CNC machine from a profile pipe with your own hands. Large do-it-yourself CNC portal milling machine. This difficult installation process
Now a little more detail on the main assembly.
So, to assemble the frame, you will need the following components:
- Profile sections 2020 (two longitudinal, 5 transverse, 2 vertical parts)
- Profile corners 16 pcs
- T-nuts M3 or M4 for groove-6mm
- Screws for installation with T-nuts (M3 or M4 respectively, 8...10 mm, plus M3x12 for fastening motors)
- Spacer (45° angle)
- Tool (screwdriver)
Since I started talking about the profile, then just in case I duplicate about the purchase and cutting of the profile from Soberizavod
This is constructive.
I bought a set of profiles cut to size for 2418 right away.
There are two options - uncoated profile (cheaper) and coated (anodized). The difference in cost is small, I recommend coated, especially if used as roller guides. 
Select the desired profile type 2020, then enter "cut to size". Otherwise, you can buy one piece (whip) for 4 meters. When calculating, keep in mind that the cost of one cut can be different, depending on the profile. And that 4 mm is laid on the cut. 
Enter the dimensions of the segments. I made machine 2418 a little larger, these are seven pieces of 260 mm and two vertical pieces of 300 mm. Vertical can be made smaller. If you need a longer machine, then two longitudinal sections are larger, for example, 350 mm, transverse ones are also 260 mm each (5 pcs). 
We confirm (must be added to the nesting map) 
Checking the cart 
The profile is obtained at 667r along with the cutting service. 
Delivery is carried out by shopping mall, you can calculate the cost using the calculator, since you know the dimensions of the profile, the weight is very well calculated in the cutting chart. For the calculation, you need the option "cargo collection from the supplier". Delivery business lines will cost less, about 1000 rubles.
Can be picked up by self in Moscow. 
In one place there is an office, a warehouse and a workshop where the profile is cut to size. There is a showcase with samples, you can pick up a profile on the spot.
So let's start building the frame. desktop machine 2418.
Here is the cut profile.
In this design, I increased the Z axis (a little more than a couple of cm than others) in order to use the machine as a CNC drill.
In the original, the Z axis is the shortest. It is up to you to decide what your goals are. To lengthen the working field, you need to buy two sections of the profile (longitudinal pair) more by the desired length (for example, +10 cm), respectively, the guides (+10 cm for a pair of 8mm shafts) and the screw (+10 cm for the T8 screw) are lengthened. In terms of money, the voiced +10 cm comes out very cheap: the cost of a 10 + 10 cm profile is about 40 rubles, the guides and the screw will cost plus $ 6 (check).
Here are the corners prepared for assembly 
This is how the T-nuts should be installed in the slot. You can not thread it from the end, but install it directly into the profile groove sideways, but then control the rotation and installation of the nut, since this does not always happen, some skill is needed. 
Profile cut is clean, no burrs 
Profile-twenty, that is, from the 2020 series, with a corresponding change of 20mm x 20mm, a groove of 6mm. 
So, first we assemble the U-shaped part of the frame, we fasten two longitudinal parts of the profile and one extreme cross member. of great importance on which side there is no assembly, but keep in mind that there is a central crossbar that is shifted closer to the back. It is part of the vertical plane, and the size of the offset depends on the overhang of the Z-axis and the spindle. Placed in such a way that the axis of rotation of the spindle was in the center of the machine (Y axis).
Next, assemble the middle cross. It is more convenient to first install both corners on a section of the profile and fix it, and then install it to the frame.
We apply a section of the profile, measure the same distance with a ruler, tighten the screws. The screws must be tightened slowly, giving the T-nut time to turn and take its position in the groove. If it doesn't work the first time, loosen the nut again and repeat. 
We install the last part of the horizontal frame. It is more convenient to crawl with a long screwdriver. Do not be lazy and check the right angles of the resulting structure with a square and a diagonal with a ruler. 
Since the corners of the structure are directed towards each other, it does not matter in what order to assemble. I did as in the basic CNC2418 design. But intuition suggests that it makes sense to increase the distance between the profiles, especially with a higher portal height. Okay, that can be done later. 
