Do-it-yourself repair of cnc machine tools

In detail: do-it-yourself repair of CNC machines; do-it-yourself diagnostics from a real master for the site my.housecope.com.

A very important issue for maintaining the normal quality of operation of CNC machines is the choice of the most rational method of troubleshooting.

In practice, there are mainly three search methods.

1. The logical method is based on knowledge of the composition and operation of the equipment, analysis of the actual information output and its comparison with a given control program, knowledge of the procedure for processing information on the nodes and blocks of the device, the correct determination of characteristic and uncharacteristic errors in the control program and malfunctions in CNC devices on the very the machine. Based on the analysis of the action of the input and the results of the output information, a logical conclusion is made about the existing defects and ways to eliminate them to ensure the normal operation of the CNC machine.

2. The practical method of troubleshooting is carried out by means of special measuring instruments. In this case, the defective chain is divided into two parts. Then the part in which the malfunction is detected is divided again. And so on - until you find the faulty board to be replaced. After that, a general check of the device is made and a conclusion is made about the quality of the CNC system and the machine as a whole.

3. The test method of troubleshooting on CNC machines is applied in the workshop environment. In this case, the operation of the CNC device as a whole or of its individual units is checked, which perform completed micro-operations by acting on them with appropriate test programs. The test method allows you to relatively quickly identify a defect and take the necessary measures to eliminate it.

Video (click to play).

Malfunctions of an input unit with a photo-reading device, as well as a linear interpolator and a speed setting block are the most typical for the used CNC systems on modern metal-cutting machines. The causes of faults in the input unit are most often the aging of photodiodes or contamination of the optics of the photoreader and tape drive.

For the preparation and control of control programs at factories and associations where CNC machines operate, specialized sections have been created, equipped with the necessary equipment.

When using CNC machines, increased requirements are also imposed on the electrical equipment installed on them. It must provide the ability to quickly eliminate interference in the places where it occurs, and also have the ability to reliably control high-current equipment and electric motors through weak signals or contacts.

CNC machines, unlike conventional machines, are equipped for each controlled coordinate of movement with a separate feed drive, which operates from the control system and must ensure high positioning accuracy and sufficient speed. For this, high-speed drive motors are used — hydraulic, electro-hydraulic (stepping or tracking), and electric. Constructive and technological methods ensure the maximum elimination of the gap in the kinematic chain (for example, by replacing conventional screw gears with ball screw pairs) and minimizing friction in the guides, selecting the optimal masses of moving units, etc.

Particular attention should be paid to the care of the hydraulic drive.The grade of oil for filling in the hydraulic system must comply with the requirements of the instruction manual for this equipment. The oil must be clean, filtered and homogeneous (it is not recommended to mix different brands of oils). Do not allow a violation of the tightness of the hydraulic system, leakage and decrease in the permissible oil level. Before starting the machine, it is necessary to turn on the hydraulic system for a while to warm up the oil.

According to the current regulation, all measures for the preventive maintenance of equipment and apparatus, as well as for other types of maintenance of CNC machines, should be carried out only by specially trained personnel who have the appropriate admission, and the machine operator is prohibited from independently performing any operations on the machine that are not part of his duties. Nevertheless, the operator must not only know when and what activities are provided for by the schedules for the maintenance of the CNC machine on which he works, but also systematically monitor their implementation in accordance with the established schedules, and, if necessary, directly participate in them, providing all possible assistance and assistance to maintenance personnel of repairmen.

Taking this into account, it is advisable for production workers servicing CNC machines not only to know the features of these machines and the procedure for detecting faults on them, given above, but also in general terms to familiarize themselves with the characteristic reading errors and methods for their elimination on CNC devices (Table 6) ...

Table 6 Reading errors and methods for their elimination when working on CNC machines

There is a need for repair / restoration of the CNC machine:

Do constant errors and breakdowns disrupt the execution of the production plan?
Do you need to restore the control system of a purchased used CNC machine?
lacking functionality?
does the enterprise lack the necessary qualified specialists?

