Communication issue? Grind noise, then position loss

[bleeth]

David:
It could be that there is a service kicking in on your computer resulting in a sudden loss of comm and hence lost steps. The grinding noise is likely the stepper losing steps. You mentioned you were using your laptop, and if this computer is used for other things and has not been "cleaned" then it could be as simple as another program looking for an update or some other scheduled task like an antivirus scan or automatic de-frag.

[Brett1970]

defragged and disk cleanup regularly. I followed the guide on here, for cleaning it up, turning off unneccessary services, etc. It does not go online (disabled) and i use it for nothing except the shopbot exclusively. I am still baffled. On the speed test, i get almost 75% and i've dropped my speed to 3.5" a second and using new bits. What is the absolute BEST setup to get maximum USB speed?

[danhamm]

[QUOTEThis time, it's more like it hit a speed bump, just a quick THUNK sound][/QUOTE]
Static discharge, probably on the z-axis, from the spindle.. get a ohm meter..and resistance test every thing on it "using" a direct cable or ground wire to a referenced grounding lug on your service..

I know youve done it.. but your clues are quite obvious...copper and aluminum will coat with time and become resistive..then become a capacitor...then discharge... causing a floating reference...if your going to get rid of your headache...lol.. I'll trade you...

[adrianm]

defragged and disk cleanup regularly. I followed the guide on here, for cleaning it up, turning off unneccessary services, etc. It does not go online (disabled) and i use it for nothing except the shopbot exclusively. I am still baffled. On the speed test, i get almost 75% and i've dropped my speed to 3.5" a second and using new bits. What is the absolute BEST setup to get maximum USB speed?

75% should be fine anyway. I never get over 73% and mine is fine.

Do you have all the power saving features of the laptop disabled? Even on mains power I've come across laptops that turn off the hard disk after a few minutes, reduce CPU power and turn off USB power etc.

[bleeth]

I use an APC Hub and a serial/USB convertor rom Radio Shack. I get 84%.
I don't think it is that though.
Dan has a good point-How long since you grounded it? Have the ends or connectors built up "crud"? (You may not even be able to see it) Think how the cables on your car battery get.
Was the air humidity higher or lower on the "good" day? This won't cause a problem, but it could be an indication of where the problem is. Please don't say you have the issue when there is an electrical storm!!
You can also be having the bad luck of someone nearby cranking up a heavy welder or something and so getting surges.

[jimmya]

Cutting at 4 inches a second, I think is to fast for the standard machine. If I get over 3 inches a minute I start losing steps. Just for the heck of it slow it down and see if you still lose steps. Just a thought.

Jimmy

[Brett1970]

well, it just did it AGAIN!

The grounding was done earlier this year, and problem seemed to go away. I don't know why, i don't have near as many problems cutting melamine than i do ply. I was cutting 3.5" a second, 12,500 rpm (spindle) and a new 1/4 double flute full carbide bit. Just turned on the laptop and machine, first sheet i cut. This isn't anything complicated i'm cutting..




I had the pockets and inside cutouts as 1 file, i ran that. 2nd file was to cut out the parts, outside the line. I'm doing .375 depth passes. It cut the square on the left, the two squares towards the right side of the sheet, then it went to cut the square 2nd from the left.. it made 1 full pass, plunged, went about 5 inches, and i hear "THUNK"

totally at a loss here.

[danhamm]

What do "you" think that clunk was..? my guess is its lost communication and because it lost communication with no ramping it went clunk..!!

I wouldnt be putting anymore plywood in that machine until I had licked my problem...its not going to disappear on its own.

Get and ohm meter and a long piece of grounding wire heavy stuff 1/4 to 3/8 in. hook one end to your wire goin to your ground rods or casing ground.. and check every piece on the machine...

[srwtlc]

Just out of curiosity, is that screenshot from the computer that you run the bot with? It appears that you have a lot of programs resident in your sys tray (by the clock) that could cause issues depending upon what they are for and doing (monitoring).

[Brett1970]

nooo design computer is what i'm using now, i do all my design work on the PC in the house, and use a flash drive to take files to the laptop in the garage. I don't leave the flash drive in the pc either lol i download, remove hardware, and pull the drive.

Personally, i think it's a communication issue. I have a friend bringing me a new desktop next weekend to replace the laptop. Also bringing me a new powered usb 2.0 hub. As i said 74 - 75% and 3.5 inches a second.

Ryan from shopbot suggested i cut melamine at 4" a second at 12,500 and it worked great for a while, then i started having the thunk issue. I have ran a ton of melamine with hardly an issue at 3.5