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RAPIDCHANGE ATC Bringing Automatic Tool Changing to Small Shop CNC Routers (Original unedited version.) Years ago
I wrote some articles for Woodshop News. At
the time I was running my curved moulding
business and enjoyed this diversion at the end of my work day. The first of those
articles was a review of
the newly introduced SawStop table saw.
I happened to be returning to Connecticut from IWF
in Atlanta on the
same flight as A.J. Hamler who was the editor of Woodshop News. Our conversation soon
turned to the SawStop
and the pending first shipment arriving in the US.
Since I had just ordered one I suggested that
I might write the magazine’s review.
Mr.
Hamler agreed and thus began my Woodshop News writing career. The
review of the SawStop was unquestionably favorable.
I was a big fan of the technology from the
first moment I saw it in action with a sliding hot dog.
When it turned out the saw was as
extraordinarily well engineered and designed as it was a giant leap
forward in
safety, it became easy to put together a positive review. (SawStop
review .....June 2005) Now, over
20 years later, something else quite different has
come along. While
this product isn’t
going to change the woodshop and construction worlds the way the
SawStop did, I
believe it will have a big impact on many small shop CNC router owners. RAPIDCHANGE
ATC Automatic
tool changing is somewhat of a holy grail in the light
to medium duty CNC router market.
Adding
an air activated ATC system to a CNC purchase is expensive. An ATC spindle, tool
holders, tool rack and
air drying system must all be added to the base router price. This means $10,000 or more
for a name brand
setup, or perhaps half to a third of that for a Chinese clone version. Either way it is a
disproportionately large amount
in relation to the base cost of an economical class CNC router. In my
retirement shop I have a 20 year old 4x8 CNC that I
purchased used and to which I did all the appropriate improvements and
upgrades.
As it sat I
had a pretty sharp
system. But what I didn’t have was
an automatic tool
changer. I had been
looking for a long
time for a good condition used name brand spindle for the heart of the
system but
never pulled the trigger for one reason or another.
I even considered going new with the Asian
import clone spindles but still held back. With
all the required accoutrements beyond the
spindle purchase it just seemed a disproportionate investment in
relation to
the overall value of my old machine. Then
one day while doing yet another online
search for ATC opportunities I stumbled on the Rapidchange ATC (patent
pending).
After
visiting the website (www.rapidchangeatc.com),
watching some
videos and reading some online reviews I emailed the company and
quickly got a
call back from Don Greilick. Don
is the person
behind this mechanical tool changer and a bunch of fun to talk with on
the
phone. He has a
strong background in
both the arts and engineering and along with his computer code savvy
son
developed the Rapidchange ATC. This tool
change system, at well under $1000 all in for even
the largest and most sophisticated of the options available, is a game
changer. And that
is what Don means it
to be. An
affordable automatic tool
changing system for the non-industrial classes of CNC routers. It is available with or
without a retracting
dust cover and in 4 to 8 slot variations with the possibility of more
tool
slots on a custom order basis. The
concept for this system is actually a fairly simple.
Your
spindle runs in forward to load a collet/nut assembly with your
pre-loaded
router bit, and in reverse to remove it. This
assembly is sitting in one of the tool slots
in the rack which Don refers to as the “magazine”.
The
spindle is typically set to run between 700 and 1000 rpm during loading
and
somewhat higher for unloading. After
loading the bit assembly and giving an initial amount of locking torque
to the
collet nut, the Z-axis will raise about ½” and while still spinning
lower again
into the tool slot to “tap” the grab ring to provide a secondary torque
down of
the nut. On each
tap the rotational
force as the spindle stops creates the torque needed to tighten the nut. This
works because each location in the tool magazine has a spring-loaded
lock ring designed to grab the collet nut the same way as your wrench
would. This is the
case whether your
collet nuts have milled slots for the wrench to grab or are simply hex
shaped. The spindle
rpm is set low
enough so that the downward motion of the Z-axis can drive the nut onto
the
grab pins in the lock ring while being fast enough to create the needed
torque
to tighten the nut. Depending
upon the
collet design, that is ER11, ER16, ER20 and others, two or three total
“taps”
of the tightening procedure will do the job. There are
various length tool magazines available so you can
size the system to your needs. The
magazines
are specifically designed to accommodate each of the different
collet/nut types. Don
has most of the major styles already
covered and is adding to the repertoire on a regular basis. In fact, the SYOZ-20 setup
on my Perske 5hp
spindle was a new one for him. TECHNICAL
DEVELOPMENT The idea
for the Rapidchange ATC occurred to Don in 2022
while cutting some material on his own CNC router.
