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4-axis CAM software for ShopBot machines

ShopBot uses a proprietary NC file format

A well-known brand of CNC milling machines in the USA is ShopBot. They make machines in various sizes, up to 5-axis. Shown below is the smallest model: the 'Desktop MAX'.

Photo of two Shopbox machines
Two ShopBot desktop machines running DeskProto files on a Maker Faire (New York, 2012).
The machine on the left has a rotation axis (indexer) installed.

In order to work with a ShopBot machine some background information is needed, as ShopBot does not use industry standards but applies a number of proprietary solutions to control the machine.

Most important is the NC file format: ShopBot does not use G-code, the machines need NC files in the proprietary .SBP format. Here are a few lines of NC code, to machine a simple square.

This is the G-code: 
	G00 X0.000 Y0.000 Z5.000 S2000
	G01 Z-1.000 F1000
	G01 X100.000
	G01 Y100.000
	G01 X0.000
	G01 Y0.000
	G00 Z5.000
And this is the SBP-code for the same square: 
	J3, 0.00000, 0.00000, 5.00000, , , 
	M3, 0.00000, 0.00000, -1.00000, , , 
	M3, 100.0000, 0.00000, -1.00000, , , 
	M3, 100.0000, 100.0000, -1.00000, , , 
	M3, 0.00000, 100.0000, -1.00000, , , 
	M3, 0.00000, 0.00000, -1.00000, , , 
	J3, 0.00000, 0.00000, 5.00000, , ,
So "J3" (3-axis jog) instead of G0 and "M3"(3-axis move) instead of G1.
More importantly: no characters ("X", "Y", "Z") to indicate for which axis the coordinate is meant: that is defined by the position on the line. So ALL comma's are required. DeskProto comes with a postprocessor that fully supports this SBP format.

A second difference is the Feedrate. DeskProto by default will reduce the feedrate in case of a high chipload (when removing material over the full width of the cutter) and for plunge movements. However, the ShopBot control software (SB3) cannot handle a feedrate that changes all the time. So for ShopBot we had to disable Feedrate control in DeskProto: you need to set the feedrate in SB3 before starting the program. In order to not forget this a message will pop up:
As ShopBot does not like DeskProto's frequent speed changes no speeds have been set. Set your speeds in the ShopBot software (under 'VS') before continuing.

One of DeskProto's unique selling points is the support for rotation axis machining (4-axis). That also works great on a ShopBot machine. Here as well a small difference: ShopBot calls their 4th axis module an Indexer. So that is the word that you need to use when looking in the ShopBot documentation.

You can find more information on all issues mentioned above in the ShopBot software documentation.