Since 2000
ELECTRONICS by Millwood
Determining which electronics will control a numerically controlled cutter is not an easy one decision. The electronics (also called driver), is used to make different parts of a NC cutter work: the mechanics with its stepper motors, the computer with which it is connected via the parallel port or the USB port and the management program cutter (see Mach3, LinuxCNC, TurboCNC, etc etc). There are many types of electronics suitable for the control of a cutter for hobby use, such as my MillWood, on the web you can find hundreds of diagrams and also many offers for drivers in kits or even already assembled. For kits to mount or ready-made drivers, I do not give you any links to avoid being biased and not to hurt anyone. If the mechanics of the cutter are similar to my MillWood, a 2-2.5 Amp / phase bipolar driver is already more than enough. These are drivers based mainly on the TB6560 ICs, or on the A3977 but also on the old ma always valid L297 / 298.
One thing that is often underestimated is the choice of stepper motors, I often see people using 4Amp / phase electronics combined with mediocre motors recovered from who knows what printers or disused equipment.
For the stepper motor it is essential that it is of good quality and with good performance.
Finding a catalog motor that is 3-4 Amp / phase and has a high torque may not be enough to save you from surprises.
The datasheet of the motors must be able to interpret it, often the characteristics shown refer to tests carried out with the maximum currents and above all with the maximum working voltages (70 Volts), values that we will hardly reach with our drivers.
Even the working torque could be maximum, however, at low rotation values, with a significant decrease at higher speeds.
It is true that motors with six wires can work in a bipolar way excluding the central wire, but the characteristics of this motor will not be great.
For my cutters I rely only on the practical test of the motor, evaluating its performance directly by combining it with the electronic driver, I have tried dozens of types of motors and at times I have had to discard them because they are not adequate.
But let's go back to the choice of the driver.
Do we get it with parallel port or USB port output?
It is true, by now the parallel port is disappearing from the computer, but it is also true that we can easily find an old computer used for a few euros, with the parallel port, and combine it with the management of the cutter, I assure you that it will cost you less than l '' purchase of a controller for USB port, however at the following link you will find some of my considerations.
Programs like Mach3 (on Windows XP operating system, 7,8,10 32-bit), or LinuxCNC (on Ubuntu operating system), are excellent programs more than adequate for hobby and perhaps even professional cnc cutters.
Don't look for electronic drivers with stratospheric features, mind-blowing functions, and consequently, high prices.
I have used different types of drivers, from the simplest to the most complex, but I assure you that for a hobby-type cutter, high or professional functionality is not required.
It would be like mounting a Ferrari engine on a Fiat 600: you would never exploit its power.
Duty note on electronics of Chinese origin
By now 95% of the electronics available on the web, and very often resold on Italian sites in the sector, are Chinese-made. They are electronic devices that I have personally tried, noting that they present various kinds of problems, if you go to the various Italian forums, but also American ones, you will find confirmation of this. In most cases, these are problems of loss of steps during processing, sometimes they have problems with overheating in the 12-5 Volt voltage regulators or the electrolytics of the motors current jump (read at what maximum voltage they can work before apply the power supply voltage). In the case of the loss of steps, I had to bypass or change the signal inputs, in one case I literally replaced the amps, because the mounted ones were of poor quality; for the overheating of the power part, I opted for an external power supply. If you search the web for a specific solution for a card, you will find dozens of possible solutions, one different from the other and often not solving the problem, it is a situation that I found myself with a type of card. In the end I understood why a certain solution was not found: the board seems to be always the same, but in reality it is different, that is, it mounts different components (capacitors for the frequency, optocouplers for the signals and quality of the power amplifiers), probably the printout is the same, but it is then assembled in different areas of China and by "more or less" competent producers, moral: you may have the card that works well (... rare), or with an undefined problem, that's why a same card you will find who is comfortable, who has applied a modification to the frequency capacitor, who has removed the optolysulator, who has added a signal inversion card and who, by dint of doing tests, has burned all the amps and now he is desperate and confused. The Chinese cards that I use are all modified, tested and checked to avoid problems of this kind.
Now let's see a small roundup of electronics that I used in my cutters:
I currently use electronics made up of three single drivers using the TB6600hq chip
The TB6600HG was released in 2012 by Toshiba and is the evolution of the TB6560
The main features are:
- Single power supply - there is a 5V regulator inside the chip
- Control via step-dir-enable pin
- 1/1 up to 1/16 step
- 5 Amp max current / phase (3.5 is a more credible value)
- Integrated thermal, low voltage and excess current control
- Current level selectable by means of trimmer (Vref)
- Monitor and alert pins
- Up to 200Khz clock
- Pulse duration of steps of only 2.2 us.
The electronics communicate with the computer via the parallel port, there is an output for 220V on the front panel of the metal box, this output is controlled by a relay and will be used for the automatic control of the power tool.
