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I am planning to build a CNC machine with 3 axis 21Kg-in stepper motor each.
Kindly suggests me if DRV8811 would server the purpose. Also kindly help how best I can build this machine
Hi Elamaran,
You are definitely undertaking one of the most appealing projects out there, so hopefully I'll be able to help you with your question. Some time ago I built a CNC router and am now building a CNC plasma cutter. For the CNC Plasma cutter I will use either the DRV8811, or the DRV8825 as they are more than plenty. However, for the project you are thinking of building, none of these devices will be strong enough. Here is an explanation why.
You are going to use a 21Kg-in motor. This is a weird torque unit, but I am going to assume it is accurate and take it down to oz-in, which is the typical you see steppers rated at. In this case, you are looking at roughly a stepper rated at 740 oz-in, which is quite a powerful motor. To get a better picture, I did a quick search and found that only NEMA 34 stepper sizes would offer such a strong torque parameter. Luckily I also found the current requirement for such a stepper which seems to be anywhere in between 5A to 7A.
Before we go on, what you need to understand is if you truly require this amount of torque. If you do, then the high current is pretty much set in stone and the driver must be selected accordingly. I would go with at least a 6A driver, 7A if possible.
None of our integrated drivers wil get you there. For example, the DRV8811, can only give you a 2.5A sine wave peak, although this is quite hard to reach without proper heat sinking. The DRV8825 has better RDSon so it will give you the 2.5A considerably easier, even with a 2 layer board. This is too far away for what you need.
In the event that you can use as little as 4A, the DRV8829 would be a possible solution. This is what I used for my CNC router and it was enough to carve wood. I never tried carving metals, so I am not certain of whether this will work or not. Chances are you want to stay with your 6-7A driver and be able to tackle all the materials that show up your way.
In that case, you can feel assured the DRV8412/32 should be able to tackle this application as these devices can do up to 12A per phase if the proper heat sinking is utilized. You will need a microcontroller or a DSP to drive the power stages, but all of this is carefully documented on the respective webpages. http://focus.ti.com/docs/prod/folders/print/drv8412.html
You can also download and install ControlSuite which has all the documentation on how to utilize these devices, including DSP code, schematic, etc.
To build a CNC machine you will need to do quite a lot of research, but luckily there is a humongous amount of material on the web. First place you should visit and become affiliated with is www.cnczone.com. The amount of information including pictures, videos, etc is quite overwhelming. It is a forum community so your questions are answered within days, if they have not been treated already. Do a search first, as chances are your question has already been answered before.
But if you want to get a quick primer on CNC, what you need to know is that there is PC computer running a control software. There are two popular versions: MACH3 and EMC. I prefer MACH3, but you have to pay for a license. EMC is Linux based, and it is free. This software is in charge of running the GCODE which is generated by your CAM (Computer Aided Manufacturing) software. What it does is generate a series of pulses on the STEP and DIR line on a per stepper basis. Since the three (or four) axis are synchronized, the machine moves in accordance with the piece that is to be built.
The computer is connected to an interface board which is often called a CNC Parallel Port Board. It accepts the parallel port 25 pin connector which is where the STEP DIR signals are generated. The signals are then distributed to the drivers which then apply power and respective control "information" to the stepper motors, which then move either the lead screws or the belts, which then move... Well, you know!
I know this is not all the information you would want in order to build your first CNC machine, but I think it should be enough to get you started.
BTW, on my CNC Plasma cutter I will use the DRV8825 because it gives 2.5A sine wave peak easily and because it has 32 degrees of microstepping which is excellent for any small sized CNC machine. In this case, I'll be moving a plasma cutter head which has zero resistance as cutting is performed. This is why 2.5A is way much more than actually needed.
Hope the info helps. Best regards,
Jose Quinones
Hi Elamaran,
You are definitely undertaking one of the most appealing projects out there, so hopefully I'll be able to help you with your question. Some time ago I built a CNC router and am now building a CNC plasma cutter. For the CNC Plasma cutter I will use either the DRV8811, or the DRV8825 as they are more than plenty. However, for the project you are thinking of building, none of these devices will be strong enough. Here is an explanation why.
You are going to use a 21Kg-in motor. This is a weird torque unit, but I am going to assume it is accurate and take it down to oz-in, which is the typical you see steppers rated at. In this case, you are looking at roughly a stepper rated at 740 oz-in, which is quite a powerful motor. To get a better picture, I did a quick search and found that only NEMA 34 stepper sizes would offer such a strong torque parameter. Luckily I also found the current requirement for such a stepper which seems to be anywhere in between 5A to 7A.
Before we go on, what you need to understand is if you truly require this amount of torque. If you do, then the high current is pretty much set in stone and the driver must be selected accordingly. I would go with at least a 6A driver, 7A if possible.
None of our integrated drivers wil get you there. For example, the DRV8811, can only give you a 2.5A sine wave peak, although this is quite hard to reach without proper heat sinking. The DRV8825 has better RDSon so it will give you the 2.5A considerably easier, even with a 2 layer board. This is too far away for what you need.
In the event that you can use as little as 4A, the DRV8829 would be a possible solution. This is what I used for my CNC router and it was enough to carve wood. I never tried carving metals, so I am not certain of whether this will work or not. Chances are you want to stay with your 6-7A driver and be able to tackle all the materials that show up your way.
In that case, you can feel assured the DRV8412/32 should be able to tackle this application as these devices can do up to 12A per phase if the proper heat sinking is utilized. You will need a microcontroller or a DSP to drive the power stages, but all of this is carefully documented on the respective webpages. http://focus.ti.com/docs/prod/folders/print/drv8412.html
You can also download and install ControlSuite which has all the documentation on how to utilize these devices, including DSP code, schematic, etc.
To build a CNC machine you will need to do quite a lot of research, but luckily there is a humongous amount of material on the web. First place you should visit and become affiliated with is www.cnczone.com. The amount of information including pictures, videos, etc is quite overwhelming. It is a forum community so your questions are answered within days, if they have not been treated already. Do a search first, as chances are your question has already been answered before.
But if you want to get a quick primer on CNC, what you need to know is that there is PC computer running a control software. There are two popular versions: MACH3 and EMC. I prefer MACH3, but you have to pay for a license. EMC is Linux based, and it is free. This software is in charge of running the GCODE which is generated by your CAM (Computer Aided Manufacturing) software. What it does is generate a series of pulses on the STEP and DIR line on a per stepper basis. Since the three (or four) axis are synchronized, the machine moves in accordance with the piece that is to be built.
The computer is connected to an interface board which is often called a CNC Parallel Port Board. It accepts the parallel port 25 pin connector which is where the STEP DIR signals are generated. The signals are then distributed to the drivers which then apply power and respective control "information" to the stepper motors, which then move either the lead screws or the belts, which then move... Well, you know!
I know this is not all the information you would want in order to build your first CNC machine, but I think it should be enough to get you started.
BTW, on my CNC Plasma cutter I will use the DRV8825 because it gives 2.5A sine wave peak easily and because it has 32 degrees of microstepping which is excellent for any small sized CNC machine. In this case, I'll be moving a plasma cutter head which has zero resistance as cutting is performed. This is why 2.5A is way much more than actually needed.
Hope the info helps. Best regards,
Jose Quinones