Next, we begin to assemble the mount of the vertical portal 
We install the assembled portal on the horizontal part, fasten it with 6 corners (installed in the direction in three directions from the vertical profile). 
We establish, observe the perpendicularity of the segments (along the square). Then I tightened all the screws one by one. 
In the original, a special 45° extrusion angle is used to reinforce the vertical. I could not find a similar one for sale, I replaced it with a 3D printed one. The link to the model is at the end of the topic.
update A: turned out to be original 3D printed too.
If anything, you can replace it with perforated fasteners from stores, or furniture corners. It won't affect the quality in any way. 
The design turned out at first glance strong, not shaky. It can be seen that the plate with the engine is shorter than the KP08 + SK8 caliper bundle. I will spread it wider. 
In fact, this frame is a copy of a similar design of the CNC2418 machine, except that I did not directly copy the dimensions, I did a little more in order to have less trim from the guides and screws.
The assembly of the frame is completed, now you can start installing the engines. I use 3D printed flanges to mount motors. It is advisable to make the upper ones assembled with guide holders, the lower ones - without holders, since the Y-axis should be wider. It is advisable to install the Y axis on calipers SK8 and KP08, as in original machine. The calipers themselves can be printed on a printer or bought (links at the end of the topic, and were also in the first post).
For one of the axes (the X and Y axes are the same length for me), I took a “sighting” one. I did not yet know my “Wishlist” for the dimensions of the machine. As a result, the trimmings from the screw will go to the Z axis, you will only need to purchase a T8 brass nut. 
Was packed in a cardboard box, inside each item in a bag separately 
The kit looks like this: a motor with a short wire, a T8 lead screw, two KP08 calipers and two 5x8 couplings. 
There is a similar and, as well as without an engine on (with calipers and a nut).
If you take without a large margin, then the 400 mm option will work well for the “larger version” of the machine
Additional information - photo of the kit separately
Engine marking RB Step Motor 42SHDC3025-24B-500, seat Nema17 
Comes with a short cable for connection. Conveniently, you can simply increase the length without touching the connectors. 
T8 screw, nut 
Calipers KR08. 
Easy to mount on the profile. If a wide flange is used for installation, then it is better to use the version of the KFL08 caliper, it allows you to mount the screw not on the profile, but on the flange. 
Coupling 5x8 - a split coupling for connecting the motor shaft to the propeller. 
This is how the engine is mounted in the original on the X axis. On a small aluminum plate.
I did the same, only with a printed plate. At the same time it will be a support for the guides.
I already cut off the excess length of the screw for the Z axis (the Z axis is in the process for now, the information will be separate, most likely also 3D printed).
Most likely it will be necessary to lengthen the wires of the motors in order to neatly route it along the profile in upper part to the electronics board (most likely it will be CNC Shield). Yes, and it would not hurt to install limit switches for extreme positions.
The basic information on the assembly is already there, you can start estimating the costs))))
Calculation
Now, as requested in the comments in the first part, I propose to discuss costing. Naturally, I spent less than indicated, since I had the engines and most of the components in stock. Strongly cheaper will be if you use home-made printed corners for the profile, calipers, flanges and so on. To the work of the drilling machine printed circuit boards and milling soft materials this is unlikely to affect. Another good option is to use perforated plates from construction / household stores. Suitable for reinforcing corners, including vertical ones and for installing an engine, provided that the central part is drilled under the shaft. In place of perforated fasteners, you can use self-made aluminum sheet or plywood.
Definitely a must buy profile 2020 otherwise it will be a completely different type of machine. You can do the same from an aluminum corner or rectangular pipe, but only for the love of art))) There are more optimal designs in terms of rigidity for assembly from a corner / pipe.
Definitely needed for the profile T-nuts. You can buy T-bolts, but T-nuts are more versatile (as any length of screw can be used).
But the rest can be changed at your discretion, you can even instead of running screw T8 use hairpin from stainless steel. Unless the number of steps per mm will have to be recalculated in the firmware.
Engines can be removed from old devices / office equipment and plan seats already for a specific type.
Electronics almost any (Anduino UNO / Anduino Nano, CNCShield, Mega R3 + Ramps, A4988 / DRV8825 drivers, you can use an adapter board for Mach3 and TB6600 drivers. But the choice of electronics limits the software used.