Why the restoration and repair of CNC machines should be ordered from professionals:
The accumulated practical experience in repairing machine tools and restoring control systems allows us to offer reliable and high-quality solutions from both Russian and foreign manufacturers;
The developed documentation must comply with the main regulatory and technical documents in force in the territory of the Russian Federation;
Drawing up several variants of estimates for the repair of CNC equipment (taking into account the preferences of the Customer, equipment configuration and economic feasibility);
Competently designed projects allow you to save on operating costs, on costs associated with frequent repairs, as well as on electricity consumption;
Development guarantee and expert technical support.

Comprehensive equipment diagnostics
Economic assessment of the proposed options for repair / restoration of the machine

Electronic repair of CNC equipment is carried out at the component level using the latest high-precision and high-tech equipment
Replacement of feed drives, motors and power cables (if necessary);
Comprehensive project support: design of process control systems including selection of equipment, programming, Construction and Installation Works, commissioning, warranty and post-warranty service. At the request of the Customer, we are ready to implement the ability to collect information and monitor the state of the fleet of CNC machines (readiness, reasons for downtime, malfunction, etc.).

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we clarify the necessary information, if necessary, with a visit to the customer's enterprise

for the repair / restoration of the machine, together with your technical specialists (list of purchased products, assemblies, assemblies and components)

After agreeing on the conditions, a contract is drawn up, and we carry out work on the machine, CNC programming and setting up drives

After the completion of all work, we transfer the machine to the employees of the enterprise on the basis of documents

Five reasons to order services for the modernization and restoration of CNC machines from us:

We provide a full range of services for the repair and restoration of CNC machines: from inspection to post-warranty service.

We carry out repairs using CNC control systems from foreign manufacturers such as: Siemens, Fagor, Fanuc, FIDIA, HEIDENHAIN, Mitsubishi Electric, etc.

We develop design documentation in accordance with the requirements of GOST, PUE, SNiP.

We guarantee professional service at a competitive price.

We use an individual approach to our Customers.

We believe that LLC Volgopromavtomatika is staffed with qualified personnel, which allows solving the most complex technical tasks of automation of technological processes, timely and with high quality to perform all assigned work, both at LLC Volgograd GIPS and at other enterprises. It's a pleasure to work with such a partner, and Volgograd GIPS LLC intends to continue to cooperate ...
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O.A. Gusakov Chief Engineer of LLC "Volgograd GIPS"

The employees of Volgopromavtomatika LLC in a short time automated the following objects in TPTs-2: horizontal induction furnaces of the 5500 line, a piercing press, a cooling table. Within a month, employees of "VPA" LLC carried out dismantling of equipment, installation of a new one and commissioning. We are pleased to cooperate with a company that clearly fulfills the terms of the contract ...
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N.V. Guryanov Head of APCS TPTs-2 VTZ JSC "Volzhsky Pipe Plant"

We recommend VPA LLC as a reliable supplier of equipment and services in the field of automation of power supply of technological equipment ...
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A.A. Shnyp Head of Procurement Department, Togliattisintez JSC

I would like to express my gratitude to Volgopromavtomatika LLC for the high-quality work performed, the professional approach to work when performing work on the visualization and dispatching system of the technological process at Water Treatment. Your specialists have done a great job. All work (installation, commissioning, installation of a PC and writing a program on WinCC) Volgopromavtomatika LLC performed on its own, efficiently and on time ...
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D.V. Krasilnikov Industrial Automation Engineer JSC "SUN InBev"
branch in Volzhsky

„Diagnostics„- a set of methods for determining the technical state of a unit, device, unit and mating parts without disassembling them. Diagnostics of the technical condition consists in the logical processing of some objectively existing information coming from the operating CNC equipment in a certain period of time. This information comes in the form of external signs that directly or indirectly characterize the state of the equipment. Ensuring high accuracy and reliability of the operation of CNC machines during their operation is associated with a system of their maintenance, timely and high-quality performance of preventive commissioning and repair work.

