How Prepared Are You for Geometric Dimensioning & Tolerance?

When the DIN EN ISO 8015 was released in 2011, it was not a big topic in the PCB industry.

The PCB drawings were simple and clearly arranged. The tolerances, such as ±0.1mm, could be understood by everyone around the world and the result of measurement told us exactly where the deviation from the reference value was.

Another fact is the development software for PCB. Today more and more companies use 3D CAD tools to create the complete PCB specification and documentation.

The PCB drawings today appear more like mechanical drawings for engines rather than for electronic components. Topics like Geometric Dimensioning & Tolerance (GD & T) also known as Geometrical Product Specification (GPS) and ISO 8015 are coming up and various symbols and their meanings are often not clear.

MMC

Image 01: position accuracy requirement with round tolerance zone and MMC (maximum material condition)

 

 

GD&T is a common set of rules and definitions used on engineering drawings and models to define the allowable deviation of feature geometry. It enables engineers and designers to communicate what they require with regards to the product design. Then manufacturers use GD&T to understand the design to determine the set-up requirements for production. GD&T involves dimensions, tolerances, symbols, definitions, rules, and conventions that can be used to precisely convey the requirements for the location, orientation, size, and form of each feature of the product.

The drawing’s purpose is to completely and precisely visualize the representation of a product so that the manufacturer knows all the requirements to produce the product. According to official studies [Jor 17] around 80% of all drawings are either incomplete or ambiguous.

To deepen our knowledge and understanding about the requirements and develop a clearer picture of what our customer expects from us, our engineers at CML enrolled in a two-day intensive training about GD&T and ISO 8015. The training covered the following subjects:

  • Basics of form deviations
  • Development of form and position tolerances
  • Correlation of dimension, form and position tolerances
  • Principles of tolerancing (DIN ISO 8015 and DIN ISO 14405)
  • General tolerances for form and position tolerances
  • Tolerance zones of all symbols according to DIN ISO 1101
  • Drawing specification
  • References and reference systems
  • Maximum-Material-Condition / Minimum-Material-Condition
  • Reciprocity condition / projected tolerance zones
  • Methodology of defining tolerances
  • Verify form and position tolerances
  • Exercises and PCB based discussions

We are more than well prepared for the coming challenges of today’s production drawings and ready to help you fulfil your mission.

One of the biggest challenges that PCB manufacturers face though it may seem simple but is often overlooked: Missing essential information describing the product. Changing a drawing at this stage of the product life cycle is not a big problem. But it is costly to change the drawing when it is already released for production. To change the drawings that are already released in production can create considerable extra expenditures due to delay in production and wrong material selection. However, these problems can be easily avoided. At CML, we always review and check all drawings very carefully to see if there is any relevant information missing required for production. For this part, it is very important for us to be involved in the design development process as soon as possible.

If you let our engineering team be part of your development process, we can describe and visualize your product properly, in a more efficient (cost & performance) and less prone to error way.

Link between design and development

Image 02: drawings, the link between design and development, production and quality assurance

 

This also includes the evaluation of the necessary measurement methods. A lot of the requirements of GD&T are coming from the mechanics, like for shafts or bearings, which must fit together. Some of these GD&T are not well known in the PCB industry and in some cases there is no measurement tool available to conduct the final inspection. Together we will find a solution to use the various symbols in the right way to describe a PCB and define a suitable measurement method.

Let’s get prepared for GD&T

CML is your partner! We support you in any kind of questions related to this topic.
Get in contact with us and benefit from our experience and knowledge:  Sales@cml.ag 

 

 

 

Reference:

[Jor 17]  Jorden, W. und Schuette W.: Form- und Lagetoleranzen – Handbuch fuer Studium und Praxis; 9. Aufl. 2017, S.14