For drilling, you can use any engine direct current, which allows you to install collet and has decent turnover. In the basic version, there is a high-speed 775 motor. For milling, you can use 300 watt b / c spindles with an ER11 collet, but this greatly increases the cost of the machine as a whole.
Approximate costing:
profile 2020 (2.5 meters) = 667 rubles
profile 2080 (0.5 meters) to the desktop = 485 r
Two 300 mm 2x$25
. Lot of 20 pieces comes out to $5.5 with delivery
about 4r / piece if you take a large package. You need at least 50 pieces (mounting engines, calipers). I don’t count the screws for them, usually a few kopecks / piece, depending on the quality. Total about 400 ... 500 rubles.
Engines 3 pcs $8.25 each
Electronics $2
$3.5
A4988 three pieces for $1
The machine comes out around $111. If adding a spindle:
$9
$7.78,
then total cost about $128
3D printed parts do not appreciate. Can be replaced with perforated plates / corners from crepe market and similar stores. Wires, electrical tape, the time spent also do not appreciate.
Let me remind you that not all CNC2418 configurations have such good 775 engines and, moreover, an ER11 collet.
Options cheaper.
Knowing that it is a complex technical and electronic device, many craftsmen think that it is simply impossible to make it with their own hands. However, this opinion is erroneous: you can make such equipment yourself, but for this you need to have not only it detailed drawing, but also a set of necessary tools and related components.
Processing of duralumin blanks on a homemade desktop milling machine
When deciding to make a homemade CNC machine, keep in mind that this can take a significant amount of time. In addition, certain financial costs will be required. However, not being afraid of such difficulties and having the right approach to solving all issues, you can become the owner of affordable, efficient and productive equipment that allows you to process workpieces from various materials with a high degree accuracy.
To make a milling machine equipped with a CNC system, you can use two options: buy a ready-made kit, from which such equipment is assembled from specially selected elements, or find all the components and assemble a device with your own hands that fully meets all your requirements.
Instructions for assembling a homemade CNC milling machine
Below in the photo you can see the with my own hands to which is attached detailed instructions for manufacturing and assembly, indicating the materials and components used, accurate “patterns” of machine parts and approximate costs. The only downside is the instructions English language, but it is quite possible to understand the detailed drawings without knowing the language.
Download free instructions for the manufacture of the machine:
The CNC milling machine is assembled and ready to go. Below are some illustrations from the assembly instructions for this machine.
"Patterns" of machine parts (reduced view) Beginning of machine assembly Intermediate stage Final assembly stage
Preparatory work
If you decide that you will design a CNC machine with your own hands without using a ready-made kit, then the first thing you need to do is to opt for circuit diagram, on which such mini-equipment will work.
The basis of CNC milling equipment can be taken from an old drilling machine, in which the working head with a drill is replaced with a milling head. The most complex thing that will have to be designed in such equipment is a mechanism that ensures the movement of the tool in three independent planes. This mechanism can be assembled on the basis of carriages from a non-working printer; it will ensure the movement of the tool in two planes.
It is easy to connect software control to a device assembled according to such a concept. However, its main drawback is that it will be possible to process on such a CNC machine only workpieces made of plastic, wood and thin sheet metal. This is explained by the fact that the carriages from the old printer, which will provide movement cutting tool, do not have a sufficient degree of rigidity.
In order for your homemade CNC machine to be able to perform full-fledged milling operations with workpieces from various materials, a sufficiently powerful stepper motor must be responsible for moving the working tool. It is not at all necessary to look for a stepper-type engine, it can be made from a conventional electric motor, subjecting the latter to a slight refinement.
The use of a stepper motor in yours will make it possible to avoid the use of a screw drive, and functionality and characteristics homemade equipment it won't make it any worse. If you still decide to use carriages from the printer for your mini-machine, then it is advisable to pick them up from a larger model of the printing device. To transfer force to the shaft of milling equipment, it is better to use not ordinary, but toothed belts that will not slip on the pulleys.
One of the most important components of any such machine is the milling mechanism. It is its manufacture that needs special attention. To properly make such a mechanism, you will need detailed drawings which must be strictly followed.
