Maslow Brings The Wall Plotter Into The Woodshop

Hanging plotters, or two steppers controlling a dangling Sharpie marker on an XY plane, are nothing new to our community. But have you ever thought of trading out the Sharpie for a wood router bit and cutting through reasonably thick plywood sheets? That would give you a CNC machine capable of cutting out wood in essentially whatever dimensions you’d like, at reasonably low-cost. And that’s the idea behind [Bar]’s Maslow. It’s going to be a commercial product (we hope!), but it’s also entirely open source and indubitably DIYable.

[Bar] walks us through all of the design decisions in this video, which is a must-watch if you’re planning on building one of these yourself. Basically, [Bar] starts out like any of us would: waaaay over-engineering the thing. He starts out with a counterweight consisting of many bricks, heavy-duty roller chain, and the requisite ultra-beefy motors to haul that all around. At some point, he realized that there was actually very little sideways force placed on a sharp router bit turning very quickly. This freed up a lot of the design.

His current design only uses two bricks for counterweights, uses lighter chains, and seems to get the job done. There’s a bit of wobble in the pendulum, which he admits that he’s adjusted for in software. Motors with built-in encoders and gearing take care of positioning accurately. We haven’t dug deeply enough to see if there’s a mechanism to control the router’s plunge, which would be great to cut non-continuous lines, but first things first.

Taking the wall plotter into the woodshop is a brilliant idea, but we’re sure that there’s 99% perspiration in this design too. Thanks [Bar] for making it open! Best of luck with the Kickstarter. And thanks to [Darren] for the tip.

55 thoughts on “Maslow Brings The Wall Plotter Into The Woodshop

    1. Yup…
      Plus you have an uneven resolution all across the work area.
      Get some wood, maybe add more ratio to the motors to make em stronger, use on a table, done.

      I also love those “we did not patent this because…” sentences – yeah because this has been public domain for 10 years and there is nothing to “patent” in the first place. Also your code is very likely to be 80% GNU licensed libraries…

      1. I don’t think you understand how patents work. You can patent a small but important addition or innovation without having the right to patent the overall concept. In fact, it’s rare to patent a new overall concept since so many of these concepts have already been developed at a high level or are obvious. Most patents are standing on the shoulders of giants.

      2. I am certain they solved one or more unique problems in building this solution that are patentable. You can patent any invention no matter how small, even if it is just a small improvement to existing technology, or a new application of existing technology.

      3. Just from the design overview video I can see at least four patentable innovations for which they would have a very strong case and likely no prior art. Remember that they set out to do something that had never been done before at that price point and shop floor footprint. Their solutions to the problem of how to do that took invention and experimentation, and protecting that investment is the essence of why the patent system was originally created.

    2. 1/64″ is about as good as anyone can hold with normal woodworking skills so this is more than adequate for most woodshops. If you think you need more accuracy than that, you are working with a more dimensionally stable material than wood.

    1. I realise this has limitations, however they are the kind of limitations that I find acceptable for a large format cutter that is very cheap and basic. Start doing fixed bed XYZ and even hack it yourself, costs will double, triple and quadruple easily, especially if you think you’re going to be anywhere near accurate. Anything that can cut you parts out of an 8×4 at better than 1/8″ accuracy is freaking awesome.

  1. “At some point, he realized that there was actually very little sideways force placed on a sharp router bit turning very quickly. ”

    Yes, until the bit jumps from a knot in the wood and starts bouncing around the hole, wobbling out of control.

      1. It’s not about the flinch, but the fact that the bit can start rolling along the wall of the cut as it cuts it.

        It’s similiar to what happens with an old sleeve bearing that’s worn loose and poorly lubricated, and the axle starts to roll in the hole and make a huge HRRRRRNNNNGG noise before it seizes up completely.

        If you hold a hand router sloppily and loosely so the base isn’t flat against the workpiece, the moment the bit bites into the wood the whole thing spirals out of control. Same thing could happen with this cord-suspended router if it bounces and tilts under the cutting forces and the base lifts off the wood, because it will start precessing like a spinning top and cutting wider and wider and wobbling more and more.

