Persistent Com Return Problem

[Christopher_C]

I am a student shop proctor at our engineering college working on improving our shopbot PRS Alpha 48x96.I recently did a major job for a professor at a neighboring college, and in the 34.5 hours of cutting time, the machine randomly had a "com return missing on COM port 4" error no less than 4 times. It always happened right when we had paused and re-started the file the next day, or when we started the file for the first time. Every time the machine's origin was more than an inch misplaced, necessitating another half-hour with a machinist's indicator dial in the spindle sweeping in a known hole location to re-zero (the job precision was too high to allow use of the "home using proximity switches" command which on our machine is terribly inaccurate).

The machine reports a speed rating of 77.2%, which seems fine based on reading other forums. I checked in device manager-the shopbot is listed as residing on COM3 and COM4. The SB3 software finds it on COM1. Finally, in the USB viewer tool in utilities, I get the shopbot appearing in two different categories. It appears once under a generic Intel USB1 host controller alongside the mouse. It appears again under a generic USB hub by itself, which is itself sub-listed under an Intel USB2 enhanced host controller.

It is a standard PRS Alpha. The USB cable from the VFD is plugged into the computer directly on a back panel USB port, and the control box is plugged into the generic usb hub that came with the shopbot, into another back-panel usb port. The mouse is plugged in alongside the other two.

Any ideas? It's an old computer but it was powerful when new; 6 Gb ram, dual-core 3 GHZ, generic motherboard and USB hardware. SB3 is set to highest priority next to realtime. (I'm afraid to give SB3 realtime priority because it crashes about once per ten hours while cutting, which is always scary.)

[michael_schwartz]

Have you tried a powered USB hub, rather than the unpowered one that is supplied by ShopBot?

[dana_swift]

Christopher- I will bet you are using a standard desktop pc with all the services on, networking, the works.

What is most likely happening is one of these background "features" is using the machine and starving communications.

If you don't have administrative access to the PC, get one where you do.

Go to BlackViper.com and disable all the services that are indicated as not essential. You may want to do this a few services at a time, so if you do have a problem, you know what you just switched off. You can go switch them back, and continue.

What you will find, is when the PC can dedicate its attention to the ShopBot it works very reliably.

Hope that helps-

D

[dana_swift]

Also note- the new Beta software from ShopBot addresses communications reliability in a very constructive way. The jury is out on how well it works, but it may be worth a shot if you cannot disable the services that are causing your troubles..

D