The choice of controller for stepper motors, engraving, milling, lathes, foam cutters. CNC milling machine with an autonomous controller on STM32 DIY CNC control unit
Among the wide variety of controllers, users are looking for self assembly those schemes that will be acceptable and most effective. Both single-channel devices and multi-channel devices are used: 3-axis and 4-axis controllers.
Device options
Multi-channel controllers of stepper motors (stepper motors) with sizes of 42 or 57 mm are used in the case of a small working field of the machine - up to 1 m. When assembling a machine with a larger working field - over 1 m, you need a size of 86 mm. It can be controlled using a single-channel driver (control current exceeding 4.2 A).
To control a machine with numerical control, in particular, it is possible with a controller created on the basis of specialized microcircuits - drivers intended for use for stepper motors up to 3A. The CNC controller of the machine is controlled by a special program. It is installed on a PC with a processor frequency of over 1GHz and a memory capacity of 1 GB). With a smaller volume, the system is optimized.
NOTE! When compared with a laptop, then in the case of connecting a stationary computer - top scores and yes, it is cheaper.
When connecting the controller to a computer, use the USB or LPT parallel port connector. If these ports are not available, then use expander boards or converter controllers.
Excursion into history
The milestones of technological progress can be schematically described as follows:
- The first controller on the chip was conditionally called the "blue board". This option has drawbacks and the scheme needed to be improved. The main advantage is that there is a connector, and the control panel was connected to it.
- Following the blue, a controller appeared, called the "red board". It already used fast (high-frequency) optocouplers, a 10A spindle relay, power decoupling (galvanic) and a connector where fourth-axis drivers would be connected.
- Another similar device with a red marking was also used, but more simplified. With its help, it was possible to control a small desktop-type machine - from among the 3-axis ones.
- The next in the line of technical progress was a controller with galvanic power isolation, fast optocouplers and special capacitors, which has an aluminum case that provided protection from dust. Instead of a control relay that would turn on the spindle, the design had two outputs and the ability to connect a relay or PWM (pulse width modulation) speed control.
- Now, for the manufacture of a home-made milling and engraving machine with a stepper motor, there are options - a 4-axis controller, a stepper motor driver from Allegro, a single-channel driver for a machine with a large working field.
IMPORTANT! Do not overload the stepper motor by using large and high speed.
Scrap controller
Most DIYers prefer control via the LPT port for most amateur level control programs. Instead of using a set of special microcircuits for this purpose, some people build a controller from improvised materials - field-effect transistors from burnt motherboards(at voltage over 30 volts and current over 2 amperes).
And since a machine was created for cutting foam, the inventor used automobile incandescent lamps as a current limiter, and SD was removed from old printers or scanners. Such a controller was installed without changes in the circuit.
To do the simplest machine Do-it-yourself CNC, disassembling the scanner, in addition to the stepper motor, also removes the ULN2003 chip and two steel bars, they will go to the test portal. In addition, you will need:
- Cardboard box (the device body will be assembled from it). A variant with textolite or plywood sheet is possible, but cardboard is easier to cut; pieces of wood;
- tools - in the form of wire cutters, scissors, screwdrivers; glue gun and soldering accessories;
- a board option that is suitable for a homemade CNC machine;
- connector for LPT port;
- a cylinder-shaped socket for arranging a power supply;
- connection elements - threaded rods, nuts, washers and screws;
- program for TurboCNC.
Assembling a homemade device
Having started working on a homemade cnc controller, the first step is to carefully solder the microcircuit on breadboard with two power rails. Next, the connection of the ULN2003 output and the LPT connector will follow. Next, the remaining conclusions are connected according to the scheme. The zero pin (25th parallel port) is connected to the negative pin on the board's power rail.
Then the stepper motor is connected to the control device, and the power supply socket is connected to the corresponding bus. For the reliability of the wire connections, they are fixed with hot glue.
Easy connection Turbo CNC. The program is effective with MS-DOS, it is also compatible with Windows, but in this case some errors and failures are possible.
By setting the program to work with the controller, you can make a test axis. The sequence of actions for connecting machines is as follows:
- Steel rods are inserted into holes drilled at the same level in three wooden bars and fixed with small screws.
