Guidance for Updated G0704 Electronics Design

[JJ0704]

I am a total CNC neophyte. I'm even very new to machining and know almost nothing about electronics. I'm not going to let that stop me from the fun challenge of converting my recently acquired G0704 to CNC. I've tried to do as much learning as possible though the 'zone' (took two full months to read both of Hoss's epic G0704 threads) and purchased Hoss's excellent conversion download. But, I still have some questions and would appreciate any good advice on selecting 'updated electronics' for my pending build because boards, motors, etc. are always evolving. Here goes...


1. I started out thinking I would purchase the 'Hoss Heavy Duty Digital' setup, but am now considering possibly going with a closed-loop hybrid stepper setup. I realize that these aren't true closed-loop systems, but I assume they do provide at least a warning and prevent further part damage if a stepper motor misses a step. I really like that (in theory), but if I select the proper motors/drivers and don't push it too hard, how often will I actually miss steps and unknowingly ruin a part or end up with a part out of tolerance? Any suggestions for 'best value' hybrid-steppers and drivers (Leadshine, eBay Leadshine knock-off, Clearpath, others...?) for the G0704?


2. I have an irrational aversion to attaching my CNC electronics to my computer using an archaic DB25 cable. I am almost dead-set on using an Ethernet smooth-stepper (ESS). I also need to pick a CNC machine controller software and am leaning toward Mach4 since it is 'newer' than Mach 3 and I don't know squat about the Linux OS to even try LinuxCNC. It seems that the Warp9 and PMDX boards don't support backlash compensation plug-ins (which I would like, and arguably may need for the Phase 1 part of the conversion), thus leaving the expensive but very nice Hicon Integra-Hobby board. Are there any other ESS boards that I have missed that may work?


Thanks in advance and my apologies to those who find these kind of simple questions annoying.


JJ

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[Wiggles84]

I have a ESS and use backlash comp in mach3. I'm not going to tell you it makes perfect round pockets, but I have no issue hold .001" to .002" on rectangle pockets.

Also you could look into the MASSO

MASSO home page


Andrew

[samco]

Too bad you don't want to give linuxcnc a spin..

https://mesaus.com/index.php?route=p...&product_id=66

$199
Ethernet
5 axis stepper
analog spindle control/spindle encoder - (rigid tapping, threading and such)
48 isolated i/o
expandable.

backlash is implemented in the motion controller that is in the computer - works for all external interface hardware.

Sam

[DJEkim33]

I use the Mesa boards and love it. You don't need to know much about Linux if you use these boards as they generate the steps for you. Linux really functions like an old version of Windows with some DOS thrown into it. With a mesa 5i25 and 7i76 and a home built computer I was out the door for under $280. As mentioned the controller takes care of everything as far as backlash. And is a solid complete controller unlike a mach3 trial or mach4 that can be buggy. You can also upgraded to tormach path pilot with this setup.

You already have a learning curve ahead of you. May as well learn a little Linux.

As far as steppers I have been happy with lichuan servos. I would use there closed loop steppers on my next build. There service was great. Manuals are easy to read.
http://n.xlichuan.com/m/prod_view.as...90&Fid=t3:75:3

They are also available on ebay:
LC60H2102+LCDA257S set 4.5 Nm 60mm Nema24 DC Hybrid Servo stepper motor 20-50V | eBay but they are cheaper if you contact directly. This link is for the equivalent to a 570 oz in motor (little more torque actually). You would need to make some changes based on shaft size etc.

Hoss has great plans but make sure to do some research as there are now some better options and designs out there. For me personally I was not happy with the AC bearing conversion and found an upgraded set of tapered roller bearings that worked much better. As with everything there is more than one way of doing things.

[JJ0704]

You already have a learning curve ahead of you. May as well learn a little Linux.

This is a very good point. It was the reason I thought I should just learn Mach4 and skip Mach3 altogether. By that same logic, I should consider LinuxCNC as well. I think I will partition a hard drive, install Ubuntu and Linux CNC and get my feet wet.

Hoss has great plans but make sure to do some research as there are now some better options and designs out there. For me personally I was not happy with the AC bearing conversion and found an upgraded set of tapered roller bearings that worked much better. As with everything there is more than one way of doing things.

This is good advice. While I really like Hoss's plans, they are several years old and intentionally kept quite simple (in a good way). Learning more about what others have done and new hardware/electronics options is what has prevented me from jumping into his plans verbatim.

Those closed-loop steppers look very interesting and a nice price to boot. I'll start spec'ing out a system design with the mesa cards and those motors.

