This article will take you through the pros and cons of where to set job file datum.
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You can position the job file datum anywhere on the surface of the job file. There are, however, certain positions that are better than others, depending on your application.
When you position the job file datum, consider how it will align with SmartBench’s working datum, and where your stock material will be in SmartBench’s workspace.
Choosing the position of the job file datum in the XY plane
It is most common (and easiest) to position the job file datum either in the centre of the stock (A), or one of the corners of the stock (B).
When should I position the job file datum in a corner?
When using rectangular shaped stock material, a corner is a good place to put the job file datum; when the job is loaded onto SmartBench, it will be very easy to line up the tool or laser crosshair with the corner of the stock.
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The bottom left corner is the easiest place to set the job file datum, as you will then set SmartBench’s working datum at the corner of the stock material that is closest to the home position, and closest to the user operating the console.
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One potential downside of using the corner is that if the corner of the material is damaged, or non-square, you won’t have a sharp reference point to set SmartBench’s working datum against.
When should I position the job file datum in the centre of the job?
Using the centre of the material as the datum is useful when you are processing pre-cut material, for example: if you are engraving onto a piece of material that is already cut to size, and you want to guarantee that the engraving is centred on the material.
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We recommend marking the centre of the stock, so that it is easy to line up your tool or laser crosshair when you set SmartBench’s working datum.
Using a straightedge and a pencil, draw two diagonal lines from the corners of the stock, such that they cross in the middle.
When you position SmartBench’s working datum, use the centre of the cross as your reference.
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Using the centre can also be a good option if the stock material you are using is an odd shape, or not the same size or shape that you originally specified in your CAD/CAM package.
If the stock material you are using is longer than SmartBench’s Y Bench, position the job file datum in the centre of the job, as you will not be able to position the tool or laser crosshair over a corner.
Choosing the position of the job file datum in the Z axis
You can position the job file datum either on the top (A) or bottom (B) surface of the stock material.
When you come to set SmartBench’s working datum it needs to match the job file datum (so both datums should either be set on the top or bottom surface of the material).
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If you position the job file datum on the bottom surface of the stock material, you will set SmartBench’s working datum against the spoilboard.
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The best place to position the job file datum depends on your application.
When should I position the job file datum on the top surface of the stock?
The top surface of the material is easier to access, especially when working with a large sheet, so it can be a good option if your stock material is covering your whole spoil board.
The top surface is also a good option if you are only working on the top surface of the material, for example: engraving or pocketing as opposed to contouring.
The main drawback to using the top surface is that it doesn’t account for the variation in material thickness. This can lead to worse finished part accuracy as well as inconsistent tab thickness when contouring.
When should I position the job file datum on the bottom surface of the stock?
Using the bottom surface of the material does account for variation in material thickness which will increase the finished part accuracy, as well as improving the quality and consistency of your tabs when parting off.
The main disadvantage of using the bottom of your stock material is that it can be hard to access if your stock material covers your spoilboard.
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If the material is thicker than specified in your CAD/CAM toolpath, referencing the bottom surface as your datum will mean that the first pass of the tool will be cutting more material than expected, which may require you to alter your feed rate for that pass.
You can alter the feed rate during the job, using the controls on the SmartBench Console.
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