MonkeyCAM uses three configuration files, one to describe the board/ski, one to describe the binding inserts (optional, no inserts if omitted), and one to describe the details of how to machine the board. The board definition file describes the shape of the board, and the thickness and taper of the core. The binding definition file describes the placement of inserts. The machine and tool definition file describes machining parameters used by various programs (rapid and various cutting heights and depths, raw material thicknesses, etc.) and parameters of each tool used.
See the MonkeyCAM v4.0 User’s Guide for an overview.
The configuration files are in JSON format, which makes them easy to parse programmatically and also pretty easy for humans to read and edit.
You don’t really need to understand much JSON to be able to edit these effectively. Only a subset of JSON is used, and it’s formatted very simply. The following example shows three parameters and their values:
"name": "Sample-snowboard",
"nose length": 18,
"effective edge length": 136,
The string before the : is the name of the parameter, in this case
name, nose length, and effective edge length. The string or
number after the : is the value of the parameter. Thus the name of
this board is Sample-snowboard, the length of the nose is 18cm,
and the length of the effective edge is 136cm.
The values may be strings or numbers as defined here.
| Datatype | Definition |
|---|---|
"string" |
a sequence of zero or more characters, delimted with double-quotation marks. |
number |
a signed decimal number that may contain a fractional part. May denote inches or centimeters, depending on the parameter. |
Furthermore, we define a percentage as a number from 0.0 to 1.0.
Avoid changing the structure of the file, i.e., the braces ({, })
and names of the parameters. Only change the values.
The board configuration file contains two sections, one to describe the overall shape of the board and one to describe the thickness profile.
{
"board":
{
parameters
},
"profile":
{
parameters
}
}
The board section describes the complete, final shape of the ski or
snowboard. These are the measurements after it is completed, not of
the core or base material. If you specify that a board has a waist
width of 24.6cm then when you measure the width of the base with edges
it will be 24.6cm wide.
Note that you do not specify the width of the nose and tail, it is computed from the combination of the waist width, effective edge length, sidecut radius, and taper.
"name": string
Name of the ski or snowboard. This will be used as the prefix of all generated files.
"splitboard": boolean
true if the snowboard is a splitboard, false otherwise. Optional,
and if missing will be assumed to be false.
"nose length": number
The length, in centimeters, of the nose from the tip of the board to the start of the effective edge.
"effective edge length": number
The length, in centimeters, of the effective edge of the board. This is the length of the board between the nose and tail. The sidecut will be made along this length.
"tail length": number
The length, in centimeters, of the tail from the end of the board to the end of the effective edge.
"sidecut radius": number
The radius, in centimeters, of a circle which will be used to form the sidecut along the effective edge.
"waist width": number
The width, in centimeters, of the waist of the board. The waist is located at the center of the effective edge. Note that because of the taper, this is not necessarily the narrowest part of the board.
"taper": number
The taper, in centimeters, of the board from nose to tail. The tail will be narrower than the nose by this amount.
The nose shape specifies parameters to control the shape of the nose, specifically the curve from the start of the effective edge to the tip of the nose.
"nose shape":
{
"type": string,
"end handle": percentage,
"transition handle": percentage
}
The type may be "Basic Bezier" or "Flat", other
options will be available in the future. "Basic Bezier" specifies a classic
Bezier curve with two control points for one half of the nose shape,
and this curve is mirrored to get the other half. "Flat" is similar
but includes an additional flat section of specified width at the tip. The control points
are constrained to ensure that the Bezier curves join properly at the
nose and to the effective edge.
The end handle is a percentage of half of the nose width, and
determines how far away from the center of the nose the control point
is, and therefore how much it pulls on the Bezier near the tip. A
smaller percentage will result in a pointy tip, while a lager one will
form a tip which is more blunt.
The transition handle is a percentage of the nose length, and
determines how far away from the transition between nose and effective
edge the control point is, and therefore how much it pulls on the
Bezier near this transition point. A small percentage will cause a
sharper transition from nose to effective edge, and a larger one will
smooth it out.
A percentage is used to define the control points because this results in noses which hold their relative shape fairly well even as the length and width of the nose changes, so you’re not constantly having to update the nose definition as you play with other design parameters.
The edge shape specifies parameters to control the shape of the effective edge.
"edge shape":
{
"type": string
}
The type may currently be only "Basic Arc", though other options
will be available in the future. This specifies a very simple arc for
the effective edge, and has been sufficient for every board I’ve built
to-date.
