CNC ROUTER origin points can be set quickly with lasers or
digital cameras.
In part two of this series, several techniques and
tools were shown for accurately setting origin points. You can use line-of-sight,
feel, extrapolation from a known diameter, edge finders, wigglers, 3D sensors
and more. Accuracy is critical and although all these tools and processes work
well, setting origins can be time-consuming. So, in my own shop, I often use
other methods and tools to locate and set my origin points. As a result, I’m
able to set my zero positions in 30 seconds or less.
How do I do it? Three different
methods. Two involve modern tools and the third is the use of the grid system
that I’ve designed for the bed of my CNC ROUTER. All three approaches speed up
the process of finding origin points.
he trick with lasers is a sharp focus, good alignment and
splitting the beam right on the edges of the board.
Set your origin point with a cross laser
A few years back, furniture maker and
friend, Bob Spangler started using a cross laser as an alignment tool. A great
idea that I adopted and took a bit further. Essentially, you mount a cross beam
laser on the moving plate on your CNC ROUTER’s gantry and set the crossing
beams to align with your X and Y axis. I suggest that you don’t mount it on the
moving Z axis so that it travels up and down with your spindle. The reason is
you’ll create parallax errors and the beam will move as your Z height moves up
and down.
To use the laser, start by centering
the cross beam lines over the corner of a board that’s in alignment to the
axises of your CNC ROUTER’s table. Make sure your beam is focused and sharp.
Use your CNC ROUTERs smallest movements to get it exactly in place. If you can
split the two beams on the edges, you’re there. Now, reset the X and Y axis to
zero.
Next, you need to move and center your spindle.
This is the time to be as accurate as you can. Use measuring tools, like an
edge finder or other technique mentioned in previous posts. Save and record the
offset X and Y distance from the laser’s position to the spindle’s position.
You’ll use these coordinates often so it’s worth making the information easy to
access. I keep it as a little G-code file stored on a desktop sticky note on my
PC-based CNC ROUTER, and as a macro in my controller program and also as a
stored mini program on my Laguna IQ. Now, all you have to do is align the
laser, reset X and Y to zero, move the offset distance that you recorded
earlier and reset to zero, once again. This method is fast.
In the future, I’ll write a full how-to article
and suggest components for laser installation as part of this CNC ROUTER Origin
Points series and post it here. Since I’ve installed a cross beam laser on a CNC
ROUTER a number of times, I’ve worked out the issues and sorted through the
choices of laser — more powerful is not better, btw. And, walk you through
alignment, the choices of holders and different power sources.
With the right software, camera and CNC ROUTER bed setup, you
get a bird’s eye view of your target. This view can be magnified.
Set your origin point with a camera
The laser method works very well. But,
going back and forth between your controller and the table it takes some time
to line up the beams to a corner or a drawn target. And, because the beam is
directly over the alignment point, it’s a little difficult to be accurate.
I’ve found a method I live even better.
This is what gets my setup time down to 30 seconds or less. Because I have a PC
hooked up to my CNC ROUTER, more often I use a CNC ROUTER mounted endoscope and
special software that puts a target on the screen and magnifies the image.
Alignment is easier if you’re right on top of the target. This solution works
great and I use it daily. The process is exactly the same as the laser method.
Center over the target, find the offset between the camera’s cross lines
and the center of the spindle, use and record the information to move from
camera position to the spindle position.
As with the laser method, I’ll also do
a CNC ROUTER Origin Points article on how to set this up and which equipment to
buy and how to set it up. After much trial and error, I’ve found that there are
more wrong camera choices then right choices, so be careful if you choose to
jump ahead. The mounting considerations for a CNC ROUTER camera are similar to
the laser. However, routing the camera’s cable presents a few new challenges.
Setting Origin Points on the Fly
The final solution that I like to use
is based upon the way I’ve set up the bed of my CNC ROUTER. This will take
another article, a lot of explanation and photos and videos to fully explain,
but let’s just say that I keep my bed milled flat and set it up as an accurate
grid system and I know every position on it. I take full advantage of this for
material, fixture and jig placement. I can set origin points quickly and align
and hold parts on the grid. It all starts with a known home or default position
that can be tested, as needed. My goal is to use the CNC ROUTER’s built-in
digital accuracy to do as much work for me as possible. I even incorporate the
setup into my CAD drawings so that when it comes time to mill, everything lines
up. With good workflow, accuracy and origin points are just a few clicks away.
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