PDA

View Full Version : Reasonable Z?



Zephrant
06-05-2003, 01:16 AM
What is a reasonable Z range for a home setup? At this point, I can't think of anything over a few inches tall that I would want to do, but don't want to limit myself of course.

Table size is 5'x10' usable...

Zeph

Laff Riot
06-05-2003, 08:17 AM
5x10 useable?? Details! Pictures! What motor type? Gantry or moving table?

What do you plan to cut most? What type of bits?

I find a 6" Z is too small but the 10" optional setting sounds like a bucket of marbles.

balsaman
06-05-2003, 08:25 AM
More is better for z axis travel but also adds complexity. If you are going to cut out parts probably 2 or 3 inches is enough.

The problem comes when you have longs bits. If you have 3" of travel and your bit is 3" long you won't be able to lift the bit over a 3/4" plywood. if you design the machine to hold a 3" bit 1" over the table and you have 3" travel, if you put a wee bit in that sticks out of the collet 1/4" you won't get it all the way down to the table for engraving.

That said, most bits are not 3" long. 1 or 2" is common and tho so maybe 2" of travel is on the small side.

Eric

ToyMaker
06-05-2003, 08:47 AM
And then there is the situation where you have 6" z travel and want to surface something 7" high :)

robotic regards,

Tom

balsaman
06-05-2003, 08:49 AM
yeah you can't win....:)

HomeCNC
06-05-2003, 11:09 AM
Also if some day you want to add a 4th axis to turn spindles with some art work wrapping around the shaft, you will need more height to get the rotary table under your spindle.

wjbzone
06-05-2003, 11:47 AM
Most of my work only involves a few inches of Z travel because the tools are that long max. It is nice to be able to move Z out of the way with extra travel.

You want to have room for a vise or clamps (and a forth axis) so your clearance to the table is something to consider. You can always add a support under shorter work pieces.


Bill

Zephrant
06-05-2003, 12:24 PM
Thanks all-

LR- It is still in the planning stages- As soon as I finish the gantry design, I'll order the framework. I've got the go-ahead from the boss, so I've got to start burning the money. :)

I started drawing it up with a 12" Z travel, which makes a minimum Z platform that is 18" high (along the Z axis) that means I need slides that are 18" long too. So when the bit is all the way down, the Z platform is extended from the gantry 12", putting the router out on a 12" long arm to wobble around on.

I'm concerned that I'll give up a lot of accuracy unless I make a big beefy support for the Z.

Anyone have some more pictures of a home-made Z with around a foot of travel?


I'll be mostly cutting 1/4" to 1" acrylic, but want to keep the options open for becoming a general purpose CNC shop.

Zeph

ger21
06-05-2003, 05:27 PM
I should have about 8" of travel when I'm done, but only about 5" of clearance under my gantry. 18 1/2" shafts with linear bearings 8" apart.


Gerry

balsaman
06-05-2003, 05:29 PM
I don't know if you have seen my "Building my second cnc router" thread. There you can see my machine which wil have a 6" z travel. I think perhaps you are now going to the other extreme at 12". You are correct larger z axis requires a beefy structure. Perhaps a happy medium 6 to 8" is in order as a comprimise?

Eric

Zephrant
06-06-2003, 12:17 AM
Yep, 6-8" is sounding more reasonable. It would be pretty hard to change later if it was too short is all.

Thanks for the help-

Zeph