How can GD&T help you reduce production costs?

Geometric Dimensioning and Tolerancing (GD&T) is critical in production, assembly and maintenance area. When I was working in production and maintenance departments, these parameters helped to deliver the outputs quickly. Reduced Inspection Costs: GD&T allows for more precise and efficient inspection processes. Inspectors can check CTQ dimensions specified by GD&T, saving time and resources. Reduced Scrap and Rework: With clearer and more specific tolerances, there are fewer instances of parts being rejected due to manufacturing variations. Reduced Assembly Time: When parts are manufactured with GD&T, they are more likely to fit together correctly, reducing the time and effort required during assembly. Improved Interchangeability

GD&T plays a pivotal role in manufacturing as tolerance defines what would be the process & the cost of manufacturing and how well the assembly of mating parts will function for the desired applications

GD&T to the designer is like the toolbox to the mechanic. It enhances the skill and ability of the designer to design and commmunicate unambigiously the relationships of design features to ensure proper fit, assembly and function of the product. GD&T which consists of mainly geometric symbols provide very clear meaning of the geometric controls needed for the particular feature or its relationship to other features or datums, hence preclude any wrong interpretation or misunderstanding which commonly occur when such controls were done using notes and traditional plus-minus dimensioning method.

For my long experience in plastic industries to minimise costs reduction and rejection must need to follow the standard operating procedure(SOP) emplemented by the head of the organisation.

GD & T is a method to communicate the design requirements in the fabrication of the part and inspection. The design intent should clearly flow from the model itself that has been tested in a virtual environment. It’s helpful to do some tolerance analysis prior to documenting the final design. Symbols should clearly state the condition, and values should reflect a manufacturable tolerance. I find that using published industry-specific standards help drive creation and understanding of how GD&T is interpreted. Another consideration should be towards leveraging a tool like DFM to validate that the manufacturing method that will be used can create a compliant part.

For me GD&T is crucial for the communication of the critical design requirements, the problem I have found in the practical world is that not many people understand GD&T correctly and some people don′t understand it at all. I′ve seen workshop tool owners that quote a project by adding an extra cost for each GD&T call-out, but not even take the time to understand why it is been specified.

For me GD & T must be in such way that "Completely Toleranced"which means that the geometries of the workpiece are completely defined and Toleranced. Nothing shall be left to the individual judgement of the manufacturer or inspector. Same time use the tolerance responsibly based on product requirements. Tighter tolerance for non critical geometry will impact fabrication cost.

De acuerdo con todo lo anterior el GD&T nos indica las características a cumplir basado en su simbología por eso es importante que toda empresa tenga a un experto que conozca y sepa interpretar la simbología indicada en los dibujos 2D para después en en un dise?o surgido de este se aplique correctamente durante el DFM para la fabricación del herramental hablo para un molde de inyección de plástico y por supuesto considerar las características de contracción del material plástico que serán fundamentales para lograr las características citadas en el 2D sin olvidar un análisis de mold flow que te indicaran hundimientos, efecto diésel, pandeos, y la contracción final del producto .

GD&T is perfect for both the simple and the complex assemblies. You set the exact rules needed to define your design so that after manufacturing components everything fits together.

Definitely it will! For starters, it will ensure the right tolerances to be used in piece part component. For example too small or too large tolerances used in any dimensions without understanding the manufacturing process will generate too many defects. Stacking tolerances issue is another common mistake happening in any part’s drawing. Without considering the tolerances after assembly of few parts dimensions correctly will always have form, fit and function issue.

There are several effective ways to become proficient in GD&T. In my experience, students must possess competency in reading and interpretation of mechanical drawings and an understanding of basic mathematics. Our company trained personnel using a variety of methods, including traditional classroom coursework and use of online software, with advanced training accomplished via instructor-led seminars. A key strategy was to "train the trainer" in which a few individuals were trained to a higher level than the baseline instruction. These individuals acted as mentors and often provided refresher training for others.

