On Saturday 15 August 2020 00:57:10 Chris Albertson wrote: > What you want should be possible, if only some one would spend some > months working of the software. I use this little STMF104 for > motion control (but not for CNC) and the STM32F104 can generate pulses > far faster them my motors can move. What is the point of 300,000 > steps per second if the motos cn't move that fast. > Ahh, but they can Chris albeit with vanishing torque, I commonly test motor/driver combo's loose on the table, and find that the speed limit is usually the opto-isolators in the average driver, which are commonly dead at around 300k pulses a second. But in playing with the tb6560 based drivers, and big nema=17's rated for 92oz/in of low speed torque, have left the running at 500 kilohertz. Thats something over 3000 rpms. However, with the current programmed at the motors rated current or slightly above, both the driver and the motor are seriously sear your your fingers hot. These harmonic drives won't live with a 150C motor shaft stuck into them. I am still waiting on the 4mm bolts and nuts needed to assemble them for final testing. But its clear I can't run them at their rated currents. What remains to be seen is, with the limited current being 20%, or about an amp, will they do the job without their heat destroying these drives. I think I can as I can't stop them at 500 rpms with my fingers, when set at this 20%.
We may have to shop carefully, but faster motors are on the horizon with the advent of 3 phase steppers that think they are servo's. When I cnc'd that old Sheldon, I reused that 1600oz/in motor, a honking big nema-34 I took off the GO704 because its Z speed limit was about 28 ipm, not enough to really do rigid tapping. Without all that weight to lift, and geared down 32 to 42 on the Z screw, it could do around 60 ipm. But its step vibration rattled anything on the lathe that wasn't bolted to it, off onto the concrete floor by the time it had moved a foot. Hard on carbide chips at $15+ a copy. So I recently made a nema-34 to 23 adapter and replaced that motor with a 3NM, 3 phase step-servo with smart currant control. It moves ghostly quiet, doesn't shake tools off the carriage, and does it at 120 ipm or at .0001" a step from the jog dials. And, it tells linuxcnc when it has faulted. The ultimate test was to position it to hit a chuck jaw with a carbide chipped tool mounted, and at 2 or 3 ipm keyboard jog, run it into the stationary chuck, it faults, disables the driver output and with the motor then free, bounces back about 5 thou from the chuck, and does NOT damage the chip. And unhomes the lathe in addition to disabling all motions with an F2 release. And does all that with a 10C rise in temp over ambient at the motor, and zip at the teeny driver, which is smaller than a dm542. Triggering the fault causes the F2 release which removes the AC power to the motors psu and resets the fault when they die. Whats not to like? > Most 3D printers use Marlin software that runs on an 8-bit Arduino and > it runs all four axis up to the limit of the motors speed. The > STM32F103 is and order of magnitude more powerful them an 8-bit > Arduino. There is not reason an STM32 can't drive a full size > 5-axis milling machine. We just need someone to decide to do it. > > On Fri, Aug 14, 2020 at 1:21 PM cogoman via Emc-users < > > [email protected]> wrote: > > On 7/23/20 2:15 PM, Chris Albertson wrote: > > > What is really needed is for someone to write firmware for the > > > common STM32F103 "Blue Pill". These have the hardware to do > > > things like step > > > > gen > > > > > and quadrature decode at MHz speeds and talk to the PC over SPI > > > I2C or > > > > USB > > > > > and cost under $3 from 100 different vendors. I use these for > > > motion control when I can but not with Linux CNC. It is really > > > "just a > > > > matter > > > > > of software" but I'm not about to spend months of my time to save > > > the > > > > cost > > > > > of a 7i92. > > > > May I suggest the shoulders of KevinOConner to stand on. > > > > Check > > out https://www.klipper3d.org/ > > > > He has set up a 3D printer program that uses python on the Raspberry > > PI for the G-Code interpreter. He used OctoPrint to feed the USB > > serial port, but the arduino doesn't have to interpret G-Code, so > > with an arduino he can max out at 102,000 steps per second, with the > > STM32F104 in the Blue Pill Board he can max out at 360,000 steps per > > second, both with 3 steppers stepping. > > > > https://www.klipper3d.org/Protocol.html > > > > https://www.klipper3d.org/Features.html > > > > The benchmark is a little cryptic to me, but I think it says the > > blue pill board can step three steppers at less than 10uS per step > > max (for a $3 board). If I read this properly, you can sink up 2 > > blue pill boards and control 6 to 8 steppers. Yes there are limit > > switches connected. It also handles the slow speed PID control of a > > heated bed and extruder. > > > > I would like to see LinuxCNC set up to control my router through > > the blue pill board (or two) without needing the OctoPrint, or the > > Klipper3D python interpreter. I have been running my router with > > GRBL, and though it's an amazing feat of programming prowess, > > sometimes wrestling with FreeCAD and either FreeCAD's PATH toolbench > > or JSCUT makes me wish I had the subroutines, named variables, math, > > and looping constructs LinuxCNC makes available. Many times I've > > spent hours or days doing something I felt confident I could do in > > LinuxCNC in about an hour. > > > > I would like to see LinuxCNC able to control a small machine > > through a $14 CNC controller. > > > > http://www.zyltech.com/arduino-cnc-kit-uno-r3-shield-4x-a4988-driver > >s/ > > > > The protocol and the microcontroller software is already done, > > though I'd guess it doesn't use synchronous transfers, but just > > buffers the steps to keep latency from stalling the steppers. > > > > > > > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
