Shopbot Buddy Jerking

[kuobenj]

We've been using a shopbot buddy for at least 4 years now, but recently its developed aw problem of jerking.

I believe it is primarily in the y direction.

This occurrence seems almost completely random, because we've on occasion been able to cut out perfect cuts, but it is hit or miss.

I know that this is not a software issue.

When a jerk happens its almost as if the machine gets held up, then suddenly "gets over" the issue, with a rather loud noise. (The cut is also botched) however, while powered off, one can push the moving parts on the shop bot with ease.

Often times the jerk misaligns the job, and the shopbot stops the job throwing an error.

Finally, this may or may not be related to an incident plunging to low once, but I believe the E stop button was hit in time to prevent too much damage.

Are there any ideas what may be wrong with the shopbot?

[Brady Watson]

There are 2 places to look.

1) Make sure the table rack to motor pinion is correctly & fully engaged. It is easy for it to be partially engaged & to skip a tooth under cutting load.

2) Your computer. Read this thread (http://www.talkshopbot.com/forum/showthread.php?t=15547) to the end, and make sure you are compliant with all of the recommendations. Take nothing for granted.

-B

[cowboy1296]

I just recently went through this. Not sure what caused it and not sure what cured it.

What I have done:
re-did my shop bot setup:
reduced the depth of cut;
used bits with longer flutes then the total depth of cut.

now when i thought that everything was ok i had another issue raise its ugly head just two days ago. In my absense i found that the router motor had stopped, the z had gone deeper and the bit broke. the bit breaking probably saved my project. i checked the brushes and they were totally worn out. So i am not sure if the brushes being worn may not have caused my problem all along.

Since the brushes were replaced i have done 10 hrs of 3d cutting with no more issues.

so hopefully this will at least give you some direction.

[zeykr]

Check that pinions are tight on motor shaft.

[garyc]

SK...
After you complete the above and if the problem has not been resolved, here are a couple more things to check:

1) Back off the adjustment screws on the motors, slide them away from the racks and verify that all axes move freely thruout their full range. Clean thoroughly, lube, reassemble and adjust as per the manual.

2) Try running a problematic file again zeroed above the table, spindle/router on, but with dust collection off, maybe even remove the hose from the machine. Many errors that result in a loud thud and lost comm error message are static induced.

There are dozens of informative threads here on the forum that go into great detail on how others have reduced or eliminated dust collector caused static issues.

[shilala]

This is exactly what the comm errors looked like that I was dealing with when I switched laptops.

[cowboy1296]

@Gary. While on the subject of brushes, my last set seemed to burn out way too soon. Any guess on what could have caused that. i do a lot of 3d but it has only been close to a year. most all projects are hardwood of some kind or another.

thanks in advance

[billp]

Rick,
By any chance are you cutting at the higher speed range of your router? Higher RPMs = shorter brush life...

[cowboy1296]

not really? 13000 for v-varving, profile cut outs, roughing. 16000 for 3-d finsh. how does that compare?
thanks

[billp]

Well since you'll usually spend more time doing the 3D cuts you're running the router at higher speeds much longer than when you V carve. Have you tried backing off on those speeds for the 3D work? if so was the result (if different) very noticeable?

[cowboy1296]

i can certainly try it. the only reason i went with 16k was due to the fact that read it on here somewhere. not saying that it was a good idea i just read it on here. what speeds do most run 3d?

[billp]

That has a lot to do with the material, etc. I always opted to go with slower speeds when I ran a PC router largely because of the obnoxious sound it would make at higher speeds. Much of my work was done in foam. It wouldn't hurt to try the slower speeds in a test situation, because again you'll tend to get much longer brush life when you do, but you'll have to weigh that against the quality of the cut you are getting. it was rare for me to cut at speeds higher than 10,000...

[garyc]

Rick...
Other than my collection of hand held routers I have no CNC experience with them, so, I cant be of any help to you. I am sure there are many that can.

[steve_g]

Rick

At Bills suggestion in an earlier thread... I cut my V-cutting RPMs down to the 10K range. I didn't notice any difference in cut quality in hardwoods or MDF. I was however able to hear better at the end of the day!

SG

[cowboy1296]

Thanks for that laugh. Maybe I have been doing this all wrong and need to slow down. Sounds like my first mistake in 2012, : )