
Wo
o
rk
kh
ho
old
di
in
ng
g Cla
am
mps
Another tip: Guarantee that the Z axis is perpendicular to the material in both the X- and Y-axis directions. Use a pitch indicator to ensure a cut- ting-head angle of 90 deg. relative to the cutting table. In addition, be sure to properly seat the machine’s mixing tube, otherwise the machine will not cut with an accurate Z axis. For machines equipped with an Omax A- Jet or Tilt-A-Jet, operators can use the Calibrate Perpendicular feature avail- able in the Intelli-Max Make Setup menu.
Taper may result from uneven wear in the mixing tube. This is not a func- tion of the motion-control equipment, but rather a consequence of how the abrasive wears inside the mixing tube. Rotating the mixing tube 90 deg. for every 8 to 10 hr. of cutting time allows the mixing tube to wear more evenly and last longer, while preventing taper.
Keep Learning
Lastly, to keep unwanted taper at bay, stay abreast of current techniques by following manufacturing and trade blogs, social media and magazines. Become comfortable with your abra- sive-waterjet machine, and learn how it behaves and how to work its idio- syncrasies. And, measure parts peri- odically to ensure accuracy. Knowing how a particular machine will react to certain materials under certain con- ditions is the best method for predict- ing taper outcomes. MF
Information for this article was sup- plied by Omax Corp., Kent, WA; www.omax.com.
Series GRM Sheet metal
C5091
Se
er
ri
ie
C
RM1
s G
GR
Co
om
m
p
p
a
ac
c
ct
t
t s
h
h
he
ee
et
t
t
assembly
1-800-624-8511
32
MetalForming/November 2018
www.metalformingmagazine.com
for more information, visit:
phdinc.com/clampad