CNC milling machine drawings
Let's start assembling the equipment
The basis of home-made CNC milling equipment can be a rectangular beam, which must be securely fixed on the rails.
The supporting structure of the machine must be high rigidity, when installing it, it is better not to use welded joints, and you need to connect all the elements only with screws.
This requirement is explained by the fact that welds tolerate vibration loads very poorly, which in without fail will be subject to Basic structure equipment. Such loads will eventually lead to the fact that the frame of the machine will begin to collapse over time, and changes in geometric dimensions will occur in it, which will affect the accuracy of equipment settings and its performance.
Welds during the installation of the frame of a homemade milling machine often provoke the development of play in its nodes, as well as the deflection of the guides, which occurs under severe loads.
In the milling machine, which you will assemble with your own hands, a mechanism must be provided to ensure the movement of the working tool in a vertical direction. Best use for this screw gear, the rotation of which will be transmitted using a toothed belt.
An important detail of the milling machine is its vertical axis, which for homemade device can be made from aluminum plate. It is very important that the dimensions of this axis are precisely adjusted to the dimensions of the device being assembled. If you have a muffle furnace at your disposal, then you can make the vertical axis of the machine with your own hands, casting it from aluminum according to the dimensions indicated in the finished drawing.
After all the components of your homemade milling machine are prepared, you can begin to assemble it. Begins this process from the installation of two stepper motors, which are mounted on the equipment case behind its vertical axis. One of these electric motors will be responsible for moving milling head in the horizontal plane, and the second - for the movement of the head, respectively, in the vertical. After that, the remaining components and assemblies of home-made equipment are mounted.
Rotation to all components of home-made CNC equipment should be transmitted only through belt drives. Before connecting to assembled machine program control system, you should check its performance in manual mode and immediately eliminate all identified shortcomings in its operation.
You can watch the assembly process on the video, which is easy to find on the Internet.
Stepper motors
In the design of any CNC milling machine, there are necessarily stepper motors that provide tool movement in three planes: 3D. When designing a homemade machine for this purpose, you can use electric motors installed in a dot matrix printer. Most of the older dot matrix printers were equipped with electric motors with sufficient high power. In addition to stepper motors from an old printer, it is worth taking strong steel rods, which can also be used in the construction of your homemade machine.
To make a CNC router with your own hands, you will need three stepper motors. Since there are only two of them in a dot matrix printer, it will be necessary to find and disassemble another old printing device.
It will be a big plus if the engines you find have five control wires: this will significantly increase the functionality of your future mini-machine. It is also important to find out the following parameters of the stepper motors you found: how many degrees it rotates in one step, what is the supply voltage, and also the value of the winding resistance.
The drive design of a homemade CNC milling machine is assembled from a nut and a stud, the dimensions of which must first be selected according to the drawing of your equipment. To fix the motor shaft and to attach it to the stud, it is convenient to use a thick rubber winding from electric cable. Elements of your CNC machine, such as clamps, can be made in the form of a nylon sleeve into which a screw is inserted. To make such simple structural elements, you will need a regular file and a drill.
Electronic filling of equipment
Your do-it-yourself CNC machine will be controlled by software, and you need to choose the right one. When choosing such software (you can write it yourself), it is important to pay attention to the fact that it is efficient and allows the machine to implement all its functionality. Such software should contain drivers for controllers that will be installed on your mini milling machine.
AT homemade machine with the CNC, the LPT port is obligatory, through which electronic system control and connect to the machine. It is very important that this connection is made through the installed stepper motors.
When choosing electronic components for your do-it-yourself machine, it is important to pay attention to their quality, since the accuracy of the technological operations that will be performed on it will depend on this. After installing and connecting all the electronic components of the CNC system, you need to download the necessary software and drivers. Only after that, a test run of the machine follows, checking the correct operation of the machine under the control of downloaded programs, identifying shortcomings and promptly eliminating them.
And so, within the framework of this article-instruction, I want you, together with the author of the project, a 21-year-old mechanic and designer, to make your own. The narration will be conducted in the first person, but know that, to my great regret, I am not sharing my experience, but only freely retelling the author of this project.
There will be a lot of drawings in this article, the notes to them are made in English, but I am sure that a real techie will understand everything without further ado. For ease of understanding, I will break the story into "steps".
