Automatic drilling machine with illumination scheme. Electrical equipment for drilling and boring machines. Automatic engine speed control system depending on the load
Good evening everyone. I had a problem with drilling holes in printed circuit boards oh, then I did it with an electric drill, then a screwdriver or an electric motor with a collet clamp. Of course, it is inconvenient, cumbersome. In general, I decided to do something about it. The choice immediately fell on the speed control using PWM. The first thing that immediately came to mind was the classic NE555, which just had a couple of microcircuits in a DIP package in the bins. There are many schemes on the Internet, looking for long time, stopped at this scheme, slightly altering it for himself naturally.
I made a transformer with a rectifier on a separate board, the transformer is connected to the network through a fuse for a current of 2A, a transformer for 19V, 1 A. I had an IRLZ44 key, and applied it.
By the way, the printed circuit board with the regulator itself turned out to be quite compact. Of course, if you use planar parts, you can significantly reduce the device. But I repeat - I did from what was. Here is the circuit board itself:
The device on the NE555 chip made it possible to implement a pulse-width modulated power regulator, which is used in conjunction with devices powered by direct current. Possesses high efficiency, high load capacity and a wide range of supply voltages. Can be used to control the speed of rotation of DC collector motors, power heating appliances, incandescent lamps, with a maximum current depending on the power source and the output key.
Specifications
The device and operation of the electronic circuit:
The device is assembled on an integral timer, switched on in the pulse generator mode with a constant frequency and a powerful MIS transistor operating in the key mode. The duty cycle and the length of the pulses are changed by the position of the variable resistor slider, this allows you to adjust the PWM duty cycle, and therefore the average power in the load.
The supply voltage of the device must not exceed 27V DC. A MIS transistor operating in the key mode is used as a regulating element. Since in the open state the resistance of the drain-source junction has a very low resistance, a small amount of heat is released on the transistor, even when switching currents of 10A. But just in case, I installed a 50cm2 radiator. I mounted the design into the case from the nearest radio market:
On the front panel there is a potentiometer with a knob for adjusting the speed, a power indicator, a power toggle switch, a fuse holder in which a 2A fuse is installed, which protects the regulator output from overload or short circuit. Terminal block- for the load and separately a constant voltage of 20 V from the rectifier, you never know, suddenly come in handy.
Now the most important thing, the electric motor ... I dismantled my mother's old Soviet hair dryer (thank you mom for the hair dryer =)), removed the electric motor from there, bought a set of brass collet clamps and tried to drill.
When making homemade printed circuit boards, such thin holes are not really needed, but typical drills with a diameter of 0.5 to 0.7 mm are also quite fragile and this technological device can significantly extend their service life.
The basis of the design of this machine is asynchronous motor alternating current type ADP-1262. The rotor of this engine is a hollow aluminum cup with a wall thickness of approximately 0.5 mm. The ADP-1262 stator occupies the rest free space. It has a narrow cylindrical slot in which the rotor rotates with a very small gap. It is clear that the weight of such a rotor is negligible, so its inertial properties can be neglected as a first approximation, especially considering the weight of the chuck. Among other things, the engine has a very soft characteristic. With a decrease in engine speed, the torque on the shaft also decreases. All this guarantees long term service by any thin drills in the event of jamming and exceeding the permissible maximum torque at the cutting edge.
As a drill holder, I took a fairly widespread three-jaw chuck type 6V10, which allows you to clamp drills with a diameter of up to 6mm.
The bed is made of two main parts. Stand position 1 and rack mechanism position 2 were taken from an MBS-1 optical microscope. The base of position three is cut from steel sheet 1 centimeter thick.
The motor is fastened with a clamp, which is fixed to the feeder with 4 screws. They are shown with red arrows in the figure above. Holes are made at the vertices of the square, so the engine can be placed not only vertically, but also horizontally.
The chuck is fastened with a shaped sleeve, with outer side which cone No. 1 is machined, and inside a hole is made for a transitional fit equal to the diameter of the motor shaft about 6 mm. The bushing is made on lathe in one sitting. That is, during the turning of the cone and hole (not drilling), the workpiece was fixed in the machine and only then cut off.
For excellent fixation and the selection of quite probable misalignment, the sleeve has six threaded holes M3 for locking screws. There are 6 recesses in the motor shaft, into which these locking screws fit. The holes are made in a checkerboard pattern, which makes it possible to select misalignment, even if it appears as a result of wear of the mating surfaces. The screws are secured with locking paint or threadlocker.
