"Desk Accessory" CNC Milling Machine

Lots of "Desktop CNC" machines can fit on a desktop. But do they fit _on_your_desk_? Like, between the stapler & paper tray?

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Developing a pattern for a usefully capable CNC milling machine with footprint & cost more like a stapler than a desk.

Ok, "stapler" is a little dramatic. Just a little. Footprint smaller than a paper tray for sure.

Proof of concept:

Companion project

Starting with blocked-out volumes representing components that are working at #Minamil: a minimal CNC mill and vertical configuration, I've considered a couple of layout ideas:

Perhaps the more sensible & easier to make stiff: footprint about 14 x 20 cm (8 x 6 in)

The more aggressively compact: footprint about 14 x 14 cm (6 x 6 in)

For evidence of progress beyond CAD and hand-waving, here's a three minute video:

The telescopic axis design contributes to compactness when not operating.

Transparent panels for debris enclosure -- sides but maybe not top or bottom -- can fold compactly around the retracted axes for storage. Assessment of ventilation requirements required.

These depictions assume a Dremel-like spindle. Assuming a general-purpose tool that anyone might have or acquire for general use apart from this machine reduces the scope of what "the machine" includes. OTOH a dedicated spindle could avoid making the operating configuration taller, and get closer to always-ready a la stapler, at cost of added cost.

AFAIK the WEN 2305/7 rotary tool I've used so far represents a Dremel 395-type tool and other similar clones. It weighs half a kilogram, as does half a liter of any aqueous beverage. The machine does not include the counterweight. It includes the rigging for a counterweight, stowed inside the basic bounding box, to be set up when needed for operation. The user will provide an ad hoc counterweight as/when needed.

Companion project #Minamil develops the CNC mechanics. This project started as an aspiration to make that project reproducible from a short BoM and a laser cutter. Since then I've shifted toward thinking the working parts (that project) and the frame (this project) should remain separable for practical usability -- at cost of growing insignificantly larger than a tightly integrated unit. As a result, the "short BoM and a laser cutter" emphasis stays with the Minamil mechanics while this focuses more on improvisation-friendly cabinetry.

  • closer to all-in-one: first try building in new box

    Paul McClay07/25/2023 at 20:38 0 comments

    Earlier this year..

    The CNC mechanics of #Minamil: a minimal CNC mill had been working encouragingly well for a while but depended on a bunch of other stuff that could be integrated into a compact enclosure but wasn't. A few months ago I made a new XY stage with longer leadscrews that couldn't fully extend within the frame/enclosure I was using at that point. In the parallel universe where I have better executive function, I simply put the new CNC mechanics in the old box for initial testing with useful if not maximal X range and -- as it turned out -- more work to get it the new thing working as well as the old thing. Instead I started thinking about a different enclosure and that got out of control for a while before I got back to getting the actual CNC part to work.

    That was a usable first draft and useful for finding pain points to motivate a second try.

    Unfinished bits included:

    • switched AC for spindle still not inside the box, but at least consolidated to a hacked power bar
    • negative ventilation motor wired but filter & outlet not done

    In addition to supporting the CNC parts, the box encloses spaces in the top and bottom. AC power stays isolated in the top part. The bottom part is divided into space for the air filter/fan and space for the control electronics.

    A scavenged unenclosed 5V/12V supply with output through PCB headers and lots of little wires doesn't help the top end look any less chaotic inside. At least it keeps AC away from the rest of the works.

    I figured everything should fit and I've already learned that wires fill more space in real life than in diagrams, but once again underestimated the challenge of connecting lots of things in a small box.

    Doing this once spawned ideas for how to do essentially all of it differently. I really super very much wanted to do a completely new build that I thought some people might appreciate at MRRF this year -- with fairly specific plans and seemingly adequate time. But life. So less time. So when I did get some time I spent it furiously scrambling to finish just a few betterments before MRRF instead of writing log entries. At least I took some pictures while tearing down the "first draft". Then MRRF. Then more life. RIght now I have some time, and a backlog of ideas. But with this year's HaD Prize "Gearing Up" challenge on, it's time to squeeze in some writing too...

    New box, and first try at getting more stuff inside the box

    yes, the picture is a repeat -- because a bunch of words got in here after the first instance. 