The change in the technical condition of the equipment during the period of its normal operation is a random process of a probabilistic nature. The transition from the state of correct operation of the machine to the state of faulty operation characterizes the onset of a malfunction, that is, it is a conditional failure.

If the metal-cutting equipment is in a faulty condition, then in order to prevent the actual failure, it is necessary to carry out adjustment or repair work.

To establish the relationship between the technical state of the CNC machine and the error in the parameters of the finished part, as well as to select a diagnostic method on this basis, it is advisable to develop control charts for CNC machines of various technological groups.

The need for maintenance and repair is not unambiguously determined by the life of a particular machine. Each time period corresponds not one, but many different states. Therefore, the diagnostics of software equipment sets the task of removing this uncertainty and identifying from the set of states the only one in which this machine is at a given time.

When diagnosing and repairing CNC machines, difficulties arise due to their great complexity. It takes a lot of time to find faults, use fault diagnosis systems, complex instrumentation, as well as the availability of highly qualified service personnel. Diagnosis is often hampered by the variety of CNC systems used, and by the lack of specialists for their maintenance.

The design of CNC machines provides technical solutions that improve and facilitate maintenance, troubleshooting and repair. These include: the modular principle of creating CNC machines from unified elements, which enhances their reliability; equipping CNC machines with diagnostic systems that provide quick detection of malfunctions and their indication on the display of the CNC device, as well as the use of test programs for finding complex malfunctions, etc.; development of documentation for diagnosing and repairing a specific CNC machine or a group of these machines.

In practice, the diagnosis of CNC machines consists in the logical processing of some objectively existing information coming from the operating equipment in a certain period of time in the form of external signs characterizing the state of the equipment.

Diagnostics software equipment includes: 1) study of working CNC machines to be diagnosed, their possible failures and signs of their manifestation; 2) building a model of a working machine and a CNC device to be diagnosed, identifying faults; 3) determination of the amount of information and construction of a diagnostic algorithm that satisfies the required detail of troubleshooting by analyzing the object model; 4) the choice of instrumentation that provides the implementation of the diagnostic algorithm.

To obtain diagnostic information, measurements are made of the values of vibration, acoustic vibrations (noise), parameters of the processing process (productivity, cutting conditions, duration of processing cycles, travel speed, temperature, etc.).

Diagnostics of software equipment is a complex process, when the detection and elimination of faults of average complexity is carried out by specialists from the CNC machine maintenance group. Complex malfunctions, if they cannot be eliminated by the specialists of the service group of the customer plant, are corrected after consultation with the specialists of the service department of the manufacturer of the CNC machine tool.

Failures of CNC machines can be classified: by their external manifestation - latent and explicit (latent is a failure, the external manifestations of which may depend on several reasons; the explicit include failures that can be detected visually); by interrelation - independent and dependent, independent failures occur for any reason, except for the influence of another failure; dependent (secondary) failures are caused by the influence of the primary failure.

Each CNC machine with intensive use sooner or later depletes its resource, which leads either to a complete failure of the equipment, or to partial breakdown of parts or assemblies of machine tools.

Typically, the main reasons for machine failure are:

Violation of operating rules, including overloading of individual mechanisms and assemblies.
Violation of the adjustment of a specific unit or mechanism.
Deterioration of individual parts and assemblies, failure of individual mechanisms, loss of accuracy.

Technical consultations with remote access and onsite to the customer;
Diagnostics of CNC machines, their malfunctions;
Preventive inspection of spindles and spindle assemblies, diagnostics of emergency spindles with subsequent repair;
Repair of CNC machine warranty, post-warranty, overhaul at the customer's enterprise and at our own production base;
Delivery of spare parts and components as soon as possible;
Commissioning works;
Maintenance and programming of CNC systems: Heidenhain, Siemens, Fanuc;
Setting the parameters of the kinematics of the machine;
Restoration of damaged units to be replaced;
Equipment performance monitoring.