On the upper projection of the motor shaft there is a fixed flange with a small slot, which, together with the bar on the motor housing, is nothing more than a classic locking mechanism. It allows you to manually tighten the cartridge without using a key. The use of a wrench asymmetries the clamping mechanism and leads to strong and uneven wear, which is the main cause of drill runout. When using thin drills, this causes a noticeable eccentricity of the working part of the drill.
For more than a year now I have been the proud owner of a Prusa i4 3D printer. To be honest, today I have no idea how I used to cope without it. By the way, this is a gift from my beloved wife!
But let's leave the lyrics. Today I present to your attention my version of a drilling machine for printed circuit boards. All radio amateurs are well aware that drilling a board, holding a motor with a cartridge in hand, is at least troublesome. Hard drills are not suitable here because of their fragility. Slightly warped and drill in half. BUT conventional drills dull quickly. And even the inlet is not even, but the outlet is torn. If the tracks on the board are thin, this is completely unacceptable. Get rid of these problems drilling machine.
There are many on the Internet finished projects. But they all seemed to me (may their authors forgive me) primitive toys. One of the worthy candidates for repetition I found here: https://www.youtube.com/watch?v=xlxfG9IEH7Y&t=34s.
However, the aesthetics scratched. After all, anything can be printed on a printer. So why not make it pretty? I sat down tightly with Solid Works, and then for printing. Mistakes corrected along the way. And so this is the third option:
I have designed several housing options for various engines. I must say right away that not all engines that are sold on AllExpress are suitable here. This one won't work for example:
But this is what is needed. Engine - 775. Reliable axle. front bearing. No beats. Power.
Need to check with the seller whether the bearing is installed? Engines go to different versions, including bushings.
The top and bottom covers are easily screwed onto the bearing bracket and securely fix the motor inside.
The movable part of the axle bracket is assembled on two longitudinal bearings, which provide ease of sliding along the axes and are covered from above and below with decorative overlays:
By the way, the rods also have small bearings.
The stand is aluminum. In the new next version, the frame was made of plexiglass. Looks better in my opinion. cut on laser machine. ABS plastic. Printed with a layer of 0.1mm. After printing, all parts are treated with zero and tetrahydrofuran.
Well, this is the machine at work:
https://drive.google.com/file/d/1eVnMHNLl5y7OgC58LfgzOF5cP6kgi_jb/view?usp=sharing
The project continues to live. In the next modification, I want to abandon the lever. I will replace it with a stepper motor and a wireless pedal to control the machine. Happy Holidays to all guys!
Tired, in general, of drilling boards with a manual drill, so it was decided to make a small drilling machine exclusively for printed circuit boards. There are plenty of designs on the Internet, for every taste. After looking at several descriptions of such drills, I came to the decision to repeat the drilling machine based on elements from an unnecessary, old CD ROM. Of course, for the manufacture of this drilling machine, you will have to use the materials that are at hand.
From the old CD ROM, for the manufacture of a drilling machine, we take only a steel frame with two guides mounted on it and a carriage that moves along the guides. In the photo below, all this is clearly visible.
The drill motor will be mounted on the movable carriage. To mount the electric motor to the carriage, an L-shaped bracket was made from a strip of steel 2 mm thick.
We drill holes in the bracket for the motor shaft and the screws for its fastening.
In the first variant, an electric motor of the DP25-1.6-3-27 type with a supply voltage of 27 V and a power of 1.6 W was chosen for the drilling machine. Here he is in the photo:
As practice has shown, this engine is rather weak to perform drilling work. Its power (1.6 W) is not enough - at the slightest load, the engine simply stops.
This is what the first version of the drill with the DP25-1.6-3-27 engine looked like at the manufacturing stage:
Therefore, I had to look for another electric motor, more powerful. And the manufacture of the drill has stalled ...
Continuation of the manufacturing process of the drilling machine.
After some time, the electric motor fell into the hands of a disassembled faulty inkjet printer Canon:
There is no marking on the engine, so its power is unknown. A steel gear is mounted on the motor shaft. The shaft of this motor has a diameter of 2.3 mm. After removing the gear, a collet chuck was put on the motor shaft and several test drillings were made with a drill with a diameter of 1 mm. The result was encouraging - the "printer" engine was clearly more powerful than the engine DP25-1.6-3-27 and freely drilled textolite 3 mm thick at a supply voltage of 12 V.
