The computer for my HB2 CNC router was giving me fits today. At first I didn’t know what was the cause of the problem. The problem itself is the USB step generator would keep dropping off and kicking e-fault errors. There were at least a half dozens reasons or things that could make that happen.

First issue is I am running USB serial port for talking to my CNC controller from Windows 10 OS running MACH3 software. Where to start?

I have been having issues with running the computer in my 85 to 90 degree workshop. So the heat was a strong contender for the problem.

I had run the exact same program which takes about two hours to complete, three times a few days before. I had a few errors with e-stops, so I knew there was a problem lurking in the works somewhere. Today it got very bad. When I threw in the towel it was crashing almost every four minutes like clockwork. The restarts were creating some flaws in the work. Unacceptable.

After having played with at least a dozen software configurations, I finally conceited it had to be heat related. I pulled all the cables off the computer and opened up the case. I was going to blow it out with compressed air, and did.

It is really a nice little computer and well built inside. There are two fans in the case. The front one sucks in and blows cool air into the processor heat sink. The second fan is in the rear and blows out, sucking warm air from the processor heat sink. There is a plastic tunnel between the two fans that encases the processor heat sink, Pretty good engineering.

I removed the front fan so I could blow air through the heat sink and clear out any dust bunnies that may be hiding there. There were none. The fan is a drop in device and I then realized it could be installed in either direction, suck or blow. Uh-oh, which way had it been? I made sure I got it right but had it been in backwards? This PC was a $100 re-hab so someone else had probably did the same thing I had just done.

If it WAS in backwards, the processor could easily overheat in my very warm shop and maybe run OK in cooler ambient conditions. I think this was the smoking gun, literally.

I reassembled and connected everything and put the system back on line. I ran the same program again and for over an hour, there was not one single glitch.

So the strange thing is the computer itself never crashed or failed in any way. That is why it was last on my list of suspects. All it was doing was to stop talking or maybe sending garbage to the USB port. The USB device was saying, “Hey! You stopped talking to me, I better send a halt command.”

I spoiled the oak board I was cutting for the project, so I have to pick up a replacement. The dry run testing was good, so I will give it another go tomorrow.

 Update 9/5/16

Perfect two hour run without a glitch. The shop got up to 90 before it finished. The PC wasn't even breathing hard, ha! A backwards fan was causing me a world of grief and a great challenge that I finally overcame. A computer mis-assembly was NOT my first thought. Sure feels good when things go right...