Foreword from the author
Already at the age of 12, I dreamed of building a machine that would be able to create various things. A machine that will give me the ability to make any household item. Two years later, I came across the phrase CNC or more precisely, to the phrase "CNC milling machine". After I found out that there are people who can make such a machine on their own for their own needs, in their own garage, I realized that I could do it too. I must do it! For three months, I tried to collect the right parts, but did not budge. So my obsession gradually faded away.
In August 2013, the idea of building a CNC milling machine re-engaged me. I had just completed my bachelor's degree from the University of Industrial Design, so I was quite confident in my abilities. Now I clearly understood the difference between me today and me five years ago. I learned how to work with metal, mastered the techniques of working on manual metalworking machines, but most importantly, I learned how to use development tools. I hope this tutorial will inspire you to create your own CNC machine!
Step 1: Design and CAD Model
It all starts with thoughtful design. I made several sketches to get a better feel for the size and shape of the future machine. After that I created a CAD model using SolidWorks. After I modeled all the parts and components of the machine, I prepared technical drawings. I used these drawings for the manufacture of parts on manual metalworking machines: and.
To be honest, I love good handy tools. That is why I tried to make sure that the operations on maintenance and adjustment of the machine were made as easy as possible. I placed the bearings in special blocks in order to be able to quickly replace. The guides are serviceable so my car will always be clean when the job is done.
Downloads "Step 1"
dimensions
Step 2: Bed
The bed provides the machine with the necessary rigidity. It will be equipped with a movable portal, stepper motors, Z-axis and spindle, and later the work surface. To create a carrier frame, I used two aluminum profile Maytec section 40x80 mm and two end plates made of aluminum 10 mm thick. I connected all the elements to each other on aluminum corners. To strengthen the structure inside the main frame, I made an additional square frame from profiles of a smaller section.
In order to avoid dust on the rails in the future, I installed aluminum protective corners. The angle is mounted using T-nuts, which are installed in one of the grooves of the profile.
Both end plates are fitted with bearing blocks for mounting the drive screw.
Carrier frame assembly
Corners to protect the rails
Downloads "Step 2"
Drawings of the main elements of the bed
Step 3: Portal
Mobile portal - executive agency of your machine, it moves along the X axis and carries the milling spindle and the Z axis support. The higher the gantry, the thicker the workpiece you can machine. However, a high gantry is less resistant to the loads that occur during processing. The high side posts of the portal act as levers relative to the linear rolling bearings.
The main task that I planned to solve on my CNC milling machine is processing aluminum parts. Insofar as maximum thickness of aluminum blanks suitable for me 60 mm, I decided to make a portal clearance (distance from working surface to the upper transverse beam) equal to 125 mm. In SolidWorks, I converted all my measurements into a model and technical drawings. Due to the complexity of the parts, I processed them on an industrial CNC machining center, which additionally allowed me to process chamfers, which would be very difficult to do on a manual metal milling machine.
Downloads "Step 3"
Step 4: Z Axis Caliper
In the Z axis design, I used a front panel that attaches to the Y axis travel bearings, two plates to reinforce the assembly, a plate to mount the stepper motor, and a panel to mount the milling spindle. On the front panel, I installed two profile guides along which the spindle will move along the Z axis. Please note that the Z axis screw does not have a counter support at the bottom.
Downloads "Step 4"
Step 5: Guides
Guides provide the ability to move in all directions, ensure smooth and precise movements. Any play in one of the directions can cause inaccuracies in the processing of your products. I chose the most expensive option - profiled hardened steel rails. This will allow the structure to withstand high loads and provide the positioning accuracy I need. To ensure the guides are parallel, I used a special indicator during their installation. The maximum deviation relative to each other was no more than 0.01 mm.
Step 6: Screws and Pulleys
Screws convert rotational motion from stepper motors into linear motion. When designing your machine, you can choose from several options for this assembly: A screw-nut pair or a ball screw pair (ball screw). The screw nut, as a rule, is subjected to more frictional forces during operation, and is also less accurate relative to the ball screw. If you need increased accuracy, then you definitely need to opt for a ball screw. But you should know that ball screws are quite expensive.
