Losing steps while cutting

[phil_o]

While cutting HDU on a 3D finishing cut I was losing steps. I was using a new Beckwith 1/4" carbide bit. Cut was 1/2" deep with a 10% stepover at 200"/minute. The cut would be fine for quite a while and loose steps causing the cut to be slightly off track.
Other than cleaning the rack and pinion and applying fresh grease what might remedy the loss of steps. The is a 10 year old 4g Shopbot benchtop. I have recently made cuts that are much more stress on a cut than cutting HDU. I also did a USB port test with the Shopbot utility, the rate was 76.5%.
The machine has not been used heavily over the 10 years.


Thanks,

Phil

[Martin Reid]

Dear Phil

Early that day (or any time since you turned the desktop on) did you remove the device from the USB port without using the the 'safely remove hardware and eject media' option.

We have had issues when staff have 'pulled the plug' without safely ejecting. We found that doing a hard reset - shutting down the computer and turning the power off the shopbot, then waiting a short while before turning back on, prevented further problems, as long as the USB was ejected correctly.

Also is is probably best to use shielded USB leads.

Sincerely
Martin

[phil_o]

Martin, this is the first time I've heard of the safely remove hardware and eject media option. How is it done?

Thanks,

Phil

[cowboy1296]

my first experience with loosing steps, the brushes on my router needed changing and i was loosing rpms

[steve_g]

I recently experienced what I thought was loss of Z steps… turned out to be a totally warn out collet!

SG

[Rob Gunn]

Iv had issues with static electricity building up and causing the tool path to jump and act crazy. Not saying that this is you issue but maybe worth looking into. I fixed my static issue by adding a good earth ground to the machine and the vacuum hose.

[Martin Reid]

Martin, this is the first time I've heard of the safely remove hardware and eject media option. How is it done?

Thanks,

Phil

Dear Phil

The example here is off my tablet Windows 8.1; I know it is similar in 7 and there will be the option in 10.

32603

All the users in our workshop know to use this to remove the USB memory sticks which we use to transfer part files. Failure to do so has caused some weird events including missed steps, comms errors and worse.

You will need to do this if you are disconnecting your laptop or tablet from your ShopBot desktop with a USB lead.

Sincerely and in good faith
Martin

PS
Rob's right - good earthing (you would say grounding) is essential.
SG is right people don't change collets (and collet nut) as often as they should.

[coryatjohn]

I've never used the "safely remove and eject media" option on my SB computer. I just read the files, not write to them. As long as you're not writing to the USB device, the eject operation is optional.

[phil_o]

Thanks to all. I learned a lot. Not sure exactly what the problem is but I have things to look for; hot stepper motors, feed rate too high, static.
I also contacted Shopbot support and performed a few maintenance items. These links are worth a look for anyone with a CNC.
Maintenance items http://www.shopbottools.com/ShopBotDocs ... 0%2024.pdf (http://www.shopbottools.com/ShopBotDocs/files/SBG%2000203%20TroubleShooting%20Mechanicals%202014 %2010%2024.pdf)
Computer issues https://www.youtube.com/playlist?list=P ... aY2HkQMJtj (https://www.youtube.com/playlist?list=PLf632tVju0dEzZ5LnKpb98aaY2HkQMJtj)
Tips on setting up your PC https://mail.google.com/mail/u/0/#inbox ... rojector=1 (https://mail.google.com/mail/u/0/#inbox?projector=1)
I spent most of the morning checking out a number of maintenance issues. Now I hope all is good.

Thanks again,

Phil http://forum.vectric.com/images/smilies/icon_smile.gif

[phil_o]

On the Vectric forum Gary Campbell suggester that the stepper motor running for hours can build up enough heat to cause the loss of steps. I set up the file to cut as a 3D raster finishing toolpath, running left to right. So the X axis stepper motor was doing most of the work. I was loosing steps in the X axis. I'm considering setting up the file either as a raster on a 45 degree angle or an offset toolpath. Any suggestions.

Thanks,

Phil

[coryatjohn]

You could manually edit the tool path file and add a pause in the stream every hour or so. If you have one of those non-contact infrared thermometers, check the temperature.

[srwtlc]

Read up on ramping and create a set of ramp values just for 3D work. The abrupt change in direction will cause loss of steps. This can also happen with the Z axis where there are a lot of abrupt up and down movements. Along with a little slower feedrate for a standard, you'll need to soften that direction change. Doing a 45º could cause lost steps on both axes without adjusting the ramping. Write down, take a picture or save to custom, your default ramps before testing.

http://www.shopbotblog.com/2008/03/a-ramping-the-vr-command-and-how-to-tune-your-tool-for-maximum-performance/

[phil_o]

Thanks, Scott.

[Chad@TGC]

You may already know this or I may have overlooked it but the SB rep when he was out helping us set up the Bot stated that is also best to copy the file to the computer and not to run files from the flash drive. Thought it might be worth mentioning.

[coryatjohn]

I always run files from the flash drive.

[JimDav]

I always run files from the flash drive.

Yes, and you stated you never the 'eject' either, though I think you said you never write to one which would be fine.
One can often get by running a stop sign too but it's certainly not recommended.

With 40 years working with computers, I've found it best NOT to tempt the gremlins - ESPECIALLY with older OS systems such as XP. The gremlins are active enough without tempting them.
One can often get by with breaking commonly accepted practices with life and computers with no bad results BUT that one time where it doesn't work can be devastating, or at least aggravating,

Why risk it to save second or two?

Technically I suspect you could even remove the flash drive completely to run after the program has been loaded. It is loaded into the processor to execute. I seriously doubt the flash drive is accessed again.
Back in the old days with limited memory - can you say 16K/32K - overlays containing portions of the coding were swapped in and out of memory/storage unit as needed to accommodate the limited memory.