There are lots of other options, and I may add them in the future. However, the practical difference between other options and a simple arc is stunningly small, which is why I’ve stuck with an arc for so long.
The tail shape specifies parameters to control the shape of the tail, specifically the curve from the end of the effective edge to the tip of the tail.
"tail shape":
{
"type": string,
"end handle": percentage,
"transition handle": percentage
}
See the specification for the Nose Shape for details; the tail is the same.
"stance setback": number
Optional.
The setback, in centimeters, which defines how much the reference
stance of a board, or boot center of a ski, is shifted away from the
center of the effective edge towards the tail. A value of 0 keeps the
reference stance centered over the center of the effective edge. A positive
value shifts the reference stance towards the tail. Optional. If omitted a
value of 0 is assumed.
"nose and tail spacer width": number
Specifies the width, in centimeters, of the nose and tail spacer. The core at the nose and tail, starting at the ends of the effective edge, will be inset by this amount.
"nose edge extension": number
Specifies the length, in centimeters, of the edge past the end of the
effective edge towards the nose of the board. Optional. If omitted the
edge wraps around the entire nose of the board. If 0.0, the edge
ends right at the end of the effective edge.
"tail edge extension": number
Specifies the length, in centimeters, of the edge past the end of the
effective edge towards the tail of the board. Optional. If omitted the
edge wraps around the entire tail of the board. If 0.0, the edge
ends right at the end of the effective edge.
The profile specifies the thickness of the core from nose to tail. Currently, MonkeyCAM generates profiles which are constant thickness throughout the nose and tail, and are a constant thickness throughout the bulk of the center of the board. The transition from the thickest portion at the center to the thinner nose and tail is defined with Bezier curves for a smooth and highly customizable transition.
"nose thickness": number
The thickness, in centimeters, of the nose. The entire nose right up to the effective edge will be this thickness.
"center thickness": number
The thickness, in centimeters, of the center of the board. How much of the center is this thickness is determined by the nose and tail taper parameters.
"tail thickness": number
The thickness, in centimeters, of the tail. The entire tail right up to the effective edge will be this thickness.
The nose taper defines how the profile transitions from the larger center thickness to the thinner nose thickness. A Bezier is used to generate a smooth transition. To understand these parameters, first consider the distance from the center of the effective edge to the start of the nose. This is one half the effective edge length. The taper is defined using percentages of this distance, starting from the center of the effective edge.
"nose taper":
{
"taper start": percentage,
"start handle": percentage,
"end handle": percentage,
"taper end": percentage
}
taper start specifies, as a percentage of half the effective edge
length, the distance from the center of the effective edge towards the
nose where the taper will begin.
taper end specifies, as a percentage of half the effective edge
length, the distance from the center of the effective edge towards the
nose where the taper will end.
start handle and end handle specify the location of two Bezier
control points. These are also percentages of half the effective edge
length. The further a handle is from the start or end, the more it
pulls on the curve and makes the start or end of the transition more
gradual. If the handles are very close to the start and end the
transition will be sharper.
The tail taper is the same as the nose taper, simply directed towards the tail from the center of the effective edge.
"tail taper":
{
"taper start": percentage,
"start handle": percentage,
"end handle": percentage,
"taper end": percentage
}
"reference stance width": number
Optional. Replaced by '--binding-distance' keyword on command line but retained for backwards compatibility. To be removed in future version.
The width, in centimeters, between the center insert group in each pack. By default, these groups are centered at the waist of the board, i.e., the center of the effective edge.
Optional. Moved to Binding definition file (See below). Functionality is currently retained in board definition file for backwards compatibility. To be removed in future version.
Optional. Moved to Binding definition file (See below). Functionality is currently retained in board definition file for backwards compatibility. To be removed in future version.
Optional. The whole binding definition file is optional. Omit for skis or boards with no inserts.
The binding definition configuration file contains a single section which describes parameters relating to binding insert positioning.
{
“binding”:
{
parameters
}
}
"binding name": string
The name of the binding or insert pattern specification.
Inserts "packs" consist of "groups" of four inserts in a standard 4x4 pattern, with each group staggered from the other by a given amount. Packs are defined by how many groups they have, and their spacing. Typically some inserts from one group overlap some inserts from another group, and that is fine; the minimal number of cuts will be made. Think of a group as a discrete place at which you can mount your bindings, and how many such places there are in various classic packs. The most classic pack of eight inserts has three groups.
