Kaliper

Convert your 3D printer into a metrology VMM.

A vision measuring machine (VMM) measures dimensions using high definition camera(s), lasers, and other technology. Kaliper provides the toolkit for turning your FDM 3D printer into an affordable tabletop inspection machine.

Concept drawing: a camera unit on a printer toolhead, and what the camera sees Side view of a camera unit clipped beside the printer's toolhead, its lens above the nozzle tip, looking down at a part on a glowing backlight stage. Detail A is a simulated camera view of the part: a dark silhouette with a bright hole, edge points marked along the hole and the part's edges, and a fitted circle labelled 12.70 mm, 0.500 in. nozzle tip camera unit A part backlight stage DETAIL A · camera view Ø 12.70 mm · 0.500 in
The lens sits above the nozzle tip. Detail A is a simulated camera view with edge points and a fitted circle.

Inspection report

Sample part · placeholder values

Simulated Uncalibrated

  • Hole A Ønominal 12.70 mm

    12.68 mm ±U0.499 in

    Pass

  • Slot B widthnominal 6.35 mm

    6.61 mm ±U0.260 in

    Fail

  • Edge C to hole Anominal 25.40 mm

    25.47 mm ±U1.003 in

    Indeterminate

U is the expanded uncertainty. This sample shows it as ±U; a real report gives its value.

How it works

Three simple steps; always reversible.

  1. ConceptBattery or wired power, with Wi-Fi.

    Step 1

    Mount the camera unit

    A unit with Wi-Fi clips onto the toolhead, its lens above the nozzle tip. It runs on a battery or, as an option, on wired power. A laser sensor on the unit reads the part's height. A printed adapter for each machine lets it move between printers.

  2. .gcode
    Stops over each feature; no heating, no extrusion.

    Step 2

    Run a motion-only print file

    Kaliper turns your measurement plan into an ordinary print file with no heating or extrusion. The printer just moves; no plugins or firmware changes.

  3. HTML, CSV and JSON.

    Step 3

    Get an honest report

    Measurements in inches and millimetres, each with its uncertainty and a pass, fail or indeterminate decision, plus the calibration label.

Measurement accuracy

Accuracy is published per machine, only from measured calibration data and with its conditions, and every report carries its calibration label.

How a decision is made Three results drawn as bars against a tolerance zone between the lower and upper limits. A bar fully inside the zone is a pass. A bar fully outside is a fail. A bar that crosses a limit is indeterminate. LSL USL tolerance zone Pass Fail Indeterminate
Each bar is a result ± U, where U is the expanded uncertainty. Indeterminate is never shown as a pass.

Measuring moves your machine. Heaters stay off during measuring, the part is fixed to the bed, and you stay at the printer until the job ends.

  • Honest results

    Every result carries its uncertainty and a guard-banded decision. Lengths are normalised to 20 °C, and each report states the temperatures. Reports flag a tolerance too tight for the measurement: a tolerance-to-uncertainty ratio below 4:1.

  • A calibration label on every report

    Each report says Verified (calibrated YYYY-MM-DD) or Uncalibrated.

  • Reports you can re-check

    Every report is rebuilt from its saved log and images alone, and altered inputs are refused.

  • One unit, several printers

    The camera unit runs on battery or, optionally, on wired power, and moves between printers, with a printed adapter for each machine.

What it measures

  • HolesDiameter and centre position
  • SlotsWidth, length and centre
  • Edges and widthsStraight edges and the width between them
  • DistancesBetween features: hole to hole, edge to hole
  • 2D GD&TA small subset of checks, such as true position
  • ThicknessFrom side views; comes later (M8)

Backlight

The part sits on a lit glass stage, so its outline shows as a crisp silhouette.

ConceptSide view, and the simulated camera view.

Top light

A diffuse ring light shows features that don't go through, such as pockets, and parts measured in place.

ConceptSide view, and the simulated camera view.

