Which design would you chose for my router

[konalure]

need some help here from you guys with more engineering expertise than me.. I'm building a home built CNC router, hopefully with the ability to machine hardwoods somewhat reliably, I'm planning on using the router for a lot of guitar building and such.. so it has a long Y axis 55" ( 49" travel) or so and a moderate X axis 24" (19" travel) and around 5" of Z travel hopfully.. Anyways I'll be using some supported 20mm rails and blocks for all the axis with dual ballscrews on the Y axis and single ballscrews on the X and Z..( not in pictures yet because I'm decideing how to mount them..

Anyways.. my real question really is.. I have 2 design possibilities for the X axis.. after looking at these 2 pictures.. what would be the better setup.. the under and over configuration I figure would bring the router in a little tighter to the X axis gantry and would spread out the width of the bearing load on that axis.. any input would be appreiciated before I start the build.. ( the parts are coming soon..)

Aloha..,

Del

[ger21]

I'd vote for the over/under.

[brunog]

which axis will put the most force on the rail:
if X: go for the first design
If Z: go for over/under

Best regards,
Bruno

[konalure]

well, primarily I'll be using the router for making Guitars and Basses. The router will be doing a lot of cuts running down the Y axis the length of the router, while the X axis will graduate small increments from one side to the other.. ( typical 3dcarve finishing toolpath ) the Z axis will be going up and down along the process.. I figure this would best use the dual motors/ballscrews on the Y axis and be also cutting along the grain of the wood.. So, I guess the over/under setup is the better setup for this so far.. it will resist the forces best while gantry is running up and down the long Y axis? ah hell who knows I'll just try it I guess and hope it works out.. I could always change it later..

thanks for the response so far...

Aloha, Del

[mabencomo]

How does one setup a Dual Y Axis for Granty?

[konalure]

what I meant is that I will running the Y axis with 2 motors and 2 ballscrews.. I dont want any chance of racking and I figured it would be more power to move the heavy gantry along the Y axis rails, Since I plan on doing most of my 3D machining moving along this axis I figured it would be best, plus it made it a lot easier to design a sturdy table that does not need to be fully supported and raised for the gantry to tie together underneath.. I know a lot of routers do tie the gantry together underneath, but I dont think it'll be necessary with my design.. anyways, hope this answered you question somewhat, if you were wondering about configuring the motors and such for this, others could probably answer better than me about that.. I believe it not that hard just slaving 2 motors to run together and keep steps together and aligning everything periodicly.. I'm not to the stage of hooking up my motors yet and still only working on the router table and motion stuff...

heres some pictures of my progress so far with the build:

[stevespo]

I guess one advantage of putting the screw(s) underneath the table is that it keeps them clean. You should definitely consider some type of wiper system or perhaps a cover for the screws if you mount them to either side.

I personally like the idea of a dual-screw driven Y axis, particularly as the X gets wider and wider. Even with my 40" wide X and a single screw down the middle, racking has never been an issue. I can lean into it quite hard and there is almost no deflection.

Are you using steppers or servos? With steppers, if you manage to stall one motor, the other may just keep going, leading to some serious racking. If you're using servos, you'll need to make sure that if one Y motor faults, that it stops the other from moving as well. I don't have any experience with this firsthand, just from talking with friends who have had these issues.

Nice work! Looking forward to more pics and progress.

Steve

[Kipper]

You can get the axes closer together...here's how mine works.... "ish" it's covered 400 hours now....and still works fine. I use a belt drive to tie the 2 sides of the gantry together....not so much cheaper as it works just fine.

[konalure]

I probably could have used only one ballscrew/motor under the gantry and tie it underneath the table.. honestly, when I thought about the advantages I'd gain by going with 2 motor setup, and looked at the price difference for the parts and what Id be doing with the machine.. it seemed like it was a better choice for my machine.. I plan on using 425 oz Keling stepper motors.. the same motors that run my Romaxx HS1 machine I already own.. my plan is that I will build plugs for the motors and use the existing electronics on the Romaxx machine and be able to run the new machine with it.. if I want to use the Romaxx I will just power down and plug in the Romaxx motors ( which I'll put plugs on as well ) . I will run 2 different configs in Mach3 one for each machine.. I was trying to keep the cost for the new machine under $1,500 ... I'm getting close to buget after buying the motors a few days ago..

I'm wondering how these motors will work with the setup I'm building, The Romaxx machine uses belts on the X and Y axis but the new machine uses ballscrews.. I'm hoping it'll all work out and I can get the ballscrews mapped in correctly ( never messed with any of that stuff.. for now I just keep building.. )

anyway, I'll post more pics if I can get this thing finished this month hopfully..

Aloha