WTF is wrong with Fusion toolpath simulation - takes forever - SIMPLE FIX!

Dunno what is wrong with my PC. It takes almost forever to simulate the toolpath for the exhaust flange. It's not a large or complex part but I timed it consistently at 5:30 minutes to complete a simulation.

That simulation is the generation of the toolpath and, in particular, the stock removal. There are quite a few contributors to the processing time:

• I don't have a particularly powerful processor in my PC. It's a GMKTEK NUCBOX9 (SFF tiny PC thing) with an AMD Ryzen 5 5600U. This is considered to be broadly equivalent to an Intel Core i5-1135G7. It should be fine for my needs - and better than the previous PC I was running - which in turn seemed to be well powerful enough.
• It has an inbuilt Radeon Vega 7 integrated graphics, which is generally thought to be good enough to play "light and casual" games. I'm only running fairly simple CAD graphics here - and Fusion isn't that demanding when it comes to graphics. Gone are the days when you had to run a Quadra (CAD) or a high end gaming graphics board.
• I'm running 3 displays at 1080p aka FHD. That's not quite 2K and certainly not 4K resolution but it's fine for my needs and my monitors can't do better. The Radeon graphics should be fine with that.
• I have plenty of RAM now, having upgraded to 64GB. With Fusion running with 16GB, I was running out of working RAM, with the risk of having to use the swap file which slows stuff down a fair bit.
• It seems to be the adaptive toolpaths that really hammer the simulation times. Sure enough, the adaptive part of the operation dominates the time by far:
• Adaptive 2:55
• Bore 1:05
• 2D Contour 0:33
• Drill 0:07 (hard to time it precisely though)

But waiting for over 5 minutes to get a toolpath simulation completed is taking the piss. Some thing needs to be done - and it won't involve buying a more powerful PC.

In the interests of science - and to avoid losing the will to live during toolpath simulation, I tried changing various settings:

• Unselecting the various "Display Graphics Effects" options that are set by default:
• Ground plane
• Ground shadow
• Ground reflection
• Object shadow
• Anti aliasing

These made sod all difference.

• Then I messed with the settings within the adaptive toolpath, namely the tolerance and the fine stepdown, which seems to be set to 10% of the roughing stepdown by default. I increased it to 1mm.

That did f*ck all too, so I put it back to 0.3mm.

• Finally, I reduced the "Accuracy" setting in the Stock section of the simulation dialogue box. The slider has 10 positions and is set to 10 by default. Position #1 is "minimum accuracy" and #10 is "max accuracy".

This utterly transformed the performance - setting to mid position (#5) removes the bottle neck. Running just the Adaptive toolpath, we now get ~00:26, down from almost 3 minutes.

• You can then increase the speed of the displayed simulation without being held back by the processor trying to keep up. In fact, it can generate run the whole toolpath within ~3 seconds and it's the graphics that struggles to display the toolpath, not the processor doing the calculations. But what is the sweet spot? How much can I turn the "accuracy" slider back up before affecting the simulation time?
• Interestingly, when you change the slider position, a text appears, saying the stock generation is being completed. It seems to recalculate the stock automatically each time a change is made to the accuracy slider setting. As this stock generation seems to be the cause of the issue, we can simply focus on those times, rather than run the whole simulation each time. And here's what I found for the stock generation time for each slider setting:
• #5 < 1second
• #6 ~3 seconds
• #7 ~3 seconds
• #8 ~4 seconds
• #9 ~35 seconds
• #10 1:44 minutes.

Here's the "stock generation" text, visible at the bottom of the screen if you look closely:

These times are fairly approximate because it's actually quite difficult to measure without some sort of anal video capture approach. I have a life to live, so that isn't going to be how I do this. I just used the stopwatch on my phone.

But there we have it. Simply putting the accuracy slider to position #8 largely sorts the problem out. I'll leave it set to #7, at which point, the only bottle neck seen occurs if you crank up the simulation display speed to something dumb, where the graphics struggles to display enough FPS to give a smooth view.

So indeed there we have it. The fix is actually very simple. That feels like a result.