Prior to the advent of CNC (Computer Numerical Control), machinists relied exclusively on 2D engineering blueprints to delineate machining methodologies and parameters. Since then, the manufacturing landscape has undergone significant transformation, owing largely to the advent of precise 3D modeling and CAM (Computer-Aided Manufacturing) programs.
In the contemporary context of 2024, we are fortunate to possess the capability to seamlessly integrate solid 3D models into CNC machining software. These programs automate the requisite machining methodologies and parameters essential for producing the desired components. However, despite these technological strides, the importance of engineering drawings persists, particularly in defining stringent tolerances for critical features and other specialized requirements. The mastery of optimizing drawings for CNC machining remains a pivotal engineering skill.
This article aims to elucidate techniques ensuring the comprehensiveness of your drawings for any manufacturing process, while ensuring ease of understanding for manufacturing personnel. Although SOLIDWORKS serves as our primary illustration platform, the outlined process can be readily replicated using alternative engineering drawing software.
Let us delve into the intricacies of this subject matter.
Access the Drawing File and Incorporate Drawing Views
To initiate the process, procure and open the Solidworks drawing file provided, serving as the foundational framework for crafting your CNC drawing.
Subsequently, proceed with the arrangement of drawing views, commonly recognized as orthographic projections or 2D representations, essential for delineating a 3D object. The requisite number of drawing views for a particular component is contingent upon its geometric complexity. While straightforward components may be adequately depicted with two or three views, intricate ones typically necessitate more comprehensive representation. For illustrative purposes, a sample solid model of a demonstration housing part has been furnished for this instructional session.
Our engineering drawing mandates three primary views along with a sectional view, portraying the component as though it were bisected to reveal its internal features. Incorporating drawing views into the foundational drawing template entails accessing the ‘Model View’ function within the ‘View Layout’ tab and selecting the pertinent model. Detailed instructions regarding this process can be found on the SOLIDWORKS website.
Pro-tip: In the context of CNC machining drawings, the utilization of two or three orthographic views is generally sufficient for conveying the component’s geometry, dimensional specifications, and tolerance requirements.
Establishing Drawing Scaling and View Parameters
Additionally, it is imperative to meticulously adjust the scaling of drawing views to accommodate annotations, dimensional data, and mechanical symbols effectively encircling each view. Resizing views post-placement of dimensions can be cumbersome and counterproductive.
SOLIDWORKS incorporates automatic insertion of center marks into holes; however, if your software lacks this feature, manual insertion is advisable. Such a practice is conventional, serving to indicate the location of holes to manufacturers or individuals perusing the drawing. Most software platforms boast user-friendly engineering utilities capable of inserting centerlines, resizing views, and executing various other functions. Integrating construction lines into all views to delineate centerlines, center marks, and corresponding patterns is recommended.
Moreover, inclusion of reference or cross-sectional views (e.g., Section A-A) is beneficial for manufacturers, as supplementary isometric views can enhance comprehension of the fabrication process. Generally, it is prudent to incorporate a sufficient number of views to comprehensively define the component’s geometry, dimensional specifications, and tolerance requirements.
Geometric Dimensioning and Tolerancing (GD&T)
Pro-Tip: This tutorial offers fundamental insights into GD&T. For a comprehensive exploration of GD&T, complete with an extensive library of GD&T symbols, we recommend visiting the following website.
Dimensioning: The initial phase of the GD&T methodology entails dimensioning the orthographic views incorporated within the drawing. Given the comprehensive geometric data encapsulated within the solid model, this process has been notably streamlined. Begin by delineating the overall dimensions, which dictate the requisite raw material for machining the component.
Subsequently, delineate the critical part dimensions. These dimensions hold paramount importance due to their direct interface with other components. A quintessential illustration of critical dimensions lies within hole patterns—such as those positioned at the outer four corners of the demonstrative housing part. These patterns dictate the part’s mounting onto a base and must align precisely with the corresponding holes in the interfacing component.
Tolerancing: Before embarking on the tolerancing of an engineering drawing, it is imperative to consider two fundamental factors: the desired tolerance and the tolerance specification being invoked—bearing in mind that tighter tolerances invariably escalate the cost associated with CNC machined parts. Reference the overarching tolerance instructions outlined in the title block of the Fictiv drawing template.
The determination of tolerance is contingent upon the significant digits of the basic dimension, as elucidated in the ensuing table.
Assuming a designated spacing of 114.3 mm between the outer holes, a precise dimensioning approach is imperative. If denoted simply as “114”, the general tolerance, as per the provided table, would encompass a range of ± 2.5 mm. Consequently, the permissible span for the “114” dimension would extend from 116.5 to 111.5 mm, rendering such a broad range incompatible with interfacing requirements.
To ensure a more stringent adherence to this dimension, we opt for the one-decimal place format (.X), which affords a tolerance of ± 0.25 mm. Analogously, we apply the one-decimal place dimensioning for the inner hole pattern. Notably, identical dimensions necessitate solely a “2X” prefix without a separate call-out.
Moreover, it is prudent to establish geometric relationships and datum lines within the drawing. Although omitted from this discussion, further insight into datums can be found in the referenced article.
Given the lack of specific constraints on the part’s height, a relaxed tolerance regime is acceptable. Hence, the dimension to the center view is provided without decimal places, yielding a tolerance of ± 2.5 mm.
In the bottom view, the wall thickness is denoted as 6.35 followed by “TYP,” indicating typical dimensions for similar features. This streamlines the drawing by condensing multiple identical dimension call-outs.
A helpful suggestion is to utilize uppercase lettering throughout the drawing, enhancing readability and comprehension.
