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chodges
03-09-2011, 06:31 PM
Recently, we have seen a growing number of instances where (in the middle of a job) a “Com Lost” message box would appear – despite the fact that we have a very thoroughly grounded setup.

When this happens, our PRS Alpha stops moving, although the spindle is still revolving. When we stop the job by pressing the spacebar, we also have to re-zero all 3 axes because our controller has become totally confused as to the position of the bit relative to our table.

As you can imagine, re-starting an engraving job with a lot of text is very difficult to do perfectly when you have to re-zero your machine.

Coincidentally, over the past 3 months, we have been cutting & engraving quite a bit of aluminum and brass.

Here is how we solved the Com Lost problem …

On our machine, there is an inline USB amplifier (hub) with one IN port and four OUT ports. We are using the one IN port and one of the OUT ports, and the other 3 OUT ports are vacant. Guess where too much of the metal debris from our machining aluminum & brass went – right into those 3 vacant USB ports!

We blew out the USB amplifier with compressed air, and then covered the whole thing with a plastic freezer bag held on with packaging tape. No more metallic debris to short the contacts, and (for the last 10 days so far) no more “Com Lost” issues.

My hope is that this might benefit someone else along the way.

michael_schwartz
03-09-2011, 07:06 PM
Thanks for posting that I will keep an eye on mine and check from time to time.

I had some USB com related issues which I traced to the cheap keyboard and mouse I was using at the time. After I threw those out and bought a name brand keyboard and mouse the problems went away. I would advise strongly not to use USB peripherals of unkown quality or origin.

The defective keyboard and mouse had come bundled with a refurbished PC I had bought.

Brady Watson
03-09-2011, 11:14 PM
That's a really helpful observation, Charlie. Thanks for posting your findings and remedy!

-B

tracys
03-10-2011, 12:12 PM
Thanks for posting. I have had some COM issues also and this is good to know.

beacon14
03-10-2011, 08:32 PM
Not sure I would have figured that out in a hundred years. Thanks for looking out for the rest of us.