The advantages of our company:

Highly qualified staff.
High quality of work.
Many years of practical experience in the following areas: diagnostics of CNC machines, repair of CNC machines, maintenance of CNC machines.
Clear deadlines for the production of work.
Individual approach to each client.

the survey form below, our specialist will definitely contact you:

Diagnostics of CNC machines - a set of actions aimed at examining and identifying malfunctions in the design of equipment equipped with numerical control. The CNC system provides autonomous and semi-autonomous operation of machine tools. Malfunctions in the operation of the unit can affect both the quality of processing on CNC machines and the ability to properly perform the task.

Diagnostics of CNC machine tools includes a group of works that should be carried out by specialists.

It is difficult to make diagnostics outside the service center with your own hands, and there is a possibility of inaccurate determination of the cause of the breakdown.

Diagnostics is divided into two stages:

checking the condition of the machine;
checking the numerical control system.

The first stage involves identifying faults in the design of the device itself. Most often, malfunctions are associated with mechanical breakdowns. In this case, the structure is analyzed, the faulty element is removed and replaced.

The second stage is more complicated, since it requires the study of numerical control problems. For its implementation, it is required to inspect the specified program, software carrier, as well as the equipment responsible for the work performed.

If the unit is used in an industrial enterprise, special services carry out its maintenance. Companies that manufacture this type of equipment provide courses on how to use the devices, as well as how to diagnose their malfunctions. When the unit is sold, there is a manual accompanying it, which identifies the company that made it.

If necessary, you can contact this company for the purpose of taking a training course, or getting advice on an issue of interest. The installer must be able to independently diagnose the device.

CNC systems differ in structure and function. Despite this, the equipment test methodology assumes general actions. With this type of diagnostics, there are three stages that the operator must carry out:

checking the performance of the device;
adjustment of the unit;
compliance with operating rules.

Checking the CNC system is carried out using special test programs.When buying factory products, they are included with the device, and correspond to its type. If microprocessor-based CNCs are used, test programs are partially stored in the machine's memory. The instructions that follow in the kit to the machine also indicate the frequency with which diagnostics should be carried out.The test program is used regardless of whether a fault has occurred or not.If a malfunction occurs, diagnostics are not carried out without it. The main symptom that indicates the need for diagnostics is incorrect processing of workpieces. Even minor errors can indicate a failure. The test program is designed in such a way that after testing the equipment returns to its original state. The machines execute technological commands in which information is recorded.After the end of the procedure, the data is provided to the operator. It compares them with the standard values and determines which ones are out of order. The most common errors that indicate a problem are related to spindle speed and tool change. A set of actions to identify malfunctions in the operation of the unit is carried out in three options:The use of the test program corresponds to the first types of actions. This step is the easiest. Using it, there is no need to disassemble the equipment. It is enough to start the program. Diagnostics with the presence of a stand is almost the same. Instead of a machine, a plotter is used. If the machine and the stand are not available, the installer will have to use the indication organs.After troubleshooting, methods of elimination are applied. During the inspection and accuracy check, data is determined that indicate which item should be configured. Regardless of this, adjustment and lubrication of parts that are subject to stress are carried out. Lubrication is carried out using a special oil. Adjustments and repairs involve:

restoration of straightness of table movement;

reduction of sled intervals;

reduction of table spacing.

The tensioning force of belts, transmission chains, and the clamping force of fasteners is monitored. Regardless of the quality of the machine, after a certain period of use, malfunctions on the machine will begin to occur.

Diagnostics is a set of certain methods for determining the quality of the technical state of a device, unit, assembly and mating parts without any disassembly. Therefore, diagnosing the technical condition of production equipment consists in a special logical processing of some existing information that comes from a working CNC machine in a given period of time. This incoming information directly or indirectly characterizes the state of the equipment at the present time. The reliability and high accuracy of the work of CNC machines depends on the system of their maintenance, high-quality and timely performance of repair and commissioning work. It is important.