- SD is connected to the second bar, putting it on the free ends of the rods and screwed using screws.
- A lead screw is threaded through the third hole and a nut is placed. The screw inserted into the hole of the second bar is screwed up to the stop so that, having passed through these holes, it goes out onto the motor shaft.
- Next, the rod is connected to the motor shaft with a piece of rubber hose and a wire clamp.
- Additional screws are required to secure the nut.
- The made stand is also attached to the second bar with screws. The horizontal level is adjusted with additional screws and nuts.
- Usually motors are connected together with controllers and tested for correct connection. This is followed by checking the scaling of the CNC, running the test program.
- It remains to make the body of the device and this will be the final stage of the work of those who create home-made machines.
When programming the operation of a 3-axis machine, in the settings for the first two axes - no change. But when programming the first 4 phases of the third, changes are introduced.
Attention! Using the simplified diagram of the ATMega32 controller (Appendix 1), in some cases, you may encounter incorrect processing of the Z axis - half step mode. But in full version its board (Appendix 2), the currents of the axes are regulated by an external hardware PWM.
Conclusion
In controllers assembled by CNC machines - a wide range of uses: in plotters, small routers working with wood and plastic parts, steel engravers, miniature drilling machines.
Devices with axial functionality are also used in graph plotters, they can be used to draw and produce printed circuit boards. So the effort spent on assembly by craftsmen will definitely pay off in the future controller.
This is my first CNC machine assembled with my own hands from available materials. The cost of the machine is about $170.
I dreamed of assembling a CNC machine for a long time. Basically, I need it for cutting plywood and plastic, cutting some details for modeling, homemade and other machines. My hands itched to assemble the machine for almost two years, during which time I collected parts, electronics and knowledge.
The machine is budget, its cost is minimal. In what follows, I will use words that ordinary person may seem very scary and it can scare away from self-built machine, but in fact it's all very simple and easy to master in a few days.
Electronics assembled on Arduino + GRBL firmware
The mechanics are the simplest, plywood frame 10mm + screws and bolts 8mm, linear guides from a metal corner 25 * 25 * 3 mm + bearings 8 * 7 * 22 mm. The Z axis runs on an M8 stud and the X and Y axes on T2.5 belts.
Spindle for CNC homemade, assembled from a brushless motor and collet clamp+ toothed belt drive. It should be noted that the spindle motor is powered by a 24 volt main power supply. IN technical specifications it is indicated that the motor is 80 amps, but in reality it consumes 4 amps under serious load. I can’t explain why this is happening, but the motor works fine and does its job.
Initially, the Z axis was on self-made linear guides from angles and bearings, later I redid it, pictures and description below.
The working space is about 45 cm in X and 33 cm in Y, 4 cm in Z. Given the first experience, I will make the next machine with large dimensions and I will put two motors on the X axis, one from each side. This is due to the large shoulder and the load on it when work is carried out at the maximum distance along the Y axis. Now there is one motor and this leads to distortion of the parts, the circle turns out to be a little elliptical due to the resulting deflection of the carriage along X.
The native bearings of the motor quickly loosened up, because they were not designed for lateral load, but it is serious here. Therefore, I installed two large bearings with a diameter of 8 mm on top and bottom on the axle, this should have been done immediately, now there is vibration because of this.
Here in the photo you can see that the Z-axis is already on other linear guides, the description will be below.
The guides themselves are very simple design, I somehow accidentally found it on Youtube. Then this design seemed to me ideal from all sides, a minimum of effort, a minimum of details, simple assembly. But as practice has shown, these guides do not work for long. The photo shows what kind of groove formed on the Z axis after a week of my test runs of the CNC machine.
I replaced the homemade Z-axis rails with furniture ones that cost less than a dollar for two. I shortened them, left a stroke of 8 cm. There are still old guides on the X and Y axes, I won’t change them yet, I plan to cut parts for a new machine on this machine, then I’ll just disassemble this one.
A few words about cutters. I have never worked with CNC and have very little experience in milling. I bought several cutters in China, all have 3 and 4 grooves, later I realized that these cutters are good for metal, other cutters are needed for milling plywood. While new cutters cover the distance from China to Belarus, I am trying to work with what I have.
