[sybilsurf]

Forgive my newbie question, but for the life of me I can't understand why the standard R&P pivots on an eccentric?

I can almost wrap my head around needing to "tune" the motors for a slaved system so that they don't fight the pitch amount. However, it seems to me that if that was the case I would have seen some procedure published? Am I missing something? I do notice that my X sounds much happier than my Y axis...it keeps nagging me that maybe there could be some improvement in the pairing of the two steppers?

Thanks if anyone can educate me.

Ward

[ahren]

Hi Ward,

None of our rack and pinion systems actually pivot on an eccentric. Our PRO drives do have an eccentric collar bearing at the pivot, but the eccentric portion of this is just in the actual collar which locks the bearing to the shaft. The actual bearing pivots concentrically around the shaft.

Best regards,

Ahren
CNCRouterParts

[sybilsurf]

Thanks Ahren, so why an eccentric bushing? Seems to me that it adds complexity?

[ahren]

It's not really that complicated -- the eccentric collar basically just pinches the bearing against the pivot shaft. This keeps the drive from moving in and out axially along the pivot shaft without requiring a precision length shaft, and allows adjustment in this direction for applications that require it -- we have some OEM customers and a number of DIY customers who make use of this.

Best regards,

Ahren
CNCRouterParts

[ericclinedinst]

It's not really that complicated -- the eccentric collar basically just pinches the bearing against the pivot shaft. This keeps the drive from moving in and out axially along the pivot shaft without requiring a precision length shaft, and allows adjustment in this direction for applications that require it -- we have some OEM customers and a number of DIY customers who make use of this.

Best regards,

Ahren
CNCRouterParts

Just to shine some clarity on this, the drives that sybilsurf has aren't the ones from you guys Ahren. They're the "copies" we've been discussing. The "other guy" is just using a pinch collar of some type that you smash up against it then tighten. Not exactly the same setup you guys use. (Yours is much better in my opinion)

[ericclinedinst]

Also here are some pictures. So people can get an idea of just how bad the fitment is. As well as the poor rack engagement.

[LeeWay]

Many pillow block and flange bearings use the same type of locking collar. It is a very old design that works well. It basically holds the bearings position on a smooth shaft.

[sybilsurf]

Ok thanks guys. So if I understand correctly the whole point is to avoid custom shoulder bolts or shims then. I was thinking that the eccentric was to move the pinion fore and aft along the rack to "time" the slave stepper to the master.

[LeeWay]

That is done by adjusting the homing or limit switches.

[sybilsurf]

Lee, I may be missing something... I thought the limit switches were adjusted to square the gantry to the Y axis?

I just want to make sure that my slave isn't somehow fighting my master.

[LeeWay]

Yes. It does that too. When you home it, you want both the X and slave to hit and back off the switch at the same time leaving the gantry square at that point. If the gantry does get out of square somehow like during a very long program, then just re home the machine to start the next job square.
My plasma cutter can show very little difference from being run all day. It generally hits both switches at the same time. I have had it get skewed with trash on the rail before and after it hits both switches, it's back square and ready to go again.

You need identical settings for the slave and Master to be timed by the controller, but the homing switches are what aligns both together to start a job.