Therefore, the manufacture of the drilling machine was continued ...
We fix the electric motor with the L-shaped bracket to the movable carriage:
The base of the drilling machine is made of fiberglass 10mm thick.
In the photo - blanks for the base of the machine:
To prevent the drilling machine from fidgeting on the table during drilling, rubber feet are installed on the underside:
The design of the drilling machine is of a cantilever type, that is, the supporting frame with the engine is fixed on two cantilever brackets, at some distance from the base. This is done in order to ensure that sufficiently large printed circuit boards are drilled. The design is clear from the sketch:
The working area of the machine, the white LED backlight is visible:
Here is how the backlight is implemented working area. The photo shows excessive brightness of the lighting. In fact, this is a false impression (this is a camera glare) - in reality everything looks very good:
Cantilever design allows drilling boards with a width of at least 130 mm and an unlimited (within reasonable limits) length.
Measurement of the dimensions of the working area:
The photo shows that the distance from the stop at the base of the drilling machine to the axis of the drill is 68mm, which ensures the width of the processed printed circuit boards is at least 130mm.
To feed the drill down when drilling, there is a pressure lever - visible in the photo:
To hold the drill over printed circuit board before the drilling process, and returning it to its original position after drilling, serves return spring, which is put on one of the guides:
The system of automatic adjustment of engine speed depending on the load.
For ease of use drilling machine Two variants of engine speed controllers were assembled and tested. In the original version of the drill with the DP25-1.6-3-27 electric motor, the regulator was assembled according to the scheme from the Radio magazine No. 7 for 2010:
This regulator did not want to work as expected, so it was mercilessly thrown into the trash.
For the second version of the drilling machine, based on an electric motor from a Canon inkjet printer, on ham radio cat website another circuit of the motor shaft speed controller was found: 
This regulator provides the operation of the electric motor in two modes:
- When there is no load, or, in other words, when the drill does not touch the printed circuit board, the motor shaft rotates at a reduced speed (100-200 rpm).
- With an increase in the load on the engine, the regulator increases the speed to the maximum, thereby ensuring the normal drilling process.
The motor speed controller assembled according to this scheme worked immediately without tuning. In my case, the idle speed was about 200 rpm. At the moment the drill touches the printed circuit board, the revolutions increase to the maximum. After drilling is completed, this regulator reduces the engine speed to the minimum.
The motor speed controller was assembled on a small printed circuit board:
The KT815V transistor is equipped with a small radiator.
The regulator board is installed at the rear of the drilling machine:
Here, the resistor R3 with a nominal value of 3.9 ohms was replaced by an MLT-2 with a nominal value of 5.6 ohms.
The testing of the drilling machine was successful. The system of automatic adjustment of the frequency of rotation of the motor shaft works clearly and without fail.
A short video about the work of the drilling machine.
PCB drilling machine belongs to the category of mini equipment special purpose. If desired, such a machine can be made with your own hands, using available components for this. Any specialist will confirm that it is difficult to do without the use of such an apparatus in the production of electrical products, the circuit elements of which are mounted on special printed circuit boards.
General information about drilling machines
Any drilling machine is necessary in order to be able to efficiently and accurately machine parts made from various materials. Where high precision machining is required (and this also applies to the process of drilling holes), from technological process manual labor should be avoided as much as possible. Similar tasks can be solved by anyone, including home-made ones. Practically indispensable without machine equipment during processing hard materials, for drilling holes in which the efforts of the operator himself may not be enough.
The design of a bench drill with a belt drive (click to enlarge)
Any drilling machine is a structure assembled from many constituent parts, which are securely and accurately fixed relative to each other on load-bearing element. Some of these nodes are attached to load-bearing structure rigidly, and some can move and be fixed in one or more spatial positions.
The basic functions of any drilling machine, due to which the processing process is ensured, is the rotation and movement in the vertical direction of the cutting tool - the drill. On many modern models of such machines, the working head with cutting tool can also move in a horizontal plane, which allows using this equipment for drilling several holes without moving the part. In addition, automation systems are being actively introduced into modern drilling machines, which significantly increases their productivity and improves processing accuracy.
Below, for example, several design options for boards are presented. Any of these schemes can serve as a model for your machine.
Features of equipment for drilling holes in printed circuit boards
The PCB drilling machine is one kind of drilling equipment, which, given the very small size parts processed on it, belongs to the category of mini-devices.
