Erratic Z - random cuts too deep

[ljdm]

SB ver 3.4.27. 3D files, randomly cuts a pass deeper than it should. Will go a random amount of cuts, next cut is deeper, then goes to proper depth for awhile, then a deep cut, then normal, etc, etc.... Tried with/without dust collector on, same thing. Anybody have any ideas? Tried (at suggestion of SB support) reloading firmware, tried older version 3.4.26, still same thing. I have 3.4.25 to try also, anybody ever have a problem like this?

[dana_swift]

Hi Lou, just finished figuring out a problem like that on my SB. Your symptoms sound a lot like what I was trying to describe to tech support. What was ailing my SB was the connector nearest the Z motor. It had an intermittent connection that would apparently cause my Alpha SB to "lose its mind" in the Z axis. Other than the extreme annoyance of hunting down the problem, it was trivial to fix. My Z axis problem went completely away when the problem was positively identified and fixed.

[ljdm]

Anybody know how much axial play is normal with the PC router? Wondering if this could be a cause of my problems? After running for awhile, the collet is warm, and amount of axial play changes. Letting it cool down now, and see if it increases or decreases. There is definite play up and down though, wondering if as the router gets hotter, the bearing play decreases, and possibly when it tightens up, the bit could be at different end of available play, causing deeper or normal depth cuts? HMMMM......

[ljdm]

Quick observation - when cool, play up and down. After running for a minute (no load)play is gone. Wonder if it is binding sometimes at alternating lower/higher heights? Interesting theory, anybody knowedgeable with bearings have any thoughts? Of course, if it is bearings, makes me wonder if I should buy a rebuild kit, or go for a spindle? Hmmm, only about 1950.00 difference in cost. Sure would like a spindle though..........

[beacon14]

If you have any noticeable play in the arbor whether cold or hot it's time for a rebuild - or an upgrade!

[Brady Watson]

You should not be able to feel axial or end play in the router. The bearings are shot. You may be able to measure run-out with new bearings, but you'd need a good dial indicator to do this. If you can feel slop with your hand...the bearings are completely toasted.

-B

[ljdm]

Noticeable play is the key here....if .008 is normal runout on a new router, what is normal for axial play? Guess it doesn't really matter, just wanted to know, but going to rebuild anyway. Collet getting warm when running with no load is a sign either way.

[Brady Watson]

Even new PC routers get hot right out of the box. I wouldn't be suprised if the collet was still warm after you change out bearings. The good thing is that you'll be eliminating the slop by changing out bearings. Don't forget to replace brushes too.

-B

[ljdm]

Spoke with SB today, ordered rebuild kit. To all who might need them - SB is no longer going to sell the rebuild kits, only what they have left in stock.

[cnc_works]

Also, routers have much more end play by their very nature than spindles and could cause at least some small Z irregularities in a surface.

Donn