Rong Fu RF-25 Mill/Drill with 3-axes DRO.
The mill is at the upper limits of weight &
size that I could safely move down
a hill & into my lower-level walkout.
Rong Fu RF-25 Mill Digital Read-Out (DRO)
Last updated onLast updated on
Wednesday, September 20, 2023 08:59:55 AM
Mountain US Time Zone
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Offset
Milling,
Mount,
Red Filter,
DPU-550
Daughterboard Upgrade
Instrumented Mill
Rong Fu RF-25 Mill/Drill with 3-axes
DRO.
The mill is
at the upper limits of weight &
size that I could safely move down
a hill & into
my lower-level walkout.
EnclosureEnclosure
Setup shown for milling the lathe DRO case.
1-2-3 "Johnny"
blocks fixed at right angles to the table.
Plastic box sides slightly
squeezed by the blocks.
Toe clamps with protective
tape gently secure the box.
The X & Y axes DRO scales were zeroed at the
front
left corner (0, 0) using a
Starrett
wiggler center finder.
Then use the supplied layout drawing of the (x, y)
coordinates
to drill & cutout out all the holes. I like to use
a
Unibit step drill to make holes in thin materials.
Zeroing
The US made Starrett
wiggler set is
far superior to imports except Mitutoyo.
Offset Milling
To make the rectangular holes
for the LED displays,
I used the
DRO's tool offset functions.
The offset function takes into account
the end mill's diameter
when cutting.
Use
Function 5 (tool offset define) to
first specify all the
tool sizes where the
Tool # is always the numerator & 16 is
always the denominator
of a fractional size.
Tool #/16
of an inch. I find this a very easy table
layout to remember, though it is of course, arbitrary.
I used 0 for the Z offsets.
The DRO-350 will only allow
three significant numbers input
after the decimal point.
TOOL #3 TOOL SIZE
DIAMETER (inch)EQUIVALENT
FRACTION
(inch)EQUIVALENT
DECIMAL (inch)CORNER
RADIUS (inch)1 1/16 1/16 0.0625 0.03125 2 2/16 1/8 0.125 0.0625 3 3/16 3/16 0.1875 0.09375 4 4/16 1/4 0.25 0.125 5 5/16 5/16 0.3125 0.15625 6 6/16 3/8 0.375 0.1875 7 7/16 7/16 0.4375 0.21875 8 8/16 1/2 0.5 0.25 9 9/16 9/16 0.5625 0.28125
Function 6(tool offset use), followed by a
Tool # (1 to 9),
turns ON diameter
compensation & selects the previously defined tool.
First, select the tool size diameter being used. To cut
a
rectangular/square pocket or
hole, move the cutter to the (x, y)
coordinates of the
front left corner but don't plunge, yet.
If you are starting in a corner, you must compensate for
two milling
edges; e.g., both left & front. When you
press a compensation key,
you will see the scale offset by the
appropriate tool radius.
If 4, 6, 2 or 8 are pressed, the far
left decimal of the
corresponding scale lights indicating an
offset was selected.
High RPM cuts using a two-flute,
1/8" end mill.
Mount
The DRO bracket is placed closer to the keys where
pressure
is applied. I protected all exposed cables
with spiral wrap. The
80/20
aluminummarmarm (see below)
is mounted
off a triangular, 1/4" thick aluminum plate
that is held under two
of the motor-mounting bolts.
All cable plugs are
held
in
place with a spot of hot glue.
Black plastic 80/20
inserts are snapped into the channels to hold the
cables
in place &
to give the arm
a nice, finished look.
The DRO is plugged into a surge protector.
The 80/20
website has software tools to help construct a kit for assembly.
I have now removed all of the quill levers so they do
not contact the piece when working
close to the vise.
This configuration allows much better access to
the
two column locks, belt tension lock &
DRO.
I made & installed 1/2-12 threaded aluminum
plugs to give it a finished look & keep the
chips out.
I like the extra control afforded by the fine down
feed & typically have no need for
the levers.
Red FilterRed Filter
Adding a deep red filter enhances the LED
display
contrast.
The five LED indicators have
circular (punched) red filters, too. Note: the
blurred LED display is a photographic artifact.
DPU-550
Daughterboard Upgrade
The DRO-350 has been upgraded with the
DPU-550
daughterboard & overlay to add ehanced capabilities & performance.
OpenDRO User's Guide Rev 5OpenDRO User's Guide Rev 5
OpenDRO Supplemental Guide
OpenDRO Software Upload
Manual
OpenDRO
Scales'
directions & polarities must be
correctly defined in the DRO setup for
several of the functions to work properly.
Refer the Open DRO
Supplemental Guide.
DRO-350 baseline. Removal of the 28-pin PIC16F876A
(far
right) is required before soldering in the headers.
The PCB is not of the highest quality so take care
to not damage any traces when desoldering.
| DPU-550 UPGRADED | ||
| Processor Attribute | DRO-350 PIC | DPU-550 ARM7 |
| Register Width | 8-bit | 32-bit |
| Speed | 20 MHz | 50 MHz |
| Program Memory | 8 K | 256 K |
| Working Memory | 368 | 64 K |
| Non-volatile Memory | 256 | 8 K |
| Processor Registers | 1 | 16 |
| USB Device Interface | No | Yes |
| Free & Unlimited C Compiler | No | Yes |
Unassembled DPU-550 lite daughterboard kit.
