Flash Measurement for Stamped Parts: Layout First, Tolerance Second

A stamped part is usually flat, which makes it an easy optical target, and usually large or multi-cavity, which makes the layout the deciding factor. The dimensional work is straightforward; the engineering work is presenting many parts at once without giving up datum control.

In-Plane Features Are the Natural Fit

Outer contour, hole diameter and position, slot width, bend-line location, cut-out angle, and pilot-hole position relative to the contour. A backlit silhouette gives a stable edge on all of them, and the whole set can be evaluated in one shot provided the part fits the field.

Two conditions matter more than the feature list. The datum scheme has to be reproducible in the fixture — stamped parts are often located on two holes, and if those holes are themselves the features under inspection, the fixture has to locate on something else. And the part has to sit flat: a stamping with a curl will rock, and the rock shows up as position scatter.

Multi-Cavity Layouts and the Field You Actually Need

A progressive die produces a strip, and a multi-cavity die produces several parts per stroke. Either way the useful question is how many parts fit one field, because that number divides the handling cost.

Wide-field coverage on the series is Ø100 mm on IMAGE 3, 200 × 200 mm on PLUS and 300 × 200 mm on PRO and PRO-H. For a 300 × 200 mm tray, PRO or PRO-H covers the tray in one shot, which is the configuration most multi-cavity projects end up choosing. The precision-mode field on the same models stays 18 × 18 mm, so if the project needs the tighter accuracy statement it is measuring a small window, not the tray.

Model range: which IMAGE 3 fits this part

Model range, as stated in the IMAGE 3 series specification sheet. Repeatability here is the figure printed in the sheet; it is not a guarantee for your own part, your fixture or your operator. Treat it as the floor you start from when you run a trial, not as the number you can quote to a customer on day one.

The full specification sheet, including the camera and lighting options and the workpiece-to-model mapping, sits on the IMAGE 3 series product page. If you only want a first-pass sanity check on whether your part fits any model, the instant measurement selection tool takes the part envelope and returns the models that can cover it.

The Stitching Term, and Why It Catches People Out

When a feature is longer than one field, the result carries the length-dependent term. On PRO and PRO-H the stitched figures are ±(2+0.02L) in precision mode and ±(4+0.02L) in wide-field mode; on MAX and MAX2 they are ±(1.5+0.02L) and ±(2+0.02L). For a 200 mm contour the precision-mode term adds 4 µm to the base figure — small on a 0.1 mm tolerance, decisive on a 0.01 mm one.

The single-field column is only usable when the entire feature sits inside one exposure. Quoting the single-field number for a stitched measurement is the most common way a stamping project gets an accuracy claim it cannot defend.

The accuracy figures, with their conditions

L is the measured length in millimetres. The stitched column applies when the feature is longer than one field and the system has to join several images; the single-field column applies when the whole feature sits inside one shot. Read the sheet in this order: which mode, stitched or not, then the length — the three together decide the number.

Burrs: A Z Problem Wearing a 2D Costume

A burr is material displaced out of the plane at an edge. In a silhouette it appears as a local widening, which is a projection of the burr rather than its height. For a burr limit stated as height, a 2D system cannot deliver the number.

Options that do work: a height sensor where the burr face is accessible (the 8055 on MAX and MAX2, range ±3 mm, spot 17 µm), a side-view optical arrangement, or a dedicated profile measurement. Where the drawing states a burr height, the inspection plan has to name the instrument that measures it, not just the feature.

Four Stamping Inspection Mistakes

1. Locating the part on the two holes that are also the inspected features.
2. Quoting single-field accuracy on a stitched contour.
3. Reporting a projected burr width as burr height.
4. Loading a curled part on a flat plate and treating the rock as process scatter.

When Stamping Should Use a Different Route

When the gating feature is flatness or twist across a large area, a full-field height method serves better than a single-point sensor. When the part is a deep-drawn shell rather than a flat stamping, the silhouette stops being informative and a different measurement principle is needed. And when tolerance sits at the repeatability floor of the chosen model, the inspection limit is the instrument, not the process.

FAQ

How many stamped parts fit in one shot on a flash measuring machine?

It follows from the tray area and the model. Wide-field coverage is Ø100 mm on IMAGE 3, 200 × 200 mm on PLUS and 300 × 200 mm on PRO and PRO-H, so a 300 × 200 mm tray is a single shot on PRO or PRO-H. Allow clearance for edge finding when counting parts.

Can a flash measuring machine measure burr height on stamped parts?

Only with a height sensor. In a silhouette a burr appears as a projected widening, not as a height. The 8055 spectral confocal sensor on IMAGE 3 MAX and MAX2, with ±3 mm range and 17 µm spot, can probe an accessible burr face; otherwise a side-view arrangement or a profile instrument is required.

What accuracy applies to a stitched measurement on a long stamping?

The length-dependent column. On PRO and PRO-H that is ±(2+0.02L) in precision mode and ±(4+0.02L) in wide-field mode; on MAX and MAX2 it is ±(1.5+0.02L) and ±(2+0.02L). At L = 200 mm the precision-mode addition is 4 µm on top of the base figure.

How should a stamped part be located for optical inspection?

On a datum that is not the feature being inspected. Locating on two holes that are also under inspection means the measurement cannot detect their own position error. The part also has to sit flat, or a curl will present as position scatter.

Does wide-field mode change the accuracy of the measurement?

Yes. The precision-mode and wide-field-mode figures are separate columns in the specification sheet, and wide-field is the looser of the two on every model. A tray-wide shot is therefore evaluated against the wide-field figure, not the precision one.

Is multi-cavity stamping inspection a good application for a one-shot system?

It is one of the strongest, because the handling is a tray and the features are flat and in-plane. The two conditions are a datum that is independent of the inspected features, and a tray that holds each cavity in a repeatable pose.

Related reading

• What is a flash measuring machine and how does one-click measurement work
• Instant measurement vs CMM: when a one-shot system is enough
• How to read an instant measurement accuracy spec
• Height Measurement on a Flash Measuring Machine
• Closing the Loop
• Batch Dimensional Inspection

Send Us One Part and We Will Tell You Which Route Fits

The fastest way to close this question is a real part, not a discussion. Send one sample with the drawing and the features you actually gate, and we will run it and report what the measurement returns — including the features that come back as a no. A short written feasibility note is more useful than a brochure.