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  1. #1711
    Skill Collector rockyboy's Avatar
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    Quote Originally Posted by moebeast View Post
    Another benefit is that you can use separate stepper drivers for two steppers on one axis. The second extruder slot is slaved to the axis of your choice.
    Can you point a brother in the direction of how to do this? I'd love to split out the load on the drivers rather than doubling up on my Y and Z axis.

    Thanks,
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  2. #1712

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    Quote Originally Posted by rockyboy View Post
    Can you point a brother in the direction of how to do this? I'd love to split out the load on the drivers rather than doubling up on my Y and Z axis.

    Thanks,
    Look in the Configuration_adv.h tab for dual axis. The comments will help. I don't know if you can use E0 and E1 for X and Y, or just E1 for one of them. I found it when my Z axis wasn't working at all. I un-commented the appropriate line and moved the driver to E1 and was back in buisiness.
    Last edited by moebeast; 10-10-2017 at 09:50 PM.

  3. #1713
    Posted a thousand or more times jhitesma's Avatar
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    Quote Originally Posted by rockyboy View Post
    Can you point a brother in the direction of how to do this? I'd love to split out the load on the drivers rather than doubling up on my Y and Z axis.

    Thanks,
    Well you can only split the load on two axis because there are only 5 drivers - basically you use the 2 extruder drivers as X/Y instead. Unfortunately it's not a simple change. It requires patching Marlin and the patch was for an older version so would take some programming knowledge to apply it to the current version of Ramps, but details and the patch are here:
    https://www.vicious1.com/forum/topic...al-xy-drivers/


    Kevin - I thought I had told you about how we're using Marlin...but then again we may have only talked about my experiences with GRBL and UGS. Marlin is a bit unconventional for CNC, there are things I really like about it and things I really dislike.

    I'll get the dislikes out of the way first (So I can end on a positive note!) because Marlin queues gcode commands internally instead of just executing them as soon as received setup for cuts is a little different. Jogging the machine is somewhat annoying as you can't just use a joystick - you have to either enter gcode commands or use the LCD to tell it to move which axis how far. Gcode commands are quick and easy - but I don't run my machine tethered so I have no way to enter them (though I am looking into building a pendant that will let me access certain codes I use frequently at a single button press and am considering adding a number pad and a few letter keys so I can enter gcodes with it as well.) Using the LCD is...tedious. Some versions of Marlin the rotary encoder isn't read very accurately so it's very difficult to go one step at a time. And if you want to change from .1mm to 1mm or 10mm moves you have to back out two levels of menu then back in. As a result most people don't jog the machine under power. But that's not a great option since it's fairly easy to throw the machine out of square moving it manually - you can stop and measure to make sure the axes are still parallel but for me that leaves too much room for error. (It would probably be easier on the rascal since you have more flat/square surfaces to measure off of instead of our round conduit!)

    So...I take a different approach. Instead of jogging the machine to the origin of my workpiece as normal I always start my operations from "home" where I have some collars installed on my rails that let me square the machine very quickly and easily by just pulling it against them. Then I place my work and measure the distance from tooling to the work origin and account for it when doing my CAM. It's far from ideal and makes more complex operations all but impossible. It's a big part of why I want to create my pendant so I can jog the machine with the steppers powered up so it stays square...but there's another issue.

    The version of Marlin I'm currently running is a bit buggy. But...it's an old version and not recommended currently so not something most people would run into it. The problem is if I reset the coordinates "G92 X0 Y0 Z0" then the machine seems to start working ok....but....sometimes on some prints will suddenly freak out:

    Click image for larger version. 

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    I'm not entirely sure what's going on when it happens...but it seems like the machine thinks it hits a limit at some point and it's internal coordinate references are confused. At first it just acted like it was hitting an endstop and thought the work was much smaller than it was. But then it went totally nuts and started doing that triangle thing.

    Ryan who created the MPCNC suggests resetting the RAMPS board to zero the coordinates, but I'm not a fan of that method since it drops power to the steppers and risks letting the machine shift and go out of square. On a smaller build that's probably an acceptable risk...but my particular machine has the old Z parts that don't hold square as well and one goofy roller so it's very easy for my Y axis to go about 1/8" out of square if the steppers power down. So I use the method I described above.

    Which is ok if I'm just cutting parts. With the needle and foam board it actually works out very easy since machine home lines up with where I want the origin on my work to be anyway. I just use a 1/2" wood dowel as a spacer to position my work against my spoil board and line the left edge up with the needle. Cutting parts from wood sheets isn't much more difficult, I have marks on my spoil board that indicate where I should mount my work and it's a consistent 2.5" in X and 1" in Y that I have to offset my gcode.