There are a lot of similar stories on the net, and I probably won’t surprise anyone, but maybe this article will be useful to someone. This story began at the end of 2016, when my friend, a partner in the development and production of test equipment, and I accumulated some sum of money. In order not to just waste money (the business is young), they decided to invest in the business, after which the idea of \u200b\u200bmanufacturing a CNC machine came to mind. I already had experience in building and working with this kind of equipment, and the main area of our activity is design and metalworking, which accompanied the idea of building a CNC machine.
That's when the movement began, which continues to this day ...
Everything continued from the study of forums dedicated to CNC topics and the choice of the basic concept of the machine design. Having previously decided on the materials to be processed on the future machine and its working field, the first paper sketches appeared, which were subsequently transferred to a computer. In the environment of three-dimensional modeling KOMPAS 3D, the machine was visualized and began to grow over small details and nuances, which turned out to be more than we would like, some we solve to this day.
One of the initial decisions was to determine the materials processed on the machine and the dimensions of the working field of the machine. As for the materials, the solution was quite simple - wood, plastic, composite materials and non-ferrous metals (mainly duralumin). Since we mainly have metalworking machines in our production, sometimes a machine is required that would quickly process materials that are quite easy to process along a curved path, and this would subsequently reduce the cost of production of ordered parts. Based on the selected materials, mainly supplied in sheet packaging, with standard dimensions of 2.44x1.22 meters (GOST 30427-96 for plywood). Rounding these dimensions came to the following values: 2.5x1.5 meters, working space definitely, with the exception of the height of the tool, this value was chosen for reasons of the possibility of installing a vice and assumed that we would not have workpieces thicker than 200mm. We also took into account the moment if it is necessary to process the end of any sheet metal more than 200 mm long, for this the tool travels beyond the dimensions of the machine base, and the part / workpiece itself is attached to the end side of the base, thereby machining the end of the part can take place.
Machine design is a prefabricated frame base from the 80th profile pipe with a wall of 4 mm. On both sides of the length of the base, profile rolling guides of the 25th size are fixed, on which a portal is installed, made in the form of three profile pipes welded together of the same size as the base.
The machine is four axial and each axis is driven by a ball screw. Two axes are located in parallel along the long side of the machine, paired by software and tied to the X coordinate. Accordingly, the remaining two axes are the Y and Z coordinates.
Why they stopped at the prefabricated frame: initially they wanted to do clean welded structure with embedded welded sheets for milling, installation of guides and supports of the ball screw, but for milling they did not find a large enough milling-coordinate machine. I had to draw a prefabricated frame so that I could process all the details on my own with the metalworking machines available in the production. Each part that was exposed to electric arc welding was annealed to relieve internal stresses. Further, all mating surfaces were milled, and later the fitting had to be scraped in places.
Getting ahead, I want to say right away that the assembly and manufacture of the frame turned out to be the most time-consuming and financially costly event in the construction of the machine. The original idea with a one-piece welded frame bypasses the prefabricated structure in all respects, in our opinion. Although many may disagree with me.
I want to make a reservation right away that we will not consider machine tools made of aluminum structural profiles here for now, this is rather a matter for another article.
Continuing the assembly of the machine and discussing it on the forums, many began to advise making diagonal steel struts inside the frame and outside to add even more rigidity. We did not neglect this advice, but adding jibs to the design is the same, since the frame turned out to be quite massive (about 400 kg). And upon completion of the project, the perimeter will be covered with sheet steel, which will additionally connect the structure.
Let's now move on to the mechanical issue of this project. As mentioned earlier, the movement of the machine axes was carried out through a ball screw pair with a diameter of 25 mm and a pitch of 10 mm, the rotation of which is transmitted from stepper motors with 86 and 57 flanges. Initially, it was supposed to rotate the screw itself in order to get rid of unnecessary backlash and additional gears, but they could not do without them in view of the fact that with direct connection engine and propeller, the latter on high speeds would begin to unwind, especially when the portal is in extreme positions. Given the fact that the length of the screws along the X axis was almost three meters, and for less sagging, a screw with a diameter of 25 mm was laid, otherwise a 16 mm screw would have been enough.
This nuance was already discovered during the production of parts, and it was necessary to quickly solve this problem by manufacturing a rotating nut, not a screw, which added an additional bearing assembly and belt drive to the design. This solution also made it possible to tighten the screw well between the supports.