In Australia over the last 20 years, it has been almost impossible to find training in GD&T to up skill employees outside of a larger course or qualification. While the automotive industry understood the value and applied appropriate tolerancing to part drawings, other manufacturing did not. So the opportunities to learn on the job were far less. As a result, there seems to be a large proportion of Australia’s current mechanical designers that lack either this knowledge and the necessary skills to apply it consistently, or the business culture to require that it be defined and noted and not implied. Current Mech Eng graduates range from a basic understanding to none at all, and yet GD&T is fundamental when designing for manufacture.

Becoming proficient in GD&T requires a lot of practice. A lot. More importantly, it's about explaining why a dimension is out of spec and how to fix it. That's when you know your stuff.

GD&T is applicable to all aspects of manufacturing especially at AEROSPACE AND DEFENSE. Accuracy and acceptable tolerance whether in calibration or equipment commissioning and qualification GDT is a must to follow.

Learn GD&T is more practical if in addition to a courses to know and understand the symbols, is complemented with a graphical approach on the interaction of the IT (Interval Tolerances) over the design of the part concerned to control geometrically. Other aspect to consider is that to obtain a GD&T evaluation, it needs a set of raw data (e.g. "X & Y deviations for a hole or a lot of raw probe hits to get profile surface"), so the evaluation of these information will be very helpfully, to understand how the data is treated according to the GD&T requirement and most important, why on the design is required that evaluation.

An important consideration is to train across disciplines. Designers must understand not only the technical application of GD&T to their design, but also how it will be interpreted by the drawing user. Manufacturing engineers, machinists, and inspectors must have some understanding of the designer's intent in order to identify key features and dimensions to correctly plan, machine, and inspect the part.

For agile production schemes, the standardization of the communication helps to reduce the waste . GD&T provides an standard way to issue - read the Critical To Quality dimensions . “Train the trainer” provides a way . In some cases , the availability of “cell leaders” well trained, supports the continuous flow required. Part of the cyclic training for the operators, inspectors normally is set up in the LMS available - including a test . GD&T is a necessary tool for improving complex manufacturing processes regarding process stability, rejections and COPQ as part of GB / BB projects in the manufacturing area. The measurement of the economic impact of such projects is part of the data culture to foster in the production floor teams.

As part of the stakeholders do not forget suppliers, for assembly factories suppliers plays key role, therefore GD&T must be extended to the suppliers teams.

An important aspect is that the GD&T is not only a task for the QA and/ or engineer department, it requires the engage of all the parts involved on the fabrication process in interaction with the measure system, so the application of GD&T also must be understood even by the operational staff to ensure a good implementation in all levels and a quickly detection of any deviation on the process. For example on the implementation of gages and checking fixtures, all the elements that are part of these validation items must be explained according to the design requirements of the part and highlight how these will help to control the process.

There is the misunderstanding that just by using GD&T there will be a reduction of costs, but in reality, the reduction of costs comes from the parts you can save, as a design engineer I was able to "save" very expensive parts with a machining error, just by using the GD&T concepts and adjusting the part considering the function of it.

Production cost (and/or rejection rates) are intrinsically linked to allowable tolerances. Wider tolerances allow for different manufacturing and inspection processes that produce more value with less cost. As a fabricator I worked to the 1/16th, our machinists worked to the .001, our mold makers worked to the .0001. The key to GDT is when it allows the designer to open tolerances because the GD&T better communicates the key fitments that actually matter (or the key relationships that must be maintained). This allows the manufacturer to chose most efficient processes while maintaining the tolerances that matter. Use GD&T when you can do this - don't do it just to do it.

The challenge in GD&T is to determine the appropriate basis based on the priority of the manufacturing process and their arrangement based on the initial tolerances. Also, determining the appropriate tolerance value in the geometric tolerance box is proportional to the numerical tolerance.

While I understand the benefits and need for it - I’m not quite convinced or in agreement with applying GD&T to a part or assembly drawing can REDUCE production costs. Instead, machine shops need to provide training and certification for employees, design jigs and fixtures to assess GD&T for mass produced parts or invest in a CMM for high mix low volume parts which results in overall higher cost per assembly. The tighter the control, the more expensive the part or assembly.

Choosing to use GD&T may not be up to you. And does not guarantee quality. I have worked for 2 companies where drawings were made before I was born. They were very challenging in that some dimensions could not be measured correctly, especially those for interference fit. The customer owns those drawings, and only the customer can change them. Not you.