I was making a steel cam the other day which is a disk about 3" in diameter and about 3/8" thick with four cam lobes around the outer periphery. I decided to use the 2D contouring op as it is pretty efficient and produces really nice surface finishes as only the flank of the tool is used. The job assignment was the projected curve from the outer periphery, but since the workpiece was a bit larger than the worst-case OD of the cam, I also defined a tubular workpiece with the appropriate dimensions of the real workpiece. In the parameters section I defined a single step of .15" thickness so that the cutting operation would take a full depth cutting pass of the actual lobe. Finally, I selected a tangential lead-in and a roughing zone of .10" with a per/pass width-of-cut of .010" as the material I was using was not fully annealed and I wanted an clean surface finish. The operation simulated and the color-coded toolpath checker showed the part being cut perfectly with no gouging or remaining material left. However when I cut the actual part it was badly gouged in the area of the tangential lead-in.
I'm sure the issue was mixing a workpiece with a 2D contouring operation which is probably not fully supported although I could not find any warnings in the manual about this. On the second attempt I solved the problem by extruding a fixture using the lobe profile curve in order to keep the tool outside the actual part profile. In all fairness to Sprutcam, upon close inspection of the machining result in the simulation tab before the simulation was actually run there was a tiny and easily overlooked line showing the path of the tool running into the part, but when the simulator was run there was no hit of trouble in the 3D machining result. - Terry
OK, here is the project which gouges the part. Creating a fixture by extruding the lobe profile curve eliminates the problem. I've also since found that checking the strategy box "check workpiece" also fixes it. It just seems that the simulation with its part checking tool should show the gouge or warn the user (or even better yet not create the gouging toolpath in the first place). - Terry
Do you use the Machining Result With Part Compare feature when you simulate? It's on the bottom toolbar, just to the left of the calipers. Once you've simulated the program, you can click that and it will change the colors of the part to show how it compares to your model. Green is good. Yellow and Light Blue are - and + 0.001". Red and Dark Blue are - and + 0.010".
The color scheme makes gouges and extra material visible without so much eyestrain.
It doesn't fix your gouge, but it can help you find problems like this before you cut metal.
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I use that color-coded machining result compare all the time - it is very useful. But on this particular issue it did not show the gouge. I received a reply from U.K. Dave ( UK Sprutcam support guy) over on the Sprutcam Forum which should also be useful for others:
Thank you Terry for supplying this project.
The first thing that I will say is: This is not a bug! SprutCAM is behaving correctly.............why?
The 2D Contouring operation is only considering what it is given to work with: a 2D Curve. Just because the curve was created from a surface(s) does not mean that the surface (or model) is considered when the toolpath is calculated.
It is done this way for a good reason. 2D Contouring can be used to machine either on the centreline or the inside or outside of a curve. This gives us immense flexibility that is sometimes not afforded us when machining a surface / solid model.
The problem was caused by the approach and retraction moves that you have applied to this curve. These moves, which you have applied, have caused the cutter to overcut the selected curve.
This problem is easily solved by selecting either a more appropriate approach / retraction move, or, you can dynamically change the start / finish position for the machining.
If you are unsure how to do this, I have created a short video to demonstrate: http://www.download.sprut.co.uk/Foru...rt-Finish.html
The 2D Contouring operation does not require a workpiece to calculate it's cutter paths. As you have alluded to, you can apply and use a workpiece if you wish by selecting 'Check workpiece' in the Trimming section of the operation. This allows SprutCAM to trim away any cutterpaths which are outside of the workpiece.
I see that you have also cross posted this to the CNCZone forum too. I do not use that forum so could I ask that you please post a reply on there to update other SprutCAM users of this issue? Thanks.
can you post the full link for that video demo? It gets cut off in your original post.
Tormach PCNC 1100, SprutCAM, Alibre CAD