The photo shows how a 4 mm cutter burned on 10 mm birch plywood, I still don’t understand why, the plywood is clean, and on the cutter there is soot similar to pine resin.
Further on the photo there is a 2 mm four-start cutter after an attempt to mill plastic. This piece of melted plastic was then very poorly removed, biting off a little bit with wire cutters. Even at low speeds, the cutter still gets stuck, 4 grooves are clearly for metal :)
The other day my uncle had a birthday, on this occasion I decided to make a gift on my toy :)
As a gift, he made a full house of plywood. First of all, I tried to mill on foam plastic in order to check the program and not spoil the plywood.
Due to backlashes and deflections, the horseshoe was cut out only from the seventh time.
In total, this full house (in its pure form) was milled for about 5 hours + a lot of time for what was spoiled.
Somehow I published an article about the key holder, below in the photo is the same key holder, but already cut on a CNC machine. Minimum effort, maximum accuracy. Due to the backlash, the accuracy is certainly not the maximum, but I will make the second machine more rigid.
And I also cut gears out of plywood on a CNC machine, it's much more convenient and faster than cutting with a jigsaw with my own hands.
Later I also cut out square gears from plywood, they actually spin :)
The results are positive. Now I will develop a new machine, I will cut parts already on this machine, manual labor practically comes down to assembly.
You need to master the cutting of plastic, because work on a homemade robot vacuum cleaner got up. Actually, the robot also pushed me to create my own CNC. For the robot, I will cut gears and other parts from plastic.
Update: Now I buy straight cutters with two edges (3.175*2.0*12 mm), they cut without severe scuffing on both sides of the plywood.
Since I assembled a CNC machine for myself a long time ago and have been using it for hobby purposes for a long time, I hope my experience will be useful, as well as the source codes of the controller.
I tried to write only those moments that personally seemed important to me.
The link to the controller sources and the configured Eclipse + gcc shell, etc. are in the same place as the video:
History of creation
Regularly faced with the need to make one or another small “thing” of complex shape, I initially thought about a 3D printer. And even started doing it. But after reading the forums and evaluating the speed of the 3D printer, the quality and accuracy of the result, the percentage of rejects and the structural properties of thermoplastics, I realized that this is nothing more than a toy.The order for components from China came in a month. And after 2 weeks the machine was working with control from LinuxCNC. Collected from any garbage that was at hand, because I wanted to quickly (profile + studs). I was going to redo it later, but, as it turned out, the machine turned out to be quite rigid, and the nuts on the studs did not have to be tightened even once. So the design remained unchanged.
The initial operation of the machine showed that:
- Do not use a 220V “china noname” drill as a spindle best idea. It overheats and is terribly loud. The side play of the cutter (bearings?) is felt by the hands.
- The Proxon drill is quiet. The lift is not noticeable. But it overheats and turns off after 5 minutes.
- A loaned computer with a bidirectional LPT port is not convenient. Taken for a while (finding PCI-LPT turned out to be a problem). Takes up space. And generally speaking..
Why people still stubbornly torment 8-bit ATMega for relatively complex tasks, and even through Arduino, is a mystery to me. They probably love challenges.
Controller development
I created the program after a thoughtful review of the sources of LinuxCNC and gbrl. However, neither those nor those source codes for calculating the trajectory were taken. I wanted to try to write a calculation module without using float. Exclusively on 32-bit arithmetic.The result suits me for all operating modes and the firmware has not been touched for a long time.
Maximum speed selected experimentally: X:2000mm/min Y:1600 Z:700 (1600 step/mm. mode 1/8).
But it is not limited by controller resources. Just above the already nasty sound of skipping steps even straight stretches through the air. The budget Chinese stepper control board on the TB6560 is not the best option.
In fact, the speed on wood (beech, 5mm depth, d = 1mm cutter, step 0.15mm) is not more than 1200 mm. Increases the risk of cutter breakage.
The result is a controller with the following functionality:
- Connecting to an external computer as a standard usb mass storage device (FAT16 on SD card). Working with files standard format G-code
- Deleting files through the controller's user interface.
- Viewing the trajectory for the selected file (as far as the 640x320 screen allows) and calculating the execution time. In fact, emulation of execution with the summation of time.
