Lathe Chuck Table

anfänger
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2 weeks 5 days ago #350209 by anfänger

Lathe Chuck Table was created by anfänger

While getting my linuxcnc rettrofit lathe running again after moving shop. I wanted to turn close to the spindle. But my soft limits protect me from doing this. Of course you can ignore limits, but I was thinking about a "chuck table" with some more details on it like:
diameter, max rpm, z_limit, number of jaws and weight.

My concept so far...

Files:

chucks.json – Stores your database of chucks, limits, and parameters.
- current_chuck.json – Automatically created/updated to persist the currently active chuck across reboots.
  - chuck_manager.py – The Python handler script linked to your custom tab.
  Widgets:
  
  Widget TypeObject Name (objectName)Description
  QComboBoxchuck ComboBoxDropdown showing line numbers and chuck names (synced with the table)
  QPushButton activateChuckBtn confirmation button to apply limits and save state.
  QTableWidget chuckTable 7-column interactive table to view, add, edit, and delete chuck profiles.
  QPushButton addChuckBtn Button to insert a new blank row into the table.
  QPushButton saveTableBtn Button to save table modifications permanently back to chucks.json.
  QPushButton deleteChuckBtn Button to remove the currently selected row.
  QLabel lblMaxRpm Displays the maximum allowed spindle RPM for the selected chuck.
  QLabel lblZLimit Displays the active Z-axis soft limit (ini.z.min_limit).
  QLabel lblDiameter Displays the chuck body diameter.
  QLabel lblJaws Displays the number of jaws.
  QLabel lblJawsDisplays the number of jaws.QLabellbl Weight Displays the chuck weight in kilograms.
  
  At the moment I have four chucks:
  
  {
  "Standard 3-Jaw Chuck (250mm)": {
    "max_rpm": 2400,
    "z_limit": -45.0,
    "diameter": 250,
    "jaws": 3,
    "weight_kg": 25.5
  },
  "centric 4-jaw Chuck (160mm)": {
    "max_rpm": 3000,
    "z_limit": -60.0,
    "diameter": 160,
  "jaws": 4,
  "weight_kg": 4.2
  },
  "Heavy 4-jaw Chuck (400mm)": {
    "max_rpm": 800,
    "z_limit": -30.0,
    "diameter": 400,
    "jaws": 4,
    "weight_kg": 40.0
  }
  "Power chuck (250mm)": {
    "max_rpm": 2400,
    "z_limit": -45.0,
    "diameter": 250,
    "jaws": 3,
    "weight_kg": 50.0
  }
  "Spindle": {
    "max_rpm": 3000,
    "z_limit": -110.0,
    "diameter": 60,
    "jaws": 0,
    "weight_kg": 0.0
  }
  }
  
  Next is writing and debugging the script.

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anfänger
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2 weeks 4 days ago #350217 by anfänger

Replied by anfänger on topic Lathe Chuck Table

I Cheated and used Claude in the end.If anyone wants to use soothing like this also here is a manual and the necessary files

OverviewThis UserTab lets a lathe operator pick the mounted chuck from a list and enforce that chuck's limits in HAL: a maximum spindle speed and a Z soft limit. It is built for Probe Basic Lathe (QtPyVCP) and tested on a Mesa 7i97 machine, but nothing in it is hardware-specific.

Chuck table: add, edit, delete and save chucks (name, max RPM, Z limit, diameter, jaws, weight). Data lives in

Code:

chucks.json

in the config directory.
Dropdown + info line: select a chuck and see its data at a glance. The active chuck is highlighted green in the table.
Activation with confirmation: one button writes both limits to HAL after a Yes/No dialog. If

Code:

halcmd

fails, the chuck is not marked active and an error dialog appears.
Plausibility check: rejects RPM <= 0, RPM above

Code:

[SPINDLE_0] MAX_FORWARD_VELOCITY

, Z at or above

Code:

[AXIS_Z] MAX_LIMIT

, and optionally Z below a configurable floor.
Persistence: the active chuck is stored in

Code:

current_chuck.json

and re-applied automatically at startup, so the display and HAL never disagree after a restart.
Fail-safe RPM clamp: the spindle clamp is a HAL component with a conservative default, so the low limit holds even if the GUI never starts.

