IndyMill

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About

Somewhere in 2022 I decided I wanted a CNC machine. After lengthy consideration the many options I decided to build an IndyMill.

Project website: https://indystry.cc/indymill/

The building volume with my current limit switch configuration is about (X * Y * Z): 340 * 330 * 100mm

Ordering

TBD

Building

TBD

Setting up GRBL

🛑 Dies might be a bad idea, since GRBL has been abandoned since 2019…


Installing GRBL

  1. Install Arduino IDE 1.x (not 2.x!)
  2. Setup board type
  3. Setup serial/USB-connection (you might want to add your user to group dialout to allow accessing /dev/ttyUSB0…)
  4. Download as .zip: https://github.com/gnea/grbl
  5. Extract zip
  6. Open Arduino IDE

Sketch → Library Import as .ZIP → select grbl-master/grbl

File → Examples → grbl → grblUpload → →

Testing Connection

  1. Download CNCjs-AppImage: https://cnc.js.org/
  2. Launch it, set Connection parameters (device / speed)
  3. Enter something like this:
  • Get current settings with

$$ 

CNCjs 1.10.3 [Grbl]
Connected to /dev/ttyUSB0 with a baud rate of 115200
Grbl 1.1h ['$' for help]
client> $$
$0=10 (Step pulse time, microseconds)
$1=25 (Step idle delay, milliseconds)
$2=0 (Step pulse invert, mask)
$3=0 (Step direction invert, mask)
$4=0 (Invert step enable pin, boolean)
$5=0 (Invert limit pins, boolean)
[…]
$132=200.000 (Z-axis maximum travel, millimeters)
ok

GRBL-Settings

Setting step width

  • Change settings as described in Nikodem's manual for stepwidth:
$1=255
ok
$100=640
ok
$101=640
ok
$102=400
ok
$110=1000
ok
$111=1000
ok
$112=1000
ok
$120=80
ok
$121=80
ok
$122=80
ok

I changed above to meet my (micro)-stepping-setup (DIP #2 of my TB6600, micro-step 8, Pulse/Rev 1600) and ball-screws. 

$100=320
$101=320
$102=400

Hint: Make sure you reset the machine after changing values, my GRBL acted strangely when not.

Setting directions

My settings (preliminary)

CNCjs 1.10.3 [Grbl]
Connected to /dev/ttyACM0 with a baud rate of 115200
Grbl 1.1h ['$' for help]
client> $$
[MSG:'$H'|'$X' to unlock]
$0=10 (Step pulse time, microseconds)
$1=25 (Step idle delay, milliseconds)
$2=0 (Step pulse invert, mask)
$3=5 (Step direction invert, mask)
$4=0 (Invert step enable pin, boolean)
$5=1 (Invert limit pins, boolean)
$6=0 (Invert probe pin, boolean)
$10=1 (Status report options, mask)
$11=0.010 (Junction deviation, millimeters)
$12=0.002 (Arc tolerance, millimeters)
$13=0 (Report in inches, boolean)
$20=0 (Soft limits enable, boolean)
$21=0 (Hard limits enable, boolean)
$22=1 (Homing cycle enable, boolean)
$23=0 (Homing direction invert, mask)
$24=25.000 (Homing locate feed rate, mm/min)
$25=500.000 (Homing search seek rate, mm/min)
$26=250 (Homing switch debounce delay, milliseconds)
$27=2000.000 (Homing switch pull-off distance, millimeters)
$30=1000 (Maximum spindle speed, RPM)
$31=0 (Minimum spindle speed, RPM)
$32=0 (Laser-mode enable, boolean)
$100=320.000 (X-axis travel resolution, step/mm)
$101=320.000 (Y-axis travel resolution, step/mm)
$102=400.000 (Z-axis travel resolution, step/mm)
$110=500.000 (X-axis maximum rate, mm/min)
$111=500.000 (Y-axis maximum rate, mm/min)
$112=500.000 (Z-axis maximum rate, mm/min)
$120=23.000 (X-axis acceleration, mm/sec^2)
$121=23.000 (Y-axis acceleration, mm/sec^2)
$122=10.000 (Z-axis acceleration, mm/sec^2)
$130=200.000 (X-axis maximum travel, millimeters)
$131=200.000 (Y-axis maximum travel, millimeters)
$132=200.000 (Z-axis maximum travel, millimeters)
ok
>

