The Polar Bear – Open-Source, Multipurpose CNC Machine with a Rotary Axis

l00sed 2021-08-19 13:20:12 +0000 UTC [ - ]

The cantilevering arm looks as though it wouldn't have any real overall rigidity for carving or for rapid, accurate motion with any kind of resistance... But I really love that this made it to hacker news because I feel like "hacking" doesn't exclude non-software hacks and it's always awesome to see hardware for design and making alongside all the other software news.

The idea of open source robotic assemblies or mechanical assemblies is another cool, separate thing. Another cool project I came across was the AR-1, AR-2, AR-3 series of desktop 6-axis robots. The inventor/designer made all the assembly docs open-sourced and sells kits or specs to make your own.

toss1 2021-08-19 16:09:06 +0000 UTC [ - ]

Yes, this looks like a great learning device! It could also be good for prototyping controls for a more serious tool, and the pen tool and maybe even a light extrusion head might produce some good results.

But cutting anything is, umm questionable.

In general, a cantilevered configuration is inherently wobbly compared to a gantry configuration that rolls on parallel rails/beams at the outside of the workspace. Even a massive Bridgeport-style mill has issues vs a moderate gantry CNC mill (although uses a lot less shop floor space). All the force paths are working to bend the cantilever device, vs all the gantry geometry that works to minimize error.

So, while it looks like a great effort and good for some things, if they want to offer any even slightly serious cutting capability, they'll need real work on the stiffness.

SeasonalEnnui 2021-08-19 09:57:49 +0000 UTC [ - ]

Neat kinematics with a horribly flexible frame that denies any serious usage. That said - it's designed to a low budget that increases the potential audience, and that is something that can only be welcomed. I'm particularly interested in the software as that will be an enabler for future variations that have mechanical rigidity.

Nice website!

canadian_tired 2021-08-19 12:35:37 +0000 UTC [ - ]

Exactly. I can't speak for laser, extruders, knives or such, but for subtractive work (i.e. milling / drilling operations with some form of rotary tool) this design would be an exercise in frustration. Typically, you would have encoders on each axis to tell the machine where things are happening. These encoders are excellent, but any flex/slop in the chassis or moving parts is not caught by the encoder... so the software will not know that the cutter is in the wrong place. Thus, crappy parts. Any reasonably useful CNC design takes rigidity and backlash prevention seriously. Take a look at PocketCNC for a good (and yes, expensive) design.

galangalalgol 2021-08-19 16:50:05 +0000 UTC [ - ]

could you use strain gauges to measure the deflection and fix it in software?

Turing_Machine 2021-08-19 16:09:02 +0000 UTC [ - ]

You could probably use it for ECM or EDM, but yeah, not stiff enough for traditional hogging cuts as a lathe or mill.

mabbo 2021-08-19 11:24:02 +0000 UTC [ - ]

Are there similar systems- CNC with multiple heads- that don't have this problem?

I played with a wood router CNC in high school and loved it. I've also played around with 3D printers a bit. The idea of having (and building?) a reasonable system that can do both strong appeals to me.

enragedcacti 2021-08-19 13:23:28 +0000 UTC [ - ]

The closest that can do both is probably MPCNC (https://docs.v1engineering.com/mpcnc/intro/).

it is built with that modularity in mind but as other commenters have pointed out building something for rigidity makes it slower and heavier. a cheap 3d printer like an Ender 3 in addition to the MPCNC makes more sense, especially since you can save on the MPCNC by 3D printing the components yourself.