The design of the rotating nut is quite simple. Initially, we selected two tapered ball bearings, which are mirrored on the ball screw nut, after cutting the thread from its end, to fix the bearing cage on the nut. The bearings, together with the nut, fit into the housing, in turn, the entire structure is mounted on the end of the portal rack. In front of the ball screw nuts, the adapter sleeve was fixed to the screws, which later in assembled on the mandrel turned to give consistency. They put a pulley on it and tightened it with two lock nuts.
Obviously, some of you will be wondering - "Why not use a gear rack as a mechanism for transmitting movement?". The answer is quite simple: the ball screw will provide positioning accuracy, greater driving force, and, accordingly, less torque on the motor shaft (this is what I immediately remembered). But there are also disadvantages - more low speed movement and if you take the screws of normal quality, then, accordingly, the price.
By the way, we took TBI ball screws and nuts, enough a budget option, but the quality is also appropriate, since out of the 9 meters of the screw taken, 3 meters had to be thrown out, due to the discrepancy in geometric dimensions, none of the nuts simply screwed on ...
As sliding guides, profile rail guides of 25 mm size, manufactured by HIWIN, were used. Mounting grooves were milled for their installation to maintain parallelism between the guides.
Ball screw supports decided to make on their own, they turned out to be of two types: supports for rotating screws (Y and Z axes) and supports for non-rotating screws (X axis). Supports for rotating propellers could be bought, as savings due to own production 4 parts came out a little. Another thing is with supports for non-rotating screws - you can’t find such supports for sale.
From what was said earlier, the X-axis is driven by rotating nuts and through a belt gear train. They also decided to make two other axes Y and Z through a belt gear, this will add greater mobility in changing the transmitted moment, it will add aesthetics in the form of installing the engine not along the axis of the ball screw, but to the side of it, without increasing the dimensions of the machine.
Now let's move smoothly to electrical part, and we will start with the drives, stepper motors were chosen as them, of course, for reasons of lower price compared to motors with feedback. Two engines with an 86th flange were put on the X axis, on the Y and Z axes along an engine with a 56th flange, only with different maximum torque. I will try to present below. full list purchased items...
The electrical circuit of the machine is quite simple, stepper motors are connected to drivers, which, in turn, are connected to an interface board, which is also connected via a parallel LPT port to a personal computer. Drivers used 4 pieces, respectively, one piece for each of the engines. I installed all the drivers the same, to simplify installation and connection, with a maximum current of 4A and a voltage of 50V. As an interface board for CNC machines, I used a relatively budget option, from a domestic manufacturer, as indicated on the website the best way. But I will not confirm or deny this, the board is simple in its application and, most importantly, it works. In my past projects, I used boards from Chinese manufacturers, they also work, and in terms of their periphery they differ little from the one I used in this project. I noticed in all these boards, one may not be significant, but a minus, you can only install up to 3 limit switches on them, but at least two such switches are required for each axis. Or I just didn't get it? If we have a 3-axis machine, then accordingly we need to install Limit switches in the zero coordinates of the machine (this is also called "home position") and in the most extreme coordinates so that in the event of a failure or lack of a working field, one or another axis simply does not fail (simply does not break). In my scheme used: 3 terminal without contact inductive sensors and Danger button"E-STOP" in the form of a fungus. The power section is powered by two 48V switching power supplies. and 8A. 2.2 kW water-cooled spindle, respectively connected through a frequency converter. Turnovers are set from a personal computer, since the frequency converter is connected via an interface board. Turnovers are regulated by changing the voltage (0-10 volts) at the corresponding output frequency converter.
All electrical components except motors, spindle and limit switches were mounted in the electrical metal cabinet. All control of the machine is carried out from a personal computer, we found an old PC on motherboard ATX form factor. It would be better to shrink a little and buy a small mini-ITX with an integrated processor and video card. With not small dimensions of the electrical box, all the components were hardly placed inside, they had to be placed close enough to each other. At the bottom of the box, I placed three forced cooling fans, since the air inside the box was very hot. A metal plate was screwed on the front side, with holes for the power buttons and emergency stop buttons. Also, on this overlay, a socket was placed to turn on the PC, I removed it from the case of an old mini computer, it’s a pity that it turned out to be not working. An overlay was also fixed from the back end of the box, holes were placed in it for connectors for connecting 220V power, stepper motors, a spindle and a VGA connector.
