Ajax DM45 - Angular Bearing Nut

[wtecksolutions]

Before using my low usage used Ajax DM45 for the first time I have cleaned everything and all new lube for the one-shot etc. Now checking the Gibs, Lash and Tramming. Also tightened all the Allen set screws on the belt pulleys because they were all loose. I think this machine was mostly used with the DP-4 so a lot of small step cycling.

Looked at Lash on X Axis and it looks good but when checking the (TB037) Lash on the Y axis it was all over the place and looks to be about .006 in., way to much (Lash in the centroid motor setting is set at ~.0033 in. for Y axis this still seems like a lot). Hoping the play is not the lead screw I checked the axial play of the Y axis and it looked to be .0055 in. Pulled the Y axis belt pulley and checked the lead screw Angular bearing retaining nut and it was not even finger tight. I folded back the locking tab and lightly tightened the nut (just enough to take out the play). Axial play now < .0005 in. Yea!!!.

So the question is, what should the Angular bearing nut be tighten (torqued) to? I need to tighten it at least an 1/8 of a turn so I cat get to the next locking tab. Is there a spec tightening these nuts?

Is there a service manual for machine?

Is there a Belt tightening spec for this machine?

Also when I was doing some initial Tramming checks it looks like I am getting a little Nodding on the Z Axis. Are there any documents on adjusting the Gib on the Z axis? Or should I just base the Gib adjustment on motor current/PID values?

One last question... Are there any documents in your records for this machine (like all the original PID values etc.)?

[cnckeith]

First you want to isolate the lash. where is it coming from exactly? nut to screw? screw to table? nut mount to table? etc... once you have found where the lash is actually coming from only then would you adjust the nut tension on the end of the ballscrew.

for your questions.. a great resource is the old Bridgeport Boss Maintenance manuals. (you can get them on ebay) step by step...lash, gibs, belt tension..all that is covered and applies to most any CNC knee mill or small bed mill.

.you can use several rules of thumb.. you can tighten the nut on the end of the ballscrew until it begins to cause drag, or tighten until you get diminishing returns on reducing the lash. too much drag is bad and you'll get position errors if you stall the motor and even possibly over heat the servo motor.. so be careful.

another word of warning.. its a newbie mistake to start adjusting gibs if you really don't have a grip on how things work... 95% chance you'll make things worse.
fyi.. there is a great "Drag plot" feature in the control which is useful for this type of work.. it display a graph of the motor pid out/current used over the distance of the axis.
A "U" shape graph shows that the ballscrew is not aligned with the axis movement. stuff like that is hard to tell without it.

[wtecksolutions]

Thanks cnckeith,

I did do a lot of research and didn't really want to do adjustments but I didn't want to use the machine if it had a lot of slop. Also a lot of reading of the TB docs on this site.

After adjusting the lead screw nut carefully to remove the lead screw play(Y axial movement read from the end of the lead screw was .005 now .0000) I reduced the lash from .00335 to .00112. I tried to associate lash increase, PID values as well as the drag chart when adjusting the GIBs. The slop in the table is much better and actually got better results in Kg, Kv1 and Ka after doing an AutoTune when I was done with the adjustments and compared them to the original.

I will try to find the manuals you suggested....

Thanks for your help!!