I'm open to any other G0704 'updated' configurations as well...keep the suggestions coming!

v/r,
JJ

[DJEkim33]

For Linux don't get caught up on the latency issue. It is not a big deal with Mesa cards. I built an Intel d525mw mother board up with memory and a solid state drive for less than $80. You will need to do the core isolation on it but it's covered extensively on the Linux website.

Hoss's phase 3 stuff is nice, no complaints there. Get good couplers for the motors. You can make a simple belt drive if you do some research. Be very careful with which screws you order also. The labels for the y axis on his plans can be tricky. The largest one requires significant material removal from the base for the y axis front extension. That's fine if you have the ability to do it but drilling and die grinding it will take forever.
Overall just get a basic build up and running. Play with it a bit and then see where you want to go.

[ger21]

You might want to consider UCCNC with a UC300ETH. Very easy to use, better and cheaper than a Mach3/4/ESS.

[DJEkim33]

Forgot to mention you can download linuxcnc to a thumb drive or dvd and run it that way to see if you like it. No need to partition a hard drive. The operating system is less than 8gb.

[Joey5226]

For me personally I was not happy with the AC bearing conversion and found an upgraded set of tapered roller bearings that worked much better.

Tell me more please.

[JJ0704]

Forgot to mention you can download linuxcnc to a thumb drive or dvd and run it that way to see if you like it. No need to partition a hard drive. The operating system is less than 8gb.

Yes, good to know. I found that out after I installed Ubuntu and tried to use the terminal command to write the linuxcnc *.iso file to a thumbdrive...which it did, but it would not boot up. Then I downloaded it again off my windows partition and used a software tool called 'Rufus' to write it to the stick. It worked great and it is pretty neat that it can be run like that. I think I may like the Debian OS GUI that it uses better than Ubuntu also.

Is there any downside to running LinuxCNC strictly off a bootable USB drive? I did notice that the latency test results were pretty bad for the old laptop that I tried it on, which the mesa boards would make this mostly moot (I think).

Of course, since I have no boards, drivers, motors yet, I was not able to do anything with it. I was sort of hoping there would be at least a simulation mode available. Maybe I missed seeing that?

[DJEkim33]

Tell me more please.

http://www.cnczone.com/forums/benchtop-machines/336478-cnc-forum.html

This explains it all. But basically not everyone had good runout numbers with cheap ac bearings and you can find tapered roller bearings that are direct fit with less runout, less heat and they will not be your speed limiting factor.

[DJEkim33]

Technically I think you could run fully from a USB but you have a couple other issues.

First the Mesa cards need a pic slot for the 5i25
5I25 picture

So a laptop is not going to work. And you probably won't be able to get just any old computer to work. You will need to get something you can isolate down to a single core. I is the Intel d525 (found cheap on eBay) but the more popular choice seems to be the gigabyte j1900. Search the linuxcnc forums to see why and look at this link for other setups and their latency. Latency with mess cards is not important as they generate the steps not the computer. So you will just need a servo thread that is around 1000000. Don't get caught up in latency issues it's a mute point. I wasted alot of time figuring this out as I tried different setups.
LinuxCNC Documentation Wiki: Latency-Test

I think the d525 has an option of using a USB as the hard drive and you could run it off their but you may have some speed issues. I used an affordable solid state drive and have no issues. As for the different versions of Linux, you are building a machine controller not a PC. While there are not many issues with using different versions it's just simpler to use the standard version that comes with the linuxcnc download. I personally don't use the computer for anything but machine control.

Yes not being able to use a laptop sucks but linux will let you use a touch screen. Start thinking of building an electronics enclosure not just a computer. I built mine out of an old computer tower but next time I will us a box with a swinging door. The mother board will be mounted on the door and the rest inside the box. Then a simple touch screen monitor and your done. These mother boards can be built up for less than $80. So with the cost of the Mesa cards (one is the PCi card, the other is the breakout board) you are only going to be in the whole $280. Far cheaper than most smooth steppers and the cost of mach also.

I never tried simulation prior to my build but I assume you would need ini and Hal files to make linuxcnc work. Since Linux communicates back and forth with the Mesa setup it won't work without it. You could try doing a generic config in step config.

All in all linux is going to be some reading and learning but it's nice and simple.

[samco]

It all depends on latency... Yes - using mesa the latency doesn't have to be as good as if you are running the printer port lets say.

printer port - you want latency <20us depending on the step rate you are looking for.
Mesa or other external interface hardware. For a 1ms servo thread - you want to have <100us of latency. So better - but you still need good realtime response.

Couple of thing to throw out there. If you are using mesa hardware (especially Ethernet solutions) You need to run the rt_preempt kernel - not the rtai kernel that comes with the live iso.

A laptop may run rt_preempt just fine. I have a laptop here that I use for testing linuxcnc configs. It has really good latency numbers with rt_preempt as long as you don't a) mute the speakers or b) turn on the keyboard light. YMMV

Getting LinuxCNC

this explains how to install rt_preempt.