New holes for the program switch
(1/8") & USB access (1/2").
Super easy to
program the ARM-7 CPU via the USB.
DPU-550 lite daughterboard mounted onto
the DRO-350.
It is easily programmed through its USB port.
For the DPU-550 a
74LS14 Schmitt Trigger was needed
to make this particular
tachometer
setup work
reliably.
The IC (unused pins removed for compactness) was
spliced into the AUX IN to header wires & then shrink-wrapped.
Pin 7 is ground, pin 14 is +5VDC, pin 1 is the signal
in from the sensor &
pin 2 is the signal
out to the DRO.
This circuit converts the sensor's somewhat noisy
waveform to a clean,
well-defined, square-wave output.
The unused inputs
do not have to be tied to ground
because the purported power loss is insignificant.
Since any value can be displayed
anywhere;
the
X-axis position (2.3778-inches) was assigned to the top
line, the
spindle speed (1642 RPM) was assigned to
the middle
line & the X-axis feed (7.0-inches/minute)
was placed on the bottom line.
The Y-axis & Z-axis
feed rates can also be displayed on any line.
Reverse Polish Notation (RPN) calculator turned on.
Stack of four registers
bottom to top: X, Y, Z, & T.
The value in the T (Top) register copies itself as the
stack drops down, just like a
circa 1970s HP calculator.
Many advanced functions are also built-in:
SINE,
COS,
TAN,
memory in/out, power
of, Pi, square root, axis
preset, hypotenuse, fraction & axis reading.
Results of calculations can be stored
into any axis preset.
The last function used is also recalled (retained)
when the OP PRV or OP NXT
button is pressed again.
Sine function selected.
Use the Length
function to
calculate the hypotenuse
a
right-angled triangle with the Pythagorean theorem
given the
two other sides. The two sides are taken
from the
two values on the bottom of the stack.
{c = sqrt
(a^2 + b^2)}
Entering
4 & 3 (e.g., a 4:3 TV display ratio) for
the sides with the
hypotenuse
(TV diagonal) being 5.
The power of function (POW) takes
the penultimate (next to the last) value
on the
stack &
raises it to
the power
of the value on the bottom of the stack.
The example uses 2 to the 8th power = 256.
Use decimal points to key in the fractional
portion of a
number. This example is
2-1/32" for an X-axis preset.
Pressing ENTER then converts the 1/32"
to its decimal equivalent
for the X-axis.
For entering just a fraction, e.g., 1/32",
start the key sequence with a decimal
point.
The DPU-550 calculator can convert a decimal value
(e.g.,
0.1409) to a fraction plus any residual error.
OP PRV or OP NXT is pressed until the
Frac function is
displayed, then enter is pressed.
The fraction is 9/64" (0.140625")
with about a 0.0002" error.
| TOOL # |
TOOL SIZE DIAMETER (inch) |
EQUIVALENT FRACTION (inch) |
EQUIVALENT DECIMAL (inch) |
CORNER RADIUS (inch) |
| 1 | 1/16 | 1/16 | 0.0625 | 0.03125 |
| 2 | 2/16 | 1/8 | 0.125 | 0.0625 |
| 3 | 3/16 | 3/16 | 0.1875 | 0.09375 |
| 4 | 4/16 | 1/4 | 0.25 | 0.125 |
| 5 | 5/16 | 5/16 | 0.3125 | 0.15625 |
| 6 | 6/16 | 3/8 | 0.375 | 0.1875 |
| 7 | 7/16 | 7/16 | 0.4375 | 0.21875 |
| 8 | 8/16 | 1/2 | 0.5 | 0.25 |
| 9 | 9/16 | 9/16 | 0.5625 | 0.28125 |
| 10 | 10/16 | 5/8 | 0.625 | 0.3125 |
| 11 | 11/16 | 11/16 | 0.6875 | 0.34375 |
| 12 | 12/16 | 3/4 | 0.75 | 0.375 |
| 13 | 13/16 | 13/16 | 0.8125 | 0.40625 |
| 14 | 14/16 | 7/8 | 0.875 | 0.4375 |
| 15 | 15/16 | 15/16 | 0.9375 | 0.46875 |
| 16 | 16/16 | 1 | 1 | 0.5 |
The DPU-550 can hold 16
tool sizes vs. the DRO-350's, nine.
I use
Func 5
(tool offset define) to first specify
all the tool sizes where the Tool # is always the
numerator & 16 is
always the denominator of a fractional
size.
Tool #/16
of an inch. I find this a very easy
nomenclature to remember, though it is of course,
arbitrary.
I used 0 for the Z offsets. The DRO will allow up to
5 significant numbers
input after the decimal point.
Func 6
(tool offset use),
followed by a Tool #, turns ON
diameter compensation & selects the previously
defined tool.
By selecting a
predefined tool (Function 6 & tool #6
from the table) this graphic is temporarily
displayed.
Front, back, left, right cutting edges & tool #6
are
displayed. The
displays then return to positional values.
By pressing 4, the
left tool edge is selected
as temporarily indicated by this displayed
graphic.
The displays then return to their positional
values. This is the
original display mode.
The far left decimal of
the X-axis lights to
indicate that edge compensation for a 3/8" end mill is ON.
The latest software
upgrade
has changed the
edge compensation
display from symbolic to words.
Instrumented Mill,
Enclosure,
Zeroing,
Offset
Milling,
Mount,
Red Filter,
DPU-550
Daughterboard Upgrade
