[vtx1029]

Wow didn't expect that many pictures! Thanks.

I also should have said what do you guys think about ditching the pivoit and spring tension setup and just go with a hard mounted pinion. I know setup of the rack is going to be much more critical. What other disadvantages would one have with a hard mounted plate?

The reason I was thinking of ditching the spring tension setup is having a more consistent gear mesh with out the possibility of the gear mesh changing when you change direction (pinion riding up on the rack teeth).

[itod]

I also should have said what do you guys think about ditching the pivoit and spring tension setup and just go with a hard mounted pinion. I know setup of the rack is going to be much more critical. What other disadvantages would one have with a hard mounted plate?

I understood that eliminating the spring you can introduce backlash in the mechanism, unless the positioning of the pinion (and the rack alignment, don't forget!) is perfect. Spring tension is so effective and cheap solution, don't see why you don't like it.

[vtx1029]

I have a spot in my rack that in a 2' length has some variation. I believe it to be the rack, but know that my current setup is not without flaws. The plates have too much slop and I've had the pinion move and gouge into the motor plate. I tried to eliminate it with the screw mapping feature in mach 3 but I did not get good results when I tried to use it. I figure if I can make a few brackets to see if it improves my accuracy it would be cheap compared to buying a new rack or going to a ball screw. I could live with a little back lash if it improved my accuracy. A friend of mine that also has a router talked with Shop Sabre and they hard mount all of their rack and pinions. Just makes me wonder if the professionals are not using a spring loaded pinion why are we?

[itod]

Just makes me wonder if the professionals are not using a spring loaded pinion why are we?

Good question, and the guess-answer that comes to my mind is that they can do things a bit more accurate than we do. Anyway, keeps us posted how your new hard mounted plates are doing.

[dmalicky]

On disads to a fixed pinion, I don't think there are any other than the mounting precision required, as you all know. There are a few ways to do it... here's another good discussion--
http://www.cnczone.com/forums/linear...ed_please.html

JFG has used both and highly recommends the fixed pinion. He suggests a router sled to make a register parallel to the rails. I'm going to try the CRS spacer method on a 4x8 build, then add shim stock to fine tune if needed.

I think the main disad of spring loading is tooth wear, so for a hobby system it's probably appropriate.

On plate material, the plastic plates with narrow standoffs will be fairly flexible, so depth of cut will be more limited in a machine cutting aluminum. Plastic absorbs stepper noise, though, and is quick to make, of course.

Jannos, that second one is probably the stiffest frame I've seen, and such a clean design -- nice work! What components did you use for it?

[harryn]

I have been toying with the idea of spring loading the rack instead of the pinion assy. Of course, that requires some reinforcement of the rack.

You are right though, the pros do not spring load and recommend against it.