All wires from the engines, the spindle, as well as its cooling water hoses were laid in flexible cable channels of caterpillar type 50 mm wide.
Concerning software, then Windows XP was installed on a PC located in an electrical box, and one of the most common Mach3 programs was used to control the machine. The program is configured in accordance with the documentation for the interface board, everything is described there quite clearly and in pictures. Why exactly Mach3, but all the same, there was work experience, I heard about other programs, but did not consider them.
Specifications:
Working space, mm: 2700x1670x200;
Axes movement speed, mm/min: 3000;
Spindle power, kW: 2.2;
Dimensions, mm: 2800x2070x1570;
Weight, kg: 1430.
Parts list:
Profile pipe 80x80 mm.
Metal strip 10x80mm.
Ball screw TBI 2510, 9 meters.
Ball screw nuts TBI 2510, 4 pcs.
Profile guides HIWIN carriage HGH25-CA, 12 pcs.
Rail HGH25, 10 meters.
Stepper motors:
NEMA34-8801: 3 pcs.
NEMA 23_2430: 1pc.
Pulley BLA-25-5M-15-A-N14: 4 pcs.
Pulley BLA-40-T5-20-A-N 19: 2 pcs.
Pulley BLA-30-T5-20-A-N14: 2 pcs.
StepMaster v2.5 interface board: 1 pc.
DM542 stepper motor driver: 4pcs (China)
Switching power supply 48V, 8A: 2 pcs. (China)
Frequency converter for 2.2 kW. (China)
Spindle 2.2 kW. (China)
I seem to have listed the main details and components, if something is not included, then write in the comments, I will add it.
Machine experience: In the end, after almost a year and a half, we still launched the machine. First, we set up the positioning accuracy of the axes and their maximum speed. According to more experienced colleagues maximum speed at 3 m / min is not high and should be three times higher (for processing wood, plywood, etc.). At the speed that we have reached, the portal and other axes, resting on them with your hands (with your whole body), can hardly be stopped - rushing like a tank. We started testing with the processing of plywood, the cutter goes like clockwork, there is no machine vibration, but they also deepened by a maximum of 10mm in one pass. Although after going deep they began to shallower depths.
After playing with wood and plastic, we decided to gnaw on duralumin, here I was delighted, although I first broke several milling cutters with a diameter of 2 mm, while I was choosing cutting modes. Dural cuts very confidently, and it turns out enough clean cut, along the machined edge.
We haven’t tried to process steel yet, but I think that at least the machine will pull engraving, and for milling the spindle is rather weak, it’s a pity to kill it.
And the rest of the machine perfectly copes with the tasks assigned to it.
Conclusion, opinion on the work done: The work done is not small, as a result, we are pretty tired, since no one has canceled the main work. Yes, and a lot of money invested, I won’t say the exact amount, but it’s about 400t.r. In addition to the cost of assembly, the bulk of the costs and most of the forces went to the manufacture of the base. Wow, how we messed with him. And the rest, everything was done as funds, time and finished parts came in to continue the assembly.
The machine turned out to be quite efficient, quite rigid, massive and of high quality. Maintaining good positioning accuracy. When measuring a square made of duralumin, 40x40 in size, the accuracy turned out to be + - 0.05 mm. The processing accuracy of larger parts was not measured.
What's next…: There is still enough work on the machine, in the form of closing the guides and ball screws with dust protection, sheathing the machine along the perimeter and installing ceilings in the middle of the base, which will form 4 large shelves, under the spindle cooling volume, tool storage and equipment. They wanted to equip one of the quarters of the base with a fourth axle. It is also required to install a cyclone on the spindle to remove and collect chips from dust, especially if wood or textolite is processed, dust flies everywhere and settles everywhere.
As for the further fate of the machine, everything is not clear here, since I had a territorial issue (I moved to another city), and now there is almost no one to deal with the machine. And the above plans are not the fact that they will come true. No one could have imagined this two years ago. Add tags