- View the contents of files in a test form.
- Manual control mode from the keyboard (moving and setting "0").
- Starting the task for the selected file (G-code).
- Pause/resume execution. (sometimes useful).
- Emergency software stop.
After creative experiments on carving hand-drawn reliefs on a tree, and experiments with acceleration settings in the program, I also wanted encoders on the axes. Just on e-bay I found relatively cheap optical encoders (1/512), the pitch of which for my ball screws was 5/512 = 0.0098mm.
By the way, the use of optical encoders high resolution, without a hardware scheme for working with them (the STM32 has it) - it's pointless. Neither interrupt processing, nor, moreover, a software poll will ever cope with the “bounce” (I say this for ATMega fans).
First of all, I wanted for the following tasks:
- Manual positioning on the table with high precision.
- Control of missed steps with control of deviation of the trajectory from the calculated one.
However, I found another application for them, albeit in a rather narrow task.
Using encoders to correct the path of a machine tool with stepper motors
I noticed that when cutting out the relief, when setting the acceleration in Z to more than a certain value, the Z axis begins to slowly but surely creep down. But, the relief cutting time with this acceleration is 20% less. At the end of the cutting of the 17x20 cm relief with a step of 0.1 mm, the cutter can go down by 1-2 mm from the calculated trajectory.
An analysis of the situation in dynamics by encoders showed that when the cutter is raised, sometimes 1-2 steps are lost.
A simple step correction algorithm using an encoder gives a deviation of no more than 0.03 mm and reduces processing time by 20%. And even a 0.1 mm protrusion on a tree is difficult to notice.
Design
The ideal option for hobby purposes was the desktop version with a field slightly larger than A4. And I still have enough of it.
movable table
It still remains a mystery to me why everyone chooses a design with a movable portal for desktop machines. Its only advantage is the ability to process in parts very long board or if you have to regularly process material whose weight is greater than the weight of the portal.During the entire period of operation, there has never been a need to cut out the relief on a 3-meter board in parts or make an engraving on a stone slab.
The movable table has the following benefits for desktop machines:
- The design is simpler and, in general, the design is more rigid.
- All giblets (power supplies, boards, etc.) are hung on a fixed portal, and the machine turns out to be more compact and more convenient to carry.
- The mass of the table and a piece of typical material for processing is significantly lower than the mass of the portal and spindle.
- The problem with the cables and hoses of the water cooling of the spindle practically disappears.
Spindle
I would like to note that this machine is not for power processing. CNC machine for power processing is easiest to do on the basis of a conventional milling machine.In my opinion, a machine for power metalworking and a machine with a high-speed spindle for wood / plastics is completely different types equipment.
Create at home universal machine at least it doesn't make sense.
The choice of spindle for a machine with this type of ball screw and guides with linear bearings is unambiguous. This is a high speed spindle.
For a typical high speed spindle (20,000 rpm), milling non-ferrous metals (not even talking about steel) is an extreme mode for the spindle. Well, unless it is very necessary, and then I will eat 0.3 mm per pass with watering the coolant.
The spindle for the machine would recommend water-cooled. With it, only the “singing” of stepper motors and the gurgling of the aquarium pump in the cooling circuit are heard during operation.
What can be done on such a machine
First of all, the problem of cases went away for me. The case of any shape is milled from "plexiglas" and glued together with a solvent along ideally smooth cuts.
Glass fiber refused universal material. The accuracy of the machine allows you to cut out a seat for the bearing, into which it will go cold, as it should be with a slight tightness, and then you can’t pull it out. Textolite gears are perfectly cut with an honest involute profile.
Woodworking (reliefs, etc.) - a wide scope for the realization of their creative impulses, or, at least, for the implementation of other people's impulses (ready-made models).
But I haven't tried jewelry. There is nowhere to ignite / melt / pour the flasks. Although a bar of jewelry wax is waiting in the wings.
Good day to all! And here I am with new part his story about CNC - machine tool. When I started writing the article, I did not even think that it would turn out to be so voluminous. When I wrote about the electronics of the machine, I looked and got scared - the A4 sheet was written on both sides, and there was still a lot to tell.
