n a message dated 10/28/1998 3:23:24 AM Mountain Standard Time,
caporusso@picolit.diegm.uniud.it writes:
<< Is there a commercial RP system that wotks with model sliced with differen
layer widths? >>
Yes.
SLA machines (3D Systems) will build multiple thicknesses during the same run.
The process of setting up a build for multiple layer thicknesses is as
follows:
When setting up the part(s) the operator must change layer thicknesses at
vertical positions that are EVENLY DIVISIBLE BY ALL LAYER THICKNESSES used in
the build.
Example: A part that is 2.5 inches tall is to be positioned with the bottom of
the part at a Z height of .25 inches. It is desirable to run the first .25
inches of the build (supports) at .006 inch layer thickness, then switch to
.004 inch layer thickness for the bottom 1.5 inches of the part, then switch
to .0025 inch layer thickness for the next .5 inch, and finish the last .5
inches of the part at .006 inch layers.
Test 1) (All Z height levels where the slice thickness is to change must be
evenly divisible by ALL of the layer thicknesses used in the build.) .25 inch
/ .006 = 41.666667 .25 inch / .004 = 62.5 .25 inch / .0025 = 100 . . .
.006 and .004 inch layer thicknesses DO NOT evenly divide into .25 inches.
Only the .0025 layer thickness divides evenly. What is the nearest Z height
(below the part) at which all 3 proposed layer thicknesses will divide evenly?
.24 inches will divide evenly by all three layer thicknesses. Set up the part
to switch from .006 inch layers to .004 inch layers at the .24 inch Z ht.
Test 2) Using the same process, determine the nearest Z ht at the 1.75 inch Z
ht level which is evenly divisible by all three layer thicknesses. Either
1.74 or 1.80 can be used since they are the two values closest to the desired
1.75 inch Z ht where we desired to change slice thicknesses. The needs of the
particular part that is being built will determine whether it is best to
switch at 1.74 or wait until 1.80 to switch from .004 to .0025 inch layer
thickness.
Test 3) Using the same process, determine the nearest Z ht at the 2.250 inch
Z ht level which is evenly divisible by all three layer thicknesses. Either
2.220 or 2.280 can be used since they are the two values closest to the
desired 2.250 inch Z ht where we desired to change slice thicknesses. The
needs of the particular part that is being built will determine whether it is
best to switch at 2.220 or wait until 2.280 to switch from .0025 to .006 inch
layer thickness to finish the build.
If the part is set up as described above, the 3D Systems, Maestro software
will successfully slice the part(s) and create the build files needed for a
successful build.
Math simplification: A relatively easy way to determine where the division
lines may be successfully made is as follows: 1) Determine what the minimum Z
ht (above zero) which can be evenly divided by all of the layer thicknesses
that are to be used in the build. In the above example, that value is .060
inches. 2) Divide the desired Z ht value where you want to switch layer
thicknesses by .060. (Example: 1.75 / .060 = 29.1666667). 3) Multiply the
next even number (above or below) the result of step 2 by .060. (Example: 29 *
.060 = 1.74 or 30 * .060 = 1.80) See Test 2, above, for actual application
wherein these numbers are valid.
It takes a little longer to set up the build this way, but a significant
amount of build time can be saved, while producing the highest quality part if
the SLA operator will take the time to learn this process. This process
usually also saves a significant amount of post finishing time.
If any of the above process is not clear, feel free to contact me for further
explanation.
Ken Miller
Miller Technologies
395 S. 1100 W.
Farmington, UT 84025
Voice and Fax: (801) 451-7997
Email: foamcaster@aol.com
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
This archive was generated by hypermail 2.1.2 : Tue Jun 05 2001 - 22:47:02 EEST