Requirements and file layoutYou need LinuxCNC 2.9 or newer (for the writable

Code:

ini.<axis>.min_limit

HAL pins) and Probe Basic Lathe with UserTab support. Check the Z pin exists with

Code:

halcmd show pin ini.z.min_limit

Code:

~/linuxcnc/configs/<your-config>/
├── <your-machine>.ini
├── <your-main>.hal              # gets the RPM clamp (Step 1)
├── chucks.json                  # chuck database (created on first save)
├── current_chuck.json           # active chuck (written by the tab)
└── user_tabs/
    └── chuck_manager/
        ├── chuck_manager.py     # logic (class UserTab)
        └── chuck_manager.ui     # Qt Designer layout

The folder name,

Code:

.py

name and

Code:

.ui

name must match. The JSON files live in the config directory, not in the tab folder; the tab finds it through the

Code:

CONFIG_DIR

environment variable that LinuxCNC sets.Step 1: HALLinuxCNC has no writable HAL pin for the maximum spindle speed, so a

Code:

limit1

component is inserted into the speed command chain. The Z soft limit needs no HAL change: the tab writes the existing

Code:

ini.z.min_limit

pin.Find the line in your main HAL file that takes

Code:

spindle.0.speed-out-abs

(or

Code:

speed-out

) to your output stage. Insert the clamp between them. Example for a chain that ends in a

Code:

gearchange

component:

Code:

# --- load (with your other loadrt lines) ---
loadrt limit1 names=chuck-rpm-limit

# --- thread: AFTER motion-controller, BEFORE whatever reads the speed,
#     and BEFORE hm2_xxx.write ---
addf chuck-rpm-limit servo-thread

# --- wiring ---
# before:  net spindle-vel-cmd-rpm-abs spindle.0.speed-out-abs => gearchange.0.speed-in
net spindle-vel-cmd-rpm-abs  spindle.0.speed-out-abs => chuck-rpm-limit.in
net spindle-rpm-limited      chuck-rpm-limit.out     => gearchange.0.speed-in

# --- fail-safe default until the GUI activates a chuck ---
setp chuck-rpm-limit.min 0
setp chuck-rpm-limit.max 500     # RPM of your weakest chuck

Without a gearbox, connect

Code:

chuck-rpm-limit.out

to whatever

Code:

speed-out-abs

fed before (a PWM generator, a scale component, a VFD pin). The clamp sits after the spindle override and before the gearbox, so it limits the real chuck speed and the override knob cannot push past it.The pins are named

Code:

min

and

Code:

max

, without underscore. The

Code:

limit1

source declares them as

Code:

min_

Code:

max_

, but

Code:

halcompile

strips the trailing underscore.

Code:

setp chuck-rpm-limit.max_

aborts LinuxCNC startup with "parameter or pin not found".After a restart, check with

Code:

halcmd show pin chuck-rpm-limit

.Step 2: install the UserTab files

Create

Code:

user_tabs/chuck_manager/

in your config directory and copy

Code:

chuck_manager.py

and

Code:

chuck_manager.ui

into it.
Point Probe Basic at the folder in your INI, if it is not there yet:

Code:

[DISPLAY] USER_TABS_PATH = user_tabs/
Optionally copy the example

Code:

chucks.json

into the config directory. Without it the table starts empty and the file is created on the first "Save Changes".

The database is one object per chuck, keyed by its name:

Code:

{
    "3-Jaw 160": {
        "max_rpm": 3000,
        "z_limit": 5.0,
        "diameter": 160,
        "jaws": 3,
        "weight_kg": 12.0
    },
    "4-Jaw 250 Heavy": {
        "max_rpm": 1200,
        "z_limit": 25.0,
        "diameter": 250,
        "jaws": 4,
        "weight_kg": 38.0
    }
}

The values in the example are placeholders. Take max RPM from the chuck's rating plate or datasheet, and measure the Z limit on your machine. Z is in machine coordinates, so its sign depends on your machine's travel and home position.Step 3: configure and testFour constants at the top of

Code:

chuck_manager.py

control the behaviour:ConstantDefaultMeaning

Code:

AUTO_APPLY_ON_START

Code:

True

Re-apply the saved chuck to HAL at startup without a dialog.

Code:

False

only logs a warning and marks nothing active.

Code:

HAL_PIN_Z_MIN

Code:

"ini.z.min_limit"

Pin for the Z soft limit.

Code:

HAL_PIN_RPM_MAX

Code:

"chuck-rpm-limit.max"

Pin for the RPM clamp from Step 1.

Code:

Z_LIMIT_FLOOR

Code:

None

Lowest Z limit a chuck may have, in mm.

Code:

None

disables the check. Set it a few tenths of a mm inside the physical limit switch once you have measured it.The chuck limit can only make the machine more restrictive. LinuxCNC still enforces

Code:

[JOINT_n] MIN_LIMIT

and

Code:

[AXIS_Z] MIN_LIMIT

from the INI, so a chuck Z limit below them has no effect. Set the INI values to the real travel and let the chucks narrow it.Test before cutting:

Start LinuxCNC and open the tab. The dropdown and the table must show your chucks.
Activate a chuck. Then run

Code:

halcmd show pin ini.z.min_limit chuck-rpm-limit

and check both values arrived.
In MDI, command an

Code:

S

value above the chuck's limit.

