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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > parallel to usb? + can i "convert" open loop to closed loop steppers?
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  1. #1
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    parallel to usb? + can i "convert" open loop to closed loop steppers?

    Hey there a couple of questions:



    • 1: parallel ports seems a bit out of date, although I've already got "all" the electronics for a CNC mill (3 or 4 axis) - can I buy something so that I can connect to PC with USB or do I need to buy all new electronics? (I've got a Leadshine Mx3660 + another cheapo breakout board)




    • 2: I've bought a lot of CNC building stuff, but back when I got it I didn't actually know which way to go so I've got regular open loop Nema 23 + 34 steppers. - is there any encoders that can be attached to the motors so that I can convert them to closed loop steppers or do I need all new closed loop steppers? ( I ofcause also need somekind of encoder input that can connect to Mach3)




    • 3: I'm guessing closed loop steppers are the easiest/ cheapest way of minimizing the loss of steps/ improve precission - am I right or is there better ways - let me hear your thoughts on this



    I'm a student so I'm looking for a satisfying solution on a budget!
    (I'm pretty good at the hardware/ machining part, but when it comes to electronics/ software I need some guidance )

    -kind regards Teglberg
    (Denmark)

  2. #2
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    1. UC100, UC300, UC400 and Smooth stepper are some of the options. Google and look them up. I am a happy user of UC300.

    2. and 3. Why close loop? If you have accuracy problems you should solve them, not hide them.

  3. #3
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    1: I've been looking at those, think I'll go with that then (just to be 100% clear, it's: PC>USB>UC300>stepper controllers>stepper motors right?)
    2 and 3: it was just to be sure, do you recommend open loop/ do you think closed loop is excessive/ unneeded then?

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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by teglberg View Post
    1: I've been looking at those, think I'll go with that then (just to be 100% clear, it's: PC>USB>UC300>stepper controllers>stepper motors right?)
    PC>USB>UC300>BoB>stepper controllers>stepper motors

    The BoB is necessary, just like with parallel port use. It provides optical isolation.

    Quote Originally Posted by teglberg View Post
    2 and 3: it was just to be sure, do you recommend open loop/ do you think closed loop is excessive/ unneeded then?
    Just steppers. No need for feedback to Mach3, the accuracy should normally be very high anyway, and like I said, if you have missing/extra steps or other issues, you should fix those and not hide them. You are on a tight budget, and here you can save money. Spend the money on good power supply and stepper drivers, not on encoders and closed loop systems. That may be necessary for a very high speed professional machine, but for hobby use... on tight budget...

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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Thanks your advice is greatly appreciated!

    - if you don't mind I have another question besides the original post:

    do you have any experience on spindle selection (main spindle - the one that does the cutting) I was considereing using a Nema34, do you think it could work? don't know if it's strong enough, I would like to have the ability too cut steel (maybe just small chips to minimize the pressure). Also if I use a Nema34 i might get the ability to index the spindle?

    thanks again!

  6. #6
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    If you are on a tight budget, then why not stick with a parallel port? I run my milling machine on a surplus pc I got for free using linuxcnc. Linuxcnc is free as well. It works great too.

    So let's look at what it costs just so you can use USB and Mach 3/4. A uc100 is $120, mach3 is $175. Or mach4 is $200. So you are talking about $300 so you can use Mach and a USB.

    Parallel ports may be out of date, but they work just fine.

  7. #7
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Mesa has some inexpensive solutions for linuxcnc. For $89 they have in effect 2 printer ports if i/o and very expandible.

    http://mesaus.com/index.php?route=pr...&product_id=51

    Or

    7i92

  8. #8
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    The pulses timing with a UC100 is much better than with a parallel port. https://www.youtube.com/watch?v=1m3ixFcjgVo
    You get more reliable motion, higher possible feeds etc.
    With UC100 you can also use the UCCNC which again gives you better motion than Mach3 and is much cheaper, $60 only.

  9. #9
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by OlfCNC View Post
    The pulses timing with a UC100 is much better than with a parallel port.

    You get more reliable motion, higher possible feeds etc.
    With UC100 you can also use the UCCNC which again gives you better motion than Mach3 and is much cheaper, $60 only.
    Much better than mach3 through a parallel port. I don't doubt that since mach3 is running on Windows which is not a real time OS.

    Linuxcnc runs on a specially prepared realtime version of Linux, so the same may not be true of Linuxcnc

    In any case, there are many many many people running cnc machines on parallel port successfully. For a budget build there is no cheaper way.

  10. #10
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    I said "with UC100 you can also use the UCCNC which gives you better motion", please reread and interpret my post again, I did not talk about LPT ports ... they are dying out dinasours.

  11. #11
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    Quote Originally Posted by 109jb View Post
    If you are on a tight budget, then why not stick with a parallel port? I run my milling machine on a surplus pc I got for free using linuxcnc. Linuxcnc is free as well. It works great too.

    So let's look at what it costs just so you can use USB and Mach 3/4. A uc100 is $120, mach3 is $175. Or mach4 is $200. So you are talking about $300 so you can use Mach and a USB.

    Parallel ports may be out of date, but they work just fine.
    I'm also tight on space so would like to use laptop + I don't want to be stuck on one specific PC would like to change sometimes so that I can program on the go but mostly just for comfort, it's annoying to build something new that's "old" already guess it's a matter of preference

  12. #12
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Depending on your preference, you could also use a microcontroller solution. I also use GRBL on an Arduino and it works quite well, but has limitations. The way it operates is that the GRBL/Arduino actually performs all of the realtime functions and has the g-code interpreter built in. It has a basic set of G-code commands that includes the most common commands. There are CAM postprocessors for it, so you can do pretty much everything in CAM anyway. The PC used doesn't have to be anything special and there are many GUI interfaces for GRBL. This is also a very inexpensive solution. All of the software/firmware is free and the Arduino can be bought in clone form for about $5. The arduino replaces the breakout board and wires directly to the stepper drivers. It is not as full featured as LinuxCNC or MAch3, but can do a bunch. I like to tinker, so I am really enjoying GRBL by writing my own interface in VB to suit my own needs. That said there are many interfaces that are simply download, install, and go.

    If interested, here is some information.

    First is my mill running a comparison between LinxuCNC and GRBL with the same g-code. This is an older version of LinuxCNC, so GRBL and LinuxCNC run about the same speed now.
    https://youtu.be/c1mxS7WI-tg

    Here is the GRBL site on github
    https://github.com/grbl/grbl

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