The change in the technical state of the machine over the entire period of its operation is, in principle, a random process that has a probable nature. The very fact of the transition of equipment from a state of good operation to a state of faulty operation always characterizes the beginning of a malfunction and is a conditional failure. If the cutting machine is in a faulty condition, then to avoid the actual failure, it is necessary to urgently carry out repair or adjustment work.

To identify the relationship between the technical condition and the error of the finished part, as well as to select a diagnostic method on this basis, it is necessary to develop special control charts for specific CNC machines of different technological groups.

The need for maintenance and repair is categorically not determined by any period of equipment operation. Several different states correspond to each time period. It follows from this that any diagnostics of software equipment always poses a specific task to remove uncertainty and choose from a set of states the only one in which the machine is currently located.

CNC machines are quite complex, which causes certain difficulties in diagnosing and repairing them. Usually, you have to spend a lot of time troubleshooting. Therefore, it is necessary to use diagnostic systems, complex measuring equipment.In addition, you need service personnel who are able to solve any problems. If there is a problem with a lack of specialists, then you can conclude a contract for the maintenance of equipment with a company that is engaged in this work.

Diagnostics of software hardware should include in its process:

study of machines to be diagnosed, possible malfunctions and their symptoms
creating a model of a working machine and troubleshooting
creation of a diagnostic algorithm
selection of devices that will ensure the implementation of the algorithm

Diagnosing is a complex process. This work is carried out only by real specialists.

In the process of intensive operation of metalworking equipment, individual mechanisms and assemblies wear out. This is due to the rather large mechanical loads on the load-bearing elements of the power units, as well as the failure of individual units of electromechanical equipment and electronic modules. The mechanical wear and tear of most of the power equipment of a CNC machine requires overhaul with a complete replacement of components and assemblies. The normal operation of mechanisms is ensured by carrying out such types of work as spindle repair, on which the accuracy of processing of parts depends.

In practice, when using CNC machines, you can achieve high speed and accuracy of commands that come from the CNC. If timely produced repair of CNC machines, then such accuracy in the given parameters can be maintained for a long period of operation. Features of the design of CNC machines allow you to obtain the following technological advantages:

the use of several types of processing;
automatic feeding mode for workpieces;
the presence of a remote control mode;
the ability to connect to a general automatic control system.

Modern CNC machines are complex self-driving working machines organically related to computer technology. Therefore, the repair of CNC machine tools requires professionalism and knowledge of electronics. Depending on the technological characteristics and purpose, CNC machines are divided into three categories - contour, positional and combined type.

Ensuring normal technological modes is possible only with systematic maintenance of metalworking equipment with a CNC system. Regular diagnostics will allow you to timely identify the malfunctions that have arisen and prevent larger breakdowns of mechanisms and electronic modules. If necessary, repair the failed unit. For instance, spindle repair often involves a complete bushing and bearing replacement. Such types of work require high qualifications and practical skills from the foremen.

A high degree of processing accuracy is achieved by sufficient rigidity of the machine, the use of short kinematic units, as well as the use of independent drives with a minimum number of gears. Sufficiently high accuracy when processing parts ensures that there are no gaps that may appear in the mechanisms for transmitting motion. Reducing mechanical friction, which occurs in functional units, also reduces the indicators of dimensional error in the workpieces.

Knowing that a CNC milling machine 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: it is possible to make such equipment on your own, but for this you need to have not only its detailed drawing, but also a set of necessary tools and appropriate components.

Processing of duralumin blanks on a homemade desktop milling machine

When deciding to make a homemade CNC milling 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 correctly approaching the solution of all issues, you can become the owner of an affordable, efficient and productive equipment that allows you to process workpieces from various materials with a high degree of accuracy.

To make a milling machine equipped with a CNC system, you can use two options: buy a ready-made set, from specially selected elements of which such equipment is assembled, or find all the components and assemble a device with your own hands that fully meets all your requirements.

