That experience has suggested that this project is not going to be as successful as they would hope. That is because you can't depend on gravity to be stronger than the angular momentum of a router bit hitting a knot in the wood. Specifically when you're routering away and you hit material that pushes back on the router, the router may not move in a gravity planned sort of way. I've seen that in the plotters when the drawing device catches on the material that its drawing on. You get a line that goes horizontal when it should go down.
These sorts of things are pretty easy to pass off when you just hang a new sheet of paper but if it means throwing out a 4x8 sheet of plywood its going to be a bit more painful.
As for discontinuous lines you put a wall sensor on the drawing puck (or the router) and when you need it to move you tell the operator. Who goes over and lifts the pen/router off the paper. The code detects the lift, adjusts to the new position while you lightly hold the puck, and then indicates you should let it back down on the surface. Once the wall sensor activates it goes back to drawing.
I wanted to jump in here and add something. Full disclosure, It's my project.
The machine is designed to print things out of the sort of manufactured sheet materials we use in most construction these days so things like plywood, sheetrock, MDF..etc. Knots don't tend to be an issue because they are only in one ply of the plywood, meaning the force is very consistent even when passing through a knot. We've never seen an issue. Materials like drywall and MDF of course don't have knots at all.
I, too, do not want to come across negative about this. I'm very excited about it. If it isn't sufficiently strong to handle some types of wood, even just being able to drop a V-cutter into the router and having it very accurately draw out all the cut/guide lines is a win for the target price. If my work flow is "draw accurate cut lines, do a rough automated cut (leaving some extra around the edges), and finish on the scroll saw and belt sander", that's great!
I always had a list of settings to use for various combinations of materials, thicknesses, router bit sizes/types. It was a bit of a black art actually - sometimes the results of changes were counter-intuitive because of specific material properties (heat retention, etc), and that cheat-sheet wound up containing the accumulated knowledge of years of trial and error experimentation. "The only difference between Science and screwing around is writing it down" :)
source: have made guitar bodies on a normal CNC router. Material holding is difficult at the best of times.
Edit: apparently this was a myth, http://bigthink.com/strange-maps/580-the-legend-of-the-tsars...
It is strange that all the crap I heard as a kid and took for granted for most of my life can suddenly pop into my head and now be verified because of the internet.
This type of plotter was quite the "thing" after one appeared at the Maker Faire (I believe in 2010), I already had an EggBot from EMSL and the Eggbot board is set up to control two steppers. Its really easy to use, I wrote a simple Perl library for it and put it on github . The "build" was really just strapping two steppers to the corners of a stand up easel board, hang a pen in a disk to hold it perpendicular to the page (I believe we used a 2" hole saw to cut out the "puck" and then drilled a hole in the middle for the pen (friction fit with tape for added friction). Two screw eyes at the 10-o-clock and 2-o-clock positions on the puck, a string to a spindle stuck on the left stepper, and a string to a spindle on the right stepper. Then an all night hacking session and boom, drawing pictures :-). Its really straight forward.
While the feed rate of the machine looks OK, but they do not specify the depth of cut per pass. Combine this with the fact they don't show a part being cut from start to end, even speed up, is telling. I suspect a excessive number of very shallow cuts, leading to long cut times and excessive tool wear. I also suspect if the cut depth is to great you might find out the true meaning of climb cutting.
0.4mm resolution is not that great and the resolution actually changes based on how far you are from each motor!
Mounting material to cut on a vertical surface is going to be a major pain if it's not a quarter sheet of ply or bigger. And once a part is cut loose without tabs the router is liable to kick them out, that's going to be a nasty learning experience for some.
The only great things about this machine are its large cutting area, small foot print and low price.
But fair warning, the limitations will start to stack up fast I suspect, this machine would be best suited cutting flat pack furniture designs from full sheets of ply, when delivery time is not an issue. To his credit this does seem to be the market he is targeting.
The OX CNC is awesome.
You are spot on about what we're targeting. We're looking at people who are building big things, houses, sheds, furniture, kayaks, tree houses, geodesic domes, huge signs etc. Basically the kind of things that get built using hand held power tools now. The goal is to make a machine that can download and build those type of things more accurately than a guy who's really good with a jig saw.
