FAQ’s (Frequently Asked Questions)
What File Formats do you support?
Modern CAD software typically supports a multitude of file formats. We can import and work with a wide range of CAD formats however not all formats support full editing capabilities. Typically, we ask clients to provide their files in Parasolid (x_t) format or Step (stp) format. If an assembly is being sent, please assemble the parts and then export the assembly as a single x_t file. This ensures part colours and part names (within the sub-assembly) are preserved when we work on your file.
IGES or IGS format is an older format but usually imports well without problems. DXF files are typically 2D files similar to what might be printed on paper as a technical drawing. They are useful for defining shapes with vertical walls, converting fonts for engraving etc., but cannot convey the 3D CAD model information in a 3D object. Parts that are going to be water-jet or laser cut are usually defined by the DXF format.
STL files are typically used for creating 3D printable objects (i.e Rapid Prototyping) they can be scaled in 3 dimensions (e.g. to make an oversize master when allowing for casting shrinkage) but generally cannot be directly edited.
What is Solid Modelling?
Solid Modelling is the process of creating and manipulating a set of geometric shapes in a computer program which represent something that is likely going to be manufactured. Of course solid modelling goes way beyond just representing things that will be manufactured – it provides a powerful tool to aid people in visualizing, understanding and advancing their ideas – be it for imagining a DNA helix, a jet turbine engine - or just a complicated mounting bracket.
What does CAD-CAM really mean?
CAD-CAM stands for Computer Aided Design - Computer Aided Manufacture.
These days, CAD is usually performed with 3D or Solid Modelling software which allows the designer to rotate the design on the screen to view it from any angle and to see inside the "model" as it exists in the computer. In the "olden days", CAD was primarily 2D, just like drawing on paper, except the computer helped automate the drawing process and modifications were still easier than on paper.
A 3D solid model is built up of simple and complex geometric shapes such as blocks, cylinders, bevels, curves, holes, etc. and the these primary shapes are then modified to meet the needs of the design. While a conceptual design can start without exact dimensions to permit the designer to explore aesthetics and proportions, eventually it is necessary to start assigning dimensions (sizes) to the various elements in the model. This is because the CAM software needs exact dimensions with which to work.
The CAM software permits the user to take the exact solid model that has been designed and then define how it will be machined. These steps are also shown visually in the Case Study documents under Design Examples. Often a product will consist of many components and each component has to be manufactured individually, prior to assembly.
Taking the part's solid model, the CAM software allows the user to select from the available machine tools such as flat end mills, ball end mills, drills, thread taps etc., and usually in order from large to small, generally a part will be machined from a block of material starting with roughing operations (to achieve an approximate shape) and moving to finishing operations as the tools get smaller for the finer details. If a part requires machining from various sides, then fixtures will also be required to hold the parts precisely for subsequent operations.
Sometimes a part can be rotated while on the mill (this is called 4th axis machining) but it all depends on the shape and machining requirements for the part. The final step of the CAM process is to generate the tool paths in G-Code which the milling machine's control then interprets as a sequence of precise moves and feeds in 1, 2 or 3 axes.
The CAM software takes each tool's shape attributes into account when calculating the tool path. Many CAM programs also provide a visual simulator to assist with the tool path generation and enable the user to watch virtual machining being performed in the computer, prior to the actual machining.
What is G-Code?
G-Code is an ANSI standard for machine tool control. It can be written by hand and entered into an editor or it can be computer generated for more complicated parts. Typically, the final step in the CAM process is to generate the G-Code file for a specific machine. Typically the output is tailored to a machine's unique requirements via a Post Processor. This allows a general purpose CAM program to provide suitable code for virtually every CNC machine manufactured in the last 40+ years!
The code sample below shows what G-Code looks like:
(WinGcnc8 - Post Processor 09/11/10 - First Mill)
N100 G00 X0 Y0 Z0 (Go to the starting point)
N102 (Horizontal Roughing)
N103 M06 T1 (Load next Tool)
N104 M08 (Start Spindle)
N105 M10 (Turn on Mist Coolant)
N106 G00 X-11.438 Y36.167 Z4.862 (Move rapidly to this X Y Z location)
N107 G01 F500 (Set the feed rate to 500mm’s per minute)
N108 Z-0.59 (Move the tool down by this amount)
N109 F800 (Change the feed rate)
N110 X-9.688 Y38.036 (Move to this XY location)
N111 X-10.588 Y38.8 (etc.)
N112 X-11.44 Y39.879
N113 X-11.442 Y43.031
N114 X-11.254 Y42.647
The code is quite easy to read and mostly consists of a series "G" words (or codes) and X, Y, Z coordinates that tell the machine where to move. Feed rates are preceded with an "F", while tool changes are preceded by an "M" code and a "T", followed by the next tool (number) to be used. The "M" codes are usually machine specific. The CAM program generates this code and the coordinates already take into account, the changing sizes (diameters, lengths, and shapes) of each tool. Files can be just several lines or many thousands of lines, according to the complexity of the part being made. Typically, each line is called a "block".
What does Design for Manufacture really mean?
Design for Manufacture or "DFM" simply means taking into account "how" something is going to be made during the design process. Historically, designers conceived great designs with little regard to how the part or product would eventually be made. The production was usually left to another group of production engineers. This approach generally added time delays and added costs in getting a product to market. DFM was the formal recognition that there was "life after design". Now a product designer who has adopted DFM will often have familiarity with production and assembly techniques and will consult with production staff as well as service or maintenance personnel - during the design phase. Designing a product using DFM techniques usually ensures a much shorter overall time to market and a smoother transition into production. Often product life-cycle costs (warranty, repair etc.) can also be reduced. It really boils down to more open communication between departments throughout the design and production process – bringing everyone’s ideas and experiences into the design process at an early stage.
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