New Machine Build- First time design

[kvcummins]

This is grossly plagiarized from http://www.buildyourcnc.com, although I've chosen to use 1/2" MDF.

I'm hoping this will be decent enough to help build some small hobby projects (small as in boxes and trays, not PCBs), and to ultimately build its own replacement.

Due to budget restrictions (I'm skipping lunches here and there to save for materials), I'm likely going to have to use allthread screws and salvaged steppers, but I'm hoping I can still get reasonable accuracy with the appropriate tuning...

If nothing else, it will be a heck of a learning experience!

[Kammo1]

Bro that looks like a nice little machine and I would go for it, 1/2 MDF might be a little too small and I would definately go for either 18mm or 19mm MDF.
Its very surprising how rigid MDF actually is and oncee you brace the gantry up and add supports to stop it from racking it should be fine. What are you using as regards the leadscrews and nuts ?? Post some build pics as I would love to see the end results

[kvcummins]

Thanks for the comments! I went with 1/2" MDF because I will likely be using salvaged motors, and I doubt they'll have much power. If the inertia of a heavier gantry isn't an issue (i.e., minimal friction on the linear movements), 3/4" would be better...

As far as lead screws, I will likely be starting with allthread rods and hopefully delrin nuts (but I won't count out couplers for now), with the hope of moving to ACME when enough disposable cash rolls around.

I'm a full-bore computer geek, so my mechanical/electrical/handyman skills are almost as lacking as my social skills... What suggestions would you make about bracing the gantry and removing any racking?

Once I start building, I'll start posting images. Thanks again for the encouragement and insight!

[kvcummins]

Got a set of bearings today, and I'm going to try to make time this weekend to build some prototype/proof of concept pieces for my linear slides... Whoot!

[abomb55076]

Nice, very exciting, good luck!

[kvcummins]

Wow... Been busy with the rest of life...

Did some more design work, and some proof of concept mockups of the linear slides. Looking good...

Here's the current iteration of my design. I will either move the Y-axis lead to the vertical centerline of the Y-axis, or use a sliding knot anti-racking system. Probably center the leadscrew...

It's not shown, but I will probably use a sliding knot on the X-axis/table. And I'm trying to decide if I should have the gantry be static with a moving table, or if I should put legs on the table and let the gantry move.

[cdndave]

Nice!

That is so close to my first design (also "inspired" by buildyourcnc.com) Being ambitious, I decided to redesign closer to the newest design on his site.

I would make the table static with the gantry moving, I'm no physicist, but my gut tells me that would be a sturdier design.

I look forward to see this get built. I'm also extremely jealous of your skills in sketchup!

CdnDave

[pminmo]

Keep it small. Many start with too large of machine and fail.

[stevespo]

This looks like it's going to be a very nice machine. Looking forward to some building pics.

Yes, I'd say static table and moving gantry as well. Looks like less weight to push around and you'll probably have a better work envelope. I'm considering a moving table for a milling machine I have in mind, but for a wood router your size, I'd move the gantry. It should work either way.

Are you using 1/2" or 3/4" MDF? I'd go 3/4" for the uprights, possibly even adding some aluminum bracing if you can scrounge any.

This type of router bit might be useful for registering the L channel. Could also use a chamfer bit, or I guess it would be fine to bolt it to the square edge. It should self-center somewhat they way it is.

V Groove Bit

Steve

[Spiv]

Looks good; how are you going to attach the aluminum rails to the mdf?

Also, what software are you using to design in?

[Grunblau]

Looks good... Look into dowel nuts at Mcmaster Carr.

[kvcummins]

Thanks for all the feedback. I was leaning towards a moving gantry, and will stick with it. Still a little concerned with my Z-Axis, but I also need to remember that I don't need 7-8" of travel. Mostly I need 1-2" of Z-Axis. With that, I can cut the pieces for my *second* machine...

Thanks for the props on my Sketchup "skills". It's mostly brute force designing, avoiding useful work... I started out with components and groups, but it's devolved into a few groups, each made up of all the individual points, lines and faces... :P

As for how I'm attaching the aluminum angle to the MDF: Friction. That's it. I'm going to chamfer the MDF to take the plain angle, and carefully dado the sides to take the bearing-laden angle (** Bad Monty Python comment deleted **). Once it's all tightened up, there should be no movement of the aluminum. If it is a problem, some glue (epoxy or super) should do the trick. Again, this is a "toy", and will hopefully be used to produce a more exacting (and probably more complex) second generation machine.