As for # of passes, I'll throw some mention of that on the website tomorrow. I usually do 1/8th inch passes so 1/4 inch ply is a 2 pass job, 1/2inch is a 4 pass thing...yada yada
An alternative for the router brand: Makita, they offer a number of router bodies that seemingly last forever in both wood and more difficult materials (fibreglass), I've run them for 100's of hours (and probably 1000's) without a problem.
Beware of steppers when you're driving routers, you may lose steps along the way ruining your workpiece (step loss is loosely related to Murphy's law, it will happen near the end of complex workpieces).
If you build this thing out of metal with a watertable underneath it will be slightly more expensive but you'll be able to use a plasmacutter to cut metal as well as wood by swapping out the head.
Here is what I built:
(That's the first version, before making a much lighter gantry to improve speed constancy in corners, not very important for woodworking but extremely important when plasma-cutting.)
Some critical observations about 'Maslov':
Hanging plotters suffer from asymmetric curves when it comes to acceleration 'up' or 'down' which can lead to surprises in overshoot/undershoot of the intended toolpath.
Cable plotters tend to have a problem with that anyway and gravity will make this problem worse. If accuracy is important consider making it horizontal.
How did you solve the torch height control? We ended up using "digital torch height controller" - basically measure the arc voltage, compare to fixed preset and move Z axis up-down accordingly. This is a stupidly simple approach but requires complicated lookup tables of voltage vs height vs feedrate vs material and I'm thinking about how to improve it.
The arc voltage is directly proportionate to the height above the workpiece so you don't need much in terms of lookups or feedrate, all you want to do is to keep the voltage constant, so if the voltage is too high you need to get closer to the material (beware of strikes!) and if it is too low you need to back off (fast!, sometimes the material is warping towards the torch very rapidly, especially when the material you're cutting out of is thin).
Where in Latvia are you? I go there with some regularity, I'd love to come visit. Mail: firstname.lastname@example.org
Tip: you could lose quite a bit of weight on that gantry but turning it into a lattice.
Weight in a plasmacutter gantry is killing because it reduces the speed with which you can change the direction of motion while cornering in detailed work. That in turn causes you to have to slow down which will burn away fine detail so any weightloss on the gantry should be pursued.
Ideally you want constant velocity relative to the workpiece while cutting. This also helps in maintaining precision because the cone shape that the flame has will cause it to cut thinner and thicker depending on the stand-off distance.
I was working on a controller which was supposed to get it's setpoint by measuring voltage during first few seconds of a cut, but the project turned out to be outside of my EE skills at the time (isolating analog signals, high voltage resistive dividers that didn't blow up because I had no low-voltage feedback signal from plasma source etc.)
About the need for rapid accelerations- that too was one of the things we learned by building this machine. IMO it should be stressed more in discussions about plasma cutters.
In this case the blue linear slide actuator was off-the-shelf part and modifying it would require to cover the belt and linear guides inside with something else and was thought to be too much of an effort.
You'll still need to use an opto-coupler, the way I built mine was the setpoint and comparator lived on one side of the divide, then two input bits, one for 0.1 V below the setpoint or lower, -0.1 to 0.1 was both inputs off and one for 0.1 V or higher, the setpoint was scaled so that it would have a nice range mapped to the inputs of two op-amps doing the comparison. The outputs of those op-amps drove the opto couplers and the software would track the 'Z' stepper up, down or hold depending on those two inputs. Super simple really.
They did say that it has encoders and closed loop control. Perhaps overshoot could be an issue but losing steps shouldn't be.
A big problem is that this thing gets its Z position by riding on the material it is cutting. So you have to cut things out of fresh big sheets. If you cut away too much, work near the edges, or use smaller sheet stock, there's going to be trouble. For decorative scrollwork in thin stock, though, it could be useful. Expect stuff from this machine to appear on Etsy shortly.
I've used ShopBots for similar work. Those have enough rigidity for wood, even hardwood. The limitation on cutting speed is damage to the router bit; the machine has plenty of feed power.
For instance, one could now mill a vertical gardening wall-mounted planter, with community help, by joining this project: http://www.openbricks.io/app#!/project/566af15e584123b4502f4...