There are two packs, one for the nose and one for the tail.
Optional. Omit for skis or other boards with no inserts.
The nose insert pack specifies the number and relative location of the groups of inserts closest to the nose of the board. The "reference group" is the only required group of inserts and is implicitly defined. Additional groups are specified with the other parameters.
"nose insert pack":
{
"count nose": number,
"count tail": number,
"offset": number,
"horizontal spacing": number,
"vertical spacing": number
}
count nose specifies the number of additional groups to add from the
reference group towards the nose of the board. Likewise, count tail
specifies the number of additional groups to add towards the tail.
offset indicates, in centimeters, how far apart the center of each
group is.
horizontal spacing indicates, in centimeters, how far apart the
inserts within a group are from nose-to-tail, while vertical spacing
indicates, again in centimeters, how far apart they are from
side-to-side. (Think about looking at a board from above, with the
nose pointing to the left.)
This is a pack of eight inserts, separated nose-to-tail by 4cm each, and separated side-to-side by 4cm.
"nose insert pack":
{
"count nose": 1,
"count tail": 1,
"offset": 4,
"horizontal spacing": 4,
"vertical spacing": 4
}
This is a pack of 14 inserts, separated nose-to-tail by 2cm each, and separated side-to-side by 4cm.
"nose insert pack":
{
"count nose": 2,
"count tail": 2,
"offset": 2,
"horizontal spacing": 4,
"vertical spacing": 4
}
This is a pack of 6 inserts, separated nose-to-tail by 4cm each, and separated side-to-side by 4cm. The reference group is accompanied by one more group towards the tail, which adds just two more inserts.
"nose insert pack":
{
"count nose": 0,
"count tail": 1,
"offset": 4,
"horizontal spacing": 4,
"vertical spacing": 4
}
Optional. Omit for skis or other boards with no inserts.
The tail insert pack specifies the number and relative location of the groups of inserts closest to the tail of the board. The "reference group" is the only required group of inserts and is implicitly defined. Additional groups are specified with the other parameters.
"tail insert pack":
{
"count nose": number,
"count tail": number,
"offset": number,
"horizontal spacing": number,
"vertical spacing": number
}
See the Nose Insert Pack; the tail is the same.
Inserts for skis, snowboards, and splitboards can be specified at three locations: Toe (Nose), Center or Heel (Tail).
Insert locations are specified using a JSON array to specify the
position of the center of each insert. The positions are defined as
offsets from a reference point which differs depending on the type of
board being built:
-
For skis, the
toeandheelare relative to the setback and the--bindingdistparameter, while thecenteris relative to the center of the effective edge. -
For snowboards, the
noseandtailare relative to the setback and reference stance. -
For splitboards, the
noseandtailare relative to the setback and reference stance, while thecenteris relative to the true center of the board. This allows the touring insert pack to be centered over the balance point of the board independent of the other parameters.
All offsets are specified in cm along the board towards the tail (x) or across the board from left to right (y).
A JSON array consists of a series of comma seperated rows, each
enclosed in curly brackets {row}, and the whole array enclosed in
square brackets [.....]. For all the binding definition arrays each
row contains comma seperated "x" and "y" parameters specifying the
coordinates of an individual insert "x": number, "y": number.
The name can be toe or nose depending on preference. For clarity,
skis typically use toe while snowboards and splitboards typically
use nose.
"toe":
[
{"x": number, "y": number},
{"x": number, "y": number},
...
{"x": number, "y": number}
]
Optional.
Toe/nose inserts are specified with position relative to the center of the boot toe for skis, and relative to the reference stance for snowboards and splitboards. For tech/pin ski touring bindings toe inserts are specified relative to the center of the pin centerline. Note that for frame bindings with a fixed length (i.e. the distance from the front screw holes to the back screw holes is fixed as the binding is all one piece) then all of the binding inserts will be specified relative to the toe (and hence should be part of the "toe" section of the binding definition file).
"center":
[
{"x": number, "y": number},
...
]
Optional.
Center inserts are specified relative to the boot/stance center for skis, and relative to the true board center for splitboards.
For splitboards, the center pack is also duplicated and centered over each half of the splitboard. This is specifically for the touring inserts.
The name can be heel or tail depending on preference. For clarity,
skis typically use heel while snowboards and splitboards typically
use tail.
"heel":
[
{"x": number, "y": number},
...
]
Optional.