        1. It’s not held sloppily though, it’s got about 5 kilograms holding it in place. That’s a lot of momentum to move. I mean if you wanted less kick on a handheld you could also tie 2 bricks to it, but you’d find it tiring to use…

          A 60’s handheld circular saw I have, it easily weighs that, solid cast construction, now that will mow through small nails and screws without you feeling it, it will make a hell of a noise doing it, but you won’t feel it kick.

          1. I can see that, but with the motor acting like a gyroscope and the ropes pulling it, it can climb out of the cut and lift from the workpiece. It’s not very difficult, considering the sheet is nearly vertical, reducing the amount of force necessary to lift the weight.

          2. Well then you want a straight fluted bit in it, nothing helical. Preferred bit to use for cutting out duties would be a thin one anyway, don’t get real climbout probs until you go over about 3/8″ bit I’d say.

    1. that should be less of an issue in fibre board and the various composite wood types, that said has anyone tried using a third wire to control the bottom of the carriage? if one could hold it under modest tension then that might help as well.

      1. As long as you buy cabinet or interior grade plywood or stick to MDF you’re right, but once you get into the lower grades they commonly have knots, patched knot holes, or even voids between the veneers that may cause the bit to jump as it transitions between the two densities.

        1. maybe, I would wonder at the volume of water.

          it would be like the ultra dangerous turbo lance I used to use with a pressure cleaner, dick all water coming out, but at scary pressure.
          that had nowhere near as much reaction force as the other nozzle tools I used, but you could saw up pallets like they were made out of cardboard.

          1. Heh, reminds me of a detailing shop I temped at in college. Owner bought the most overspecified pressure washer he could lay hands on… then complained that it stripped paint.

          2. lol
            I almost cut my foot in half with the turbo lance!
            it tore through a heavy duty rubber boot, my thick woolen sock and took a fair bit of skin off, in under quarter of a second!
            a young bloke we had working for us destroyed the bobcat radiator and cut through a coolant hose.

            it used so little water, but the pressure and velocity were scary!

          3. More on my last comment above…

            It wasn’t a particularly well focused nozzle on the spray gun end either… first inch out of nozzle, BEWARE, bores through asphalt, next 12 inches, strips paint easily, next inch, removes dead bugs and bird crap, following 2 feet or so, water has had quite enough of this careening headlong through space nonsense and breaks up into a fine mist that can merely get things wet.

            The thing was on it’s own trailer, ran off a diesel motor, and he had to get a 4″ pipe off the watermain put in.

      1. laserjet and plasma cutter would be both good fits for this as they generate no cutting reaction force, the waterjet not so much. I can’t afford a laser setup strong enough to cut sheet steel and aluminium however, but I already have a handheld plasma torch cutter.
        I would still have to make a metal frame with mesh on it, but standing it upright on a slight angle would save shop space and reduce the cost of the electronics significantly as no need for linear rails and bearings. I dont cut sheet metal to much below 0.4mm resolution either. If I need more precision I mill things out.
        Probably have most of the stuff in a box somewhere, apart from some bicycle chains.

  2. You will have to buy all the wood cut and assemble the machine yourself. Plus you need to buy the most expensive part, the router. @ $500 I will build myself instead of supporting the kickstarter. that is a lot for very little.

      1. GitHub, linked in the post. [Bar] really did make this design totally open: soft, firm, and hardware.

        Still, after sourcing the motors, getting everything tuned up right, and working through all the “minor” hassles, I’m guessing that the price he’s asking is pretty fair. More people purchased RepRaps than ever built them from scratch.

        1. Thats true and I like supporting a good idea. I want one of these standing up in my garage. Although I will build myself. I have enough cnc stuff lying around to pull it off. Besides I will support their kickstarter at a lower level.

  3. This is a space saver no doubt about it. Though the costs are way to high for what it actually is, to me the sum of the parts isn’t good value for money. But that is because I’m thinking “hé I can build that myself way cheaper”, but not everyone thinks like that. I really like the idea, but then again I do not like the idea of a power tool not fully constrained to the workpiece/table. Because it CAN move up and dance/bounce this means that eventually it WILL do that and that scares me… a lot. The video made me laugh when the guy spoke about patents… why should a potential buyer care about whether or not this contraption is patented or not. This does not benefit the end user, this is only important to the “inventor” and honestly the innovations isn’t really huge, replace pen of pen plotter by powertool/mill… hmmm.