In the end it turned out like this manual for creating a CNC machine, working machine, from scratch. There will be three parts of the article about one machine: 1-electronic stuffing, 2-mechanics of the machine, 3-all the subtleties of setting up the electronics, the machine itself, and the machine control program.
In general, I will try to combine in one material everything useful and necessary for every beginner in this interesting case, what he himself read on various Internet resources and passed through himself.
By the way, in that article I forgot to show photos of crafts made. I'm fixing this. Styrofoam bear and plywood plant.
Foreword
After I assembled my little machine without significant expenditure of effort, time and money, I was seriously interested in this topic. I looked on YouTube, if not all, then almost all the videos related to amateur machines. Particularly impressive were the photographs of products that people make on their “ Home CNC". I looked and decided - I will assemble my big machine! So, on a wave of emotions, I didn’t think it over well, I plunged into a new and unknown world for myself CNC.Didn't know where to start. First of all, I ordered a normal stepper motor Vexta 12 kg/cm, among other things with the proud inscription "made in Japan".
While he was driving through all of Russia, he sat in the evenings at various CNC forums and tried to make a choice STEP/DIR controller and stepper motor drivers. I considered three options: on a microcircuit L298, on field workers, or buy ready-made Chinese TB6560 about which there were very conflicting reviews.
For some, it worked without problems for a long time, for others it burned out at the slightest user error. Someone even wrote that he burned out when he slightly turned the shaft of the motor connected at that time to the controller. Probably the fact of the unreliability of the Chinese and played in favor of choosing a scheme L297+ actively discussed on the forum. The scheme is probably really unkillable. the field drivers of the driver by amperes are several times higher than what needs to be fed to the motors. Even if you need to solder yourself (this is only a plus), and the cost of the parts came out a little more than the Chinese controller, but it is reliable, which is more important.
I'll digress a little from the topic. When all this was done, I didn’t even have the thought that someday I would write about it. Therefore, there are no photos of the assembly process of mechanics and electronics, only a few photos taken on a mobile phone camera. Everything else I clicked specifically for the article, already assembled.
The case of the soldering iron is afraid
I'll start with the power supply. I planned to make an impulse, I fiddled with it for probably a week, but I could not defeat the excitement, which came from nowhere. I wind the trance at 12v - everything is OK, I wind it at 30 - a complete mess. I came to the conclusion that some kind of bullshit climbs on feedback from 30th to TL494 and tear down her tower. So I abandoned this impulse, since there were several TS-180s, one of which went to serve the motherland as a power trance. And whatever you say, a piece of iron and copper will be more reliable than a bunch of crumbling. The transformer rewound to the required voltages, but it was necessary + 30V to power the motors, + 15V to power IR2104, +5v on L297, and a fan. You can apply 10 or 70 to the motors, the main thing is not to exceed the current, but if you do less, the maximum speed and power decrease, but the transformer no longer allowed it. I needed 6-7A. Stabilized voltages 5 and 15v, left 30 “floating” at the discretion of our power grid.
All this time, every night I sat at the computer and read, read, read. Setting up the controller, choosing programs: which one to draw, which one to operate the machine, how to make mechanics, etc. and so on. In general, the more I read, the more terrible it became, and more and more often the question arose “what for do I need this ?!”. But it was too late to retreat, the engine was on the table, the details were somewhere along the way - we must continue.
It's time to solder the board. Available on the Internet did not suit me for three reasons:
1 - The store that ordered the parts was not there IR2104 in DIP packages, and they sent me 8-SOICN. They are soldered to the board on the other side, upside down, and accordingly it was necessary to mirror the tracks, and them ( IR2104) 12 pieces.
2 - Resistors and capacitors are also taken in SMD packages to reduce the number of holes that had to be drilled.
3 - The radiator I had was smaller and the extreme transistors were out of its area. It was necessary to shift the field workers on one board to the right, and on the other to the left, so I made two types of board.
Machine controller diagram
For the safety of the LPT port, the controller and the computer are connected via an optocoupler board. I took the scheme and the signet from one well-known site, but again I had to redo it a bit for myself and remove unnecessary details.