Heel inserts are relative to the center of the boot heel for skis, and relative to the reference stance for snowboards and splitboards.
"toe":
[
{"x": -2.5, "y": 2.0},
{"x": -2.5, "y": -2.0},
{"x": 2.0, "y": -2.0},
{"x": 2.0, "y": 2.0}
],
"heel":
[
{"x": -1.5, "y": 1.8},
{"x": -1.5, "y": -1.8},
{"x": 3.75, "y": -1.8},
{"x": 3.75, "y": 1.8}
]
The machine and tool configuration file contains a single section which describes parameters to control the machining process. Any dimension which depends on a cutting tool, material thickness, or is related to the machining or assembly process is represented here. If your manufacturing process and materials are fairly consistent then it will be rare for you to change this file.
{
“machine”:
{
parameters
}
}
All feed rates are emitted as F codes in the G-Code programs,
without translation. The units are defined by your CNC controller
configuration. Inches per minute (IPM) or millimeters per minute
(mm/min) are common.
"rapid speed": number
The velocity at which the machine will move during rapid movements via
G00.
"normal speed": number
The velocity at which the machine will move during interpolated
movements via G01, G02, G03.
All heights and depths in the machine configuration are measured
assuming the table or part top is at Z = 0, and positive values of
Z are above the table or part.
"bottom rapid height": number
The height, in inches, at which the cutter will move during all rapid
motions via G00 when working the bottom of the board. All programs
which work on the bottom of the board use Z = 0 at the top of the
core blank, thus this is the height above the core blank for all rapid
moves.
"top rapid height": number
The height, in inches, at which the cutter will move during all rapid
motions via G00 when working the top of the board. All programs
which work on the top of the board use Z = 0 at the top of the
table, thus this is the height above the table for all rapid moves and
must be sufficient to clear the core.
"core blank thickness": number
The thickness, in inches, of the core blank. This does not have to be precise so long as it is at least as thick as your thickest core blank. A value larger than the true thickness of the core blank will cause some of the G-Code programs to be less efficient than they otherwise could be, but they will still work.
Each of these effects the Base Cutout program.
"base cutout tool": tool number
The tool, defined in the tools section, which will be used to cut the base.
"base rapid height": number
The height, in inches, at which the cutter will move during all rapid
motions via G00 when working the base and nose/tail spacer
material. All programs which work on the base use Z = 0 at the top
of the table, thus this is the height above the table for all rapid
moves and must be sufficient to clear the base.
"base cut thru height": number
The depth, in inches, at which the cutter will descend to in order to
cut thru the base material. This should be a negative number slightly
less than 0 in order to ensure the cutter completely penetrates the
base material, i.e., -0.010 or so.
Each of these effects the Guide Holes program.
"guide hole tool": tool number
The tool, defined in the tools section, which will be used to cut the guide holes in the core blank.
"guide hole depth": number
The depth, in inches, to which the guide holes will be cut thru the
core. Note that this program uses Z = 0 as the top of the core
blank, so this should be thicker than the core blank and thick enough
to ensure a reasonable hole is left in the table top for alignment
pins.
"guide hole diameter": number
The diameter, in inches, of the guide holes. Make this slightly larger
than the true diameter of your alignment pins, i.e., 0.505 inches
for half inch pins.
"guide hole offset": number
The offset, in inches, of the guide holes from the ends of the core.
Each of these effects the Alignment Marks program.
"alignment mark tool": tool number
The tool, defined in the tools section, which will be used to cut the alignment marks on the bottom of the core.
"alignment mark offset": number
The offset, in inches, of all alignment marks from the edges of the core.
"alignment mark depth": number
The depth, in inches, of all alignment marks into the core. Typically
quite small, e.g. -0.025, but adjust based on personal preference.
"alignment mark deep depth": number
The depth, in inches, of the extra-deep alignment marks near past the ends of the core that can be used to re-align the machine in the event of a horrible mistake.
Each of these effects the Edge Groove program.
"edge groove tool": tool number
The tool, defined in the tools section, which will be used to
cut the edge groove.
"edge groove depth": number
The depth, in inches, of the edge groove around the perimeter of the core to accommodate the edges.
"edge groove edge width": number
The width, in inches, of your edge stock including the tines, plus a little extra for some
play when aligning the core to the base. This parameter is combined with sidewall overhang
to form the total width of the edge groove.
"edge groove overlap percentage": percentage
The percentage of the selected tool diameter that each successive cutting pass will overlap with the prior pass.