The main benefit to swapping a 3d printer head onto the MPCNC would be the pretty massive XY size you can build the MPCNC out to. If you need to print really large, flat objects it is probably cheaper than a lot of alternatives. But at that point it probably would make more sense just to mill it out of wood anyway.

joshu 2021-08-19 11:56:15 +0000 UTC [ - ]

no. anything that is strong enough to, say, CNC will also be very slow for 3d printing or laser. different processes demand different designs.

jjoonathan 2021-08-19 12:13:52 +0000 UTC [ - ]

Depends on the price class, of course. If you spare no expense, you can employ lots of iron and lots of power to throw around the iron.

https://youtu.be/RcansEmVknA?t=150s

ivanbakel 2021-08-19 12:11:20 +0000 UTC [ - ]

>with a horribly flexible frame that denies any serious usage

What's the risk from this? That CNC work will be affected by resistance from materials, causing the frame to bend? What kind of scales would that effect be noticeable on?

_jal 2021-08-19 12:12:59 +0000 UTC [ - ]

For any real cutting, you need rigidity or nothing will be accurate.

You will not be doing any real cutting on this machine.

ivanbakel 2021-08-19 14:09:03 +0000 UTC [ - ]

But to what extent will it be inaccurate? It seems unlikely to me that anything used for machining hard materials can be 100% rock-steady. Presumably, industrial machine are simply inaccurate to very small, tolerable degrees.

abakker 2021-08-19 14:45:41 +0000 UTC [ - ]

Accuracy and Precision would be problematic with this design, but, lack of rigidity is more insidious. Most of these high speed spindles will use carbide tooling, which is highly susceptible to breakdown under vibration. A flexible horrible frame like this is going to vibrate a lot even in materials like delrin or HDPE.

Also, with a vertical spindle and CNC control, there is no reason to have a vertical rotary axis. The reduced motion doesn't buy any capability upgrade. The 4th axis that is helpful would be angular. (you could put a horizontal spindle on this, I guess, but this machine is not up to the task.

pushrax 2021-08-19 15:43:47 +0000 UTC [ - ]

Obviously there is no perfectly accurate machine for any application.

The extent it will be inaccurate depends on a lot of factors, such as tool length, material parameters, feeds/speeds, etc. You can probably cut aluminum somewhat accurately on this if you take extremely slow cuts, with a tiny tool spinning at an extremely high RPM (which keeps cutting forces to a minimum). Surface finish would still be pretty bad simply due to vibration of the arm. Likely going to break a lot of tools too. The majority of metal cutting setups you would do on a mill are simply impossible on this machine.

For a few tiny cuts, it might be handy to have one of these, but it definitely seems more useful as a 3D printer, plotter, etc. Though even most 3D printers are significantly more rigid than this design.

2021-08-19 14:52:06 +0000 UTC [ - ]

Arcanum-XIII 2021-08-19 14:22:20 +0000 UTC [ - ]

I have a small mill, it still weight around 1250kg… to be accurate at 0,01. And for that I would need to lock the unused axis and respect the power of the machine. This is not CNC, where the forces are often higher because they can work faster, with curve and some other things I’ll have a hard time doing.

bluGill 2021-08-19 13:54:59 +0000 UTC [ - ]

The frame will vibrate resulting in chatter and in turn your cut will have waves and dips.

SeasonalEnnui 2021-08-19 14:17:11 +0000 UTC [ - ]

The risk is that you will only be able to mill materials that are very soft; materials that could be cut with a pair of scissors (card, foam). Anything harder will be an exercise in frustration (friction rubbing instead of cutting, frame flexing, motors stalling, terrible tolerance).

ezconnect 2021-08-19 14:30:18 +0000 UTC [ - ]

You have limited use for subtractive CNC work. Materials it can work on will be like chalk, charcoal, graphite. It might be usable on machine wax but I doubt it.

ZeroGravitas 2021-08-19 12:52:03 +0000 UTC [ - ]

Whats the definition of "serious" here? Is there a standard measure of tolerance or material compatability that it can be rated against to see if it would work for a specific need?

icegreentea2 2021-08-19 13:33:12 +0000 UTC [ - ]

CNC (and mfg in general) will have different tolerance needs. And the flex on this machine will depend on the material and work speed.

