The universal machine for conducting DIY tests, Part 1
In continuation of the topics ( first , second ) about testing machines, I want to assemble a budget version of a console-type machine for a small load (20 kg), for testing various materials ...
After writing the previous two articles on this topic, I was asked questions related to modernization and development. This prompted me to write an article. It will consist of two parts - in this I will talk about the mechanical part, and the second will be devoted to electronics, software and processing of the received data.
I decided to take the kinematic scheme as a console type, since it is easier to implement and smaller in size (compared to a two-column machine) with the same characteristics to be laid in, but it is structurally slightly weaker.
I laid the following main characteristics for my car: maximum load capacity of 20 kg or 200 N, and maximum working stroke of 600 mm.
Having started designing, he decided on the basic materials for the manufacture of machine parts. I decided to buy cylindrical guides of 20 diameters and carriages for them without reinventing the wheel. As a moving mechanism, he took a construction pin and a nut with M20 thread in 2.5 mm increments. The connecting plates of the power frame, including the base of the machine, it was decided to make of plywood with a thickness of 20 mm.
A small digression for those who started laughing: this project is planned to be quite budgetary, and is needed to develop a scheme for using the selected electronics and develop a program for managing and processing data on a personal computer.
The use of a screw in the design of the trapezoidal screw or ball screw, as well as in the place of plywood - duralumin or steel, will significantly increase the cost of the machine, but I still do not sell it, but to repeat this project, those who need such a power measuring unit. Who, which kinematic scheme will be used, and from which components is the personal matter of everyone.
I distributed the project in Compass, only the main details, with the manufacturing technology of which I immediately decided. In view of the fact that I have a CNC milling machine, I decided to process almost all the components of the machine made of plywood on it.
I laid out all the flat parts in two-dimensional projection, saved them in a vector format (* .dxf). Through the postprocessor in the CAM program, I transferred the drawings to the G-code. The machine cut out all the details in one installation of the workpiece, since the dimensions of its working field allow. Having processed the corners with sandpaper, all the mating parts came very well together.
Guides and studs were machined on a lathe. As we did not try to make a hairpin without a beating, it still remained crooked.
After preliminary assembly of the power frame, it became clear that it was necessary to strengthen the fastening of the cylindrical guides to the upper and lower plates. For this, additional supports were required, but buying them is unprofitable, but to make them of plastic on a 3D printer is the very thing.
I picked up the supports according to the catalog for the diameter of my guides, according to the available sizes I drew them in 3D, all in the same Compass.
A friend gave a 3D printer for temporary use, in a couple of days I managed to print all the supports and a few additional details. The printed supports stood very tight, and this gave the whole structure good rigidity.
On the machined ends of the studs, on landing I put on ball radial bearings. At the bottom of the bearings between the bottom plate pulled a nut. In the right way, it is necessary to use thrust bearings or tapered.
As a power plant, I decided to use a gear motor from the power windows of a VAZ 2110 car, it creates good torque. He suggested that it was enough to scroll a hairpin loaded with twenty kilograms.
The output shaft of the motor - gearbox of square section 7x7 mm., To connect it with the tail of the stud, the coupling had to be printed.
As for the engine operation with respect to the testing machine, for the correct test, the load speed should practically not change. In modern propulsion systems, this is implemented in electronic control drives. In my case, so that during the load the speed of the movable plate does not decrease, the engine must have such power so as not to notice the increasing load on it, or realize this programmatically, raising the power. But in this case, feedback is required to control the speed.
To measure the distance of movement of the movable plate, I decided to set the encoder at 24 pulses per revolution, this will allow us to measure the distance with an accuracy of 0.1 mm, this is more than enough, given that there is a backlash in the stud / nut joint. I hope that the encoder will help me in measuring the real speed of movement. The sensor decided to put aside by printing two gears with a gear ratio of one to one, as well as a bracket for mounting it to the end of the base plate of the motor - reducer. After printing, the gears turned out a little eight, but this is not scary, the main thing is that there is a gear between them.
The car turned out with two working areas, lower and upper. The 20 kg force sensor, like the assembled machine, is of the cantilever type, I installed it in the lower part so that the wires do not interfere if mounted on a moving or upper plate.