Code:

chuck-rpm-limit.out

must stay at the limit while

Code:

.in

shows the commanded value.
Jog Z slowly toward the chuck. Motion must stop at the chuck's Z limit.
Restart LinuxCNC. The same chuck must be green again and step 2 must show the same values.

How it worksEditing and activating are separate: changing the table never touches HAL, only "Activate Chuck" does.

Edit: type into the table, use "Add Chuck" / "Remove Chuck", then "Save Changes". Save validates all numbers and rewrites

Code:

chucks.json

. A row with invalid data aborts the save with a message.
Select: pick a chuck in the dropdown or click its row. The info line shows max RPM, Z limit, diameter, jaws and weight. Nothing is applied yet.
Activate: "Activate Chuck" runs this sequence:
1. Plausibility check against the INI and
  
  Code:
  
  Z_LIMIT_FLOOR
  
  . On failure: error dialog, nothing applied.
2. Confirmation dialog showing the two limits.
3. Code:
  
  halcmd setp
  
  for the Z pin, then the RPM pin. Each return code is checked.
4. Only if both succeeded: green row and
  
  Code:
  
  current_chuck.json
  
  written.
Startup: the tab loads

Code:

chucks.json

, selects the saved chuck and, with

Code:

AUTO_APPLY_ON_START

, re-runs steps 1, 3 and 4 without the dialog.

The dropdown items carry the chuck name as item data. Matching is exact, so "Collet" never selects "Collet ER32".Safety notes and limitationsThis is a software convenience layer, not a safety function. It reduces operator error; it does not replace hardware protection.

It clamps the command, not the spindle. A drive fault, a wrong analog scale or a runaway VFD can still overspeed the chuck. Real overspeed protection needs independent monitoring of the encoder speed, or a drive-side speed limit.
The clamp is silent.

Code:

S2000

with a 1500 RPM chuck runs at 1500 RPM without a warning. Surface speed and feed per rev change accordingly.
The operator must select the right chuck. The system cannot detect which chuck is mounted.
The fail-safe default only helps if it is low. Set

Code:

chuck-rpm-limit.max

in the HAL file to your weakest chuck.
Limits apply until the next activation or restart. Changing a chuck's row and saving does not re-apply it; activate again.
Keep hardware limit switches and E-stop in the drive enable chain. If LinuxCNC or the GUI hangs, only hardware stops the machine.

Use at your own risk, and test every chuck with a low commanded speed first.Pitfalls we hitThese cost the most time during development and apply to any QtPyVCP tab.SymptomCauseFixDropdown stays empty although the table loadsPyQt gives

Code:

QComboBox

Code:

__len__()

, so an empty combo box is falsy.

Code:

if not self.combo: return

returns before the first item is added.Test widgets with

Code:

is None

Code:

is not None

, never by truthiness.

Code:

QLayout

behaves the same.LinuxCNC aborts: "parameter or pin 'chuck-rpm-limit.min_' not found"

Code:

halcompile

strips a trailing underscore from pin names.Use

Code:

.min

Code:

.max

.Activation seems to work but the spindle is not limited

Code:

motion.spindle-max-speed

does not exist;

Code:

os.system()

ignored the error.Clamp in HAL (Step 1) and check the

Code:

halcmd

return code.A button does nothingIts objectName in the

Code:

.ui

(e.g.

Code:

saveTableBtn_2

after copy/paste) differs from the name in the code.Keep the names in the table below.

Code:

halcmd setp

on a LED pin failsQtPyVCP turns

Code:

_

in a widget name into

Code:

-

in the pin name: widget

Code:

LEDIN_00

becomes

Code:

qtpyvcp.LEDIN-00.on

.Look up pin names with

Code:

halcmd show pin qtpyvcp

.Object names the code expects in the

Code:

.ui

:WidgetobjectNameQComboBox

Code:

chuckComboBox

QPushButton

Code:

activateChuckBtn

Code:

saveTableBtn

Code:

addChuckBtn

Code:

deleteChuckBtn

QTableWidget

Code:

chuckTable

QLabel

Code:

lblMaxRpm

Code:

lblZLimit

Code:

lblDiameter

Code:

lblJaws

Code:

lblWeight

Code:

chuckComboBox

is missing from the

Code:

.ui

, the code creates one and inserts it into the layout named

Code:

horizontalLayout

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tommylight
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2 weeks 2 days ago #350269 by tommylight

Replied by tommylight on topic Lathe Chuck Table

That is a loooong post, thank you.

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anfänger
Topic Author
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2 weeks 2 days ago #350280 by anfänger

Replied by anfänger on topic Lathe Chuck Table

I hope this way it might help someone if he wants the same feature. Or improve it.

I think it might be interesting to see what other have as cutom features, so one knows whats possible and might be handy.

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