Losing steps on Y, no load condition

[CStevens]

So here's my issue and what I suspect could be the problem. Figured I'd post it on here and see if I'm looking in the right direction

When running a laser project (hence no load on machine), I get situations where the bot will basically freeze up for a few secs and then will continue on perfectly fine (after burning an extra deep spot in whatever I'm doing). I don't see this on small runs 5-7mins, but it seems to occur more on longer ops 20m plus.
I will also get occasions where it will lose 1/16-1/8 of steps on the Y axis...always the Y axis.

Never happens when cutting wood or carving....at least I don't notice it then. Those ops are generally not as intricate as the laser cuts.

I'm suspecting the PC is the culprit but I'm not sure. She kinda peeved me today as I was within 15m of finishing up a 2hr project and she skipped a few y steps and ruined the whole thing.
If it matters I am running at .8ips with no load at all.
Gantry machine, original steppers with a recent RBK box upgrade
Nothing else is running on the PC other than shopbot and spindle controller. I5 Pentium processor/6gb ram, windows 7. Not using a hub, just the bot, spindle, keyboard and mouse plugged directly into the PC

Thanks for any direction on this.

[Tim Lucas]

Not a Dell comp is it? Dell has known issues with USB ports when connected to Shopbot.

That said have you preformed a speed test to see what you Transmission Efficiency is ?

in SB3 select Utilities then Diagnostic Tools then Speed Test

Tim

[bleeth]

On larger files, depending on which software version you are using and also what control card, there is a limit to the number of lines of code that the controller will handle at once. When the limit is reached the tool will pause in position until the next packet loads. Once upon a time it was around 50k lines (PRT). It is much higher now but still there. Those doing heavy 3-d work learn about it quick.
You may want to break your larger files up into a couple different toolpaths.

[CStevens]

I'll have to look up the speed again. I have looked at it before. Yes, its a dell. I am a Mac fanatic but they are all in use and the dell was in the extra pile doing nothing. Unfortunately the other one thats sitting idle is a Dell as well.
The file I had an issue last had 91K lines of code. Thanks for the info. I'll start searching around for a non dell or I may have to see what parts I'm missing to build one

[scottp55]

Some have problems with the Dells, but running one for 3 years now with no issues on my Desktop with a year of production and a lot of 3D's now.
If your speed test/packet_ET test (type UT/UD) shows good data flow, you're probably ok.
For the second Desktop we bought, we did go HP though...still good after almost 3 years...neither has ever touched the internet and are stripped down though.