    I’d rather have them speak about safety regulations, now that’s important, really. This is a powertool capable of hurting everything in it’s path, now how does this project deal with that, unfortunately that isn’t mentioned at all. How about CE and FCC regulations, does this setup meet those requirements? Now that is important… patenting is not!

    I really wonder about the repeatability and backlash of this contraption, the weight of that chain affecting accuracy, would a perfect square still looks like a perfect square. 0.4mm is mentioned, this doesn’t seem like much, but a gap of 0.4mm in your project could be very annoying to look at. But this could be easily fixed with some wood filler, so I guess that shouldn’t be a too big problem in real life.

    Still the idea is very likeable, a small and relatively simple setup capable of cutting fairly large projects fully automatic.

  4. This looks very promising for wood work. Will be interesting to see how well it works.

    My mind was so blown by, Hektor, was it? Back around 2003? 2005? The spray painting graffiti inspired version of this concept.

  5. Approvals probably not as big an issue as a full machine, as they are not selling the nasty spinny cutting part, just a couple of slow motors and some chain. Questionable whether it would fall under the machinery directive in EU
    It’s effectively a kit, so will be outside the scope of some regs.
    I don’t think it makes a handheld router any more dangerous than it is when used as it was intended.

    1. I hate the noise/dust of a router. If I can get a robot to pilot the thing, I’m out on the back porch sipping mojitos (with a webcam pointed at the bot and a remote-controlled power switch) rather than hanging around the basement. Safety concerns sorted.

  6. The jump/skip factor on this concerns me a bit (as [Dax] and others have pointed out). Counterweight constraints notwithstanding, the mounting of the guide with chains from only two of four points means that the tool will jump at some point. It’s not if, but when, though the when will likely only come when the machine is used improperly (too large of a bit, dense or irregular material being cut, etc…). Hopefully there will be some failure-mode testing to determine where sane limits should be set in the documentation. And hopefully end-users will be smart enough to control access to the immediate area around the machine when it is running.

    Ideally, once the end-user sets this up, they will also place a sheet of Perspex or something between the powered machine and the operator/observer to constrain the degree of jump and prevent flying bits of the tool from befouling the squishier bits of said operator.

    Ideally, this would be on a multi-axis gantry (aluminum channel, perhaps?) that would provide some more-reliable level of tool control/constraint, as well as some sensors to act as safeguards if something should go amiss, though that would certainly raise the cost. Such construction would be far more appropriate for an educational or makerspace setting.

    Novelty of doing this sort of work in a slim vertical space rather than a large horizontal one notwithstanding, the inherent danger present in this kind of rig presents a higher-level of risk than might be immediately apparent from casual observation. I hope that future development on this type of tool will take safety into account in a stronger fashion than has been done thus far. All that said, it’s a great idea/application and I hope such development will be able to occur!

      1. in this case it’s because gravity is the third ‘motor’. the weight of the router allows it to travel down when the two top motors ‘unwind’ the chain. if it was horizontal you’d need a third motor and a lot more than 1/3rd more maths.

      2. Space is one consideration. If you want a 4×8 cnc you have to have 32 square feet to commit to it. That’s 1/8 of my shop. Also, the beams required to support the router would be substantial. You could potentially work out a chain system that drags the router across the workpiece but it would not be as well controlled.

  7. Pretty cool. It’s like a horizontal waterjet for plywood.

    Does he have a way to get to a new position or does the operator have to turn it off and hold it off the workpiece while it “rapids”?

    1. There doesn’t appear to be a Z-axis control, so you’d have to manually guide it to a new start point. I’m sure that they judged that the increased cost was a lot more bothersome than the nuisance of manually starting each cut.

    1. How so? I can see how it would facilitate construction, but not really seeing how designs would be affected much. Unless it just meant higher popularity of skin on frame types, because all those fiddly frames less daunting. But people do those anyway with jigsaws, bandsaws and patience…. or they get laser cut kits.

  8. Wow that’s my favorite design so far ideal for house work.
    Half a mil accuracy is so much better then I get with my saw or when routering by hand :)
    I’m not that worried about the thing skipping a beat, add a vibration sensor to slow down or redesign the ring around the bit with the vacuum cleaner to cling to the plate if you are that concerned.

    500 is a bit steep though.

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