I'd probably argue that anything worse than 0.5mm (~20 thou) will start giving you headaches if your making parts that are supposed to interact with each other. That said, if you're making basically oneoffs and are willing to handfit, that tolerance is probably tolerable (ha!).

SeasonalEnnui 2021-08-19 14:19:48 +0000 UTC [ - ]

Serious = harder (hence more useful) materials. As it stands I would say only materials that could be cut with a pair of scissors (card, foam) could be used on this safely without frustration.

londons_explore 2021-08-19 12:11:26 +0000 UTC [ - ]

I would like to see software compensation for frame flexibility.

Either open loop (ie. use mechanical models to predict frame flexing and compensate for them), or closed loop (have sensors to detect realtime head position).

The whole idea of having a frame which is 100% rigid seems like a simplifying assumption that makes everything more expensive, with knock on effects too (eg. making stuff stronger makes them heavier, which in turn means a bigger motor is needed, which uses more power, so a bigger power supply is needed, etc)

roderickm 2021-08-19 13:01:21 +0000 UTC [ - ]

The Shaper Origin handheld CNC router makes an impressive attempt at compensating for imperfect frame rigidity, as it's designed to be handheld. The Origin operates in only two axes and uses consumable tape placed on the workpiece as an optical reference, but its progress is noteworthy.

jjoonathan 2021-08-19 12:29:22 +0000 UTC [ - ]

I expect it would be easy to compensate position (closed loop is already table stakes in the professional tier) and extremely difficult to compensate chatter. What would it take to drive the motors of a 5 axis CNC to responses well into the kHz? You would need that, to compensate chatter. You would also still need to handle the same peak force, whether or not you do it with negligible deflection.

mankyd 2021-08-19 12:17:13 +0000 UTC [ - ]

I would think it would have to be closed loop. Material density is not always uniform (especially with something like wood) and that has one of the biggest effects on how your tool behaves.

Even then, compensating for sudden release in tension, where the tool tries to spring back, seems perhaps insurmountable.

SeasonalEnnui 2021-08-19 14:25:17 +0000 UTC [ - ]

Not pragmatic IMO - flexible usually means resonance and vibration which leads to poor finish and deafening the operator/upsetting the neighbors.

If a lighter frame was the design goal (but low cost wasn't!) then carbon fiber has an interesting stiffness/weight ratio and could have viscoelastic damping elements incorporated too. Realistically though, lightness isn't a prioritized design goal though I certainly see the appeal in marketing for home usage where you wouldn't need a crane to move the machine about.

femto 2021-08-19 12:33:32 +0000 UTC [ - ]

It could work to have two towers. The first carries the cutting tool. The second carries a measurement device and is subject to negligible forces. Alternatively some form of photogrammetry, possibly with a structured light field.

DannyBee 2021-08-19 12:37:27 +0000 UTC [ - ]

This could be greatly simplified (at higher cost) by using linear motors for the cross-slides.

It may even be more rigid than what is there now (though nowhere near rigid enough to do anything real)

The design is actually not unique at all - you can buy much better versions of it (at higher cost, obviously).

Most positioning actuators you can buy are literally built to be attached to each other in a cross-slide configuration, and to have a rotary table attached to it. They also directly sell pre-built cross-slide actuators.

If you just google "cross-slide stepper" or "cross-slide servo", you can see this (servo/stepper just gets rid of the manual ones, which also exist).

The normal reason the configuration is not used is because it has no meaningful rigidity.

dekhn 2021-08-19 14:18:02 +0000 UTC [ - ]

Are you talking about products like this? https://www.amazon.com/Electric-Sliding-Ballscrew-SFU1605-Wo...

