Hi, from Upstate NY. 5x12

[lolailando]

Hi all,
I have been lurking around this forum on and off for 6 or 7 years.
I started buying parts for a build before I new about the mechmate.

I am still far away from starting my build but this are what I have come up with:

-Size 5"x12"...I have enough space and it seems just a few more bucks on steel.
- Cut mdf, laminates, plywood etc... Thin Aluminum ocassionally.
- Cut large EPS (polystyrene) foam 2'x5'x12' aprox .
- Second gantry later for plasma head. Since most of the time I may not be cutting 12", the second gantry could just stay at the other end of the table and or take it off when I am cutting 12' (is this stupid? should I just add a couple feet of table?)
- What's the highest z-axis movement I could safely modify the mechmate to just cut foam? 24"
- would you build just a regular gantry first, then add a second head in the same gantry with larger z-movement? or would the same head cut z-24" on foam and just z-10" on mdf etc... and still be stiff enough?
-Servos: I have 4x sanyo Denki p50b08040vcks7. I bought them cheap before I discover Mechmate. I beleive they have a brake 24v, and encoders and are more than powerfull enough 400w, mounting plate plate 86mm. I also got some driver chips from a young guy in Europe who programed a really neat servo drive and used to exchange them for a few foreign beers. I would still need to build the electronic boards and solder.
- I have heard that one of this servos can be use as a cutting head/spindle with a vfd
- I wouldn't mind going with the steppers if the advice is that the servos would complicate the build too much
- I also have several of the expensive linear bearing assemblies that I bought cheap before I discover mechmate. I could use them for the z-axis or I could keep them for future CNC-Mill build.
- Table design: I would like to drop the middle of the structure like in this one:
http://www.mechmate.com/Forum/messages/2/168.jpg
but go across horizontally with the c-chanels even lower so I can fit a 2' deep block of foam. Can this structurally be solve? or would it make the table so weak it couldn't cut plywood nice? A Regular table would be bolted/pined on top for mdf and plasma cutting.
- I need really low accuracy to cut the foam...even a 1/4" off would be fine ... bt no good for plasma/plywood
- trying to make too many things at once? probably...just brainstorming to understand some limits
thanks in advance everyone

[darren salyer]

I guess I don't understand the thinking behind a convertible machine.
It seems to me a plasma cutter would be a dirtier operation with a water tabe and all.
Seems that wouldn't mix well with putting wood/acrylic plastics on the table above the water table.
Several have mentioned doing this.
Am I missing something?

[lolailando]

In an ideal world I would have 3 or 4 2000SF shops, one for metal, one for wood, one for plastics etc....
In our limited reality it may not be that difficult to empty the water table and bolt a cutting table on top of it every other week or whenever you need it. I think the extra work is worth the effort for some tinckers who like to work on different materials.
I do plumbing, roofs, plaster, brick, tile, carpentry etc.... most people would hate to something new and different every day,...other people can't live without it.
Building a second machine is another 4k plus time versus a couple hours of cleaning and changing tables whenever needed.

[lolailando]

ok, I just fond out the servos I have are AC....didn't remember. they are the best of the best but all affordable servo drives out there like gecko are made for DC servos.
So I will go with a set of sttepers and drives like everyone else for simplicity (it would cost more to buy just the servo AC drivers than a whole set of stepper and drivers).

I am still wondering what is the best structural solution to drop the table down. I am starting to think to go more conservative and drop the support table structure only 8-10".
In the future if i want to mill 2-3' thick EPS I can build a very tall gantry since flex would not be a problem cutting EPS. I guess the reason the MM has such a low gantry compare to even commercial ones is to gain stiffness in a simple/affordable way.

[smreish]

Lola,
It's easier to lower the table and build a longer z-stroke thank alter the gantry. I've done it to a MM - twice.

If you want an extreme cutting depth, then make the side sections taller and then add a cheap MDF box ontop of the spoil board to make machine standard height.
I have lowered the working deck height to the concrete floor for foam sculpting and completely removed the table all together for a 48" deep cutting area with a 48" stroke z-slide for some extreme statue work.

What I mean is instead of a C- section of 8", double that up to 16" or greater with either a built up square tube - or other method - to get your height. Or, even use steel angle 2.5 x 2.5 angle with 10-16" flat bar to make your own C-section for the side rails at about the same cost. Then, build a cheap MDF box that is 8" tall to get the table height back up to standard z-depth....nothing in the build then changes. When you need a really long stroke z- axis, build a longer slide, heavier counterbalance - and your done.

You can see how I did it in the MM #5 thread.

[lolailando]

thanks smreish,
I took a fast look thought the 17 pages post and I couldnt get to see but one picture that barely shows the structure after you lower the table.
Would you mind sending me some pics?
or did I look at the wrong post?
i would like to see how you resolved the structural steel, and if it is stiff enough to mill/cut plywood etc..
thanks

[smreish]

That machine is gone, but I will do a quick sketch to illustrate my post on Monday when back to office. The posts I referred you to was to see the elongated z slide on a standard gantry. The machine bed was removed for that series of work.

[lolailando]

thanks a lot,
I appreciate that. I do not want to reinvent the wheel.

[smreish]

The structure of the table in #5 build is a very standard MM with bolted cross bearers.
To deepen the cut envelope, I lower the cross bearers by adding a spacer.
When I build my next machine, I will build the table with more over gantry height by having a "higher" c-channel side.