Help with new design

[j2sip]

I've been toying with this design for weeks now. It uses homemade V-Bearings with the V part almost 1/4" deep.


The 2nd picture shows how they are arranged for the moving table. The angle bars are 3/16 aluminum. I know several CNC router design uses V bearings where they ride on rails vERTICAlly. Mine are horizontal held only by force, no preload. My question is will they be able to keep the table from lifting or falling? Or should I grind my own rail ala mechmate so that the V bearings will ride on proper V rails? Help will be much appreciated.

Thanks!
Jordan

[diyengineer]

I think well bring the conversation over here haha! I didn't know you had a build log going! Opps!

Upload some more pictures and ill be more then glad to help you with what i can. =)

[j2sip]

Blame me. I have completely forgotten about this post. Ok I'll update my drawings and study more about other's designs. Your machine is...scary. Nice drawings and renderings! Without a spify PC those would take weeks to render!

[CarveOne]

You will need some slotted holes on one side of the table for the V rollers so that you can keep enough pressure against the angle rails to prevent the table from gradually dropping downward as the rail and rollers wear in.

I would even recommend some sort of screw adjustment (maybe with tension springs) for the rollers on one side of the table to make it easier to adjust. As the wear increases you may even see the table move over a little in the opposite direction to the cutter travel if the looseness gets worse. Not by much, but the rollers need to stay in contact with the edges of the rails at all times or there will be some small amount of looseness. If you are engraving metal plates, you may notice things like sideways movement that distorts text. The letter "O" won't be the correct shape.

How bad these effects are all depends on what you intend to do with this machine. Something to plan ahead for.

CarveOne

[diyengineer]

That's 2 for 2 on the slotted bearing adjustments!

Originally Posted by CarveOne You will need some slotted holes on one side of the table for the V rollers so that you can keep enough pressure against the angle rails to prevent the table from gradually dropping downward as the rail and rollers wear in. I would even recommend some sort of screw adjustment (maybe with tension springs) for the rollers on one side of the table to make it easier to adjust. As the wear increases you may even see the table move over a little in the opposite direction to the cutter travel if the looseness gets worse. Not by much, but the rollers need to stay in contact with the edges of the rails at all times or there will be some small amount of looseness. If you are engraving metal plates, you may notice things like sideways movement that distorts text. The letter "O" won't be the correct shape. How bad these effects are all depends on what you intend to do with this machine. Something to plan ahead for. CarveOne

[ger21]

An eccentric bushing is better than a slot, as it's easier to adjust. There's some pics on the Mechmate forum of home made ones. Basically a bolt with a hole drilled through slightly off center.

[diyengineer]

Soo thats what they are called! Thanks Ger21! Everyone one of my bearings on my big machine has one of those suckers. It scares the **** out of me when it comes time to dial it all in and get it all level. Should be fun.. =I

But yes for adjust-ability they are awesome, once its dialed in that is..