He was captivated by the idea and with a bit
of experimenting came up with his first prototype magazine that very
day. As is always
the case when developing a new
device some parts worked right off and some needed attention. Over the next 6 months he
worked through
these details and was then ready to show the Rapidchange ATC to the
world. To do so he
created a video post on the
social media platform Discord (www.discord.com)
and literally within minutes he had people asking for more information. This led to his widely
viewed YouTube channel
and subsequently to sales to date to hundreds of users around the
world. While the
idea of just spinning a collet nut up onto a
router spindle seems like it would be pretty simple those months of
product
development were actually pretty intense.
There were a number of theoretical details that were
simple enough in
concept but a bit more complicated to actually work out. First and
most obvious was the issue of running a router
spindle in reverse for unloading.
This
can be done with most Variable Frequency Drives (VFDs) that run high
speed
spindles but not all. Then
of course
many lower cost CNC routers incorporate hand held routers not capable
of
running backwards. This
means that not
all existing CNC routers can take a Rapidchange ATC without a spindle
upgrade. However, a
2 to 3 hp spindle with matching
VFD can now be bought as an import for under $500.
So even if a CNC owner has to add that to the
cost of the Rapidchange ATC the overall cost remains a small fraction
of installing
a traditional air driven ATC system. Next up
was probably the biggest question Don faced.
What about torque?
Could the slow speed loading rpm create
enough rotational torque to solidly lock the collet nut to the spindle
shaft? Don will
admit he was initially skeptical.
However, experimentation on the prototype showed
that with some tweaking to the process, and with multiple “taps” using
the
spindles rotational force to bump the nut tighter as the spindle stops,
he
could get the nuts as secure as with a set of collet wrenches. But this
type of loading process where the spindle is
brought to a momentary stall brings up the question of possible damage
to the
spindle. To be
honest I haven’t found
any research in this area nor have my inquiries to people who sell and
service
CNC spindles provided any data. However
with hundreds of Rapidchange ATC units in service Don tells me there
have been
no reports of spindle problems during the first year plus of sales. Once the
torque issue was sorted out the last major question
was could the collet nut be made to consistently spin up onto the
spindle
without cross threading. Further,
even
if that could be done, what would happen if for some reason the nut did
bind on
the initial grab. That
could be a major
problem. You
wouldn’t want a partially
mounted collet/bit assembly running at high rpm while not being
properly seated
and tightened in place. To handle
this Don came up with a method to reduce the chance
of cross threading along with also adding safety features that address
the scenario
if it should occur. On this
issue of cross threading I will say that a new owner
shouldn’t be surprised if it happens on the first tool pickups after
initial setup. There
are some very precise alignment steps
that need to be completed in order for the tool changes to work
seamlessly. Even if
the install is being guided by a
wizard (for now only available on UCCNC control software) your first
run
through might not end up with the precision settings needed to make
this work. For
other control software packages that
don’t yet have setup wizards the process is a bit more rigorous but
doable. Don
continues to work to make
the wizards available in more CNC control packages. Doing
the installation To do the
setup in a way that will lead to repeated successful
tool pickups and drop-offs from all the tool positions you first need
to get
the magazine exactly parallel to one of your router’s axes. Getting this done is
assisted by a provided
CAD drawing of the mounting hole locations.
That drawing can be imported into a CAD program so
that the router can precisely
drill the mounting holes for you. After the
magazine is mounted to your CNC the exact location
of tool holder position #1 needs to be established.
Having done this myself I will say that it
requires a high degree of accuracy as all the other tool positions work
off of
#1. If the recorded
position is off by even
a few hundredths of an inch clean tool pickups will not happen. However doing this is
actually not all that
difficult. I’ve
done it with and without
the UCCNC wizard and once I got a feel for the process I was doing it
in a minute
or two. Plus of
course CNC routers are
high precision machines so repeatability once you get your Tool #1
location is
pretty much assured. If you
have gotten your positioning co-ordinates properly
set, and your tool magazine is level and parallel to the bottom face of
the
spindle shaft, you will get clean pickups.
I had some initial issues here but was able to
narrow them down to a few
small out of alignment factors. My
final
check was to mount a ½” rod in the router and examine the squareness to
my
spoil board. To my
surprise I found it
was off by about .03” over the 5” long rod.
This
was enough to give me some
inaccuracy during tool pickup. This was fairly easily
corrected by loosening
my Z-axis mounting plate bolts and tweaking the spindle’s vertical
orientation. Lastly,
in order to assure that a bit assembly has loaded
correctly there is an IR eye (on the retracting dust cover
model.....and soon
to be on the base model as well so visual confirmation is not required)
that
scans across the magazine after tool pickup.
If the collet nut has been threaded all the way up
and above the IR
transmitter level it will see the IR receiver on the other end of the
magazine
and an “all clear” signal will be sent to the software.