I'm not sure what you mean by "linear motor", I think these cross-slides typically use steppers or steppers with feedback.

abakker 2021-08-19 14:40:33 +0000 UTC [ - ]

A linear motor is essentially a stepper motor that has been unrolled. The Stator and rotor are flat. Kern uses them in really high end VMCs and the result is better position control and better rigidity.

dekhn 2021-08-19 15:09:44 +0000 UTC [ - ]

do you have a pointer to a reasonably accessible device I can buy? I work with CNC and 3D printers and other motion stuff a lot and always want to find better products than the cheap steppers I'm using.

abakker 2021-08-19 16:59:37 +0000 UTC [ - ]

I recommend that you use Clearpath servos. It is a step up in budget, but the motion is much smoother and there is no vibrations which are somewhat inherent in steppers.

Linear motors are great, but are overkill unless you are concerned with the lost motion inherent in any screw, r&p, or belt. servos and double nut ball screws are adequate for almost everyone (including Mazak, DMG, HAAS, etc).

jbay808 2021-08-19 15:39:17 +0000 UTC [ - ]

What is your budget?

toss1 2021-08-19 15:53:08 +0000 UTC [ - ]

Here you go:

https://www.kollmorgen.com/en-us/products/motors/direct-driv...

and their page on success in CNC seems fairly impressive.

https://www.kollmorgen.com/en-us/service-and-support/knowled...

Edit: I'm not sure how accessible these are, but they have a life sales rep chat, so they seem to want to get them to you quickly...

canadian_tired 2021-08-19 12:39:01 +0000 UTC [ - ]

Well said.

q_andrew 2021-08-19 12:22:54 +0000 UTC [ - ]

If the software was compatible with proprietary vinyl cutters, there would be a slew of stay at home moms who would love to use it. Popular manufacturers have completely destroyed their customers' faith - I recommend this excellent write-up in r/hobbydrama:

https://www.reddit.com/r/HobbyDrama/comments/mmmcy7/home_cra...

dwater 2021-08-19 13:31:16 +0000 UTC [ - ]

I interviewed a guy for a dev job a while back who had written software for a consumer embroidery machine just because he had one and wanted it to work better, that had turned into a pretty good side business and it sounded like he had the same customer base, and it was a very profitable niche. A small but devoted group of users who weren't well served by the manufacturers and didn't have the technical skills to develop a solution for themselves.

dstick 2021-08-19 09:46:00 +0000 UTC [ - ]

Here's a video on it: https://www.youtube.com/watch?v=FYIBTIHOMxI

Although a tip to the creators: just pay someone to voice-over this. The robot voice is... terrible :D

bluebirdfirewin 2021-08-19 11:07:02 +0000 UTC [ - ]

Today quality of text to speech is amazing. They could have used a better service. Take a look at these samples https://wellsaidlabs.com/

mercora 2021-08-19 11:20:15 +0000 UTC [ - ]

i could not bare it after few seconds and muted it and read the auto-generated subtitles instead. it sounds really terribly annoying to me. its weird because otherwise this video appears quite well laid out and all but listening to it was destroying the overall experience of it for me.

btbuildem 2021-08-19 14:09:17 +0000 UTC [ - ]

I agree, the voice detracts from the experience -- but perhaps this was the best they could do under the circumstances. We don't know how good their command of the English language is, maybe they can't even tell how bad it is. Or maybe they're just of the Tik Tok generation and this jarring awfulness seems normal :)

Ma8ee 2021-08-19 10:03:17 +0000 UTC [ - ]

I kind of like the robot voice. Very soothing.

beervirus 2021-08-19 12:32:13 +0000 UTC [ - ]

Less annoying than the tiktok voice somehow.

maweki 2021-08-19 09:10:31 +0000 UTC [ - ]

How does one navigate this website with a keyboard? The mouse wheel switches between the slides. The cursor key, page up/down, spacebar, don't work to navigate and the slide selectors at the right side can't be accessed using Tab as well.

Also by tabbing to some of the links you break the page as the scroll is out of sync.

throwawayboise 2021-08-19 14:31:52 +0000 UTC [ - ]

The website is a disaster. Browser scrollbars don't work, page up/down keys don't work. There's some kind of barely contrasting menu of two-letter codes on the right-hand edge of the page.