Any radio amateur knows that the printed circuit board is the base on which the constituent elements electronic or electrical circuit. Such boards are made from sheet dielectric materials, and their dimensions directly depend on how many circuit elements need to be placed on them. Any printed circuit board, regardless of its size, simultaneously solves two problems: accurate and reliable positioning of circuit elements relative to each other and ensuring the passage of electrical signals between such elements.
Depending on the purpose and characteristics of the device for which the printed circuit board is created, it can accommodate both small and great amount schema elements. To fix each of them in the board, it is necessary to drill holes. The accuracy of the location of such holes relative to each other is very high requirements, since it depends on this factor whether the elements of the circuit will be located correctly and whether it will be able to work at all after assembly.
The complexity of processing printed circuit boards also lies in the fact that the main part of modern electronic components is miniature in size, therefore, the holes for their placement must also have a small diameter. To form such holes, a miniature tool (in some cases even micro) is used. It is clear that working with such a tool using conventional drill, does not seem possible.
All of the above factors led to the creation of special machines for forming holes in printed circuit boards. These devices have a simple design, but they can significantly increase the productivity of such a process, as well as achieve high processing accuracy. Using a mini-drilling machine, which is easy to make with your own hands, you can quickly and accurately drill holes in printed circuit boards designed to complete various electronic and electrical products.
How does a machine for drilling holes in printed circuit boards
The machine for forming holes in printed circuit boards differs from classical drilling equipment in its miniature size and some features of its design. The dimensions of such machines (including home-made ones, if the components are correctly selected for their manufacture and their design is optimized) rarely exceed 30 cm. Naturally, their weight is insignificant - up to 5 kg.
If you are going to make a mini-drilling machine with your own hands, you need to pick up components such as:
- bearing frame;
- stabilizing frame;
- a bar that will ensure the movement of the working head;
- shock-absorbing device;
- handle to control the movement of the working head;
- device for fastening the electric motor;
- the electric motor itself;
- power unit;
- collet and adapters.
Drawings of machine parts (click to enlarge)
Let's figure out what all these nodes are for and how to assemble a home-made mini-machine from them.
Structural elements of a drilling mini-machine
Self-assembled mini-drilling machines can be seriously different from each other: it all depends on what components and materials were used to make them. However, both factory and homemade models of such equipment work on the same principle and are designed to perform similar functions.
The supporting element of the structure is the base frame, which also ensures the stability of the equipment during the drilling process. Based on the purpose of this structural element, it is desirable to make a bed from metal frame, the weight of which should significantly exceed the total mass of all other components of the equipment. If you neglect this requirement, you will not be able to ensure the stability of your homemade machine, which means that you will not achieve the required drilling accuracy.
The role of the element on which the drilling head is attached is performed by a transitional stabilizing frame. It is best made from metal rail or corners.
The bar and shock-absorbing device are designed to ensure vertical movement of the drilling head and its springing. As such a bar (it is better to fix it with a shock absorber), you can use any design (it is only important that it performs the functions assigned to it). In this case, a powerful hydraulic shock absorber may come in handy. If you don’t have such a shock absorber, you can make the bar yourself or use spring structures taken from old office furniture.
The vertical movement of the drilling head is controlled using a special handle, one end of which is connected to the body of the mini-drilling machine, its shock absorber or stabilizing frame.
The engine mount is mounted on a stabilizing frame. The design of such a device, which can be wooden block, clamp, etc., will depend on the configuration and design features other components of the drilling machine for printed circuit boards. The use of such a mount is due not only to the need for its reliable fixation, but also to the fact that you must bring the motor shaft to the required distance from the travel bar.
The choice of an electric motor that can be equipped with a do-it-yourself mini-drilling machine should not cause any problems. As such a drive unit, you can use electric motors from a compact drill, cassette recorder, computer drive, printer, and other devices that you no longer use.
Depending on which electric motor you found, clamping mechanisms for fixing drills are selected. The most convenient and versatile of these mechanisms are cartridges from a compact drill. If a suitable cartridge could not be found, a collet mechanism can also be used. Be sure to size the clamping device so that very small drills (or even micro-sized drills) can be clamped in it. To connect the clamping device to the motor shaft, it is necessary to use adapters, the dimensions and design of which will be determined by the type of the selected motor.
Depending on which electric motor you installed on your mini drilling machine, you need to choose a power supply. With this choice, attention should be paid to ensure that the characteristics of the power supply fully correspond to the voltage and current parameters for which the electric motor is designed.