If the nut has not spun all the way up onto
the spindle threads it will be blocking the eye’s line of sight to the
receiver. In this
case the software will know that you
don’t have a fully threaded collet nut and the router will travel to a
convenient wrenching location so you can fix the problem.
The only
other possible issue I know of with the Rapidchange
ATC would be bit slippage when sitting in the magazine.
Not all router bits are a tight fit when
inserted in a collet and thus depend upon tightening the nut for a
solid grab. As such
while loosely assembled in the magazine
the bit might slip downward in the collet. One
solution of many would be to put a dab of
hot melt glue on the butt end of the bits when putting them into the
collet. This should
be all it takes to prevent
slippage and shouldn’t cause any problem with high rpm spindle balance. Again
though, this would only be if a bit is slightly loose to start with. BIT
LENGTH MEASUREMENT Router
bits don’t end up in exactly the same spot in the
collet every time the nut is tightened.
Bit
creep as the nut is tightened or slippage in the magazine can change
the length
of a bit below the collet face.
Since
the bit/collet/nut assembly has been sitting free in the magazine it
needs to
be measured with each pickup. That means that while your
top of material
location will remain constant with bit changes, the bit length assigned
to each
tool needs to be updated with each tool pickup.
The end
slot in the tool magazine is set up to accommodate a
touch down plate (sold separately) instead of a router bit assembly if
that is
what a user wants. If
someone already
has a different style touch down plate available for permanent
mounting, or
simply wants that magazine slot for another router bit, they can mount
an
external touch down plate somewhere near the magazine.
Either way the M6 tool change macro supplied
with the Rapidchange ATC accommodates the various setups via the
software
interface. On my CNC
I even added a retracting platform that the
Rapidchange ATC and external touch down plate are mounted upon. This
is so the ATC can extend over the work surface where my spindle can
reach it when
needed and retract out of the way on my X-high side of the table when
not in
use. The
Rapidchange ATC software has an
option to run a pre and/or post tool change custom macro which I use to
activate the extending platform’s air cylinders at the appropriate time. USING
THE RAPIDCHANGE ATC The
Rapidchange ATC is used just as any other automatic tool
changing system. You
set your CAM
software to the tool changer post processor for your machine and load
up the
tool magazine in the software just as you would with an air activated
ATC
spindle system. You
will then need to
make sure your particular post processor places an “M6” in the tool
number line
in the G-code (“M6 T01” for example) as that is required to activate
the tool
change process. If
the “M6” is not there
it is typically a small change in the post processor and as in my case
with
Enroute, the CAM software company might do it in a matter of a few
minutes at a
minimal charge. Once the
correctly generated G-code is being created then just
make sure the needed router bits are installed in the magazine
positions to
match the CAM software. When
a tool is
called up in the G-code the router will go to the correct slot, pick up
the tool
assembly, measure the bit and then travel to your cut start point. As long as you’ve already
touched down to the
top of your material each tool will know exactly where that is.
This
photo sequence shows the bit loading and measuring
steps as performed on B.H Davis’s retracting platform Rapidchange ATC. WHAT’S
TO COME Don isn’t
resting on his laurels with the Rapidchange
ATC. In addition to
bringing in more CNC
controls with matching wizards he’s working on a turret magazine,
looking at bringing
the system to milling machines and working with some smaller CNC
manufacturers
to include the Rapidchange ATC right from the factory. So what
do I think of the Rapidchange ATC?
I imagine it’s pretty obvious that I am
significantly impressed. I
purchased my
first CNC router back in the late 1990’s.
It was a used 5x10, 2-head machine.
I was brand new to CAD, CAM and MS-DOS control
software (yes, MS-DOS)
and the router was the first one I’d actually ever seen in person. Yet, within a matter of
months I knew I
wanted to add an automatic tool changer.
I did the
research, bought the parts, found a deal on a
spindle, purchased an air dryer and upgraded the CNC control hardware
from
mechanical to OPTO-Isolation relays.
It
was a whole lot of education, time and money but in the end worth all
of it. When it ran
for the first time I sat and
watched it changing tools for an hour with a boyish grin on my face. Believe me when I say that
adding the
Rapidchange ATC was just as successful as that first home made
system.......and
a whole lot easier. When
it ran for the
first time I sat and watched it with that same silly grin. BH Davis For
more information Rapidchange
ATC website:
https://rapidchangeatc.com/ Early
Youtube video describing the development:
https://www.youtube.com/watch?v=RR8noEJYduA Early
Rapidchange ATC without using reverse:
https://www.youtube.com/watch?v=hXpaJrEpSnE BH Davis
setup with extending table: https://www.youtube.com/watch?v=281kVTISxws Discord
channel: https://discord.com/channels/1077383334080032898/1077383334080032901
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