My day is too short to figure this out. Moving on....

chrismorgan 2021-08-19 09:51:48 +0000 UTC [ - ]

Load it without JavaScript, and with a `.swiper-container { overflow: unset; } .swiper-wrapper { display: unset; }` user stylesheet, and it’s perfect except for the contact form which they’ve implemented badly (the fields don’t belong to a form, and they’ve just put a click handler on the submit button, which basically turns into a form submission, just done AJAXily), but you couldn’t read the form field labels anyway so maybe that doesn’t matter.

stjohnswarts 2021-08-19 15:49:07 +0000 UTC [ - ]

Works fine with Vim Vixen add on

cyborgx7 2021-08-19 09:25:12 +0000 UTC [ - ]

>How does one navigate this website with a keyboard?

One doesn't.

wiredfool 2021-08-19 09:32:24 +0000 UTC [ - ]

Nor with a trackpad apparently.

Karliss 2021-08-19 11:11:04 +0000 UTC [ - ]

Even with a mouse it's bad. If you have a free spinning scroll wheel scrolling a little can cause huge jump, but once you start scrolling faster the page will do opposite and not scroll at all (probably some kind of mechanism trying to prevent skipping over multiple pages). The fake scrollbar can't be used either and menu bar is useless because because who knows what each two letter pair means.

cyborgx7 2021-08-19 09:42:13 +0000 UTC [ - ]

I didn't have a problem navigating the page with a trackpad. I agree that it is bad that you can't use arrow key and page keys do switch between slides, but I don't see the problem a trackpad would pose.

intpx 2021-08-19 14:03:37 +0000 UTC [ - ]

So many critical comments, with albeit legitimate critiques, that are missing the point. This is an open source hobby project that is designed to be built with a 3d printer and a few inexpensive off the shelf parts. I have yet to see another rotary table based cnc project like this. does it have some inherent design compromises and short comings? yes, but this is a starting point. The initial reprap project was (an ancestor of this project, no doubt) was also very flawed. This is the starting point of a pretty novel take on desktop cnc and if it gains some traction, will also evolve and iteratively improve.

jjoonathan 2021-08-19 16:25:09 +0000 UTC [ - ]

Machining without rigidity is a Hard Problem. If someone expects to just iterate past it or trade away a bit of performance and ignore it, they are in for serious disappointment.

This isn't necessarily obvious to people without CNC experience: just look at the number of people in this thread who think deflection compensation can solve rigidity problems. There's no shame in being new to CNC and not really understanding or believing the hype about rigidity, but the Polar Bear company has a financial interest in pushing people towards learning these lessons in an expensive & time consuming manner. That's exactly what they're doing. The people with CNC experience have seen this show before, have seen the burned customers, and are just trying to make sure that expectations stay in the ballpark of reality.

SeasonalEnnui 2021-08-19 15:47:42 +0000 UTC [ - ]

I think we simply rejected the point. There are many newcomers thinking they can disrupt the space with terrible designs. Open source shouldn't mean terrible design. There are many better open source CNC already.

Fred27 2021-08-19 12:35:32 +0000 UTC [ - ]

One of those bad ideas that crops up again and again and again. Any multipurpose machine will be bad at all things. You're far better off getting a separate CNC mill, 3D printer, laser cutter, etc. Even if this costs a bit more and takes up more space, you'll have some useful machines.

Notatheist 2021-08-19 13:02:07 +0000 UTC [ - ]

Space and cost saving multi-purpose designs are ubiquitous in the professional space. At a home-gamer level "just buy all the separate machines!" is a ridiculous argument.

bjt 2021-08-19 15:22:29 +0000 UTC [ - ]

At first, yes, I agree. But folks could say the same thing about phones, cameras, GPS, etc. years ago (now all in one device). Or multi function printer/copier/scanner/fax. Over time, things improve. Who knows if that will happen here, but it seems likely to me.

antattack 2021-08-19 11:02:25 +0000 UTC [ - ]

Cantilever design will be fine for small machines. One of the bigger problems of the design would be keeping one's work piece attached to the table.