Enabling Limit-Switches

Testing

Try this: 

$H

Z-Axis-Probe

Work with CAD- and CAM-Software

Creating GCODE

JSCut.org

💡 Tipps:
  • If you're creating your own SVG, make sure the pockets are "objects", meaning "areas", not paths. Also use only infill, no stroke!
  • Adding tabs with Inkscape:



ℹ️ JSCut is awesome, but has downsides:
  • Can't create tabs (or won't work at the time of testing)
  • Won't cut open-ended paths, only closed paths. Will close path if open with strange results
  • jscut ignores stroke and follows the actual path not the visible dimensions (Say you (using Inkscape)have a square 100x100mm and stroke 10mm, then jscut will cut 5/5 to 5/95 to 95/95 to 95/5! → Design in Inkscape W/O STROKE (only fill)!

More about JSCut: https://www.youtube.com/watch?v=dVgf0Hf91vA

  • Create SVG with Inkscape
  • Launch https://jscut.org/
  • Open SVG
  • Set units correctly (in my case mm)
  • Set speeds and diameters, material strength and so on...
  • Select object
  • Generate operation
  • Preview
  • Repeat operation-generation for all your objects
  • Download
  • Hope for the best :)

PyCAM

Still needs python 2.7 and seems to abandoned since 2019.

Blender CAM

NOT TESTED YET!

https://blendercam.com/

gcad3d

NOT TESTED YET!

https://www.gcad3d.org/

Other Software (yet to test)

krabzcam

NOT TESTED YET! Looks much like jscut, but a bit more sophisticated.

FreeCAD

See also

Do:

  • Make sure you played with Inkscape-SVGs and jsCut enough to understand the basics, otherwise handling (the much more complex FreeCAD) will be very frustrating…
  • Launch FreeCAD
  • Make sure you have already created proper solids (see above)!
  • Make sure units are ok:

Preferences → General → Unit System → Metric small parts & CNC

  • Create Job:
    1. Select solid 2. Choose Path-Workbench 3. Create Job
  • Choose solid:
    Freecad solid choose gcode ksnip 2024-02-15 13-35-40.png
  • Set

Output to grbl

  • Create tools as needed:

Path → Toolbit Library Editor

  • Remove default tool
  • Choose Tool, set # to 1
  • Set H/V speed
  • TBD TBD TBD


Converting STL to solids in FreeCAD

See also: https://forum.freecad.org/viewtopic.php?t=14136

  1. Open the STL file
  2. Select object

Part → Create shape from mesh

  1. Select new object

Part → Converte to solid

Lessons Learned

General

  • Origin is in front-left corner, increasing up (Z), right (X) and back (Y)
  • Origin of SVG-designs is usually top-left corner, increasing right (X), decreasing towards you (Y)
  • Double-Check all settings before first use (most importantly step width, end switches)
  • Don't think it's as easy as 3D-Printing, where the slicer will do all the work for you!
  • You have to make decisions while creating the GCODE or even the design:
    • Which pockets should be done first?
    • Which pockets should be done last?
    • Will any operation make your part move or break?
    • Which speed is best?
    • What kind of operation do you need? Pocket? Engrave?
    • Which milling bits will you use?
  • If you don't use hard limits ($21=1), then GRBL will jog happily ahead, even if the endswitch has opened.
    • At least homing ($H) works without hard limits, since it retracts a bit to close the switches again.
    • Hard limits comes in very handy if your testing your limit switches!

