Calypso - 2 Point Diameter

What is "2 Point Diameter"? Normally, a diameter is calculated as a single average value. However, the 2 Point Diameter characteristic looks for the local minimum and maximum distances between two opposing points on a circle or cylinder. It helps identify if a part is out-of-round (e.g., oval-shaped). Requirements (Prerequisites) To use this function, your measurement must follow these rules: Scanning Only: You cannot just take a few individual points. The sensor must move in a continuous scanning path along the surface. Circular Paths: Even if you are measuring a cylinder, the scanning must be done in circular sections (slices). 180° Minimum: The scan must cover at least half a circle (180°). This is necessary because the software needs to find points directly opposite each other to calculate a diameter. Tolerance Standards (Tolerances) When you define how much the part can deviate from the perfect size: You don't have to manually calculate the limits. The software supports ISO 286 standards. You can simply enter tolerance classes like H7, g6, or js10, and the system will automatically apply the correct numerical limits. In Plain English: Think of this as a "caliper simulation." If you were to measure a hole with a manual caliper at different angles, you would find a slightly different size if the hole isn't perfectly round. This software feature does that automatically by scanning the shape and telling you the largest and smallest "twin-point" widths it found, then checking if those fit within official engineering standards (ISO). How the (LP) Calculation Works Think of this as a two-step process to find the "true" thickness of a hole or cylinder: 1. Creating the "Reference" (The LSQ Feature) First, the software takes all your scanned points and calculates a perfect average circle. This is called a Gaussian (LSQ - Least Squares) element. It uses this perfect circle as a "baseline" or a guide to understand where the center is. 2. Finding the Pairs The software looks at every single point the probe touched during the scan. For every point, it looks directly across the center to find the symmetrical point on the opposite side. It measures the distance between these two points (the "Two point distance"). 3. Picking the Winners After checking all possible pairs around the circle: It identifies the absolute smallest distance (the narrowest part). It identifies the absolute largest distance (the widest part). It then records exactly where those specific points are on your part. In Simple Terms: Instead of just guessing where the diameter is, the software uses a perfect mathematical circle to find the "exact opposite" for every point you measured. It then searches through all those pairs to find the extreme narrow and extreme wide spots. Why is this useful? It's much more precise for checking ovality. A standard average diameter might hide the fact that a hole is "egg-shaped," but this (LP) mode will catch it by showing you that the smallest diameter is much shorter than the largest one. The Envelope Condition (E) is based on the ISO 8015 standard. Its goal is to ensure that a part doesn't just have the right "average" size, but that its entire shape fits within a perfect boundary (the "envelope"). How it Works: Two Checks in One To pass this check, the part must satisfy two rules at the same time: Form Check: The "outer skin" of the part cannot cross a perfect geometric limit. Size Check: Every individual "two-point" measurement must be within the allowed tolerance. Inner vs. Outer Features The software looks at the part differently depending on what it is: For a Shaft (Outside Feature): It uses a Circumscribed element. Imagine sliding the smallest possible perfect ring over the shaft. The software then finds the Smallest Distance (A)—the tightest spot where the part is at its minimum diameter. For a Hole (Inside Feature): It uses an Inscribed element. Imagine sliding the largest possible perfect plug into the hole. The software finds the Largest Distance (B)—the widest spot. The Calculation Process Scanning: Just like the previous mode, it uses the scanned points. Symmetry: For every measured point, it finds the exact opposite point on the other side. Point Assignment: It identifies the specific pairs of points that represent the extreme limits (the minimum for shafts or the maximum for holes) and records their location. In Simple Terms: The Envelope Condition is the "Will it fit?" test. It ensures that a part isn't so bent or "wavy" that it won't slide into its matching component, even if its average diameter seems okay. It checks that the entire volume of the part stays inside a perfect boundary while also checking that no individual spot is too thin or too thick. Please note that you are learning this at your own risk. The best course of action is always to contact a Carl Zeiss.