One side of the board is powered via the USB port, the other, connected to the controller, is powered by a + 5V source. Signals are transmitted via optocouplers. I will write all the details about setting up the controller and decoupling in the third chapter, but here I will only mention the main points. This decoupling board is designed for safe connection of the stepper motor controller to the LPT port of the computer. Completely electrically isolates the computer port from the machine electronics, and allows you to control a 4-axis CNC machine. If the machine has only three axes, as in our case, unnecessary details you can leave them hanging in the air, or not solder them at all. It is possible to connect end sensors, a forced stop button, a spindle enable relay and another device, such as a vacuum cleaner.
It was a photo of the optocoupler board taken from the Internet, and this is what my garden looks like after installation in the case. Two boards and a bunch of wires. But there seems to be no interference, and everything works without errors.
The first controller board is ready, I checked everything and tested it step by step, as in the instructions. I set a small current as a trimmer (this is possible due to the presence of PWM), and connected the power (motors) through a chain of 12 + 24v bulbs so that it was “nothing if nothing”. I have field workers without a radiator.
The engine hissed. Good news, so PWM works as it should. I press a key and it spins! I forgot to mention that this controller is designed to control a bipolar stepper motor i.e. one with 4 wires. Played with step / half step modes, current. In half-step mode, the engine behaves more stable and develops high speeds + accuracy increases. So I left the jumper in the "half step". With the maximum safe current for the engine at a voltage of about 30V, it turned out to spin the engine up to 2500 rpm! My first machine without PWM never dreamed of such a thing.))
The next two motors ordered more powerful, Nema at 18kg/s, but already “made in China”.
They are inferior in quality Vexta After all, China and Japan are two different things. When you rotate the shaft with your hand, the Japanese do it somehow softly, but the Chinese have a different feeling, but so far this has not affected work. There are no comments for them.
I soldered the remaining two boards, checked through the "LED stepper motor simulator", everything seems to be fine. I connect one motor - it works fine, but not 2500 rpm, but about 3000! According to the already worked out scheme, I connect the third motor to the third board, spins for a couple of seconds and gets up ... I look at the oscilloscope - there are no pulses on one output. I call the fee - one of IR2104 pierced.
Well, maybe I got a defective one, I read that this often happens with this mikruha. I solder a new one (I took 2 pieces with a margin), the same nonsense - it turns STOP for a couple of seconds! Here I strained myself, and let's check the field workers. By the way, my board has IRF530(100V / 17A) vs. (50V / 49A), as in the original. A maximum of 3A will go to the motor, so a reserve of 14A will be more than enough, but the difference in price is almost 2 times in favor of the 530s.
So, I check the field workers and what I see ... I didn’t solder one leg! And all 30V from the field worker flew to the output of this "irka". I soldered the leg, carefully examined everything again, put another one IR2104, I'm worried myself - this is the last one. I turned it on and was very happy when the engine did not stop after two seconds of operation. Modes left as follows: engine Vexta- 1.5A, engine NEMA 2.5A. With this current, revolutions of about 2000 are achieved, but it is better to limit them programmatically in order to avoid skipping steps, and the temperature of the motors during long-term operation does not exceed the safe for motors. The power transformer copes without problems, because usually only 2 motors are spinning at the same time, but additional air cooling is desirable for the radiator.
Now about the installation of field workers on the radiator, and there are 24 of them, if anyone has not noticed. In this version of the board, they are located lying down, i.e. the radiator just lays down on them and is attracted by something.
Of course, it is desirable to put a solid piece of mica to isolate the heatsink from the transistors, but I did not have one. Found a way out. Because in half of the transistors, the case goes to plus power; they can be mounted without insulation, just on thermal paste. And under the rest, I put pieces of mica left over from Soviet transistors. I drilled the radiator and the board in three places through and through and tightened it with bolts. I got one large board by soldering three separate boards around the edges, while soldering around the perimeter for strength copper wire 1mm. All electronic stuffing and placed the power supply on some kind of iron chassis, I don’t even know from what.
I cut out the side and top cover from plywood, and put a fan on top.
The article describes homemade machine with CNC. The main advantage of this version of the machine is a simple method of connecting stepper motors to a computer via the LPT port.
