Anyone preparing drawings for quality assurance meets the same job under several names: ballooning, bubbling, and — if your customer is German — stempeln. All three describe one thing: giving every inspectable characteristic on a drawing a number. This article explains what that number is actually for, what needs one, and the numbering rules that keep the result usable.
Ballooning in one sentence
In ballooning, every inspectable characteristic on a technical drawing — every dimension, every tolerance, every feature control frame, every surface finish and thread callout — gets a consecutively numbered circle: the balloon. The number is not decoration. It is the key by which the drawing, the inspection plan, the measurement record and the CMM program all refer to the same characteristic. Without it the measurement list says “bore 20.008” and nobody knows which of the four bores was meant.
What a balloon refers to
A balloon is a cross-reference. On the other side of it sits the bill of characteristics, which carries, for each number, the nominal value, the tolerance, the limits and the gauge. The bill of characteristics becomes the inspection plan, and the inspection plan with measured values entered becomes the first article inspection report: as a measurement sheet to PPAP or VDA Volume 2, in aerospace as AS9102 Form 3. Whoever writes the CMM program carries the same numbers as characteristic names, so that the readings drop into the report without a detour. The number on the drawing is the start of a chain that runs all the way to a signed report.
What needs a balloon
The most common beginner’s question — and the most common source of gaps. A balloon goes on every characteristic the customer could inspect: linear dimensions with and without their own tolerance (those without fall under the general tolerance from the title block, and they are measured all the same), diameters, radii, chamfers, angles, threads, geometric tolerances, surface finishes. Depending on the customer, also title-block entries such as material, hardness or coating — these are not measured but evidenced, and they need a number for that. A dimension that is on the drawing and has no balloon will be found as a gap when the customer reconciles the report.
Numbering: the rules that hold up
One number per characteristic. A dimension with its tolerance is one characteristic; a feature control frame with two datums is one characteristic. Split a dimension across two balloons and you get two readings for one thing.
Consecutive, without gaps. The order may follow the views, the reading direction or the manufacturing sequence — what matters is that it is traceable and unbroken. Some customers prescribe a starting number or a prefix; that belongs in the agreement before ballooning starts, not after.
The balloon sits beside the characteristic, not on top of it. It must obscure neither the dimension nor another balloon. On dense drawings this is the real manual work.
A new drawing revision means a new numbering. When the drawing changes, the bill of characteristics changes. Carrying the old numbering forward and “filling the gaps” is how characteristic 37 comes to mean one thing in the report for revision C and something else in the report for revision D.
By hand or automatically
Three routes lead to a numbered drawing. The rubber stamp on paper — rare today, but not extinct. The CAD viewer with a click per characteristic: the inspector places one balloon after another on screen; cleaner than paper, but at 150 characteristics it is still half a day’s work, and missing one remains the risk. And automatic detection: the software reads the drawing, finds the characteristics, numbers them and writes out the bill of characteristics at the same time. In a vector PDF exported from CAD the dimensions are present as text and can be read directly; a scan or a TIFF needs text recognition first. DrawingStamp Pro takes the third route — what that looks like in detail, with formats and honest limits, is on the Ballooning drawings page.
The German word you will meet: “stempeln”
If you supply German customers, their drawings and e-mails will say Zeichnung stempeln — literally “to stamp a drawing”. The word comes from the age of paper. The inspector walked through the drawing with a numbering stamp and pressed an impression with the next number next to each dimension. The impression was round with the number in the middle: the inspection stamp looked like a balloon long before anyone called it one. That is where Prüfstempel (inspection stamp) and Stempelprogramm (the software that does it today) come from. English kept the picture of the balloon, German kept the picture of the stamp. The job is identical.
English and German: the same thing, different words
Working with customers in both languages, it helps to have the table in your head:
Ballooning, to balloon a drawing – Zeichnung stempeln. Balloon, bubble – Prüfstempel, Ballon. Ballooned drawing, bubble drawing – gestempelte Zeichnung. Characteristic – Merkmal. Bill of characteristics – Merkmalsliste. Inspection plan – Prüfplan. First article inspection report (FAIR) – Erstmusterprüfbericht (EMPB). First article inspection (FAI), initial sampling – Erstbemusterung. Gauge, measuring equipment – Messmittel, Prüfmittel. Upper and lower limit – Grenzmaße. General tolerance – Allgemeintoleranz.
Why it matters
Ballooning looks like the least important step in quality assurance — mere numbering. In fact it decides whether everything downstream fits together: whether the reading finds its dimension, whether the customer can read the report, whether the measuring machine speaks the same language as the drawing. Work completely and traceably here and the first article inspection report is half finished before the first part is measured. What the software takes over for the report itself is on the FAI report software page.