Below in the photo you can see a self-made CNC milling machine, which is accompanied by detailed instructions for manufacturing and assembly indicating the materials and components used, exact "patterns" of machine parts and approximate costs. The only drawback is the instruction in English, but it is quite possible to understand the detailed drawings without knowing the language.Free download instructions for the manufacture of the machine: Homemade CNC milling machine The CNC router is assembled and ready to go. Below are some illustrations from the assembly instructions for this machine.If you decide that you will design a CNC machine with your own hands, without using a ready-made set, then the first thing you will need to do is to choose a schematic diagram according to which such mini-equipment will work.Diagram of a CNC milling machineAs a basis for CNC milling equipment, you can take an old drilling machine, in which the working head with a drill is replaced by a milling one. The most difficult thing that will have to be designed in such equipment is the mechanism that ensures the movement of the tool in three independent planes. This mechanism can be assembled on the basis of carriages from an inoperative printer, it will provide movement of the tool in two planes.It is easy to connect software control to a device assembled according to such a schematic diagram. However, its main disadvantage is that only workpieces made of plastic, wood and thin sheet metal can be processed on such a CNC machine. This is explained by the fact that the carriages from the old printer, which will ensure the movement of the cutting tool, do not have a sufficient degree of rigidity.Lightweight version of the CNC milling machine for working with soft materialsIn 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 motor; it can be made from a conventional electric motor, subjecting the latter to a slight modification.The use of a stepper motor in your milling machine will make it possible to avoid the use of a screw transmission, and the functionality and characteristics of homemade equipment will not deteriorate from this. If you nevertheless decide to use carriages from the printer for your mini-machine, then it is advisable to pick them up from a larger-sized model of the printing device. To transfer force to the shaft of the milling equipment, it is better to use not ordinary belts, but toothed belts that will not slip on the pulleys.One of the most important components of any such machine is the router mechanism. It is his manufacture that needs to be given special attention. To correctly make such a mechanism, you will need detailed drawings, which will need to be strictly followed.The basis of homemade CNC milling equipment can be a rectangular beam, which must be securely fixed on the guides.The supporting structure of the machine must have high rigidity; during its installation it is better not to use welded joints, and all the elements need to be connected only with screws.Fastening unit of machine frame parts by means of a bolted connectionThis requirement is explained by the fact that the welded seams are very poorly tolerant of vibration loads, to which the supporting structure of the equipment will necessarily be subjected. Such loads will eventually lead to the fact that the machine frame will begin to collapse over time, and changes in geometric dimensions will occur in it, which will affect the accuracy of the equipment setup and its performance.

Welding seams during the installation of the frame of a home-made milling machine often provoke the development of backlash in its nodes, as well as deflection of the guides, which is formed under severe loads.Installation of uprightsIn the milling machine, which you will assemble with your own hands, a mechanism must be provided that ensures the movement of the working tool in the vertical direction. It is best to use a helical gear for this, the rotation to which will be transmitted using a toothed belt.An important part of the milling machine is its vertical axis, which can be made from an aluminum plate for a homemade device. It is very important that the dimensions of this axis are precisely matched to the dimensions of the assembled device. 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.Upper Carriage Assembly Placed on Cross RailsAfter all the components of your homemade milling machine are prepared, you can start assembling it. This process begins with the installation of two stepper motors, which are attached to the equipment body behind its vertical axis. One of these electric motors will be responsible for moving the milling head in the horizontal plane, and the second for moving the head, respectively, in the vertical plane. After that, the rest of the components and assemblies of homemade equipment are mounted.The final stage of assembly of the machineRotation to all nodes of homemade CNC equipment should be transmitted only through belt drives. Before connecting the programmed control system to the assembled machine, you should check its operability in manual mode and immediately eliminate all identified deficiencies in its operation.You can watch the process of assembling a milling machine with your own hands in the video, which is easy to find on the Internet.