It is a right of passage for a homeowner who DIYs to create a workbench. I haven't created mine yet but have investigated approaches. One novel approach is a torsion box-based workbench. The painstaking process one must undergo to create the lattices could be replaced by a fitting together CNC milled, continuous pieces. So cool.
I'm so ready to join this movement..
It's okay that they choose a non commercial license. But it may make me less interested in supporting it.
But I'll check out their PCBs and see if I can help make any improvements. I like this project.
p.s. oh man, make a chair design, and then just set these babies to run day in/out. that could be an fun factory!
This device is more akin to a regular 4x8 cnc router, like ShopBot, or an off the shelf Chinese CNC machine. The innovation here is an experiment with the drawbot mechanics popularized around 2010, but with a much heavier toolhead. If it works, awesome - it's an order of magnitude cheaper than a shopbot. Even if it's not ready for production, it's an interesting enough idea for a few shops, garages, or hackerspaces to replicate the project.
This is really an awesome idea, and comparing it to a startup with questionable investors does it a disservice.
1. this isn't really printing, its subtracting. I think its important to make this distinction.
2. feed rate is REALLY important with getting good tool life as well as good cut quality. Relying on gravity to control a 1-2 HP router is not going to counter the cut forces well except at seriously sub-optimal cut rates.
e.g. A carbide 2 flute upcut end mill with .5" diameter cutting plywood works nicely with a cut depth of about .5" and a feed rate of somewhere around 200-300 inches per minute. Even that may not yield the optimal chip load to keep the bit cool. That assumes a router speed of ~20k RPMs and 3.25 peak HP (AC motor @ 110v).
I have never built one of these, I wonder why they do that.
I would think 3 strong steppers would be capable of some pretty amazing forces and would be quite well constrained. Or perhaps 4 steppers or more.
I've spec'd out NEMA 42 frame steppers that could quite easily start my car (under the theory that a pony engine need be a tenth size to start a larger engine and my commuter car only has 100 ft-lb torque, so 20 or so ft-lb of torque should easily be adequate to start the engine)
Lets see a KollMorgan KM11 with 3750 in-oz of torque applied to a six inch pulley is 40 pounds of force. That should accelerate a ten pound router with some authority, 4 G or so. I know from experience I can push a traditional router against a jig or fence or table much longer and more comfortably than I can curl 40 lb barbells so 40 peak should be more than adequate.
A stepper of that output retails qty one to end users for like $150 delivered maybe? So figure maybe $300 for three in bulk order shipped by pallet-full?
Over the course of my life the prices of steppers and control electronics doesn't seem to change but the torque seems to go up an order of magnitude per decade for several decades now, so it might be a matter of waiting until 2026 to unleash something like the above.
The issue with gravity is not really motor strength so much as it is rigidity. There is no z axis rigidity in the setup because it only has a chain. So it can't exert pressure against the material from the axis.
The lack of rigidity is the real problem. As mentioned in other parts of this thread, .01" accuracy is not going to give you great tolerance for pieces where that error can be cumulatively compounded.
Your project will involve plenty of time and effort at other stages than the plywood cutting bit.
Still, I'd consider getting one (perhaps on v2 after the Kickstarter has played out, and v1 gotchas figured out). It is cheap enough to get "just for fun."
Now that the US is first-to-file, doesn't that mean someone else can patent it and use the patent against them? Isn't the best thing to patent it and give royalty-free licenses?
Publication or public practice of their work is prior art. It immediately precludes third parties from patenting their work. (And, after a grace period will preclude them as well)
First to file deals with interferences, when two parties try to patent the same work at the same time-- it doesn't change how prior art works.
Of course, it is still useful to file defensively since relevant prior art is much more likely to be discovered when it exists as a patent... if it's not discovered a patent could be incorrectly issued. (The patent would be invalid-- but could still be used to harass people until put out of its misery by a court. :) )
On a related note: I'm pretty excited for the ShaperTools handheld router: https://shapertools.com/ You get the benefit of big work pieces & CAD-based routing, but in a hand-tool form factor.
