ShopBot 5-axis CNC error: "Parameter value below range for VS..."

[Anonymous]

When posting toolpaths created in Fusion 360 using the Autodesk post processor for ShopBot (https://cam.autodesk.com/posts/download.php?name=shopbot) I constantly get the above error. I have modified the line in the post processor to say ‘fiveAxis: true’, but have not edited anything else. 

When using 3-axis or 3+2 functionality, I can post .sbp files without issue, as these files only contain "MS" commands and not "VS". 

When attempting to use ANY 5-axis functionality, such as Multi-Axis Tilting, the post processor writes lines including 'VS' commands, which generally have two numerical values, and one of those values is always 0. However, the usable tolerance value of VS needs to be between .05 and 12 in order to function. No matter what variables I adjust, I cannot find a usable sweet spot and will always get an error message that the parameter value is either ABOVE or BELOW the range for VS. 

I understand that VS denotes degrees-per-minute (dpm) rotational speed, but can't seem to find the variable within Fusion 360 that correctly outputs a useful value. 

The only viable "workaround" I have found is to edit the posted .sbp file manually (using find and replace) to change the VS value from 0, to a value within the tolerance range. This is obviously not a sustainable practice, as there can be hundreds of thousands of lines of code in a post file, and can take hours to do. Additionally, when I do this, the machine accepts the values, but moves in a very jittery and stuttering fashion, which is also unacceptable. 

I have been back and forth with ShopBot tech support, but they have been occasionally unresponsive and not helpful, and have told me to consult with Autodesk tech support, as they don't have a fix for this. (?!)

Is there a modification for the post processor or a variable within Fusion 360 that outputs usable VS values in the .sbp file so that I can utilize 5-axis functionality in my ShopBot Router?

[brink.gregory]

I had the same problem.  I tried inserting limit checking code to make sure the values were never low enough to cause the error.  That got around the error but the motion was jerky.  I observed that the shopbot controller does fine controlling 5 axis moves on its own so I commented out the code that inserted the VS lines.  I played around with speed settings in the shopbot control software and eventually found values that give satisfactory results.  My theory is that updating the rotary axis speeds without the other 3 axes was causing the chunky behavior.

I can do simultaneous 5 axis operations (e.g. Flow, Swarf, and multi-axis contour) but I can't do 3 + 2 positional.  It appears that the Fusion 360 (and probably HSM) CAM algorithms assume the rotary axes are in the table so the XYZ motions are not transformed for the 3 + 2 workPlane.  Your post suggests you're able to perform 3 + 2 operations:  is that correct?  I'm not having success with 3 + 2.  It looks like I'm going to have to add code that transforms the XYZ motion when the workPlane is not the same as the wcsPlane.  I really need to get the 3 + 2 functions operational and so far I haven't had any luck with help finding a post that has the logic to make the transformation for a machine with rotary axes in the head.