First CNC design.. comments, critiques, or ill remarks welcome...

[silverHaloCW]

As many a brave soul before me, I am embarking on the CNC build journey. Most of my inspiration has come from studying the threads on this site and I am very grateful for all that have come before me and shared their triumphs and sorrows.
So after many months and beers later I think I have finally settled on a design. Much is owed to CarveOne and his amazing spirit, I have read and re-read his thread many, many times over - Thanks.

Well, on to business...
The unit will be roughly 5'x5' and have a cutting area around 4'x4' and mainly constructed out of extruded aluminum. I have settled upon CNCrouterparts for the majority of the components as well as their rack and pinion units for the X and Y axises.

Any critiques would be welcome before the building begins, hopefully I can flush out any weaknesses in the design....

Thanks guys!

[CarveOne]

Wow, what can I say except that I'm truly humbled. Thanks!

What you are showing for your gantry is pretty much identical to my plans to upgrade my gantry to R&P later in the spring. Be sure to make a solid connection to the gantry uprights because a wide gantry can easily twist at these connection points.

When I transfer the whole mess over to a steel frame my plans are to raise the rails higher above the bed and shorten the gantry uprights correspondingly for two reasons. One is to stiffen the upright supports by making them shorter, the other is to place the rails about 4" higher above the cutter tip for most 2D cutting jobs.


CarveOne

[silverHaloCW]

Thanks for replying CarveOne, your input is greatly appreciated!

Visualizing the changes you stated seem to be inline with what Arbo did with his 24x80 machine. Short gantry with a deep bed, great rigidity without sacrificing the Z travel depth. I will take that into consideration as I finish up the design this week. The great thing about building with extruded aluminum is that it is easily worked and can be rescaled quickly if need, so changes aren't difficult to make on the fly.

I still haven't settled on the gantry height, something that I figured I would commit to after the Z axis is completed. That way I would know how much travel I would have to work with.
I found a guy in my city on the CL who was selling the Aluminum for a buck a foot but its all metric 4080 and 4040. It will be a challenge to build this beast using mixed standards, since all the parts from CNCrouterparts are milled for 1530. So the frame will end up in metric and the Z axis in standard..... fun fun.
The gantry uprights are a mix of steel plate and aluminum extrusion with lots' o bolts to insure maximum stiffness.
I really liked your placement of the R&P on the side rails by running the bearings vertically as opposed to horizontally, I think that design gives the unit more strength and less tendency to rack.
Also I plan for a wood shelf underneath the bed to further stiff the frame and have a place for extra material storage.

Thanks for the pointers as I can't wait to start the construction!
Keep up the good work!

[Arbo]

Looking nice. Yeah, I'm a firm believer in a very short gantry so there is less chance of any sort of flex.

For your R&P drive on the Y, it appears you would be making extra blocks to extend Ahrens carriages to get the R&P to the back, is that correct?

I know some would be concerned with dust getting into it, but I personally would probably put the R&P on top. I really don't get much of any dust back up there, so I don't think it would be a problem. And it simplifies making custom parts.

You would need spacers to raise the rack up, unless you shifted the whole Y rail down so only 1/2 inch stuck above the 8020.

[eigstein]

nice use of ahren's parts. the over all design looks spindly. the right angle joints need beefed up,and the legs look like they were made for a card table. not enough attention is given to the bases these machines set on. thats why they drive piling to bed rock to build a blast furnace or sky scraper its only as good as the foundation. has the makings of a nice machine.

sincerely,

rjs

[silverHaloCW]

Thanks Arbo for the idea, I will have to research this setup. It would simplify the build not having to custom fab extensions off the bearings for the Y pinion motor mount. I'll muck around in Sketchup and see what I can find out about top mounting.

As far as "spindely" looking I see what you mean. I will have a bottom shelf underneath the bed to increase rigidity. Also building with extruded aluminum you can always easily add more support later if there is any flex. I understand the MDF machines and the need for stiffness there, but
extruded aluminum is quite stiff and strong material, I think people see it and think it looks too weak because of the size. I'm always amazed how heavy and stiff it is, but cuts like butter with a carbide saw blade...

I've seen so many monster machines on this site that are "over-built", ugly,huge and bulky. I'm personally trying to find the balance between strength and style, as I am a minimalist by heart. Why sacrific extra materials, time, and space when it you can find a better way?

Thanks again guys for the comments!