The ShopBot “Virtual” Toolchanger

Recently, the Thermwood Corporation and ShopBot Tools, Inc. introduced a new product called “The ShopBot Link”. The ShopBot Link is a nesting and toolpath program that allows us, the ShopBot user, the same ability to cut files on our ShopBots as were previously only afforded to Thermwood owners. These cutting files are generated by Thermwood’s eCabinets software which is a very feature rich cabinet design suite that is production based with an end goal of increased production thru CNC cutting of nested base cabinet and furniture components. eCabinets has thousands of users and the network created by those users may be the largest of woodworking professionals in the world. Thermwood has spent millions developing and refining the eCabinets software into a respected professional design program. The best news for us as woodworkers, is that they do not charge for it. It has been touted to be on equal par with programs that cost upwards of $20,000.

The eCabinets design software was designed for use on only Thermwood branded CNC cutting machines. As this would apply to their CNC flatbed routers, which are single head machines with automatic toolchangers that allow bit changes within a cutting file to increase speed and expand cutting capability with the use of special purpose bits, it would also not apply to the majority of ShopBots in use today. Most of the ShopBot machines have a single head, with a single cutting bit. A small number have a second cutting head and/or drills attached to increase capability. ShopBots with automatic toolchangers are extremely rare. Most of these have been custom built for commercial applications. There has also been a recent announcement by ShopBot that they now have an Automatic Toolchanger as an option to their PRSalpha line of products.

For those of us that are not going to call and order an ATC from ShopBot to bolt on our machines, how is it that we take code that is designed for the multi bit “Big Iron” and get it to work on our smaller, sometimes self modified, ShopBots? One of the solutions lies within the advanced toolpath engine inside the ShopBot Link itself. You will be able to set cutting, routing and drilling parameters that match both your machines cutting and hold down capabilities. Once set, these parameters will allow you to add tabs, onion skin, multiple passes, reduced last pass cutting speeds, or whatever is needed, simply by entering part size parameters. For example, you can set a narrow width of 3 or 4 inches and assign tabs and/or reduced speed for the final pass. There are many more options that will allow you to cut better parts with less waste than previously possible with the vector based CAD/CAM software that has been our standard.

Another solution lies within a group of Custom Cut files that has been reserved for a toolchanger. These are the Custom6, Custom7 and Custom9. Most of us without a toolchanger have already found a perfectly good use for these files as easy access to often used cutting files. If you use, or plan to use the ShopBot Link to process eCabinets designed files, and unless you have a single axis machine, you will need to add some specific content to your Custom6, Custom7 and Custom9 files. These are the files called up in a toolchange routine by most post processors and now, more specifically, by the ShopBot Link, as it progresses thru various segments of the cutting file. If you have a single axis machine, with no attachments such as a drill, you will have to enter the text “END” in each of these files and not use them for anything else if the SB Link is to operate properly. Sorry, your favorite C#, just like mine, has to be renumbered.

If you have a single axis machine, you should plan on this when designing your files. Design around your preferred bit. Most likely this will be either a 5mm or ¼” compression bit. This bit size will be determined by the smallest hole that you have to drill in your files. If you wish to take full advantage of the hardware drilling and positional accuracy of CNC then 5mm will be the bit of choice. You should then design your dados smaller, use mortise and tenon systems or use a design that lowers the number of large dados which will eat up machining time. Process your 35mm hinge holes on a press, as these do not machine quickly with a small bit.

If you have multiple cutting heads as I do, then we need to find a way to enter all the differences in both location and operational control, and trick the SB Link output into thinking we have a single tool with multiple bits, instead of multiple heads that may be in as many as 6 different locations. Each of these tools could be called up a dozen times each in a multi sheet cutting job. This is where the 3 “custom” files come into play. In general terms, the 3 files serve the following purposes:

Custom6: This file starts your spindle or router if it is being used for the current cutting segment. It will also switch on any outputs you require for vacuum, dust collection, etc. It is always called up after a C9

Custom7: This file turns off outputs, spindles and routers, retracts plunged drills, and resets any offset required for other heads back to that of the primary cutting axis. This file is called up before any toolchange and at the end of a file.

Custom9: This file, which was originally designed to drop off and pick up bits from a tool rack, will now have the job of tricking the SB Link into thinking it is dealing with a single axis machine. Luckily for us, ShopBot is implementing a few new commands into the SB3 software and adding some new parameters to some old familiar ones. These new additions will make this “trickery” much easier. If we have added heads to our machines, the control software knows where all the additional tools are located. SB3 stores these distances, called offsets, in the my_variables.sbc file. Every offset for every tool is stored with a specific name describing what it does. These offsets will be used to offset the primary cutting axis instead of being added or subtracted to a position as we have been used to in traditional output from CAD/CAM post processors. With traditional CAD/CAM we selected a proper post processor that added the offset to the required position. When using the ShopBot Link we will have single axis commands coming into SB3 and no option to select a different post processor. Hopefully this article will give you an idea of what we need to do. As many of our machines are configured differently, we may all have a slightly different version, making these truly custom cut files.

The Thermwood tech team has been kind enough to decrypt some of the files I have processed thru the Link. In typical cutting file format, here is what happens in one of these files.

1)FILE START Link asks for wasteboard thickness. (most of us will not use this, and may not come up if it has been set to zero in settings)

2) Link asks for a sheet number or accept sheet 1 to start Link outputs “(Locate 3/4 Generic then click OK to start operation” as message box we are used to (this will be the name of the material used in the cabinet design)

3) Callup C#,90 (my_variables file)

4) Link outputs “&ZSHIFT” variable as exact material thickness (this allows us to zero 1 time to spoilboard and cut any thickness material accurately

5) C7 (makes sure spindles are off, offsets are reset, and axes are at default)

6) &tool = *** (this is the next tool needed for cutting)

7) C9 (here is where, using the tool#, we swap axes Z & A if needed, apply any offsets required, plunge a drill, select the proper output switch to on etc.)

8) C6 starts spindle, or router and switches on any required outputs

9) …(Lines of cutting code here)…

When cutting segment with this tool is complete:

C7 AND REPEAT as needed.

This will happen for every tool that is required for each sheet and for as many sheets as have been selected for cutting. Those of us that are testing the ShopBot Link for Thermwood and ShopBot are building and testing these routines on our machines. They seem to work very well. Each “Virtual Toolchange” goes by in a few seconds, much faster than an ATC could change a cutting tool. We seem to be in agreement that the ShopBot Link will be a tool that we will not want to be without.

Next Month: What is actually in the files and how to customize them to your own preferences.

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