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 Image to
G-Code converter uses two methods to create the g-code file. The first
method was designed to emulate laser cut with a cnc router or mill, and
is base on color depth. The theory of this method is to prepare the
surface to apply some kind of stain that will penetrate the cut indents
and create the necessary shades and shadows that will make the image to
appear on the cut stock. To enhance the image light sanding is applied.
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What
tool should I do use? Raster images store
color information in a pixel unit. The pixel unit size depends on the
image resolution and device capabilities. Image to G-Code defaults to
0.01 in. pixel size, the X-Y resolution is set to the pixel unit size.
A tool size equal to the X-Y resolution gives the optimal results but
the risk of breaking the tool is very high, plus increases the cutting
time.
The following examples show how to
combine the image size, resolution, k-factor, and the recommended tool.
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G-CODE CONVERTER PAGE
1 OPTIONS
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Bitmap size: The bitmap size is given in pixel and
represents the actual bitmap width and height. The Ratio is the width
divide by the height. The size of the bitmap is used to calculate the
resulting carving dimensions. |
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X-Y Resolution: Represents the area of one pixel
information and is equal to the maximum tool size required to cut the
image without overlapping other pixels information and is directly
proportional to the machined area. |
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Carving dimension: The carving
dimension represents the size of the bitmap to be machined projected in
the material stock. Image to G-Code will try to maintain the aspect
ratio of the original bitmap. The initial value is set by the program. |
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Combine: When YZ Axis is checked
linear motion on the Y and Z axis are combined, creating a wave effect.
If not checked change on the Z Axis offset 90 degrees with respect to
the Y Axis motion. |
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Depth: Maximum depth penetration on
the Z Axis. In the color table white is equal to 0 and black is equal to
the depth value. If the reversed option is checked then black is equal
to 0 and white is equal to depth value.
K-Factor: X-axis scan line
interpolation, a value of 2 will move the tool every other line, a value
of 3 every two line etc…
Close enough: Minimum distance
before tool change position on the Z Axis.
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The math between bitmap
size, X-Y resolution and carving dimension. |
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X-Y resolution has an initial value
[default] of 0.01 in
A 240 x 200 bitmap has a carving
dimension of:
240 * 0.01 in. = 2.4 in. and 200 *
0.01 in = 2.0 in.
Image to G-Code does not allow
changing the original bitmap aspect ratio.
Example A: |
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Increasing the carving
dimension x times. |
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Carving Dimension. |
X-Y Resolution. |
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X = 2.40 in. * 3 = 7.2 in.
Y = 2.00 in. * 3 = 6.0 in. |
X = 7.20 / 240 = 0.03 in.
Y = 6.00 / 200 = 0.03 in. |
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If the tool size recommended is
equal to the X-Y resolution then the effect of increasing the carving
dimensions allows for bigger tool diameter, in this case from 0.01 in to
0.03 in. This method was used to cut three of examples shown above
using a 0.03 flat end mill. Because the cut time is proportional the
bitmap size and the amount of color shades in the image; projecting the
image to larger size does not have an increasing effect on the cutting
time. |
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Example B: |
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Using a sharp pointed
vee cutter (90 degrees or 60 degrees) |
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In general a very sharp vee tool
works the best. For better details use the defaults value set by
converter and uncheck the K- Factor and Close enough Boxes.
To reduce the amount of overlapping
(tool collision) Set the K-factor to a value of 2 and ensure that the
check box is checked. This also reduces the cutting time by 2.
For less detail and small output
files set close enough to about 1.5 % of the maximum depth value. In
other words what you really need is the tool to go deep into the dark
areas and barely touch the surface in the sections with very light
colors. After the image is cut apply the stain and remove the excess,
let it to dry. After the stain is dry start the sanding procedure.
For vee cutters keep the maximum
dept of cut between 0.02 and 0.03, going deeper will cause the wider
part of V to penetrate and destroy the previous cut or left no material
for the next one.
If you want to go deeper then reduce
the image size in the image editor and then increase the carving
dimension. This will increase the X-Y resolution and allows for bigger
tool diameter. Remember raster bitmaps only contains color information
(pixels), modifying the pixels information will also modify the
appearance of the image. This is why Image to G-Code uses projective
transformation.
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Example C: |
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The Child and the Dog
example. |
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To cut this example we use the
following procedure: The image was converted to gray scale, (the image
was very well defined and not adjustment was required) On the G-Code
Converter the X-Y resolution was set to twice the default value (0.01 *
2 = 0.020). Note that the carving dimension does not change with a
change in the X-Y resolution. In this case Image to G-Code resample the
original image to a factor that results in the projected image (x * X-Y
resolution = Carving dimension).
The depth value was se to 0.035, the
K-Factor was check with a value of 2, and Close enough was unchecked.
Because the tool size was increased
by changing the X-Y resolution and by using a K-Factor of 2, this allows
us to go deeper into the wood and create a lighted 3-D effect.
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Example D: |
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The Marilyn example: |
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For the Marilyn example we use a
procedure similar to the Example A. the only change was to use a piece
of stock that was pre stained and varnished. This appears to give a
cleaner cut. Also when we apply the stain to the cut area this did not
penetrate the areas with the varnish applied, after sanding some of the
hair areas took some type of golden color. |