    But it's not as accurate as being able to position the machine right at my desired origin and that makes it trickier to do some kinds of operations. I can do them - but have to jog the machine through the LCD which is tedious.

    I really need to upgrade my firmware though...that should fix the issue with zeroing the coordinates and it should make the LCD work smoother. It also apparently improves laser performance. But I've been lazy about it since the machine is working so I hate to mess with it and since it's not tethered I have to disconnect the ramps and move it over to my computer or dig out a notebook and bring it out there to reflash. Plus I've customized the LCD menus to add some extra commands that are helpful for the CNC and I've been too lazy to port them to the newest version.


    Now...as for what I like about RAMPS/Marlin over a more traditional CNC control setup. The big difference is that I can run untethered. No need to tie up a computer. Plus as I mentioned earlier Marlin processes the gcode - it happens on the controller not on the computer. With GRBL and other more traditional setups the processing happens on the computer and the controller is pretty dumb - it basically just translates the steppers commands and all the heavy lifting of interpreting the gcode is done on the PC. Which is why those setups generally use parallel port connections - it makes the timing easier as PC's done run a real time OS and controlling the steppers requires very precise timing. Offloading all that to a dedicated micro just makes a lot of sense to me.

    But...it's still not ideal as I outlined above. And while most of those issues are magnified by my particular setup they're still somewhat limiting. There are options...for example estlcam has it's own firmware which supports RAMPS and makes it work more like a traditional CNC - but you have to be tethered which doesn't work well for me. Marlin is working on some changes to their firmware to improve things for CNC users - but they're very preliminary right now.

    None of the downsides prevent me from doing anything - they just make some things trickier, slower, or more involved. On the other hand for the simple things that make up 99% of what I wanted a CNC machine for the RAMPS/Marlin setup is super quick and easy to get up and going with (especially if you're already familiar with it from a 3D printer as I was.)

    Frankly I should spend some time upgrading Marlin on mine....and finish my pendant....but I'm having so much fun using the machine I just can't bring myself to spend time working on it instead of using it
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  4. #1714
    interesting...

    So your design needs all 5 drivers then?

    Could you modify the design so it would only take 4? I admit I haven't looked at the MPCNC really close. Seems like you would use 2 drivers for your Y, one for your X, and one for your Z. You could use a CNC Shield (less than $20 all up) and get away from marlin..
    The shield has a PWM output that would easily drive your ESC for your needle cutter. I understand you want a stand alone machine, seems like it would be smoother without marlin. I read before you don't trust windows to send your code, it has worked pretty flawlessly for me the last 2 1\2 years.

    Just an idea.. Party on Garth!

    thanks
    Kevin
    Last edited by blackkrystal73; 10-12-2017 at 03:26 PM.

  5. #1715
    jhitesma said

    "Frankly I should spend some time upgrading Marlin on mine....and finish my pendant....but I'm having so much fun using the machine I just can't bring myself to spend time working on it instead of using it "


    lol I hear ya, agreed.. Who's got time for that.. That's the main reason It's taken me so long to get Rascal out. To many irons in the fire and to many passing squirrels.. lol

    Kevin

  6. #1716
    Posted a thousand or more times jhitesma's Avatar
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    Quote Originally Posted by blackkrystal73 View Post
    interesting...

    So your design needs all 5 drivers then?

    Could you modify the design so it would only take 4? I admit I haven't looked at the MPCNC really close. Seems like you would use 2 drivers for your Y, one for your X, and one for your Z. You could use a CNC Shield (less than $20 all up) and get away from marlin..
    No, I only use 3 drivers. One for X one for Y and one for Z. The X and Y both driver 2 steppers. I run them in series but some people have switched to parallel for more power. I've considered trying it but don't even have my current turned up anywhere near what my steppers can handle yet so don't feel a need. But I'm not doing aluminum and don't have any plans to (Mainly due to where my machine is located and not wanting metal chips in my office!)

    The shield has a PWM output that would easily drive your ESC for your needle cutter. I understand you want a stand alone machine, seems like it would be smoother without marlin. I read before you don't trust windows to send your code, it has worked pretty flawlessly for me the last 2 1\2 years.

    Just an idea.. Party on Garth!
    If I was going to move away from Marlin I'd go full Mach3...but don't have the budget for Mach3 and as a software developer myself don't have any interest in things like the sainsmart boards that come with a "license" for Mach3 which is really just pirated/hacked. And honestly...I'd probably go LinuxCNC if I went that route as I've been a Linux user for close to 25 years now (Started with SLS back before even slackware was created) and Linux is far more stable and capable of running in real time mode unlike windows.