Cutting Speeds

🚧 This is very much likely to change - I'm still learning every day!
material challenges tool diameter (mm) speed (mm/min) attack (mm) rpm spindle cooling notes Links
Plexiglas (PMMA) melts at 160°C (even earlier than your printer's PLA or PETG). These are the key challenges:
  • Make sure the chips leave the flute so they can't friction weld
  • Finding the highest cutting volume (diameter*speed*attack) while keeping the tool as cool as possible

Methods to keep cool: reduce speed (less than 500mm/min) and attack (0.5-1.0mm)

single-flute 2.0 300 1.0 10,000 500W china none yet to test! Great tipps: https://www.cnc-step.de/plexiglas-fraesen/
material challenge tool diameter speed attack rpm spindle cooling comments
material challenge tool diameter speed attack rpm spindle cooling comments

Troubleshooting

10mm are not 10mm

Check $100, $101, $102, your driver's micro-step-settings and your ballscrews.

CNCjs-AppImage won't run on Lenovo T60

The T60 is kinda 32bit, that might be the catch.

Try installing with npm: https://www.npmjs.com/package/cncjs

Run it: 

heiko@T60-1951-debian:~$ cncjs
2024-02-18T15:29:24.819Z - info init Loading configuration from "/home/heiko/.cncrc"
(node:20609) Warning: Accessing non-existent property 'padLevels' of module exports inside circular dependency
(Use node --trace-warnings ... to show where the warning was created)
2024-02-18T15:29:25.386Z - info init Starting the server at http://127.0.1.1:8000

Use it: 

http://127.0.1.1:8000

Cut freezes

The Problem

The cutting, or, to be more precise, the motion stops. The grbl console in CNCjs shows some garbled messages, mostly one "o" or "k". Status is then idle, and can be continued by pausing and restarting the cut. When using UGS, it shows a message about a stream (serial connection) can't be established. The problem is not 100% reproducible - sometimes the machine runs flawless for 15 minutes (my test cut), and sometimes it stalls every 10 seconds.

The Analysis

  • Similar problems from the net:
  • Try another G-Code-Sender (like UGS instead if CNCjs) (UGS is more chatty when encountering problems than CNCjs)
  • Disable spindle
  • Disconnect limit-switches (and turn $5 off accordingly (set to 0 if using normally-closed (as you should be))
  • Check stepper frequencies (vs. micro-stepping-settings) - can your Arduino UNO produce the required frequencies?
  • Disable steppers (shutting off power supply)
  • Disable WiFi
  • Try another, short, shielded USB-cable
  • Try an USB-isolator, I used some 18€ item from amazon, and it seems to worsen the problem, maybe this is just snakeoil
  • Unplugging the arduino power adaptor seems to help a little
  • Use another computer
    • Lenovo M72e: no luck
    • Lenovo T60: no luck
    • Apple MacBook Pro 13" (plug the power adaptor into Apple MacBook Pro 13", not the docking station → seems to work most of time)

I think it's safe to say, that the Arduino UNO (please note, that mine is a cheap-8€-knock-off from china) has a badly designed serial interface with shielding/grounding issues.

The Workaround

None of the above brought up a viable solution.

This is what works for me as a workaround:

  • Keep humidity low and temperature on a comfy level
  • Unplug the arduino power supply, let the PC power the UNO
  • Use MacBook Pro 13" with NO power supply attached (or maybe plugged in the MBP, not the docking station)

The Solution

Dump the crappy not-genuine UNO board and get a genuine one. Works like a charm.

Footer

  • Links
    • TBD
  • Footnotes:
  1. ↑ https://forum.makerforums.info/t/how-do-i-invert-the-y-and-z-axis-of-my-grbl-cnc-arduino-uno/80114
  2. ↑ https://www.diymachining.com/downloads/GRBL_Settings_Pocket_Guide_Rev_B.pdf
  3. ↑ https://linuxcnc.org/docs/html/user/user-concepts.html#_machine_configurations
  4. ↑ https://www.cnc4fun.com/wp-content/uploads/2019/12/Grbl-Commands-v1.1-2.pdf
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