For controller software I would recommend customizing klipper[1] that runs on RPi/most controllers for custom kinematics. It's written in python and C and it's well documented.

https://github.com/KevinOConnor/klipper

abakker 2021-08-19 14:54:29 +0000 UTC [ - ]

If you need open source control, use LinuxCNC. If you need open source designs a) why? b) download any of the many designs on the internet constructed out of 8020. If you need to budget less than 8020, use maker slide.

I've build multiple BIG cnc routers. One with 8020, one out of steel. The industrial design of the frames are not that hard, its more cable management, PLC stuff, sensor placement, and calibration that get you. Linear rails (e.g Hiwin rails) offer excellent linear motion and rigidity. Rolled ball screws also work great.

I've also converted some older manual mills to CNC, most recently a Bridgeport that is running a Masso G3 controller.

The reality is that the need for open source in this space is limited because most of the hardware that is available for Mach3, Mach 4, UCCNC, is highly versatile, and the "closed source" software still allows scripting, etc to modify buttons and routines to suit you. And again, if you really want to control everything, LinuxCNC works.

If you are new to this space, I recommend buying or building a gantry router. It gives you 3 axes of motion with a vertical spindle, and depending on the level of weight and rigidity you add will influence the hardness of the materials you can cut.

aaronblohowiak 2021-08-19 15:30:56 +0000 UTC [ - ]

What are your thoughts on ballscrews vs r&p? Is whip an issue with higher ipm on a long machine (4x8)?

abakker 2021-08-19 16:56:06 +0000 UTC [ - ]

ball screws are better, more expensive, and more rigid. to get them longer than ~50 inches you probably want to either get ones with a very high lead angle, or use ones with a driven ball nut design.

R&P works totally fine for wood and aluminum, and is significantly cheaper and easier to implement.

Once consideration is that in driven ball nuts and R&P the motor must traverse with the moving axis. In standard ballscrew config the motor can be static which makes cables and packaging easier.

jamessb 2021-08-19 10:16:01 +0000 UTC [ - ]

This reminds me of the Dual-Disc Polar Printer: https://hackaday.io/project/177633-dual-disc-polar-printer

mdaniel 2021-08-19 15:35:02 +0000 UTC [ - ]

> The PolarBear CNC machine needed special CAM software to use the full potential of the PolarBear. So I decided to start an open source Cam software project.

> It's kind of necessary. Because there is no powerful and complete open source CAM software that is useful and easy for everyone.

That helps me understand where this falls on the plausibility scale

imtringued 2021-08-19 09:47:32 +0000 UTC [ - ]

Ok, I'll bite. Can this machine be used to 3D print a part and then switch to a sanding/engraving tool to achieve a nice surface finish? The machine is too "floppy" to do any serious milling but it is good enough for some cosmetic surface operations and depending on your target audience, cosmetics might matter a lot.

knicholes 2021-08-19 10:11:50 +0000 UTC [ - ]

I'm pretty sure this is addressed in both the video and the website. There's a whole section where it shows swapping out various tools at different angles for different functionality, including 3d printing and CNC milling.

But if you looked at their CNC example, the result was pretty dang coarse. Painting on something like XTC-3D from Smooth-On is one way to get a better finish while avoiding tedious sanding.

unholiness 2021-08-19 11:53:03 +0000 UTC [ - ]

It wouldn't be easy to secure a printed part, especially without adding slop. Also, is there any overlap between materials you can 3d print with in this thing, and ones you can mill (or even polish) without shattering the part?

