Home CNC router as an alternative to 3D printer, part one - the choice of machine
Recently, topics devoted to 3D printing in general, and home 3D printers in particular, are increasingly appearing in Habré. And almost in everyone in the comments a holivar flashes between romantics who have not seen 3D prints in their lives, and practitioners who have once touched and disappointed. At the same time, the second ones for some reason do not provide adequate alternative technologies, the comments are either purely critical, or they offer obviously more expensive alternatives. Nevertheless, there is a worthy alternative - a CNC milling machine.
Sounds amazing right? Somehow the very word machine is popularly associated with production, with individual rooms and specially trained personnel. In fact, there is a large class of CNC machines designed for desktop use in the office and in small industries, and if desired, at home. At the same time, the price of small CNC milling machines is approaching (not to say equal) to the real price of 3D printers.
Life has turned out so that the last year with hook I am engaged in the manufacture of molds for polyurethane products on a CNC router. Since before that, he had spent 10 years in IT retail, and education had nothing to do with either engineering or CNC, I had to master technology from scratch. Over the past year, I grew from the position of a milling machine operator to a design engineer, and then to the deputy director of technology, through my efforts at the company's CNC-park, I grew from a single old Roland to 5 different-sized machines. In this connection, the experience of choice, purchase, commissioning, tuning, operation and repair of various CNC machines is still fresh and relevant.
')
And so - I decided to share my experience with the community. I realize it myself, and ask the reader to take into account that I am self-taught without basic engineering education, all of the following is based solely on personal experience.
After long pangs of choice, writing an article-opposition or an article-review of technology won the third option: write a series of articles describing the slightly abstracted experience of the CNC machine - from choosing a machine, commissioning and tools, through the selection of materials, software and operating modes, to tuning and refinement.
Under the cut, the first article of the cycle is a brief description of the CNC router milling subsystems, with comments and recommendations for selection.
First of all, we define tasks.
Since we are looking at alternatives to 3D printers for home / hobby use, the main working materials we will have are plastics, wood, MDF, chipboard, plywood, PCB and a little bit of colored metal. Dimensions - no less than home 20 * 30 cm - A4 sheet size.
The spindle is a working tool of the machine that rotates the cutter. The spindle power is derived from the desired material removal rate: I have quite a good experience in milling aluminum with 60W spindle, but with poorly small feeds and depth. In most Chinese machines, 600-800 W spindles are installed, which is enough for a clean removal of plastic / wood with a depth of 1 mm at a speed of 2 meters per minute.
Separately, I warn you against using Kress FHE / FE series spindles: they are much louder and less accurate than the Chinese. If the seller suggests the installation of such a spindle, better order the normal spindle on the aliexpress yourself, or better yet, find another seller.
On hobby machines, at best, the frame will be represented by a structural profile at the base and 10–15 mm aluminum on the portal racks and the Z axis. In principle, this is sufficient for home-hobby tasks, the main thing is to make sure that it is. In my memory there is one Chinese frameless design, whose longest axis was frameless - its function was shifted to the table. Naturally, the machine was extremely weak.
For sounded sizes fit machine on round guides 16-21 mm.
In general, the rule of thumb for the stated objectives of "length-guides":
<15cm - 12mm round
15-40 cm - 16 mm round
40-90 cm - 22 mm round with base
Since we have declared the color to be used, the transfer of force from the motors to the axle must be sufficiently rigid. Therefore - down the belts, long live the ballscrews and screws. A ball screw is a ball screw, in fact, the same screw, only the grooves of the threads are polished and the nut is a ball bearing. Ball screw has a much smoother stroke, higher accuracy and reliability. So the screw, perhaps, is valid only on the Z axis, which is by definition less mobile than the rest.
The transfer of force from the motors to the screws for our tasks is not critical - sufficient belt rigidity is provided by the belt drive, and the gearbox and clutches. Again, the main thing is that there is something between the motor and the screw, which compensates for the axle beating and the sharp efforts at the beginning of the movement, and the Chinese can also directly step the screw into the screw to save money, which will adversely affect the life of the motor.
In the hobby segment, stepper motors uniquely steer, they are also shagoviki. And for the stated purposes, virtually any modern engine is sufficient, ranging from 42/48 with a force of 5.5 kgcm. Of the additional buns offered by machine tool builders, we can note the handles on the axis, encoders, and so on - this is uncritical in our tasks.
Since we are considering the purchase of a finished machine, suppose that the drivers and the power supply match the installed engines. It makes sense except to note the presence of a spindle control with CNC - some Chinese save on the frequency changer.
The table should be. Since the accuracy of a part is largely determined by the rigidity of the mount, the table must be rigid. And then - go variations. The Chinese in their machines love to put tables from the constructional profile with T-shaped grooves - quite comfortable and versatile, but not very tough. Much better - a plate with a grid of threaded holes. The most versatile, but expensive and confused in operation - a vacuum table.
Important help are the end sensors on all axes and the zero axis sensor Z.
Specific additions are an additional (rotating) axis, a DSP controller, a position sensor, a probe, encoders, special clamps, etc., but all this, perhaps, is already beyond the scope of the article for beginners.
Since we are talking about milling machines of the lowest price category on stepper motors without encoders, the standard interface will be, at best, a slightly customized PCI-LPT controller with optocoupler, at worst, simply a cable to the LPT port of the computer. In my opinion, about one hell, at least I did not notice the difference in work.
The software is diverse, but it is functionally reduced either to a simple G-code interpreter in the signals of stepping motor drivers, or to a more advanced emulator of the machine control rack. In any case, if the standard program does not satisfy, you can suffer a little and dock the machine with LinuxCNC, which in terms of functionality and convenience is not inferior to advanced proprietary solutions.