The first part on this came to an end, enjoy reading, friends!
PS: Please indicate any errors in a personal message.
After writing the previous two articles on this topic, I was asked questions related to modernization and development. This prompted me to write an article. It will consist of two parts - in this I will talk about the mechanical part, and the second will be devoted to electronics, software and processing of the received data.
I decided to take the kinematic scheme as a console type, since it is easier to implement and smaller in size (compared to a two-column machine) with the same characteristics to be laid in, but it is structurally slightly weaker.
I laid the following main characteristics for my car: maximum load capacity of 20 kg or 200 N, and maximum working stroke of 600 mm.
Having started designing, he decided on the basic materials for the manufacture of machine parts. I decided to buy cylindrical guides of 20 diameters and carriages for them without reinventing the wheel. As a moving mechanism, he took a construction pin and a nut with M20 thread in 2.5 mm increments. The connecting plates of the power frame, including the base of the machine, it was decided to make of plywood with a thickness of 20 mm.
A small digression for those who started laughing: this project is planned to be quite budgetary, and is needed to develop a scheme for using the selected electronics and develop a program for managing and processing data on a personal computer.
The use of a screw in the design of the trapezoidal screw or ball screw, as well as in the place of plywood - duralumin or steel, will significantly increase the cost of the machine, but I still do not sell it, but to repeat this project, those who need such a power measuring unit. Who, which kinematic scheme will be used, and from which components is the personal matter of everyone.
I distributed the project in Compass, only the main details, with the manufacturing technology of which I immediately decided. In view of the fact that I have a CNC milling machine, I decided to process almost all the components of the machine made of plywood on it.
I laid out all the flat parts in two-dimensional projection, saved them in a vector format (* .dxf). Through the postprocessor in the CAM program, I transferred the drawings to the G-code. The machine cut out all the details in one installation of the workpiece, since the dimensions of its working field allow. Having processed the corners with sandpaper, all the mating parts came very well together.
Guides and studs were machined on a lathe. As we did not try to make a hairpin without a beating, it still remained crooked.
After preliminary assembly of the power frame, it became clear that it was necessary to strengthen the fastening of the cylindrical guides to the upper and lower plates. For this, additional supports were required, but buying them is unprofitable, but to make them of plastic on a 3D printer is the very thing.
I picked up the supports according to the catalog for the diameter of my guides, according to the available sizes I drew them in 3D, all in the same Compass.
A friend gave a 3D printer for temporary use, in a couple of days I managed to print all the supports and a few additional details. The printed supports stood very tight, and this gave the whole structure good rigidity.
On the machined ends of the studs, on landing I put on ball radial bearings. At the bottom of the bearings between the bottom plate pulled a nut. In the right way, it is necessary to use thrust bearings or tapered.
As a power plant, I decided to use a gear motor from the power windows of a VAZ 2110 car, it creates good torque. He suggested that it was enough to scroll a hairpin loaded with twenty kilograms.
The output shaft of the motor - gearbox of square section 7x7 mm., To connect it with the tail of the stud, the coupling had to be printed.
As for the engine operation with respect to the testing machine, for the correct test, the load speed should practically not change. In modern propulsion systems, this is implemented in electronic control drives. In my case, so that during the load the speed of the movable plate does not decrease, the engine must have such power so as not to notice the increasing load on it, or realize this programmatically, raising the power. But in this case, feedback is required to control the speed.
To measure the distance of movement of the movable plate, I decided to set the encoder at 24 pulses per revolution, this will allow us to measure the distance with an accuracy of 0.1 mm, this is more than enough, given that there is a backlash in the stud / nut joint. I hope that the encoder will help me in measuring the real speed of movement. The sensor decided to put aside by printing two gears with a gear ratio of one to one, as well as a bracket for mounting it to the end of the base plate of the motor - reducer. After printing, the gears turned out a little eight, but this is not scary, the main thing is that there is a gear between them.
The car turned out with two working areas, lower and upper. The 20 kg force sensor, like the assembled machine, is of the cantilever type, I installed it in the lower part so that the wires do not interfere if mounted on a moving or upper plate.
The first part on this came to an end, enjoy reading, friends!
PS: Please indicate any errors in a personal message.