Posts Tagged 3018 CNC
In the unlikely event you’re in Poughkeepsie this evening, I’ll be doing a talk on my Algorithmic Art for the Poughkeepsie ACM chapter, with a look at the HPGL and G-Code transforming math into motion:
The PDF of the “slides” lacks my patter, but the embedded linkies will carry you to the blog posts & background information:
See you there! [grin]
A dark ring of epoxy around the screw holds a shortened M3 brass insert in place:
As it turned out, the original recess left only a few threads for the M3 SHCS, so the much longer screw wobbulated alarmingly. I drilled out the threads, turned the knurls off the insert, shortened it a bit, masked the pretty knurls on the aluminum ring, then glopped the insert in place while the Sherline held the screw vertical:
While I was at it, I added a thin ring of foam rubber under the knurled ring to keep it from clacking against the upper bushing.
Now I can’t lose the hex wrench when I take the thing out for Show-n-Tell sessions …
I just caught George Bulliss in a weak moment. [grin]
You can say you knew me before …
Although the original Tektronix Circuit Computer had relentlessly monochrome scales, a dash of color added a festive holiday look:
Well, OK, that’s excessive.
The intent was to see how the pens behaved, with an eye toward accenting general-purpose circular slide rule scales with a few colored characters.
The green pen shows how I built the arrows by drawing a line through vertical arrow characters:
I like blue ink entirely too much, having used a blue pen as my daily writer for most of my adult life:
Red ink for “backwards” scales and suchlike would work well, even if it’s too vivid for the tick marks:
Those are all on unlaminated plain paper, with plenty of room for improvement.
Seeing as how I’d be doing all the “tool changes” manually, optimizing the plotting sequence would be mandatory: one pen change per color per deck!
Cheap 1 mm pens produce scratchy lines:
More expensive 0.5 mm Pilot Precise V5RT pens produce well-filled lines:
For reference, the cheap pens use a collet holder:
The Pilot V5RT pens use a custom holder:
A 3D printer really simplifies making things!
Although the bCNC GUI has conspicuous Run / Hold buttons, it’s easier to poke a physical switch when you really really need a pause in the action or have finished a (manual) tool change. Rather than the separate button box I built for the frameless MPCNC, I designed a chunky switch holder for the CNC 3018XL’s gantry plate:
The original 15 mm screws were just slightly too short, so those are 20 mm stainless SHCS with washers.
The switches come from a long-ago surplus deal and have internal green and red LEDs. Their transparent cap shows what might be white plastic underneath:
I think you could pry the cap off and tuck a printed legend inside, but appropriate coloration should suffice:
Making yellow from red and green LEDs always seems like magic; in these buttons, red + green produces a creamy white. Separately, the light looks like what you get from red & green LEDs.
The solid model shows off the recesses around the LED caps, making their tops flush with the surface to prevent inadvertent pokery:
The smaller square holes through the block may require a bit of filing, particularly in the slightly rounded corners common to 3D printing, to get a firm press fit on the switch body. The model now has slightly larger holes which may require a dab of epoxy.
A multi-pack of RepRap-style printer wiring produced the cable, intended for a stepper motor and complete with a 4-pin Dupont socket housing installed on one end. I chopped the housing down to three pins, tucked the fourth wire into a single-pin housing, and plugged them into the CAMtool V3.3 board:
The CAMtool schematic matches the default GRBL pinout, which comes as no surprise:
The color code, such as it is:
- Black = common
- Red = +5 V
- Green = Run / Start (to match the LED)
- Blue = Hold (because it’s the only color left)
The cable goes into 4 mm spiral wrap for protection & neatness, with the end hot-melt glued into the block:
The model now includes the wiring channel between the two switches, which is so obviously necessary I can’t imagine why I didn’t include it. The recess on the top edge clears the leadscrew sticking slightly out of the gantry plate.
The LEDs require ballast resistors: 120 Ω for red and 100 Ω for green, producing about 15 mA in each LED. Those are 1/8 W film resistors; I briefly considered SMD resistors, but came to my senses just in time.
A layer of black duct tape finishes the bottom sufficiently for my simple needs.
A doodle giving relevant dimensions and layouts:
I originally planned to mount the switches on the other gantry plate and sketched them accordingly, but (fortunately) realized the stepper motor was in the way before actually printing anything.
The OpenSCAD source code as a GitHub Gist:
It seems bCNC doesn’t update its “Restart Spindle” message after a tool change when you poke the green button (instead of the GUI button), but that’s definitely in the nature of fine tuning.
Yeah, a Portrait mode plot kinda squinches the annotations into the corners.
Rotating the coordinates to put the X axis along the length of the new platform is, of course, a simple matter of mathematics, but it’s just a whole lot easier to rearrange the hardware to make the answer come out right without fancy reprogramming.
The first step is to affix an MBI-style endstop switch to the left end of the gantry upright:
Shut down the Raspberry Pi and turn off the power!
At the CAMtool V3.3 board:
- Swap the X and Y motor cables
- Move the former Y endstop switch to the X axis input
- Plug the new endstop switch into the Y axis input, routing its cable across the top of the gantry
- Abandon the former X axis switch and its cable in place
Modify the GRBL configuration:
$3=4– +Y home @ gantry left, +X home @ frame front
$130=338– X axis travel along new frame
$131=299– Y axis travel across gantry
Tweak the bCNC config similarly, if that’s what you’re into.
Verify the new home position!
I reset the G54 coordinate system to put XY = 0 at the (new!) center of the platform, redefined G28 as the “park” position at the (new!) home pulloff position, and set G30 as the “tool change” position at the -X -Y (front right) corner of the platform, with bCNC icons to simplify moving to those points.
And then It Just Worked™:
The Spirograph patterns definitely look better in landscape mode:
I eventually turned the whole machine 90° clockwise to align the axes with the monitor, because I couldn’t handle having the X axis move front-to-back on the table and left-to-right on the screen.