[kenny1]

Hello...

I'm a noob here but I've been machining for awhile.

I need to build a 3 axis CNC router to fit these parameters:

I need to cut plastic, brass or nickelsilver sheet only (no steel) up to .065 thick using either 2x2 foot or 2x4foot sheets. These finished pieces will be varying shapes and 4.000 x 1.000 inches or less in finished size.

The issue is these cuts need to be as accurate in X and Y axes as possible.

I was thinking about maybe a design that the table moves and the column stays still, also possibly using a vacuum table to hold the work down.

Any ideas?

Thank you,
kenny1

[thkoutsidthebox]

Hi Kenny. Welcome! And congrats on your first post.

There are many here who can offer much more experienced and better advice than me, but AFIK from reading here a while, a moving table design offers more ridgidity and accuracy than a moving gantry, but of course it requires more space.

Anyway, I'll bump this back up to the top of the New Posts list for you!

[kenny1]

Hello... and thank you for welcoming me to your group.

I make various artistic objects from thin metals, so I thought a router table
would work well. I have been reading many of the posts on this subject here, so now I have some idea of what I'm looking for.

I have plenty of room in my shop so space is not an issue. I went to a local
junkyard awhile back and found about 8 feet of scrap 6"x6" 6061 aluminum square tubing with walls about 1/4" thick I think now would make a good head support.

I hate using doublestick tape to secure my work, because removing it from the worktable without bending it is sometimes almost impossible. So, I also have a junked air hockey table around here somewhere and I thought if I reversed the fan so it sucked in air instead of blew out I could have a vacuum table.

Thank you,
Ken

[thkoutsidthebox]

Im not sure that the air hockey table will provide enough suction to hold down your metal pieces while milling them. You'll need quite a bit of suction. Of course their weight may relieve the problem a bit. Also, if your only doing metal and an odd bit of softer stuff you might be better of with a cnc mill than a router....

[Coogrrr]

I would suggest the small table from http://www.solsylva.com/ The tolerances are going to make it to within .01 and maybe .001 the plans base it off wood and screws and a gantry but with aluminum I think that you would be quite happy with the solution and the tolerances. Email David at that site and ask him about your setup/needs and he will let you know.

I am doing a hybrid/modified version of those plans and am useing steel frame and aluminum gantry to save wieght.

How good or close a cut is going to depend on the resolution of the stepper/motor/software and with a xylotex setup with mach 3 you can certainly get well within your range. The issue might be the woble of the bit itself etc.

I like moving tables to some degree but when your saying vacuum and those large of pieces it becomes cheaper to make a rigid gantry and a vacuum table then it does a moving vacuum table.

There are some threads on vacuum tables here and I will try to find them again.

Anyway thats what I would do and I am working with Wood/Plastic/Corian/Stone/Aluminum



just my .002 worth

[kenny1]

I can live with a slow machine as long as the tolerances are there.

I went to the solsylvia site and checked out their routers, there is some interesting ideas there too.

I think I want my vacuum table to only move in the X axis, the aluminum tubing would make an arch for Y and Z axes over the vacuum table and the arch would be bolted to the frame of the router.

The main problem I'm having is my finished parts are relatively small, and I don't want them flying around when I'm trying to cut them.

I was also thinking about a steel baseplate and lots of little magnets to hold the parts down, since everything I cut is nonferrous. What do circuit board cutters do to keep the work they are cutting in their machines, since those machines are actually really big router tables?

Ken

[ddgman2001]

Vacuum doesn't work well for small parts unless maybe you have a dedicated fixture for each part with index pins to keep the part positioned in the X and Y and just use the vacuum to hold the part down.

[kenny1]

Maybe I would be better off with thin strips of DS tape down the table to keep the parts anchored down. How do the RC airplane builders round here hold their work down on their tables? Maybe there is something I'm missing here.

I thought of just buying a mill, but I need many small parts, not just one at a time.

Thank you for the advice,
kenny1

[sc351cobra]

Kenny1
If your parts are complex you could clamp double side tape a thicker sacrificial piece then glue your part stock to it. Use water or acetone soluble glue.
Would not want to do this for a 2' X 2' piece of stock but if your largest finished item is on 4" X 1" it should work fine. Have you looked at widgitmaster Mini CNC?
http://www.cnczone.com/forums/showthread.php?t=21872
It's a lot smaller only about 6" X 9" but looks to be very well made.

[kenny1]

My problem is that I need lots of those 4"x1" pieces, so the 18"x36" router.

Widgitmaster made a cool looking router though. I wish I knew he was selling his router before he sold it so I could have bid.

I'm going to build either a 4"x4" or 6"x6" aluminum tube arch for the Y and Z axes, this will be only about 12" tall. I have two 24" long Thompson shafts with bearings for the Y axis, I will bolt these to the arch. I will have only about 4" movement in Z, and the X axis table will move back and forth under the arch for maximum cutter head stiffness.

I really need to find good X axis linear bearings and a router motor. I have a couple of large Craftsman routers and an big older cast aluminum cased Rockwell, but I don't know if they will hold up cutting sheetmetal.

Thank you,
Kenny1