About Z axis (using CncrouterParts carriages)

[LabSkis]

Hello,

I am designing a 8020 aluminium frame CNC.
I will post someday pictures of the full machine I intend to do.
It is partly based on what Arbo has made, but adapted to european standards/shops.

For the moment, I have troubles with my Z axis design that you can see in pic 1.

For those who know, I have used carriages from Ahren Cncrouterparts.
My concern: how to get the maximum travel on z axis.
Lets have a closer to my design on pic 2
On this picture, I have put the z axis as low as possible.
For me, the available travel is min 30 mm (cf. picture), depending on the length of the bit I will use.

How can I increase this travel?
Fix my router further down on the interface plate? I fear cantilever...
For the moment the router is fixed 30 mm below the carriage (see pic3)
Can I increase it?

Other solutions you have used?
Like the one proposed by Ahren on his site, consisiting in fixing the carriages on Y axis & letting the 8020 of the Z axis move up & down? Any feedbacks on this?

Thanks

[DonFrambach]

I think that the CNCRouterParts.com Z axis works much better when the carriages are mounted back to back instead of on the Z plate that you have in your current design. I originally made my Z axis that way and had the same concerns that you have about travel and placing the cutter too far from the bottom bearing.

CNCRouterParts.com also sells what they call their "high Z plate" that allows for what I believe is a much better back to back mounting of the carriages. I made my own plate because I wanted to incorporate a spacer needed for my design. Here's a link for their plate: CNCRouterParts and a photo:

[LabSkis]

Yeah, that was what I meant with my sentence "in fixing the carriages on Y axis & letting the 8020 of the Z axis move up & down?".

I won't be able to use that plate either, because it won't fit with my european design!
Are you happy with it? What "travel" did you get?

[DonFrambach]

What I made is listed in post #20 and #24 (and others following) in this thread: http://www.cnczone.com/forums/diy-cn..._router-2.html

So far I'm real happy with the design. I made mine to have 5" of travel but that length is arbitrary because I could have used a longer or shorter piece of steel to increase or decrease my Z axis travel.

Don

[LabSkis]

OK, I have just redesigned it according to your idea.
Now I have about 70mm for z axis, but i can change it!

Unfortunately, I have had to add many interface plates (like in pic 3, corresponding to Z axis rail & carriage) to allow me to use dumpstercnc nuts. They are are about 30mm high, whereas the distance between the top of the carriage and the metal rail is something like 25mm (see pic 4). I fear cantilever again!

Any advice to avoid that?

[ger21]

What about mounting the screw on the side, rather than behind the plate?

[johngalt47]

The design I am working on the z axis uses the carrages back to back design
the area in the box shows details of the z axis. Notice that the motor moves with the router it adds a little weight but I have added two gas springs to couterbalance the weight. this is not a finished drawing but it shows the details that you are dealing with

[johngalt47]

let try this again i hope it is clearer