Giuliano M published a new build:

Read more about this build...

Thanks!

I'm working on making the spoilboard area modular, with a central 48x48" piece that you can replace easily with a half-sheet (48x48) of MDF.

The areas in the sides and back will be for hold-downs.

I'll post the model in a bit, after I make some further mods..

Modified the gantry to add the 3rd 20x60 beam, and squeezed in a third set of wheels, both on top and bottom.

Sketchup's dimensioning is saying there's about 0.3 - 0.45mm of play in the set up, but I'm sure it will be fine.

It's a very weird thing to have this mix of Imperial and Metric involved...

The extra thick gantry requires the axle bolts to be longer - an 85mm M5 socket head cap screw from McMaster-Carr is just about the perfect length.

I'm probably going to incorporate drilling holes through the sides of the 20x60's to bolt the 3 beams together horizontally for rigidity.

I am also planning to build a 4' x 4' CNC which is very similar to what you just showed us.
Your build will help me a lot! I also wanted to strengthen the gantry part like you did.

There will be some differences but, overall, your build and mine will be viewed almost like twins.
I will post my build when ready.

Good luck and thanks, Guiliano!

Since I have discovered the Openbuilds community I have learned that building a cnc is very similar to shopping for a new TV, if you see a bigger one that fits in your living room you want it
I had a 1000mmx1500mm build in mind but looking at your model I think I want a bigger screen
Looking forward to your progress

Probably won't be until March when I can start ordering parts - starting with the rails.

In the mean time I'll work on designing a 2x4 stand for this beast, since it won't fit on a table.

Also, about the motors - think the 175oz steppers will be enough to get started?

Also, about the motors - think the 175oz steppers will be enough to get started?

How About These Baby's...
http://www.karlssonrobotics.com/cart/Stepper-Motor-267-oz.in-NEMA23-200-steps-rev/

Much better!

Massive vacuum table?

Sure, why not!

48"x48" 3-sheet MDF box, 2" border, 10" squares of 1/4" holes spaced 3/8" apart, with 1" in between the squares.

Just laid out the top layer - going to carve out the middle layer and cut a hole in the bottom for the hose attachment.

Wow! Getting more and more interesting!

Cheers!!!

Middle layer of the vacuum table.

I'm trying to design it so that you can cut it in-place with the router, and then glue the layers together.

I have no idea how much vacuum pressure will be required to hold anything of size down, but it's an interesting task nonetheless.

Trying out another hole layout for the top layer:

That's a 48"x48" sheet with 12" square sections, each with a 32x32 hole grid (1024 holes), 1/4" holes spaced 3/8" apart.

That's 16,384 holes!

Sketchup damn near crashed...


I may instead try a recessed slot grid arrangement with a single larger hole in the centers of each square... not sure yet.

Yeah, I saw that video - may do something similar.

It's entirely a work of progress, so who knows...

I can't wait for your next update on the build...

Thoughts and Suggestions.
Vacuum Base.

It's not so much, the area that you want to (excuse the phrase) "suck on", it's more the area, that you don't want to suck on. i.e. If you put a work piece of only 12" x 12" in the middle of the 48"x48" bed, think how much suction you will be losing in the surrounding area.

As a suggestion, and I haven't really thought it through, I might add:-

Sliding slats. What about making it up out of 2 or 3 sheets of 6mm ply, or thinner, sitting on top of a slim vacuum base.
The idea being that each of the 12"x12", or smaller zones, be an independent, sliding, slatted, area. So if not covered by the work piece, it can be slid shut, (I don't know how, I'm just the "ideas man" here), allowing for maximum suction in the required areas. It would also allow for, a reduced rate of suction required, as not so much would be wasted in the surrounding area.
I know this is fraught with potential problems, but it's an idea to knock around I think.

Thought: If the bed is sucking all the time, where does the swarf and cutting dust go? Need one of those cyclone thingies there I think.

Opportunity: In fact, if someone could come up with a cheap and easy'ish solution to this problem they would have it made. He, or she, could produce, cheap, suction beds, complete with a suitable pump, of varying size, for the likes of us to just drop onto our work-beds.

Other Thought: What you really need, is a method of moving a, "smaller area of high suction, but, all the suction", around and beneath the bed to selected areas. Now that would really utilise the vacuum to it's full potential.

Counter Thought:
You could always just have a selection of 6mm squares of various sizes, on one side, and use them to cover the unused areas. "Occam's Razor".

So maybe this thread was a waste of time after all.

Then again: "Constructive thoughts are never a waste of time."
I wonder who said that? Oh yeah. It was me.

Cheers
Gray

Just noticed the date on the above threads. Should have started a new thread.

Gray

Regrettably, this project isn't on my priority list any longer, so I'm not sure if/when it may happen.

Did you buy it or make it? Knowing you, I can guess. I get the idea, what sort of pump do you use?

Gray

I was thinking today, as I drove to Westbury in the sun with the top down. If my baseboard was marked off into 6" squares, and full of holes, I could glue a half inch wide metal framework on the underside, in the 6" square pattern. Then, using a 6" square fitment, made by my fair hand, or a square tumble dryer vent connector reducing down to a vac pipe size, which had a magnetic strip along its top edge and then connected to my shop vac. So, after placing the workpiece on the table, I slide the amazing suction bit under the table, and beneath the workpiece, where it magnetically adheres to the metal strip square. Voila, the suction is allocated to the area required.

I really don't know where I get these marvelous ideas! Sometimes I amaze myself.

I still like Tweakie's though.

Gray

Shop vacs and vacuum pumps are not exactly interchangeable. You'll burn up a shop vac trying to hold suction like this unless you allow a fair amount of bypass which in turn will greatly reduce suction.

Tweakie: That acrylic suction jig is pretty ingenious.