If you want to go cutting edge - there is currently a livecd using debian stretch (latest released debian) with rt_preempt and linxucnc.

Index of /testing-stretch-amd64-rtpreempt

rt_preemt defiantly seems to run better on newer hardware. Isolating cpus also helps as stated above.

Clear as mud?

sam

[Joey5226]

http://www.cnczone.com/forums/benchtop-machines/336478-cnc-forum.html

This explains it all. But basically not everyone had good runout numbers with cheap ac bearings and you can find tapered roller bearings that are direct fit with less runout, less heat and they will not be your speed limiting factor.

Thank you for the link. I was thinking tapered bearings on the X&Y ballscrews as the preload is very temperamental on the preload.

I may also consider the spindle because I am getting some spindle run-out.

[DJEkim33]

It all depends on latency... Yes - using mesa the latency doesn't have to be as good as if you are running the printer port lets say.

printer port - you want latency <20us depending on the step rate you are looking for.
Mesa or other external interface hardware. For a 1ms servo thread - you want to have <100us of latency. So better - but you still need good realtime response.

I mentioned this in my post. My point was more don't waste time following along in the directions for the latency test as these try to optimize the base thread and for mesa you just need an ok servo thread which is very achievable with the boards I recommended.

Couple of thing to throw out there. If you are using mesa hardware (especially Ethernet solutions) You need to run the rt_preempt kernel - not the rtai kernel that comes with the live iso.

A laptop may run rt_preempt just fine. I have a laptop here that I use for testing linuxcnc configs. It has really good latency numbers with rt_preempt as long as you don't a) mute the speakers or b) turn on the keyboard light. YMMV

Getting LinuxCNC

this explains how to install rt_preempt.

If you want to go cutting edge - there is currently a livecd using debian stretch (latest released debian) with rt_preempt and linxucnc.

Index of /testing-stretch-amd64-rtpreempt

rt_preemt defiantly seems to run better on newer hardware. Isolating cpus also helps as stated above.

Clear as mud?

sam

This is not entirely accurate as the 5i25/7i76 combo works just fine with rtai kernel. You may be confusing the need to switch to rt-preempt if you go with a 7i92 etc. As I mentioned the 5i25 and building a pc, installing the recommended wheezy iso that will be the simplest way to go as it uses the standard RTAI. He already stated his laptop did not have favorable latency. I am trying to save him the trouble of poking around with a bunch of different computers focused on the wrong stuff, which is what I did. You need to remember that the OP has no Linux experience and jumping right into different versions with new kernels and "you can use a laptop if you do all this" is not going to be useful. In fact I would say that its this type of stuff that actually scares people off Linuxcnc. It gives the impression that to make a functioning system you have to understand 100% everything in all those links you just posted. As he is new I am trying to point him in the simplest cheapest way to get started and be reliable, not worrying if his speakers are muted or the keyboard light is on.

As for the original post I did miss that you wanted to go with a ethernet based setup. But in defense of the 5i25/7i76 combo, they do use a db25 to go from the card to breakout board but the 5i25 connects to a pci slot so its not a system based on the pc's parallel port and thus will function much better.

[DJEkim33]

I have no issues on the x and y using AC bearings and would stick with them. My complaint with AC bearings is just on the spindle.

[JJ0704]

In fact I would say that its this type of stuff that actually scares people off Linuxcnc. It gives the impression that to make a functioning system you have to understand 100% everything in all those links you just posted. As he is new I am trying to point him in the simplest cheapest way to get started and be reliable, not worrying if his speakers are muted or the keyboard light is on.

Yes, so true!!! I have spent my very small windows of available free time (I have 4 kids under age 8, my only free time is from 11pm until I get too tired to stay up) over the past week trying to learn more about LinuxCNC. My single biggest 'gripe' about LinuxCNC is that the development community has not spent enough time to simplify it for the general public to consume...probably since there is no marketing department or financial incentive to do so. That being said, the more I learn about it the more I like it and I have all but committed to go this route for my CNC build. Heck, I even know what "sudo" means now!


I found out that installing the 'Ubuntu 16.04.2 LTS desktop' distribution as my OS was a waste of my time since the installation of the LinuxCNC *.iso file actually installs the 'Debian Stretch' distribution as the OS. I swear that nowhere does it say that the standard LinuxCNC download comes with its own operating system. As a side note, for a bunch of software nerds developing a kick-butt CNC machine controller, they REALLY SUCK at developing a user-friendly web page! And, it turns out that you can install it on a much older version of Ubuntu (version 12.04, aka "Precise Pangolin") but it also looks to be a more difficult installation. I'm in no mood to mess with RTAI (Real Time Application Interfaces) Linux kernel patches to get stuff working right now.