GravitasFailure 2021-08-19 10:09:52 +0000 UTC [ - ]

Maybe? Not all plastic plays nice with machining, but E3D demoed mixing additive and subtractive manufacturing with their tool changer setup, which is a much more rigid Cartesian system.

donquichotte 2021-08-19 09:05:27 +0000 UTC [ - ]

Very cool project. I guess actual subtractive manufacturing can only performed on very soft materials like foams - I have an eShapeoko which is stiffer than this construction and the frame starts flexing quite easily.

abdullahkhalids 2021-08-19 09:35:42 +0000 UTC [ - ]

What do you mean? Lathes have been used to do subtractive manufacturing with metal for thousands of years. Modern Lathes are CNC types and can build a lot of stuff.

https://en.wikipedia.org/wiki/Lathe

donquichotte 2021-08-19 09:53:51 +0000 UTC [ - ]

Rigidity of the frame is key for accurate and safe subtractive manufacturing.

You do not want your frame to flex while a spindle is cutting aluminium at 20kRPM. See Marco Reps and Kris Temmerman on youtube, they built formidable high precision CNC mills out of steel and concrete. For machines that rely on frames made out of extruded aluminium, flexing has always been an issue, even with much sturdier designs such as the Avid CNC machines.

Also, FYI, in a lathe the workpiece spins, and in a mill the tool spins.

sschueller 2021-08-19 09:49:12 +0000 UTC [ - ]

This thing is not very rigid and the interconnections are made of plastic. There is a lot of flex and anything other than soft materials can not be milled with any precision.

One main reason professional 5 axis CNC machines are so expensive is because they are very rigid yet can move quickly and precisely.

GravitasFailure 2021-08-19 09:56:18 +0000 UTC [ - ]

That cantilever design is known for having rigidity problems for 3D printers and isn't used at all for subtractive manufacturing. Compare it to a MaxNC 10[0] or a Taig[1] micro mill and you'll be able to see how much more robust their construction is.

[0]http://millingaccessories.biz/2015/04/07/maxnc-10-cnc-millin... [1]https://lh3.googleusercontent.com/-TkXnpUUXqLg/T4Qj3qVU9JI/A...

imtringued 2021-08-19 09:53:31 +0000 UTC [ - ]

And they were built using solid cast iron. Meanwhile this machine consists of one big aluminum extrusion and a thin extrusion. It's clearly built for speed not rigidity.

Turing_Machine 2021-08-19 16:02:22 +0000 UTC [ - ]

> Meanwhile this machine consists of one big aluminum extrusion and a thin extrusion.

With long cantilevers (i.e., supported at only one end) on both, to boot. Long cantilever, thin material = slop.

Even a small bench top lathe has hundreds of pounds of cast iron in the bed and ways, as you said.

That aside, a lot of the jobs they show in the video (pen-plotting, wood-burning, 3d printing, etc.) don't really demand a huge amount of rigidity. I wouldn't want to try any serious milling or turning with this machine, for sure, but for those jobs it looks like a totally reasonable design.

And I do like the fact that it's designed to be 3D printed itself (other than the extrusions and stepper motors, etc.), so well done on that.

erdii 2021-08-19 09:45:35 +0000 UTC [ - ]

Lathes are kind'a more rigidly built though and I think that is what GP tries to point out.

chrisco255 2021-08-19 09:32:35 +0000 UTC [ - ]

Highly recommend watching the explainer video. Very versatile tool!

kuroguro 2021-08-19 09:46:23 +0000 UTC [ - ]

They should embed the video in the front page, glad I went back to watch it!

Don't understand why they used a robot voice for an otherwise well thought out and high quality video tho.

pulse7 2021-08-19 10:12:46 +0000 UTC [ - ]

Maybe the author speaks English with a strong accent so he decided to use a voice robot...

octopaulus 2021-08-19 08:17:45 +0000 UTC [ - ]

Cool project, I think it's probably doable to print a cube, cut acrylic and laser some cardboard on this machine. Sadly It's not going to excellent at any of these things. I wish the project success, but really it doesn't look like a tool, more a concept of super tool changing toy

cfontes 2021-08-19 10:36:41 +0000 UTC [ - ]

I love 3d printers and this is a refreshing take on it.

