TinyG with parallel port based stepper motors.

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  • November 14, 2013 at 9:03 pm #4947
    jm82792
    Member

    I want to use my Massmind THB6064AH which works great since it runs at 48 volts at 3 amps per phase with good resonance dampening. I need it for my machine, however I loath how my LinuxCNC computer is stuck with latency issues. Long story short I have an old P4 computer that runs it, I tried it on a new intel atom board, my steppers were waay smoother, then I magically fried my atom board due to me being stupid. (EI I ws using a screw driver to short out the power button pins and I shorted the wrong pin)
    Anyways I’m sick of it and want a TinyG along with being able to use a standard parallel port based stepper driver.
    Furthermore, I do a ton of 3d profiling, and HOPE the G64 has the P variable so I can change the tolerance of the velocity mode.

    November 14, 2013 at 9:05 pm #4948
    jm82792
    Member

    Thanks for your input, and as much as a newbie this posts sounds like I’ve been using a CNC machine for two years now 🙂

    November 14, 2013 at 10:14 pm #4949
    tomking505
    Member

    I did pretty much what you seem to want. My CNC machine had a parallel port driver board. I disconnected the motors from that, and connected to the TinyG.

    However, TinyG does not support 48 volts. Mine ran at 36 volts, but no go. The driver chips on the TinyG can only handle 30 volts max. In my case, I had to replace the power supply, about $40.

    (But believe me, I am thrilled to be able to connect my CNC to my laptop. I do not keep a desktop unit connected anymore. To use my CNC, I would have to find a monitor, find a keyboard, etc. Now, anytime I want to run my CNC, my laptop handles it.)

    If you want to run 48 volts with the TinyG, you would have to connect external 48 volt motor drivers to the step and direction pins on TinyG. I haven’t done it, but I thought about it. In the end, it was less hassle for me to drop to 24 volts than buy four drivers.

    Also, I don’t know how your software will interface with TinyG.

    By the way, are you sure you fried the board and not the power supply?

    I hope that helps.

    Tom

    • This reply was modified 11 years ago by tomking505. Reason: addition
    November 19, 2013 at 3:16 am #4965
    jm82792
    Member

    I am hoping to just disable the driving chips and use my current drivers that are more robust. Years ago I’d just do it and have wires everywhere. However, I’m polarized against rat’s nest of wires since I’ve been living so ghetto with my small business that’s centralized around one CNC machine and slowly I buy stuff to organized my setup 🙂 The chips the TinyG uses probably aren’t a match for Geckos or THB6064AH when at 48 volts so I’d like to stick with what I use. When I did a motor swap and some other work I went from 30 IPM of cutting to about 130, and I don’t want to ever go back.
    For the atom board I think it’s fried or maybe something else since it powers on but only shows the intel screen, then the BIO config screen if I strike the key fast enough, then the screen just stops working before it loads ubuntu or even if its in BIOs for 2 seconds. I’ve tried two LCD monitors and can confirm it’s not them. Next step I guess is to try a new stick of ram and remove the SSD, then boot of a CD. But I really think it’s the onboard GPU unfortunately 🙁
    But with a TinyG I can use any cheap netbook that stays on and not worry about latency!

    • This reply was modified 10 years, 12 months ago by jm82792.
    November 25, 2013 at 2:56 am #4972
    tomking505
    Member

    What kind of drivers do you have?

    November 27, 2013 at 12:25 am #4977
    jm82792
    Member

    I use THB6064AH drivers (PMinMO connectors) from Massmind. I NEVER have stalls and the torque is amazing.
    It drives three nema 23 steppers at 2 amps per phase at 48 volts using1/8 microstepping
    The machine has 6 tpi 3/8 acme screws with delrin nuts along with 5/8″ Thomson shafts with oolite bushings. It only has a square foot of working area but has 180+ IPM (limited due to current linuxcnc box) rapids, with a cutting speed of 120 limited by machine rigidity, and I get about 60IPS^2 of acceleration to boot 🙂
    But I hate the big ugly box that’s starting to give me nice error messages and I want to see how much smoother the machine is with TinyG.

    November 27, 2013 at 12:27 am #4978
    jm82792
    Member

    I’m tempted to buy an Arduino Due and try TinyG2 but I don’t know how easy that is.
    How does the g64 command work? Is there a tolerance setting for it (constant velocity like mode with a variable for tolerence?)?