Each of these effects the Insert Holes program.
"insert tool": tool number
The tool, defined in the tools section, which will be used to cut the insert holes.
"insert rim depth": number
The depth, in inches, of the outer edge of the insert holes.
"insert rim diameter": number
The diameter, in inches, of the rim of the insert holes.
"insert hole diameter": `number
The diameter, in inches, of the barrel of the inserts.
Each of these effects the Top Profile program.
"top profile tool": tool number
The tool, defined in the tools section, which will be used to profile the core.
"top profile transition speed": number
The feed rate used when transitioning to the next larger profiling pass. Since the cutter is typically quite large, a slower feed rate when driving it into the core blank to start the next pass is advised.
"top profile deep speed": number
The feed rate used at maximum cutting depth during core profiling. Typically slower than the normal feed rate due to the likely large diameter of the cutter.
"top profile overlap percentage": number
The percentage of the selected tool diameter that each successive profiling pass will overlap with the prior pass.
"top profile lead-in length": number
The distance, in inches, over which the cutter will ramp into the core blank before reaching the full cutting depth. A longer lead-in may be appropriate for thicker core blanks, or larger cutters.
Each of these effects the Top Cutout program.
"core cutout tool": tool number
The tool, defined in the tools section, which will be used to cut out the core.
"sidewall overhang": number
The amount, in inches, of sidewall which will remain past the edges, outside the final board shape. Leave a few mm to account for core-to-base alignment error.
This parameter is combined with edge groove edge width to form the total width
of the edge groove used in the Edge Groove program.
Each of these effects the Nose Tail Spacers program.
"spacer end overhang": number
The minimum amount, in inches, of spacer material which will be left past the ends of the final board shape.
"spacer side overhang": number
The minimum amount, in inches, of spacer material which will be left past the sides of the final board shape.
Each of these effects the Edge Trench program.
"edge trench width": number
The width, in inches, of the edge trench. This should be the width of your sidewall material, and of any additional stringers you want to lay down perfectly along the effective edge. Recognize that a portion of this trench will extend past the final board shape as determined by the sidewall overhang.
"edge trench extension": number
The distance, in inches, the edge trench will extend past the ends of the effective edge. This distance needs to be sufficient to ensure sidewall and extra stringer material will fill the core a bit past where it will be shaped by the core cutout program, but not so long that the trench cuts beyond the boundaries of the core blank.
Currently this measurement is a bit of trial-and-error, though a value
of about 3 inches is typically sufficient. See the issue about improving this.
Each of these effects every program generated, as the core is widended down the center to allow the board to be cut in half after pressing.
"splitboard center gap": number
The width, in inches, of the gap to leave down the center of the board for the board to be split after layup. This should be the width of your bandsaw blade plus a little bit of slop for error to ensure the blade doesn't bind and dig into the metal center edges. You will seperate the edged base halves by this amount while preparing for layup.
"splitboard center trench width": number
The width, in inches, of the center trench. This should be the width of your sidewall material, and of any additional stringers you want to lay down perfectly along the center of the splitboard.
Note carefully that the splitboard center gap does not effect this
trench width, and that the portion of your sidewall material within
this gap will be lost when you split the board after layup. In effect,
this "gap" is much like the sidewall overhang and ensures that
sidewall material can be trimmed back to the center edges during
finishing.
The tools section has an entry for each tool which will be used by
the generated G-Code programs. Each tool is given an id which is
used to reference the tool from other parameters, and is called the
tool number in the documentation for those parameters.
"tools":
[
{
"id": 1,
"name": "Quarter Inch Upcut Spiral",
"diameter": 0.247,
"G-code #": 1
},
{
"id": 2,
"name": "Quarter Inch Straight",
"diameter": 0.250,
"G-code #": 1
},
]
"id": tool number
A unique numeric id for the tool, so it can be referenced from other machine configuration parameters.
"name": string
A name for the tool, which can be whatever you like and will appear in the header block of the G-Code programs which use this tool.
"diameter": number
The diameter, in inches, of the tool. Be precise and measure carefully
with precision calipers. If you have a quarter-inch cutter which is
really 0.247 inches in diameter, then enter that.
"G-code #": number
The tool number, as defined in your CNC controller, which will be
emitted via G43. I.e., G43 H1 T4 if the number is 4. This is for
CNC machines with automatic tool changers, or for those who configure
tool height offsets in the CNC controller.