    But while I have stacks of old computers I don't really have room to set one up and don't want to deal with the hassle of configuring all that and having to boot another computer when I want to cut something. With Marlin I plug the machine in and 10 seconds later I can be cutting. Honestly it takes me longer to lookup from plugging it in than it does for it to boot and be ready to cut (I still need to cleanup my wiring and install my estop and some outlets for my vac and router...right now plugging things in is pretty haphazard.)

    My machine has actually smoothed out a lot in the past month since I upped my stepper current. I had them running way too low and it was causing things to drag a bit on the rails. I never worried about it because the cuts were still straight and clean even if watching the gantry it looks janky as all get out. And I know that upgrading to a current release of Marlin would solve 95% of the issues I currently have...but they aren't big enough issues for me to bother with the 10 minutes it would take to reflash - so that puts how "major" the issues are into perspective

    And that would make the workflow smoother as well (not sure if you meant smooth referring to the machine movement - which I admit is visible not the greatest in some of my videos - or workflow.) With the current release most people can reset the coordinates no problem so using an arbitrary home point is much simpler. Ryan who created the MPCNC also has a patch for marlin out that adds dual endstop homing so the machine can auto square it's gantries - it hasn't merged into the official Marlin yet but there is a request to have it merged open. Basically you put two end stops on both axes but on the same side (So instead of one for min and one for max you have two for min both on the same axes) and it can then run the steppers individually (So I'd also have to swap a few wires so steppers are on independent drivers) and will run both sides until one endstop triggers, then only run the other side until the other goes so it pulls itself square when homing. It's a nice trick and could even be helpful on your machine - or any other that runs dual steppers on any axis to help assure the machine stays square when steppers are disabled.

    I'll probably get marlin updated on mine soon....and get my pendant built....but...neither are a super high priority. Need to get an ESC and build this FT-29 and find some better material to cut new plates for my goofy danaus style quad out of - both of which are higher priorities than improving the workflow on my machine
    Stop in and say hi in the unofficial FT IRC channel!

  7. #1717
    Skill Collector rockyboy's Avatar
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    Quote Originally Posted by jhitesma View Post
    No, I only use 3 drivers. One for X one for Y and one for Z. The X and Y both driver 2 steppers. I run them in series but some people have switched to parallel for more power. I've considered trying it but don't even have my current turned up anywhere near what my steppers can handle yet so don't feel a need. But I'm not doing aluminum and don't have any plans to (Mainly due to where my machine is located and not wanting metal chips in my office!)
    That's how I have my lowrider configured at the moment (except it's Y and Z with dual steppers), but I do intend to cut MDF and aluminum on it so figuring out a parallel driver option is on my todo list.

    I also might need to double up on the X axis stepper too (which the design is ready for). That would give me six steppers to run - all could be done in series initially, but at that point I might be outgrowing the RAMPS platform entirely though. -And I have the same reservations about Mach3 as you mention.
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  8. #1718
    Posted a thousand or more times jhitesma's Avatar
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    Just catching up on e-mails...and see that the dual endstop code has now been submitted against Marlin 2.0 (which the Marlin team is also talking about trying to have out the door as an official release within a month or so) and the lead dev of Marlin is saying he wants to fast track merging it: https://github.com/MarlinFirmware/Marlin/pull/7943

    So...that's nice to see! The submission for it against 1.1.0 has been gathering cobwebs for a month or two and I was worried the Marlin team wasn't interested in it.
    Stop in and say hi in the unofficial FT IRC channel!

  9. #1719
    Quote Originally Posted by jhitesma View Post
    My machine has actually smoothed out a lot in the past month since I upped my stepper current. I had them running way too low and it was causing things to drag a bit on the rails. I never worried about it because the cuts were still straight and clean even if watching the gantry it looks janky as all get out. And I know that upgrading to a current release of Marlin would solve 95% of the issues I currently have...but they aren't big enough issues for me to bother with the 10 minutes it would take to reflash - so that puts how "major" the issues are into perspective

    And that would make the workflow smoother as well (not sure if you meant smooth referring to the machine movement - which I admit is visible not the greatest in some of my videos - or workflow.)


    I tried a set of DRV8825 drivers on Rascal. Im using 1\32 stepping and they are high current. It really, really smoothed out the machine..

    I think you can get a set from china cheap, if you want to mess with it. lol I know, who has the time.. Right?

    Kevin

  10. #1720

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    Hey guys, I wrote an article on my LowRider style simplified machine. https://www.flitetest.com/articles/a...m-board-cutter

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