CNC Router Skills: Part One: All about Origin Points
For accurate woodworking operation, Origin Points
are extremely critical. Never more so, than for digital woodworkers. The
intersection of the X (red), the Y (green) and the Z (blue) axises is the
origin point.
The Origin Point is your prime reference position
No matter what kind of woodworking you
do, reference points and accurate measurements are critically important for
woodworkers. This is particularly true when using any kind of woodworking
machinery. For example, if you’re using a table saw to rip a board to 4” wide,
set your fence to 4”. To set up that fence to a precise 4” distance from the
blade, the critical reference point is the edge of your saw blade where the cut
is made. It’s from that position that all measurements are made. It’s your
“zero” point.
Assuming you’ve adjusted the fence
properly — you’ll get perfect 4” cuts. The same is true if you were using stops
from the edge of the cut on a crosscut sled, a miter saw station, a router
table, bandsaw, planer or any other power tool that uses a fence, stops or some
other position limiter. You get the idea — all measurements are made starting
from the key reference point: zero.
The cut edge to the right of the saw blade is where all
measurements start. From here you measure out to the fence.
As important as “zero” is for power
tool woodworkers, it’s even more critical for digital woodworkers. Three
reasons: First, we move between digital drawings, our tools and layout
constantly and all have to agree. Second, we work in three dimensions – whereas
almost every shop tool I mentioned earlier works in a single dimension.
Third, it’s a world where everything is measured in thousands of inch or
fractions of a millimeter.
With all that precision, you’d think it
would be easy to find and set reference positions, but as it turns out, it’s
not — it’s an ongoing challenge with techniques to learn and absorb in context
because you’ll use them often. Why? There are several reasons. For one thing,
you’re moving between the digital and real world. In the physical
world, it can be a challenge to take precise measurements. In the pure
digital world of CAD and CNC, everything is defined by crisp, clean and pure
numbers. Plus, unlike a table saw or other fixed woodworking tools where you
rarely adjust your setup, digital woodworkers need to change setups and make
adjustments often. Digital woodworkers have to find, move and create new
reference positions — called the origin or zero point, to different locations —
all the time. As digital woodworkers, we need to be skilled, efficient, and
accurate about finding, setting, and moving origin points.
On this workbench, the origin point is located straight down
from the corner of the top where the red, green and blue lines intersect.
Knowing where zero is, makes it possible to locate an object in
three-dimensional space.
What is the origin point?
In the digital world, the origin point,
or zero point is clearly defined. Think three dimensionally. The origin point
is the intersection of the X, Y and Z axis. From where you’re sitting that
would be left to right, up and down, in and out. And, because everything in
digital is done by the numbers, this is described as X = 0 and Y = 0 and Z = 0.
All dimensions either increase or decrease, positive or negative, from that
position. If you know the origin point, you can find and locate an object’s
position inside its three-dimensional world. There are plenty of reasons why
this matters but here are four important ones…
Your drawing…
Your design resides inside the two or
three-dimensional space of a CAD drawing and you need to know it’s location
based on a reference point that you can match up with…
Your CNC…
The same defined position on your CNC’s
bed that agrees with your drawing and…
Your material…
You need to position the blank material
you’re cutting and finally…
Synchronize…
It all has to work together. Your CAD
drawing, your CNC setup and your material have to match up. The place to do it
is the intersection of X, Y, and Z. The origin point.
Three parts to be cut out of one board. How do you line up the
material with your drawing? The lower left-hand corner is the origin point.
A four-part challenge
Working with origin points on a CNC is
a four-part challenge. The first, it takes a bit of time to adjust to working
at a very high level of accuracy. Most woodworking is about tape measures and
rulers. These machines are very accurate —.001+ precision, which means you’re
required to work methodically that way with software, set up your hardware,
layout, and material at the same level. It’s not hard, but it takes a little
time to learn different methods and techniques and to absorb the results.
Working with this accuracy on a regular basis is the best way to learn. Second,
to accommodate a range of digital woodworkings tasks, you need to change and
set up different kinds of origin points quickly and efficiently. Third, you
need to work in positions all over the CNC’s bed so you’ll move the zero point
often. Fourth, once you put all this together, there’s much to be gained if you
can set origin points up repeatably with speed and accuracy.
Much more to Come
As you can see, there’s a lot going on
when it comes to origin points and reference positions — in fact, entire books
have been written about this in the machinist world. This is about digital
drawings. This is about setting up the machine. This is about what you’re
machining. And, most of all, this is about methods of work and good practices.
If that sounds dull, I can assure you that it’s not. There are some incredible
benefits to using grids, jigs and fixtures based upon accurate zero points and
reference positions. With much to cover, I’ll come back to the topic often in
this first CNC
Skills Popular Woodworking series:
Origin Points. Below, I’ve already outlined several related topics that
you should know about, so I’ll be back soon.
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