Perhaps, this article can be completed, there will be questions / suggestions / additions - we would like to say in the comments and drugs.
In the next part - a review of the cutting tool, fasteners, aspiration, coolant at home.
Sounds amazing right? Somehow the very word machine is popularly associated with production, with individual rooms and specially trained personnel. In fact, there is a large class of CNC machines designed for desktop use in the office and in small industries, and if desired, at home. At the same time, the price of small CNC milling machines is approaching (not to say equal) to the real price of 3D printers.
Life has turned out so that the last year with hook I am engaged in the manufacture of molds for polyurethane products on a CNC router. Since before that, he had spent 10 years in IT retail, and education had nothing to do with either engineering or CNC, I had to master technology from scratch. Over the past year, I grew from the position of a milling machine operator to a design engineer, and then to the deputy director of technology, through my efforts at the company's CNC-park, I grew from a single old Roland to 5 different-sized machines. In this connection, the experience of choice, purchase, commissioning, tuning, operation and repair of various CNC machines is still fresh and relevant.
')
And so - I decided to share my experience with the community. I realize it myself, and ask the reader to take into account that I am self-taught without basic engineering education, all of the following is based solely on personal experience.
After long pangs of choice, writing an article-opposition or an article-review of technology won the third option: write a series of articles describing the slightly abstracted experience of the CNC machine - from choosing a machine, commissioning and tools, through the selection of materials, software and operating modes, to tuning and refinement.
Under the cut, the first article of the cycle is a brief description of the CNC router milling subsystems, with comments and recommendations for selection.
What to buy and how to choose
First of all, we define tasks.
Since we are looking at alternatives to 3D printers for home / hobby use, the main working materials we will have are plastics, wood, MDF, chipboard, plywood, PCB and a little bit of colored metal. Dimensions - no less than home 20 * 30 cm - A4 sheet size.
Spindle
The spindle is a working tool of the machine that rotates the cutter. The spindle power is derived from the desired material removal rate: I have quite a good experience in milling aluminum with 60W spindle, but with poorly small feeds and depth. In most Chinese machines, 600-800 W spindles are installed, which is enough for a clean removal of plastic / wood with a depth of 1 mm at a speed of 2 meters per minute.
Separately, I warn you against using Kress FHE / FE series spindles: they are much louder and less accurate than the Chinese. If the seller suggests the installation of such a spindle, better order the normal spindle on the aliexpress yourself, or better yet, find another seller.
Frame
On hobby machines, at best, the frame will be represented by a structural profile at the base and 10–15 mm aluminum on the portal racks and the Z axis. In principle, this is sufficient for home-hobby tasks, the main thing is to make sure that it is. In my memory there is one Chinese frameless design, whose longest axis was frameless - its function was shifted to the table. Naturally, the machine was extremely weak.
Guides
For sounded sizes fit machine on round guides 16-21 mm.
In general, the rule of thumb for the stated objectives of "length-guides":
<15cm - 12mm round
15-40 cm - 16 mm round
40-90 cm - 22 mm round with base
Mechanics
Since we have declared the color to be used, the transfer of force from the motors to the axle must be sufficiently rigid. Therefore - down the belts, long live the ballscrews and screws. A ball screw is a ball screw, in fact, the same screw, only the grooves of the threads are polished and the nut is a ball bearing. Ball screw has a much smoother stroke, higher accuracy and reliability. So the screw, perhaps, is valid only on the Z axis, which is by definition less mobile than the rest.
The transfer of force from the motors to the screws for our tasks is not critical - sufficient belt rigidity is provided by the belt drive, and the gearbox and clutches. Again, the main thing is that there is something between the motor and the screw, which compensates for the axle beating and the sharp efforts at the beginning of the movement, and the Chinese can also directly step the screw into the screw to save money, which will adversely affect the life of the motor.
Motors
In the hobby segment, stepper motors uniquely steer, they are also shagoviki. And for the stated purposes, virtually any modern engine is sufficient, ranging from 42/48 with a force of 5.5 kgcm. Of the additional buns offered by machine tool builders, we can note the handles on the axis, encoders, and so on - this is uncritical in our tasks.
Electronics
Since we are considering the purchase of a finished machine, suppose that the drivers and the power supply match the installed engines. It makes sense except to note the presence of a spindle control with CNC - some Chinese save on the frequency changer.
Table
The table should be. Since the accuracy of a part is largely determined by the rigidity of the mount, the table must be rigid. And then - go variations. The Chinese in their machines love to put tables from the constructional profile with T-shaped grooves - quite comfortable and versatile, but not very tough. Much better - a plate with a grid of threaded holes. The most versatile, but expensive and confused in operation - a vacuum table.
Buns and supplements
Important help are the end sensors on all axes and the zero axis sensor Z.
Specific additions are an additional (rotating) axis, a DSP controller, a position sensor, a probe, encoders, special clamps, etc., but all this, perhaps, is already beyond the scope of the article for beginners.
Interface and software
Since we are talking about milling machines of the lowest price category on stepper motors without encoders, the standard interface will be, at best, a slightly customized PCI-LPT controller with optocoupler, at worst, simply a cable to the LPT port of the computer. In my opinion, about one hell, at least I did not notice the difference in work.
The software is diverse, but it is functionally reduced either to a simple G-code interpreter in the signals of stepping motor drivers, or to a more advanced emulator of the machine control rack. In any case, if the standard program does not satisfy, you can suffer a little and dock the machine with LinuxCNC, which in terms of functionality and convenience is not inferior to advanced proprietary solutions.
Perhaps, this article can be completed, there will be questions / suggestions / additions - we would like to say in the comments and drugs.
In the next part - a review of the cutting tool, fasteners, aspiration, coolant at home.
Source: https://habr.com/ru/post/208318/
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