    November 27, 2013 at 12:58 pm #4982
    alden
    Member

    G64 in tinyg does not round corners like it does on LinuxCNC (it’s not NURBs). What it does is reduce the velocity through corners to keep the machine within jerk and centripetal acceleration tolerance. The exact path is followed. In most cases this makes corners slow down, but not stop.

    G64 is most useful when hand coding Gcode. Most CAD/CAM packages generate lots of tiny little lines and some can do the corner rounding for you, compensating for the lack of true G64 on the tinyg.

    Hope this helps

    November 27, 2013 at 10:55 pm #4990
    jm82792
    Member

    Hmm. I do a lot of organic shapes that aren’t at all square.
    I am trying to wrap my head around this so here it goes.
    So TinyG goes point to point without any “curves” (smoothed interpolation is the term I think of since I used to do computer animation) between each point or gcode line? If I were trying to switch over I’d need to control my milling speed by how many points or “accuracy” (EI Gcode lines for the modeL) since the controller WILL hit each point. So in essence what separates it from exact stop mode? Between each point will I get a straight line or a curve? If it went up and down a “bump” would it go straight from each dot or naturally follow the arc to a certain degree? How will LinuxCNC fair against TinyG overall with speed if they are both being fed a reasonably smooth program?
    Just to show I’m not crazy here is a bit of my work, it’s an island that’s 50 miles from where I live.
    .125″ ballnose bit, .003″ accuracy, and I was getting maybe 80IPM for 3d profiling but the machine likes to shake some :/
    My work

    • This reply was modified 10 years, 11 months ago by jm82792.
    • This reply was modified 10 years, 11 months ago by jm82792.
    • This reply was modified 10 years, 11 months ago by jm82792.
    • This reply was modified 10 years, 11 months ago by jm82792.
    November 28, 2013 at 5:45 am #4996
    alden
    Member

    Let me see if I can answer your questions. TinyG behaves as “exact path mode” (G61.1) G64 is mapped to G61.1. If a program emits a G64 it should accept it, but it’s treated as an exact path just like G61.1. More of an explanation is provided here: https://github.com/synthetos/TinyG/wiki/TinyG-Gcode-Support#g61-g611-g64-path-control-modes.

    You don’t have to control the milling speed, beyond setting the feedrate limits for the machine and doing normal tuning. The joins will be decelerated as needed to keep the tool within limits. The position (path) will not be interpolated – the job should run exactly as the Gcode produced by the CAD/CAM.

    It’s not exact stop mode because the tool does not stop between line. The lines between points will be “lines”, not curves, because no curve interpolation is performed by the controller – the Gcode file is executed exactly as it’s provided.

    Your question on achievable speed depends on a lot of factors and I’m afraid I can’t answer that other than 80 IPM (~2000mm/min) is quite achievable with TinyG.

    November 28, 2013 at 11:50 pm #4997
    jm82792
    Member

    This subject isn’t something I’m very experienced with so I’m attempting to get some conclusions drawn up 🙂
    I’m 21, have a few years of college for a business degree, and then there is my two years of CNC experience;
    but past that I know nothing about CNC machine control software/hardware. My experience is how poorly exact path mode is in LinuxCNC and how shaky my machine would be if I used it.
    If TinyG operates smoothly for 3d profiling then that’s what I want.
    For the experience I’m thinking of just picking up an arduino due then seeing what an axis does under it’s control.

    • This reply was modified 10 years, 11 months ago by jm82792.
    • This reply was modified 10 years, 11 months ago by jm82792.
    • This reply was modified 10 years, 11 months ago by jm82792.
    November 29, 2013 at 7:22 am #5001
    alden
    Member

    If you post the contour file in the picture above I can dry run it at 2000 mm/min and see what it does. I’ll make a movie of some of the movement and post it on Youtube. This will take a few days as I’m not at my shop right now.

    November 29, 2013 at 7:38 pm #5002
    jm82792
    Member

    That would be great to see what happens with it 🙂
    https://www.dropbox.com/s/x0tuftjne9brvj9/1_8FP.ngc
    This is a LONG program so maybe just the first part and when it hits parallel passes?
    If this all works out I’ll be more than happy to show off what TinyG can do on my machine.

    • This reply was modified 10 years, 11 months ago by jm82792.
    December 4, 2013 at 12:47 pm #5014
    jm82792
    Member

    To clarify, if you’d like I can pull a line or two out of it, otherwise just a few passes of the first portion, and a few of the parallel passes would be excellent.

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