> More details for nerds below
I'm not knocking the person who said this fairly innocuous statement (I catch myself saying similar things), but it goes to show our unresolved social biases against technical people. Yes, some people care about numbers and details and engineering. Unfortunately, that associates them with a term that implies low social value.
If another country overtakes the US in terms of innovation and engineering, you can be sure that they will be showing greater respect to their technical class of peoples.
(Off topic, but a hanging plotter (for drawing) would be rewarding project to build with a kid!)
I'm pretty sure they are also not including the router runout (since it uses a router and not a spindle, add about 0.005-0.010, or, rather, halve their precision again)
Now, don't get me wrong, it's a neat idea.
It may be really cool for construction (though drywall/etc guys are a lot faster than this machine is), but ...
But you actually could not likely use this for real cabinet parts, etc.
To give you some idea:
Encoder Resolution: 8148 steps/rev
Real World Precision: +- 1/64th inch (.4 mm) or better
Max feed rate 48 inches/minute
Specs on my pretty basic 36x36 wood CNC router:
Encoder Resolution: 4 million steps/rev (22bit). Electronically gearable to whatever (they are servo motors)
Real world precision: +-0.001 (1/1000) inch
Max feed rate 1200 inches/minute
Now, obviously, there is a range of costs and other machines between these two machines :)
But building precision CNC routers, even with good closed loop servo motors and ball screws, is not anywhere near as expensive as it used to be.
Sure, other more expensive machines have better precision. But how many people actually need that much? Even plywood is going to experience changes in length due to temperature/humidity greater than 0.001" (0.025mm). Solid wood (which I guess this machine isn't really designed to cut) is going to be even more.
What use case?
"construction" is mentioned, but plywood guys and drywall guys can make cutouts and curves far faster and more accurately than this machine can cut.
So seriously, what is the real use case other than "fun toy"?
" 0.4mm or 1/64" is way more accurate than almost anyone can do with traditional power tools."
This is just flat out false.
With a simple track saw, i can easily get within 1/128th without even trying.
Hell, i can do that with a circular saw and a straight edge without a track.
You can get to within 0.005 pretty easily if you have bothered to tune your tools at all and don't beat them up.
You can definitely get 0.005 if "traditional power tools" includes routers.
Of course, if you go to hand tools, getting within 0.001 is utterly trivial with good hand planes.
"But how many people actually need that much? "
Wood certainly moves, but 0.005 is about being able to make nice fitting joinery repeatably.
"With a mortise of 0.503", here's how the tenons fit:
Realistically, the total range of latitude is about 0.005" for a good fit. And this is using spruce, which is a very forgiving soft wood. For mortise and tenon joints in hardwoods, accuracy is even more critical. "
Remember that this is jut the 'precision'. It says nothing about the repeatability.
I have strong doubts it's repeatable to even that level.
"but first you need to somehow draw a line to follow, a challenging task in itself for complex shapes"
It's really just not that hard. In the absolute worst case, you use graph paper and cut it out. Most of the time, you just use a protractor or a bow and cut it nearly perfect anyway.
Given the tolerances pretty much restrict this to "construction work", you can get the same result quite easily.
"This tool can do CAD, a big benefit."
I'm also going to assume you've not used much cad/cam software, because for most people, it's infinitely faster for a one off to draw it by hand than it is to draw it in a cad program and generate gcode for it using cam software.
People have enough trouble using sketchup, let alone something real :)
The advantage for most people for CNC is the ability to repeatedly do the same thing.
Unless you invest 100k in automated workflows, you aren't ever going to get to the point where it's simply "draw in cad, click button, have machine cut it". It's just never that simple, from workholding to what have you.
Which is another reason why i think it's neat, but has no real use case.
The sources of problems are endless, even in a rigid machine:
1. spindle runout.
2. bit diameter changes (its is labeled at .25", but its really .246
3. climb vs conventional milling yields different characteristics in different materials.
4. bit deflection in certain cutting actions (plunge, tight corners, etc)
5. bit wear during the job.
6. dust removal / chip recutting
7. lost steps
8. dust in the ways of the machine
9. linear motion system misalignment.
10. workpiece slippage/hold down.
