Reverse engineering machine parts: process and deliverables

When does reverse engineering make sense?

The typical case is an older machine or production line that still works well while its builder has stopped supporting it. A gear, a shaft, a housing or a custom fixture wears out, there is no drawing on file, and nobody sells the part. Reverse engineering also helps with imported equipment whose spares have long lead times, and with parts that fail repeatedly and should be redesigned in a better material.

It makes less sense when the original part is still available at a reasonable lead time, or when the part is simple enough to be drawn from a few caliper readings. Check the legal side too. A part covered by a valid patent or registered design may not be freely reproduced, even when the measurement itself is allowed.

How does the process work?

Good results depend more on the first and last steps than on the scanner. The intake decides what the part has to do, and the verification proves that the new part does it.

• Intake: photos, any surviving drawings, the mating parts and the operating conditions such as load, speed and temperature
• Measurement: tactile measurement for fits and datums, 3D scanning or laser tracking for free-form and large geometry
• CAD modeling: rebuilding design intent, so worn surfaces are modeled at nominal size rather than as measured
• Tolerances and fits: taken from the mating parts and from standard fit systems such as ISO 286
• Material: identified by hardness testing or chemical analysis where the drawing must specify it
• Drawings and parameter list, then a check of the first manufactured part against the model

Which measuring instruments are used?

The choice depends on size and shape. Bores, shafts and fits are measured by touch, because a tactile probe gives reliable values on functional surfaces. Free-form surfaces, castings and worn areas are captured with a 3D scanner as a dense point cloud. Large parts and machine frames call for a laser tracker, which measures points across several meters in one coordinate system.

API Metrology is an example of a maker covering that range, with laser trackers, iScan 3D scanners and, for checking the machines themselves, the XD Laser for CNC calibration. Other instruments of this class are listed under measuring instruments in our catalog.

Accuracy has a limit that no instrument removes: the part itself. A shaft that has run for years is worn, maybe bent, maybe repaired once with weld and regrinding. Measuring it perfectly only records the damage. That is why the engineer works out the original nominal size from the mating bore, the bearing seat or a standard series, and uses the scan to confirm the shape rather than to copy it. When two or three used parts of the same type are available, measuring all of them shows which surfaces are worn and which are true.

What deliverables should you receive?

Agree the deliverables before work starts, because they depend on what happens next: manufacturing, repair or buying an equivalent part.

Equivalent part, new manufacture or OEM?

Once the documentation is ready there are usually two practical routes. If a manufacturer in our catalog makes a part or unit that meets the key parameters, an equivalent is often simpler and comes with that maker's support. If nothing fits, the part is manufactured to the new drawings, provided this does not infringe the original manufacturer's patents, design rights or software licenses. We compare both routes with you, and our equipment selection service covers the search for equivalents.

Our own reverse engineering service covers single parts, assemblies and complex process equipment, and the result is technical documentation you can keep using: the CAD model, drawings and the list of parameters a replacement has to meet. Send photos and a short description, and we will tell you what can be measured and what you will receive.