Also looks super cheap to build which is good news.

Being from a country where 3d printers have a 100% tarif this is great, because the BOM is simple and one can just buy the parts and assemble it without too much of a hassle like a cantilever style (this looks even simpler than that), doesn't look complex to assemble like i3 Prusa or Core XY designs.

Tade0 2021-08-19 12:58:45 +0000 UTC [ - ]

Unrelated question: I heard that over the last 20 years or so machining has become considerably more precise. By how much?

abakker 2021-08-19 14:58:38 +0000 UTC [ - ]

Go watch some videos of Kern machines. Their demonstrations of drilling through human hairs with a VMC are pretty compelling.

it might be better to say that machine components and coordinate measuring systems have become cheaper, so that high accuracy is more attainable.

Good machines 50 years ago could hold .001" tolerances with care. Most machines nowadays can do that without that much care. Some machines nowadays can hold .0001" tolerances with care, and some can do even better.

dylan604 2021-08-19 15:08:30 +0000 UTC [ - ]

terms like thousandths of an inch are thrown around like it's nothing in machine shops, so I'd say pretty damn precise.

stjohnswarts 2021-08-19 15:51:22 +0000 UTC [ - ]

They have, but they're also still quite expensive.

kitd 2021-08-19 09:48:19 +0000 UTC [ - ]

Donated.

I guess the limits of this are the tools & attachments available. Do they have to be specially prepared for use with this? And does the controller s/w need to be adjusted depending on what tool you are using?

danboarder 2021-08-19 07:32:41 +0000 UTC [ - ]

Very cool project. I read the GitHub notes and agree on the need for more (and better) open source CAM software!

siscia 2021-08-19 10:31:00 +0000 UTC [ - ]

Maybe a trivial way to support the project would be to sell pre-assembled kit to build the Polar Bear itself?

Or just affiliate with some shop that sell the parts?

tohnjitor 2021-08-19 09:28:38 +0000 UTC [ - ]

I'd like to see one of these with aluminum or steel framing.

numpad0 2021-08-19 12:43:32 +0000 UTC [ - ]

This is just a Prusa i3 clone assembled the most wrong way possible

diego_moita 2021-08-19 13:10:54 +0000 UTC [ - ]

This would be so cool for cake decorations!

taf2 2021-08-19 12:59:32 +0000 UTC [ - ]

I wonder if this would be good at PCB traces

redis_mlc 2021-08-19 16:44:06 +0000 UTC [ - ]

For cutting copper, maybe for THT, but it's not rigid enough for SMT traces.

For additive (inks and resists), probably.

pulse7 2021-08-19 10:11:06 +0000 UTC [ - ]

I am waiting for assembly instructions...

nathias 2021-08-19 09:28:38 +0000 UTC [ - ]

this is amazing

senectus1 2021-08-19 09:00:12 +0000 UTC [ - ]

oh man, this'll be amazing if it becomes a reality

chrischen 2021-08-19 09:15:33 +0000 UTC [ - ]

It looks like it's already reality... you just have to print and assemble yourself.

JrProgrammer 2021-08-19 09:29:50 +0000 UTC [ - ]

While the project itself is interesting, the styling of the website is quite enchanting as well!

LukaD 2021-08-19 09:35:52 +0000 UTC [ - ]

It looks really nice but it's a usability nightmare in my opinion. Swiping back with the touchpad doesn't work. Pinch to zoom doesn't work. Page up/down and home/end don't work. Most clickable elements are not focusable I'm not trying to shit on the devs here. I just wish more developers were more mindful of usability/accessibility. Bonus: Press tab a couple times to break the scrolling.

JrProgrammer 2021-08-19 09:44:39 +0000 UTC [ - ]

Oh yeah, I see what you mean and I agree with you!