CNC Router V1.0 (For Cutting Multiple Materials)

[biketrialsdave]

"I'd be interested to see a front view as your design you seems to have a full height side plate on the gantry. Do your x-axis screws stick out a long way?"

Not quite sure what you mean by that?

Here are some options for the gantry..really don't know which route to go down now...Option A would allow an internally mounted motor (without increasing the side plate width). However I am also leaning towards option B. No matter which option I go with I still need to do something about the big gap where swarf could get to the ballscrew.

[Wobblycogs]

Option A isn't going to be very strong, it has almost no vertical bracing. Essentially all the stiffness would come from the bolts through the side plates into the profile.

Option B is ok but Option C is going to be a bit stronger. If you want the space internally to mount the stepper then you could go with option A but put a 10 or 15mm plate across the back (I assume the sloped side is the front). You should really have a look through some of Jazz's threads if you want to see a good design that keeps everything internal, the design I'm thinking of has a 20mm plate a the front of the gantry with a slot machined out of it for the screw connection. It served as inspiration for my design.

If you want to do a quick experiment get a couple of lengths of 2x4 timber and nail them to some ply in roughly the design of option A, it'll take 5 minutes to build and you'll immediately see why it won't work as a gantry as it'll wobble around like a jelly. Grab yourself a bit of hardboard and nail it across the back, you could probably stand on it them.

[JAZZCNC]

If you want a simple design that works is strong and neat then try this setup. This machine design with higher sides is just for cutting woods and soft materials but you can use the same "L" arrangement without the high sides. Before anyone says it the ballscrew at the rear makes no noticable difference to cutting and the advantages of keeping chips away from screw are clear to see has is the neatness.

If you want stronger than this then look at the All aluminium gantry but it's much more expensive, thou it is very strong and again neat with good protection to components.

[biketrialsdave]

Thanks Jazz! I had thought of something similar but was afraid monting the ballscrew like that would cause problems. Is the general idea of the gantry sides to keep them as short as possible? Well not the sides, but the distance between the top and bottom profile carriages on the X axis?

[JAZZCNC]

Thanks Jazz! I had thought of something similar but was afraid monting the ballscrew like that would cause problems. Is the general idea of the gantry sides to keep them as short as possible? Well not the sides, but the distance between the top and bottom profile carriages on the X axis?

Yes if you want the best possible strength then you want short stubby sides but this is only really required if you want to cut hard materials most of the time. Gantry height just needs to be high enough to provide support to the Y/Z axis and resist Twisting/flexing. With this design the height of the gantry supports and takes the full load of the Z axis bearings with just the ballscrew and motor above the gantry.
The red machine in the pictures is twin ballscrew driven and this cuts aluminium no problem with resoanable quality of finish but it's not designed to do this all the time and it would eventually take it's toll on the machine, where has with woods etc it will happily cut 24/7.

With regards to the ballscrew at the rear then IME it hardly makes any difference unless wanting to cut hard materials with deep DOC. Which in this case then you'd want a stronger gantry design. For all wood and lighter aluminium use then it's no problem at all, if it was I wouldn't be using this design.!

To be honest if your wanting to cut all materials then you have to lose something somewhere. If you build for cutting the hardest materials then you need strength and weight, this comes at the cost of speed unless you increase the strength of motors etc and this costs cash.
This is wasteful if your only ever going to cut hard materials 5% of the time. So IMO you get a much better machine if you target the main use and design for the optimum doing this.! . . . Jack of all trades works but truely is master of none and you have to accept this other wise you'll be sadly dissapointed.!

[biketrialsdave]

Finally feeling like I may be going in the right direction now! (*awaits comments saying I'm not* =P).

There's just enough room to mount the X axis motor on the inside of the gantry.

[JAZZCNC]

Won't need that top piece it's only adding weight and expense.