Mechanical
bed
The bed of our machine is made of plastic 11-12 mm thick. The material is not critical, you can use aluminum, organic glass plywood and any other available material. The main parts of the frame are attached using self-tapping screws, if desired, you can additionally decorate the attachment points with glue, if you use wood, you can use PVA glue.
Calipers and guides
Steel bars with a diameter of 12mm, length 200mm (on the Z axis 90mm), two pieces per axis, were used as guides. Calipers are made of textolite with dimensions 25X100X45. Textolite has three through holes, two of them for the guides and one for the nut. The guide parts are fixed with M6 screws. Supports X and Y in the upper part have 4 threaded holes for fixing the table and the Z-axis assembly.
Caliper Z
The Z axis guides are attached to the X support through a steel plate, which is transitional, plate dimensions 45x100x4.
Stepper motors are mounted on fasteners, which can be made of sheet steel with a thickness of 2-3mm. The screw must be connected to the axis of the stepper motor using a flexible shaft, which can be used as a rubber hose. When using a rigid shaft, the system will not work accurately. The nut is made of brass, which is glued into the caliper.
Assembly
Assembly homemade CNC machine, is carried out in the following sequence:
- First you need to install all the guide components in the calipers and screw them to the sidewalls, which were not initially installed on the base.
- We move the caliper along the guides until we achieve a smooth ride.
- We tighten the bolts, fixing the guide parts.
- We attach a caliper, a guide assembly and a sidewall to the base, we use self-tapping screws for fastening.
- We assemble the Z assembly and, together with the adapter plate, attach it to the X caliper.
- Next, install the lead screws along with the couplings.
- We install stepper motors, connecting the motor rotor and the screw with a coupling. We pay strict attention to the fact that the lead screws rotate smoothly.
Recommendations for assembling the machine:
Nuts can also be made from cast iron, you should not use other materials, screws can be bought at any hardware store and cut to fit your needs. When using screws with M6x1 thread, the length of the nut will be 10 mm.
Machine drawings.rar
We turn to the second part of the assembly of the CNC machine with our own hands, namely to electronics.
Electronics
power unit
A 12V 3A block was used as a power source. The unit is designed to power stepper motors. Another voltage source at 5V and with a current of 0.3A was used to power the controller microcircuits. The power supply depends on the power of the stepper motors.
We present the calculation of the power supply. The calculation is simple - 3x2x1 \u003d 6A, where 3 is the number of stepper motors used, 2 is the number of powered windings, 1 is the current in Amperes.
Control Controller
The control controller was assembled on only 3 microcircuits of the 555TM7 series. The controller does not require firmware and has a fairly simple circuit diagram, thanks to this, this CNC machine can be made by a person who is not particularly versed in electronics with his own hands.
Description and pin assignment of the LPT port connector.
| Pin. | Name | Direction | Description |
| 1 | STROBE | input and output | Set by PC after completion of each data transfer |
| 2..9 | DO-D7 | conclusion | Conclusion |
| 10 | ASK | input | Set to "0" by an external device after receiving a byte |
| 11 | BUSY | input | The device indicates that it is busy by setting this line to "1" |
| 12 | paper out | input | For printers |
| 13 | Select | input | The device indicates that it is ready by setting this line to "1" |
| 14 | Autofeed | ||
| 15 | error | input | Indicates an error |
| 16 | Initialize | input and output | |
| 17 | Select In | input and output | |
| 18..25 | Ground GND | GND | common wire |
For the experiment, a stepper motor from an old 5.25-inch was used. In the scheme, 7 bits are not used. 3 engines used. You can hang a key on it to turn on the main engine (cutter or drill).
Driver for stepper motors
To control the stepper motor, a driver is used, which is an amplifier with 4 channels. The design is implemented on only 4 transistors of the KT917 type.
You can also use serial microcircuits, for example - ULN 2004 (9 keys) with a current of 0.5-0.6A.
The vri-cnc program is used for control. Detailed description and instructions for using the program are on .
Having assembled this CNC machine with your own hands, you will become the owner of a machine capable of machining (drilling, milling) plastics. Steel engraving. Also, a home-made CNC machine can be used as a plotter, you can draw and drill printed circuit boards on it.
Based on materials from the site: vri-cnc.ru