    Part of the main idea is for the closed box to be just another box and trivial to stash away wherever without snagging or squishing vulnerable bits.

    With the box closed up, I want four flat sides like a plain box with no projections. No hinges, no latches, no buttons, etc. And I want it to be not fragile. In this iteration, moving the hinges away from the corners makes those two corners not fragile. Also the corner where the doors meet is not fragile in compression because the solid panel of each door transfers the load straight into solid material at the hinged corners. For a quickie solution in this case, a single magnet and iron peg (i.e. screw) hold the doors closed, but I have ([1]had?) a plan for a more robust closure. The block in the corner where the doors meet I cut wrong. The idea was to have a single solid piece with the bottom end aligned to rest on top of solid material next to the XY table and the top end in the plane of the top of the box so that, along with the two solid sides of the square, the top can bear load if whatever lands on top has a flat bottom.

    Also I have ([1]had?) a plan to replace the metal top clips that hold the straight sides straight when "open" with a closure for the enclosure that would hold the two panels perpendicular where they meet when functioning as a enclosure for the running machine. That's a little tricky...

    Read more »

  • enough "sensible", let's try "more aggressively compact" ... and 3d printing

    Paul McClay03/04/2023 at 09:12 5 comments

    Trying something(s) different here:

    • different layout for more compact footprint
    • 3d printed parts instead of laser cut parts
    • longer and now cheaper generic flavor of motor+screw unit for larger work area

    It's still work in progress, but seems like it might work out ok.

    The mechanics are a lot like #Minamil: a minimal CNC mill. And friends., but different. Re-design for 3d printing the mechanical parts is not just trivially different from design for 2d laser cut parts. I don't know yet whether to expand that project or start a new project.

  • Beyond handwaving: proof of concept

    Paul McClay01/06/2021 at 04:30 0 comments

    For evidence of progress beyond CAD and hand-waving, here's a three minute video:

  • "the more aggressively compact" might work...

    Paul McClay10/06/2020 at 22:23 0 comments

    Being distracted while not doing something else...

    ...I think I've figured out how to make the compact corner/angle configuration stiff without just making it bigger.

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dekutree64 wrote 08/30/2020 at 20:32 point

For the spindle, my machine uses a 5010 brushless DC motor turning a 5mm rod that goes down into a wood block with a big 16x35x11mm bearing at the bottom, which fits around an ER11 extension chuck. Having the bearing so close to the bit gives excellent rigidity. It does cover up the wrench flats in the chuck, but instead of using two wrenches you can just grab the rotor of the motor while you tighten the ER11 nut with a wrench.

But the 5010 motor needs an ESC, and a servo tester to tell it what speed to go, and some kind of power supply to provide appropriate DC voltage for it, so that may increase the machine size beyond what you save with the smaller motor. Also the big bearing on mine gets hot and I'm not sure why. It really should be an angular contact bearing, but unfortunately there are none available with 16mm ID. I'd like to use a C10 ER11 chuck (10mm integral shaft rather than an extension chuck) with an 7000AC (10x26x8mm) angular contact bearing, but then the motor can't turn it directly like the 5mm shaft. 

Regarding overall machine design, one thing you might consider is making it usable as a little drill press. Very handy to have around if you don't have space for a big one. Try to make it so you can at least get a 2x4 through with enough side-to-side room that you can drill a hole anywhere in it. And put a manual crank on at least the Z axis. But manual cranks on all 3 axes are wonderful to have, even just for positioning after you get the workpiece clamped down. Also nice being able to do simple milling operations without having to mess around with the computer.

  Are you sure? yes | no

Paul McClay wrote 08/31/2020 at 01:42 point

Hi. Thanks for your interest and for sharing your experience and ideas.

I haven't given much attention to the spindle question yet, but appreciate your data points.

Room to pass a 2x4 and manual control sound like great ideas. At first think, I don't know how to add manual cranks without reducing travel distance of the lead screws. Unless maybe... Hmmm...

Start a project to describe your machine?

  Are you sure? yes | no

dekutree64 wrote 08/31/2020 at 03:08 point

Indeed I should :) I'll see if I can get some photos together tomorrow.

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dekutree64 wrote 09/02/2020 at 00:20 point

  Are you sure? yes | no

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