Steve Bush January 28, 2021
Yesterday I wrote some articles about my small cheap cnc router and what I plan to do to make it better.
Here is more information about other cnc routers that use the same or similar components.
1810 refers to the 18cm x 10cm cutting bed. My "professional" part means that it has processed plastic ("bakelite", according to the manufacturer) x gantry support column and y-axis end plate. The non-professional version has aluminum extrusions (commonly referred to as "1610"). Pro units are easier to assemble and may be stronger, but not as easy to upgrade as some aluminum profiles and alternative linear guides can be bolted to non-Pro versions more easily to increase rigidity.
This style fixes the y-axis (front and rear) and x-axis (left and right) gantry on the frame (see picture), and the workpiece slides on the y axis. The z-axis (up and down), carry the tool, and slide on the x-axis.
The other sizes of this format are 2418 and the more popular 3018-the latter is also available in professional and non-professional versions. They share many identical or similar parts and are not reinforced in the larger size. That said, the enhancement is the smaller gem-like and higher-quality 1310, which shares format but not parts-more on that later.
Disruption of SMEs: Although I would say that 3D printers are an easy-to-learn, low-cost way to make fixtures, brackets, and prototype enclosures or produce enclosures in small quantities, I conclude that cnc routers do not yet exist, unless You spend more money and prepare to study for longer (of course, or learn about machining). In addition, as far as I know, compared with 3d printing software, free cnc software is not as powerful and more difficult to use-I will explain in detail later. End interrupt
The bed size derived name has largely become synonymous with machine type-so all 1810 and 3018 (I've seen it) have the same fixed X frame and axis.
An example of random selection in 2030, from Dowin Technology through Alibaba.
Another form of machine (such as the picture on the left) fixes the bed on the frame, sliding the x door frame back and forth along the y axis. These are often in the next price range, including (rare) 1419, 2030 and 3040.
This is a format, and then directly use the router to cut 8 x 6'plywood (ie 2.4 x 1.2m).
These are not enough to be a milling machine (I don't know where the definitions of milling and milling cross).
I will stick to the low-end 1810 3018 style that I have at least some experience with.
It turns out that my machine is a good machine to start climbing the cnc learning curve-there are almost no consequences when the wrong command is executed (almost inevitably it will happen), because the stepper motor is not strong-so no fingers or bending Of steel.
In other words, I have a bunch of broken cutter bits, mainly by stuffing them into the work bed-here is just a warning, pcb copper cutting bits have sharp, fragile needle-like ends, if you break them, they will fly Go sideways in space, so wear goggles.
As the confusion of fledgling operators begins to become clear, the shortcomings of bargaining CNC machine tools will soon become apparent.
Not really noticing when cutting soft materials-which is their purpose-limitations include inaccuracies due to slack and bending on the x-axis (pressing on the motor by hand) (high rod running to the left) And chatter (tool resonance) on the right side of the top photo) and z-axis (a bar running up and down behind the motor).
Ways to reduce bending and slack
Compared with the 3018s, the Flex in the 1810s was not bad, because the length of the 10 mm diameter x-bars between the supports was only 240 mm, while in the 3018s they were still 10 mm, but about 360 mm long.
Next are the cylindrical bearings that run on these rods. The tolerances of rods, bearings, and housings mean that there is often slack between rods and bearings, and between bearings and housings.
There is a similar situation on the z-axis, except that the rod (8 mm in diameter) is much shorter and less likely to bend.
Replacing better bearings and rods is a way for people to get rid of this slack, and 3D printing new z-assembly plastic parts can get rid of the slack of the shell in many ways.
When 3D printing the component, some people took the opportunity to redesign the part to accept a stiffer 12mm or 16mm x-rod and 10mm z-rod.
The 12mm x-rod mod is very simple. 16mm is available on non-professional cncs, but reaching 16mm on the professional version requires a new side panel, because the rods are close and the aluminum profile passing behind them will harden the side panel ( Almost visible in the top photo-the rectangular part at the back is the control panel). Update-Mine may only have space... the breadth of waiting to be weakened...
A note on structural rigidity
I am not a mechanical engineer (so if I am wrong, please correct me), but I quickly browsed some equations and it seems that the deflection of the lateral force in the solid rod decreases with the 4th power of the radius and increases with the length of the cube.
This means (if I calculate correctly) using the 12mm rod in 1810 reduces the absolute x deflection to the same amount as the 16mm rod in 3018 (2x in both cases). That said, even the 16mm rod in the 3018 is considered too flexible by some people trying to cut aluminum accurately (none of these machines are designed to cut any metal-except for the foil on the pcb. Warning 1310).
Relative diameter stiffness, according to non-mechanical former engineers-again, please correct me if I am wrong
Relative length stiffness, same warning
Therefore, the rigidity of small machines with thick rods increases exponentially.
If I could make a new board (precise counterbore housings stopped me), the first thing I would try is a 16mm x rod and a 10mm z rod. Update-they may fit without drilling in my mine-there are subtle differences between some machines, such as the 68 or 72 mm internal rod spacing on the x-axis.
1310, a more advanced machine (photo from cnc1310.ru)
What is less known is that there is a smaller "1310" class (126 x 88 mm bed) cnc with excellent bearing retention and excellent almost all other features. Combined with their shorter length (I estimate it is 190 mm), the deflection of its x-bar should be half of the 12 mm modified 1810-or 12 times the unmodified 3018 (see table above). Check out this site from people who use 1310 and fix its design flaws.
