The Journey: DXF to G-Code

Sheet metal fabrication shops have to work with many different file types as their customers place parts orders using output files from their own CAD programs. The in-house CAD/CAM software of the sheet metal fabricator has to be able to import or read these files and convert them to file types the in-house software can use. The .dxf (Drawing Exchange Format) CAD file type is a common type of input file for the fabrication of sheet metal parts and other file types are often converted to dxf before further processing. Merry Mechanization's SMP/IS CAD/CAM application can read a wide variety of file types including DXF files.

Merry Mechanization's SMP/IS CAD/CAM application can read a wide variety of file types including DXF files.

Once .dxf files are available, the parts drawings can be processed but before the G-Code specifying tool paths can be written, there are several additional steps that have to be carried out. Steps that result in efficient layouts and short tool paths are time-consuming to carry out manually and the results are often not optimized fully. Sheet metal software, such as SMP/IS, can help operators create code that maximizes throughput.

The SMP/IS software has a powerful feature called AutoMate Express and it can speed up the gcode creation process and improve the final result. It automates routine functions but also has an interactive mode in which the operator can make specific changes to meet the requirements of a particular job. The result is optimized code that is customized to deliver top quality output. In other words, dxf to gcode.

Choosing the Machine and the Material

Before the sheet metal software can write gcode, operators have to specify what machine will be used and what material will be cut and punched. They may be able to select the material from a material library or they can specify the type of material and its thickness. When they choose a CNC machine, the software may assign punches (or lasers) or they can make the assignments manually.

Sometimes a part may require a tool that is not available on the machine the operator chooses. Replacement tools may be selected from a list within the program or another available machine can be chosen. Operators can often choose available tools to carry out cuts and punches for which different tools were originally specified. In each case, the operator can review the list of tools and replace or change any if needed.

The software will display the resulting layout and the operator can then still make changes to use the sheet optimally.

Specifying the metal sheet size helps determine the parts layout. Before the software places the parts on the sheet, the operator has to define part spacing and room for clamps. The software will display the resulting layout and the operator can then still make changes to use the sheet optimally. Depending on how many parts are needed and the size of the sheet, specified values for clamp areas, parts spacing and parts placement can be changed to reduce waste to a minimum.

Optimizing the Process

Once the layout is finalized, there are several optimization tools that the operator can use to reduce cutting and punching times. Tool travel represents a substantial percentage of the time it takes to complete a job so reducing the tool path length can make the whole sheet metal fabrication process more efficient. SMP/IS has automatic tool path optimizing features and can also optimize tool by tool and with operator input in interactive mode. The software gives the operator a read-out on tool path length and optimization can often reduce the tool path length by as much as 50 percent or more.

The original tool path often looks disorganized, crossing over the entire sheet and jumping from part to part in an apparently random fashion. An initial optimization cleans up the path so that it looks like a series of rectangles with the tool processing the parts in sequence, always jumping to the nearest next part. To start the automatic optimization process, the operator can ask for an automatic optimization of all tool paths. This gives an overview of what optimal tool paths could look like and an indication of how short a tool path is possible for each tool.

While such an automatic optimization is usually an improvement over the non-optimized path, reducing tool path lengths substantially, the automatic process ignores specific requirements that may be present for a particular job. Sometimes holes or certain contours have to be punched or cut first or a given sequence of hits may have to be followed. With SMP/IS the operator can change the sequences and impose the constraints required for the job.

The combination of automatic and manual features in SMP/IS allows operators to make the manual changes required for an optimized tool path while retaining the speed of automatic optimization.

At this point the operator can make several adjustments. With interactive optimization, he can choose the starting point and work tool by tool. There may be a concern with sheet rigidity that requires a given sequence of cuts and punches or certain holes and contours may have to be cut first. SMP/IS lets the operator make these adjustments easily and quickly.

One way to impose sequencing is to introduce zones where all operations within a zone have to be completed before the tool can move on to another zone. Zones are usually vertical columns or horizontal fields and they allow the operator to set priorities for which parts have to be cut or punched first. A combination of zones can give the operator tight control over the sequence of operations required for the job.

The combination of automatic and manual features in SMP/IS allows operators to make the manual changes required for an optimized tool path while retaining the speed of automatic optimization. They can run the automatic program and then make changes tool by tool or they can impose starting points for each tool path and zones to constrain the automatic sequencing.

G-Code Creation

When the operator is satisfied with the tool paths, he can give the command for G-Code generation. G-code is text-based and SMP/IS can display the code for operator review. In each case, from file importing and conversion to generation of the final G-code, SMP/IS speeds up the process with fast automatic functions while always allowing for operator review and operator changes. This combination of automatic features and interactive modes is an efficient process that results in optimized code adapted to the requirements of each job. Generally SMP/IS sheet metal CAD/CAM software can go from dxf to gcode in under a minute per CAD file.