Supported machines

MachineHow Kaliper drives itStatus
Elegoo Centauri Carbon Motion-only print files Reference printerMotion test passed (2026-10-11)
Marlin printers (Prusa, Ender and similar) Motion-only print files Planned · M3
Klipper printers Print files; live control later PlannedLive mode at M9
Desktop mills — Later · M11
Bambu Lab printers — Not supportedFirmware-validated job files

Roadmap

Milestones in order, with no dates. Each one is done when its tests pass or its results are measured.

  1. M0–M0bFoundationsDone

    Repository, licences and CI; the camera-first plan; a motion test on the Centauri Carbon.

  2. Simulation

  3. M1Image simulatorDone

    Camera model, rendered images, edge detection, 2D fits and camera calibration, tested in simulation.

  4. M2Plans and reportsWe are here

    Plans in inches and mm, the uncertainty budget, guard-banded decisions, and reports in HTML, CSV and JSON.

  5. M3Print-file generation

    Measurement jobs for the Centauri Carbon and Marlin, run on a virtual printer, with the session-log format.

  6. Hardware

  7. M4Camera unit

    The upgrade-ready camera unit with its height sensor, and the first runs on the Centauri Carbon.

  8. M5Calibration and published accuracy

    Measured accuracy for the Centauri Carbon, with its conditions. Camera-only kits follow once the required certifications are done.

  9. Later

  10. M6Scales

    Scale simulation, reader firmware and scales on the Centauri Carbon: the Camera + Scale tier, with across-bed results measured and published.

  11. M7CAD import

    Plans from a slicer 3MF, then from STEP and STL.

  12. M8Fixtures and parts placed later

    Fixtures, a locate pass, rotation and side-view thickness.

  13. M9Live mode

    Live control of Klipper printers. The goal: the same results as print files, faster.

  14. M10Other sensors

    Optional: a touch probe with a Klipper module, decided after the scale data.

  15. M11Desktop mills

    The same measuring workflow on desktop CNC mills.

Licensing

Kaliper is source-available: free for noncommercial use, with commercial licences available.

PartLicenceCommercial use
Software PolyForm Noncommercial 1.0.0 Needs a commercial licence; commercial licences are available
Hardware designs CC BY-NC-SA 4.0 Needs permission
Documentation and this website CC BY-SA 4.0 Allowed, with attribution and share-alike
Configuration, example plans and logs CC0 1.0 Allowed

Commercial licences and other questions go through GitHub issues, once the repository is public.

Questions

How accurate is it?

It depends on the printer, the camera setup and the part, so there's no single number. Kaliper publishes accuracy per machine, only from measured calibration data and with its conditions, and every result shows its own uncertainty.

Is it a certified measuring machine?

No. Kaliper is a tabletop vision measuring machine that follows good measurement practice. It isn't certified, and it isn't a replacement for professional quality control.

Which printers work?

The Elegoo Centauri Carbon first. Marlin printers are planned through print files, and Klipper printers through print files and, later, live control. Bambu Lab printers aren't supported.

Do I need to change my firmware?

No. Kaliper generates ordinary print files that only move the printer. No plugins, no firmware changes.

Can I add scales later?

Yes. Every camera unit is built upgrade-ready for the Camera + Scale tier. You add the scales and a harness on the printer, and the unit isn't rebuilt.

Can I use the code?

Yes, for noncommercial use. Kaliper is source-available under PolyForm Noncommercial 1.0.0, and commercial licences are available. The repository is private for now.

Can I buy one?

Not yet. Kits (camera unit, mounts, lighting, calibration targets and fixtures) are planned once calibration (M5) and the required certifications are done. The scales follow at M6. Sign up for updates to hear first.

Is it safe for my printer?

Measuring jobs only move the machine, with heaters off and with feed and travel limits. The camera sits above the nozzle tip. Fix the part to the bed and stay at the printer while the job runs.

The Centauri Carbon's firmware warms the nozzle when a job starts, so Kaliper's jobs switch the heater off right after homing.

What does indeterminate mean?

The measurement is too close to a tolerance limit to call, given its uncertainty. Kaliper says so instead of guessing a pass.