11. material not being flat/level (especially with cheap plywood, which often varies in thickness by >.005")(try making accurate box joints with that...)(also, it is never flat, it always has some twist/warp because of the way the plys are cut out of the tree).
This machine seems to be a great thing, and I very well may build one for an outdoor plasma cutter, but, I find the accuracy claims very difficult to believe. All of these sources of precision loss will effect the end result.
You just have to know what to look for.
So, for example, mitsubishi EOL'd the mr-j2-* series, and released the mr-j4 series.
If you look on ebay, you can usually find mr-j2's and mr-j3's , as new old stock, for about 300-400 for drive + motor (I'm going by the 400 watt ones, so mr-j2-40 and hc-kfs43).
If you are really good at it, you can find the mr-j4's for good prices occasionally.
There really isn't much of a resale market because in the automation world, people don't buy used or eol'd stuff (you aren't going to shove used motor into critical factory machine)
I ended up getting 3 new mr-j4-40a's and associated motors for about 1000 bucks.
You can play the same game with yaskawa, etc motors.
The short list is pretty much:
It is hard to go wrong with any of these.
Unless you are doing something nutso, you won't need more than 400 watt motors (which, being brushless dc servo motors, have enough power to pretty much destroy every other part of your machine)
And what would be the precision on this thing? It's a bit suspicious they'd leave that out... Would it be able to work at 1 mm precision?
I'm sure they can lift it up. This kind of mechanism isn't exactly new - but using it on a router is fairly new. There's a lot of projects with pen plotters built in this general pattern, see http://hackaday.com/2011/11/17/polar-pen-plotter-draws-huge-...
Even for just 2D, this is really clever for the form-factor/capabilities/price. It's in 'impulse buy' pricing territory for most people (I mean, posting here at least). It takes up basically no space. If the steppers are well-engineered, I can't foresee a failure mode other than just normal tool wear.
I was considering buying a Shaper (which is really cool in it's own right) after seeing Ben from Applied Science mess around it. With the Shaper, "you're only limited by the surface on which you can place those encoding stickers" while with this, you can build out effectively until the elasticity point of your support structure (or, I suppose, the chain has a fatigue failure). 15 thou isn't bad at all, especially if you know where the run-out is going to be (i.e. if it's gearing backlash, you can design your features around that with that in mind / build your software to compensate for it / incorporate active air cylinder brakes / etc). Edit: On second thought, they said the steppers were closed loop. So if it's any worse than 15 thou, shame on them, really.
My only concern is if the slop/run-out goes up as a function of the material you cut. The Shaper has what seems to be using some sort of active delta compensation Aluminium and a standard house-hold router can accurately mill your 6061 aluminum that's good for up to like 30k tensile with it. The collet/chuck/gantry/whatever will just actively re-orient your bit for the micro-tuning. (Though, for the $1500 they want, you can pick up one of the thousands of Bridgeports Series 1 CNC's out there, throw another 500 for your carbide cutting tools + retro-fit kit and you've got a home machine shop and come out way ahead only a few hundred behind with the ability to actually mill something structurally sound like steel.)
Either way, this is super cool - I'll wait for a few reviews, but I think I know where my money's going even if it's limited to wood.
 And those stickers smell of vendor lock-in. It's got the opposite 'feel' to it than this product.
I was just looking for something like this yesterday! I pre-ordered a Shaper Origin (https://shapertools.com), which ships in September 2017, but I need something to use now.
Once you accept the constraints of a 2-axis CNC router, you can design in a way that maximizes it and build incredible things. See https://www.opendesk.cc/ for examples of a lot of furniture that can be built this way.
(Tolerances may not be exact).
The same basic principle shows up in rigging - http://www.fdlake.com/rig-slng.html - the illustration where the straps are at 90 degrees is rated higher than 45 degrees.
There could be some error due to rotation of the entire router as it encounters friction, but it should be manageable, and whatever error remains is basically how accurate you can get.
I wonder if you could mount the router on a bearing, have each chain attach to a free side of the bearing so each side can rotate around the router. Then just figure some way to lock the routers torque that isn't the x/y control mechanism. Perhaps 1 chain pulling directly down.
I only mentioned it because the original title read something along the lines of "4 x 8 foot CNC available for purchase for under $500".