Higher End Large Format Router Mill Project

[jsage]

The site Srstol provided brought up some interesting questions that tied back to the pretzel paradox. Basically he wanted to be able to dissemble his CNC. To accomplish than and have .0005 precision he bedded and created contact surfaces for the mating end of the frame.

My original thought was true the screws, gantry (moving parts) alignment and the exactness of the frame would be less critical (within reason). After reading his explanation I'm more inclined to go for a good degree of accuracy and create good contact surfaces for attaching linear systems. What always gets me is that with all the engineering I see these CNC routers sit on pin sized adjustable feet. I have a more robust Idea, I think, I used on my workbench.

[thkoutsidthebox]

So whats the idea you used on your workbench? Dont keep us guessing!!!

[srstol]

You are right. Even the majority of factory built machining centers and cnc lathes are mounted on a serries of leveling feet. This is a good thing when it comes to leveling the machine, which is critical for tolerances, finishes, etc. At least that's what some people say...

Large conventional machines typically had foundation plans that came with the machines so the owners could place the machine on it's own foundation. Most of these foundations had mounting bolts coming out of the concrete and the machine was placed over these bolts. As it was leveled it was secured to the fountation. The idea was the foundation was monolithic and if it moved, it would move as a complete unit, as opposed to the floor cracking and one leveling foot taking more or less then it's designed load.

Some of the higher speed machining centers are grouted to the floor to keep the machine from walking around with the inertia from fast rapid moves.

Just some food for thought.

[jsage]

Having trouble posting I've wrote this three times now. Hopefully, I have become more concise.

The method I used isn't overly exciting. Just cut a rounded rectangle say 3 inches up from the bottom of a leg. Big enough to allow socket wrench and bolt movement. Use a large diameter bolt and 3 plates. A fixed tube could be added as well.

Sequence is

Large diameter fine thread bolt
Nut
Welded to
Square Plate
Welded to Leg Wall level with or just below cutout
Tube (Optional)
Nut Welded to
Cap Plate on bottom of Square steel leg

Nut welded to plate or other foot type of your choosing. You could drill 4 holes in the plate for floor mounting in heavy duty anchors as needed. However you'd have to come up with a way to make the bottom bolt foot connection free floating.

Probably have to be assembled and welded as one in jig to ensure proper alignment.


Was going to add it to design but had trouble finding dwg, dxf files for free. Know there out there.

Also made me consider perhaps six legs might be better than 4.

[Coogrrr]

If we are speaking of wood not plasma (water table) isnt leveling a relative thing. The cutting device needs to be square to the product being cut but if the whole damn thing was tilted 45 degress up a wall it would still cut straight as long as that bit was square to the product in the end.

or am I missing the point on the feet talk?

Coog

[jsage]

Coog,

My two cents, discounted value, point fify cent. Unless the router is unbelievably rigid and light if you cut a half an inch off one leg. or put a half inch spacer under one leg it would change the square of the machine slightly. This would become more critical as size, weight and precision needed increases. I'd guess the squareness from bit to cut surface would be the same on a point basis, provided you have a flexible material to be cut.

Also the original concept for the workbench was have a 100% level to be able to cast up to 4 x 8 concrete veneers in place.

[jsage]

Well,

Looks like I found the most difficult component. Did a lot of research on these but I'll need to see em. Luckily I can make a somewhat long drive 7hrs, to pick them up, check quality if needed. Hate to ask opinions after the fact but the price was right, no more no less. I did see another pair possibly still available if these turn out to be an excellent value.

auction item

http://cgi.ebay.com/Ball-Screw-for-F...QQcmdZViewItem


Here is the same machine.

http://www.equipmatching.com/used_eq...2/35/67150.php

Thanks to Jerry for the advice.

[walter]

Originally Posted by jsage ...the original concept for the workbench was have a 100% level to be able to cast up to 4 x 8 concrete veneers in place.

Or you could build that "level" into the actual machine frame using polymer concrete or epoxy/granite. Check out the thread "Polymer concrete frame" in Engineering sub-forum...

[jsage]

Walter,

Thanks. Been looking to revisit that thread.

On rereading recognized I had got through the first 10 or so pages then read from end backward. ; ). Needs a conclusions page. My conclusion is that people need to be clear that structural components with motion oriented stresses lend themselves to higher synthetic content/plastics military ceramics. On the other hand if you are leaning more towards anchoring structures and a cutting area substrate then you lean more towards optimizing the aggregate matrix.

In my mind some are missing the point. I can create the equivalent of 4"x4"x8' beam which will have flexural strength not to far removed from something milled out of solid granite. If I hit it with a sledge hammer it's going to break. Alternatively you go super massive which is great for machining tolerances but I wouldn't want to have to move the machine to re-organize my garage ; ).

The epoxy granite sounds like a winner. However if I ever need to modify it I will be reminded of hard granite is. I think there is a solution there for my needs I'm just not sure which one it is.

An adequate polymer enhanced concrete with a sacrificial higher epoxy, softer aggregate surface is what I have envisioned. Otherwise, spoil board or I get the alignment perfect and design the whole thing rigidly enough such that I never cut my table. ; )

If I was doing a small mill the economics would make sense. Still have a number of pages to visit. The workbench is my woodworking work bench. The leveling is actually done from the top with lag bolts.

A couple related things. The great strength of this medium is to cast not machine custom components.

Taking out a wall on the garage. Has one support in the middle that actually makes contact with roof beams. One thing I found is if you have two 8x4++ items space disappears quickly. I have a 30 by 20 space, 2 car garage with dark and dismal 10 by 20 storage/shop area. It's a project in itself.