Sorry, I've been really busy and it took me a while to get a chance to
pull up the docs on Google for review.
My suggestions:
* Twist the power lines going to the stepper motors. The stepper
drivers are basically small switching power supplies and they spew EMI
like nobody's business. I tightly twist the two wires that go to a
coil, then loosely twist the two pairs together to form a single cable.
You can do this after the fact if you remove the crimp contacts from one
end of the cable. I typically use an electric drill to tightly twist
the individual pairs, then do the loose twist by hand.
* Use twisted pair wiring for all the limit switches as well. You can
either make this yourself (as above) or I'll typically just pull pairs
from Ethernet patch cords, which gives you four different color-coded pairs.
* Beef up the pull-up resistors on your limit switches. The CRAMPS
board has built-in 10K pull-ups, but that's mostly just to keep the
lines from floating. If you're running long cables you'll want
something much smaller. The value to use is a complex trade-off, but a
good target current when the switch is "closed" would be similar to what
you'd use to drive an LED (eg: about 5 to 20 mA), which means a resistor
value between 470 ohm and 1K.
I'll try to take a photo of how I prep stepper motor wires and forward
it to the list, but here's a video of basically what I do. Make sure to
keep some tension on the wire while you're twisting it:
https://www.youtube.com/watch?v=aMUFZZZR7d0
On 8/7/2020 7:41 PM, Mason M wrote:
Hi All,
We are continuing to experience issues that we believe are relating to
electrical noise on our BCNC. We realize that our machine is slightly
unorthodox, so we have a folder link with wiring diagrams and assembly
videos to help you help us. We are in the process of testing the machine.
We had noise issues from the spindle power lines (which are not shielded),
but we removed them from cable bundles and that seemed to remove that
issue. We are able to run files successfully in the air, but we receive
limit switch errors when we begin cutting through material. our system
seems to be rigid enough to not be the problem and our motors are strong
enough that human force doesn't stop the system from running. We rewired
our spndle power supply to have a seperate power cable than our primary
power supply as well. We have tried adding debouncing code to our Hal file,
but this caused Machinekit to not sense our limit switches (we couldn't
complete a homing sequence).
folder link
https://drive.google.com/drive/folders/1-BqfZynZqA0JI15VOP9ZtjejnNKbGmoU?usp=sharing
BCNC tour
https://www.youtube.com/watch?v=lBFH62Z3-sc
limit switch/motor wiring
https://www.youtube.com/watch?v=_3WAHGZgA68
spindle wiring
https://www.youtube.com/watch?v=bzvBb8_dZvA
power supply wiring
https://www.youtube.com/watch?v=ADKeLWRwG3Y
On Saturday, July 25, 2020 at 12:41:04 PM UTC-4 [email protected] wrote:
Hi,
You should not make a loop of wire for the ground (gnd from switch to
switch to switch is not good).
You should have one wire for the switch input, and one wire for the
signal ground in your switch cabling.
All of the grounds from the various switches should meet at one point on
the I/O terminal signal ground point.
If possible, you should use shielded cabling. Tie all of the shields
(bare drain wires) at the same end near the inputs, but then connect them
to an *earth* ground, not the signal ground of the input. An example of an
earth ground in a system would be the green wire (or green with yellow
stripe) of a power supply, not the V- of the power supply.
2-wire 22 gauge "sound and security" from Home Depot, etc. will
typically be stranded wire with a drain wire and shielding. This would be
a good choice as it has all three of the conductors that you want. Red for
signal, black for signal ground and bare drain for shielding.
Jeff
On Friday, July 24, 2020 at 10:40:34 AM UTC-7, Frederic RIBLE wrote:
Could you describe the wiring of these switches on your machine?
I am wondering if you have two wires per switch going up to the logic
board, or only one, with ground sharing.
On 2020-07-21 19:39, Mason Millner wrote:
We are using momentary hinge limit switches (
https://www.amazon.com/URBESTAC-Momentary-Hinge-Roller-Switches/dp/B00MFRMFS6/ref=sr_1_3?ie=UTF8&qid=1535482225&sr=8-3&keywords=limit+switch)
and our spindle (
https://www.amazon.com/Koolertron-Spindle-Milling-Converter-Engraving/dp/B074XTKJTJ/ref=sr_1_9?ie=UTF8&qid=1535482152&sr=8-9&keywords=spindle+cnc)
is operating from its own power supply.
The machine is fairly rigid. No limit switches are triggered from until
material is being cut. The bamboo does vibrate quite a bit as it spans 65"
supported only on the ends, but we have been able to successfully cut this
dimension previously (on a 3-axis Techno machine).
On Tuesday, July 21, 2020 at 1:12:01 PM UTC-4 [email protected] wrote:
You didnt mention what type of limit switches you're using or how your
spindle works. The Y axis itself shouldn't be under any special stress
while cutting but the spindle generally takes a hard hit as soon as a tool
enters the cut. Is the spindle motor powered by the same power supply your
switches are on? Supply could be dropping low. Is the machine not ridgid
and vibration tripping the switches?
On Tue, Jul 21, 2020, 8:54 AM Mason Millner <[email protected]> wrote:
Hi All,
We are developing a 4-axis CNC to mill bamboo poles and are currently
running tests in just three axis (x, y, z). We can dry-run g-code files
successfully, however we receive limit switch errors (primarily on joint 1)
when we begin cutting material. We suspect that the error is occuring in
the y-axis and that possibly our drivers are causing a problem (either they
are too small or not tuned adequately).. It is difficult to tell what is
going on and how the machine is configured from the information given.
We have the z-axis running on the long x-axis, running on two shorter
dual y-axes.
The axis shaft is a ½” (12.7mm) , also the motor shaft is ¼” (6.35mm).
we are using polyurethane insert couplers (these have regularly been coming
loose though).
The motors are NEMA 23s with 3A rating/phase controlled by Pololu
TB67S249FTG drivers on a Cramps 2.2 cape on the Beaglebone Black. The
drivers have a current limit of 1.6A and are further limited to %90 for
safety. The Current limit for the board and drivers are defiantly a bottle
neck, but the motors have enough power to operate. [Could this be the
problem?]
Any help or recommendations would be greatly appreciated. If more
information is needed please let me know. I'm fairly new to the machine
development side of this project. Thanks.
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