Regarding defects, the quality of the delivered frame parts is obviously not always perfect. In the UK, a small company called Oozenest provides cut-to-length (/-0.2mm) aluminum extrusions and will pre-tap the ends.
Russian manufacturers seem to particularly like these. This website has a lot of information (English translation in the upper left corner).
These cylindrical bar machines are always red, and can cut aluminum, and seem to work within 0.1 mm.
Update: In other words, the YouTuber who designed the prototype test couldn't make him cut aluminum well (he is a skilled (if sometimes grumpy) product designer)-despite the full-width cut, there is no lubrication and may be sticky aluminum. Many people have modified the 3018s into acceptable cuts-for example, just after I wrote most of this blog, the thorough and careful people at Teaching Tech used many mods but standard 10mm rails made some thin aluminum parts , To his satisfaction-by the way, it looks like Dremel made a nice low-cost spindle upgrade.
The blue version of the red 1310s has recently appeared, which uses (nominally superior) supported rectangular linear guides instead of unsupported circular guides for movement-it looks interesting, although the design only requires soil to fall into the y-axis Rails and jam them.
In retrospect, if I knew that I would enjoy cnc machining like I did, I would initially buy the red (or, jury, blue) 1310 and consider replacing the "775" spindle motor (~100W, 6,000rpm long 5mm shaft)) equipped Longdaio LD42WS-250W brushless motor (250W 12,0000rpm, short 8mm shaft)-for a small rigid machine, the initial expenditure is about £500. This is a video of someone testing such a combination here.
With this money, you can buy a 2030 or 3040 machine, which is a mechanical advancement, with a static bed, sliding X-gantry and support rails-but these take up more space, I only make small things .
There are also non-counterfeit machines that seem to be unique to certain companies-so please search around.
The 1810 machine and its close relatives use an 8mm "dual start" (hence 4mm stroke'T8x4' per revolution) lead screw driven by a NEMA 17 size stepper motor.
This is a stepper motor of the same size (42 x 42 mm) as most 3d printers, but most 3d printers use a T8x8 (8 mm per revolution, "four starts") lead screw for the z axis. T8x2 ("at the beginning", 2 mm per revolution) lead screw also exists.
T8x4 is the least common lead screw used by hobbyists/manufacturers, and it is also a lead screw that limits the choice of anti-backlash nuts.
Those in the 1810 machines have relatively weak preloaded springs (because their motors are relatively weak and may not be able to handle all the friction associated with harder spring nuts), so once the cutting force overcomes the spring.
I can’t find any non-spring adjustable anti-backlash block in the form of OpenBuilds with T8x4 thread (left picture, via Oozenest), so to remove this source of stains, you need to use stronger springs and careful lubrication, steering without backlash" Ball screw" or more ideas.
Another source of backlash is the lack of longitudinal screw restriction-except for the motor coupler and the spring inside the motor, nothing can prevent the screw from moving longitudinally-this is not a bad solution for light-load 3D printers Scheme, but not very good for the power of the cutting tool.
Commercial linear actuators have a thrust bearing at one end of the screw (or even both ends of the screw) to transmit the longitudinal force to the machine frame. This can be easily achieved by using several cheap thrust bearings and 8 mm collars at one end of each screw (if long enough), some people even get similar by cleverly placing washers between the motor and its coupler Effect.
Hobby cnc router lag hobby 3d printer
The low-end hobby cnc router lags behind the low-end hobby 3d printer: compared to the cnc router, you can get a more exquisite 3d printer (kit or assembly) for less than £250.
A particularly frustrating omission is the axis end stop on the cncs, which doubles as a homing reference and an automatic travel limiter on the 3d printer. Usually, cnc controller boards have their connections, and software ('grbl') can use them, but there are no switches and wiring, allowing unwise instructions to crash the mechanism into the frame.
In the next year or so, I suspect that cheap cnc routers will become more sophisticated-Sainsmart is already offering 3018s for the high-end market-its 3018 prover has more aluminum and less plastic . I predict that there will also be thicker guide rods.
The backwardness of 3d printers is also reflected in software. Amateur/manufacturer-grade 3d printing software is close to commercial-grade software in appearance and feel, while similar 3d router software requires more computer knowledge to operate.
This is not to belittle the people who wrote all of this software-usually, manufacturers give up a lot of their time to create runnable software and then generously open source it for others to use. Why should you write something that suits your needs, and then give it away for free, so that even an idiot like me can do it.
Ironically, I have read (but guarantee its authenticity) that the Arduino dynamics package in the 3d printer control software Marlin is beginning to be used in the grbl cnc machine control software.
I am always impressed by what you have done and accomplished.
On the other hand, I finally got A Round Tuit and installed the bench grinder and column drill I have owned for only 20 years to the recently built workbench in my recently refurbished tin shed.
The renovation was an act of despair, and the new owner next door struck seven bells from their halftime.
I miss the quiet little old lady who used to live next door.
Hi zeitghost, you sympathize with the neighbor’s noise-for some reason, I don’t plan to record publicly here (the situation has improved anyway)... I also recalled that I lived with two old ladies During that time. It's great to renovate the shed and install the grinder and drill bit-keep up the momentum! I tend to go through the wave-once something boring is excluded, something interesting is allowed. The boring thing this time was decorating the back room, which took much longer than I expected (hope?). You're done, it's time to learn and play for a while 🙂
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