Enhanced Dimensioning and Tolerance Specification for Apertures
Upon completing the dimensioning of aperture positions and critical dimensions, it is imperative to specify the diameters, depths, and associated tolerances of the apertures, along with any necessary thread tapping requirements. For instance, our demonstration housing necessitates four countersunk outer apertures and four inner apertures threaded for #6-32 screws.
Advanced Tip: When exclusively specifying threaded apertures, the drafting process can be expedited by utilizing Fictiv’s Auto Thread Detection tool, eliminating the need for detailed drawings.
Multiple identical apertures can be collectively specified by prefacing the dimension with “4X.” In this context, we opt for UNC threads due to their widespread availability in the U.S. Additionally, two categories of apertures exist: through-holes, which traverse the entirety of the component, and blind holes, which possess a specified depth denoted by the ↧ symbol in engineering drawings. Similarly, the depth of countersunk holes is delineated using the ⌴ symbol.
Surface Specifications
In addition to conveying design details, drawings serve as a crucial means to communicate specific surface requirements to manufacturers. Surface finish dictates the choice of endmill and machining parameters such as speed for CNC operations. Typically, a 64RMS finish provides a smooth surface, albeit with slight toolpath impressions. For critical interfaces like O-ring mating surfaces and those necessitating exceptional smoothness, I advise aiming for a 32RMS or finer finish.
Utilization of CNC Surface Finish Comparator Illustration demonstrating variations in surface finishes using a comparator.
Similar to tolerance requirements, achieving tighter tolerances and smoother surface finishes incurs higher machining costs. While a 64RMS finish is indicated in our example title block, I will append a note stipulating the need for a smoother finish on the top surface of the demonstration housing.
Manufacturing Annotations
The top left corner of a technical drawing is designated for annotations pertinent to manufacturing processes, encompassing instructions for finishing or part identification. These annotations constitute the conclusive component in achieving clarity within an engineering drawing. Within our schematic, we shall incorporate annotations specifying edge breaking, alongside several fundamental annotations of utility:
Establishing units of measurement Dispensing tolerance specifications Referencing the solid model Chamfering sharp edges Stipulating surface finish criteria Prescribing cleanliness standards While not obligatory for every drawing, the aforementioned annotations serve as a robust foundational framework.
Exporting as PDF
We have successfully completed the CNC machining drawing process, and the final step entails exporting the drawing as a PDF document. In SOLIDWORKS, this can be achieved by navigating to File → Save As and choosing PDF as the designated “Save As Type”. This facilitates seamless sharing of the PDF document, facilitating the subsequent manufacturing process.
Are you in need of CNC parts with precise tolerances? Fictiv serves as your comprehensive platform for bespoke mechanical components, accommodating technical drawings and exact tolerance specifications across various file formats. Our capabilities include machining with tolerances as precise as +/- 0.0002, complemented by finishing, hardware installation, and rigorous quality inspection services. Explore our comprehensive CNC machining solutions, and register for a complimentary account to receive instant quotations and complimentary Design for Manufacturing (DFM) feedback on your designs today!
FAQs
Pro CNC Draw Download
1. Pro CNC Draw Download
Q: Where can I download Pro CNC Draw? A: Pro CNC Draw is available for download from our official website. Simply navigate to the designated download section, select the appropriate version compatible with your operating system, and follow the on-screen instructions to complete the download process.
Q: Is Pro CNC Draw available for free or is there a cost associated with it? A: Pro CNC Draw offers both free and premium versions. The free version typically includes basic functionalities, while the premium version may offer advanced features and tools tailored to specific user needs. You can explore the features and pricing options on our website.
Q: What file formats are supported by Pro CNC Draw? A: Pro CNC Draw supports a wide range of file formats commonly used in the CNC machining industry, including DXF, DWG, IGES, STEP, and more. This ensures compatibility and seamless integration with various CAD/CAM software and CNC machines.
FAQs: Source Controlled Drawing
2. Source Controlled Drawing
Q: What is source controlled drawing, and why is it important? A: Source controlled drawing refers to the practice of managing and tracking changes made to engineering drawings using version control systems. This allows for systematic recording of modifications, ensures traceability, and facilitates collaboration among team members working on the same project.
Q: What are the benefits of source controlled drawing? A: Source controlled drawing offers several advantages, including improved transparency, reduced risk of errors, enhanced collaboration, better compliance with regulatory requirements, and simplified auditing and documentation processes.
Q: Which version control systems are commonly used for managing engineering drawings? A: Popular version control systems used for managing engineering drawings include Git, Subversion (SVN), Mercurial, and Perforce. These systems offer features such as branching, merging, tagging, and rollback, which are essential for effective source control management.
FAQs: The Surface a Drawing is Created On is Called the
3. The Surface a Drawing is Created On is Called the
Q: What is the term used to refer to the surface on which a drawing is created? A: The surface on which a drawing is created is commonly referred to as the drawing board or drafting surface. It serves as the physical or digital canvas for sketching, designing, and annotating technical drawings and plans.
Q: What are the different types of drawing surfaces available? A: Drawing surfaces can vary depending on the medium and tools used. Traditional drawing surfaces include paper, vellum, and drafting film. In digital environments, drawing surfaces may consist of graphics tablets, touchscreen displays, or software applications specifically designed for drafting and illustration.
Q: How does the choice of drawing surface impact the drawing process? A: The choice of drawing surface can influence factors such as ease of sketching, precision, durability, and compatibility with drawing instruments. Factors such as texture, size, and scale also play a role in determining the suitability of a drawing surface for a particular project or application.