I was able to actually play simulations with it after the full install (rather than running it off the bootable USB drive) and the flexibility and options are quite impressive...especially for someone who doesn't even know what they are looking at! Unless there are better suggestions, I will plan to buy or build a dedicated simple single-core desktop computer with a relatively small solid state drive and 1Gbs network interface card to be the host computer for LinuxCNC. I don't need to build any fancy integrated controller contraption with a touchscreen, I am perfectly content with a computer, monitor, keyboard, mouse and an RJ45 cable strung to a separate box that will house the machine controller board, drivers, power supply, etc. Question...

1. I have seen several options for motherboards and computers as LinuxCNC hosts, are there any 'no-brainer' low cost used business/government surplus computers off eBay that I should just buy and be done with it?

As far as controller boards go, I think the Mesa 7i76e board seems to be the ticket since I can connect to my [soon to be acquired] dedicated LinuxCNC computer via RJ45 ethernet cable. Questions...

1. It appears that this card already has the ability to connect to up to five motor drivers, I don't need a break-out board (BOB) then, right?
   
2. If above is true, if I wanted to, could I still attach the nifty C35 Quick Setup BOB via DB25 cable to simplify the wiring to the drivers in my controller box?
   
3. Is there any other Mesa card that I need to or should just buy while I'm at it?

As far as motors go, I am leaning towards the LiCHUAN closed-loop hybrid steppers. In my research on this topic I have found another set of confusing terminology in this industry. It seems that quite a few people on the interwebs incorrectly refer to their closed-loop stepper motors as 'hybrid' stepper motors, while in fact they may not be hybrid. It seems that the 'hybrid' stepper is actually a particular design combination of variable reluctance and permanent magnet motors, separate from being closed-loop. Questions...

1. LiCHUAN offers both a two and three phase motor design option (not to be confused with the phase of AC power). I assume the three phase is better, but is it worth the extra cost?
   
2. I have read that it is very important to choose the correct size motor for the application (not too small, not too big). The HOSS plans suggest a 570 oz-in motor for X and Y and a 906 oz-in for Z. I have also read that hybrid steppers have a different torque curve than standard steppers. Should I go with lower torque motors for the LiCHUAN hybrid steppers or just get whatever is closest to the HOSS plans?
   
3. These motors look like they have a 5 or 9 pin serial cable for the encoder signal. Do these just connect back to the appropriate driver for that motor, or is it more complicated and I would need a MESA daughterboard or something that I would need to hook them up to the 7i76e board to close the loop?

Thanks again to all of you for suffering my ignorance, this information is really helpful! Maybe it will help somebody else out as well.
v/r,
JJ

[DJEkim33]

1. I have seen several options for motherboards and computers as LinuxCNC hosts, are there any 'no-brainer' low cost used business/government surplus computers off eBay that I should just buy and be done with it?

There are a few you can look at. I used an Intel D525mw which were commonly used in schools and businesses. Integrated graphics card and very low profile. Got mine for $25 shipped off ebay. Just need a case(or put it inside with the rest of the electronics), pico 60w power supply, RAM and an SSD. All totaled mine was $80 with a wireless card.
Intel D525MW Dual Core Atom CPU D525 1.8Ghz Mini ITX Motherboard Intel | eBay
Here is a list of computers that do and do not work based on latency, which is not a big issue with your mesa card plan:
LinuxCNC Documentation Wiki: Latency-Test

As far as controller boards go, I think the Mesa 7i76e board seems to be the ticket since I can connect to my [soon to be acquired] dedicated LinuxCNC computer via RJ45 ethernet cable. Questions...

1. It appears that this card already has the ability to connect to up to five motor drivers, I don't need a break-out board (BOB) then, right?
   
2. If above is true, if I wanted to, could I still attach the nifty C35 Quick Setup BOB via DB25 cable to simplify the wiring to the drivers in my controller box?
   
3. Is there any other Mesa card that I need to or should just buy while I'm at it?

The 7i76e is an FPGA and breakout board in one. As i understand it it will handle the step generation and I/O (input/output) functions that you would want a breakout board for. You could use the C35 but you really don't need most of what it does. Why woud you want the C35 also?
As far as other mesa cards I am not as familiar with the 7i76e and use the 5i25/7i76 combo. Which is fine for what you are doing, is very well supported and is what most folks are using who are converting to Pathpilot which is the Tormach Linuxcnc based controller. I know you want an ethernet connection but there will be no speed difference for one combo over another in your situation. The 5i25/7i76 does use a db25 but it is not a parallel port connection like you may assume. The 5i25 goes into the pci slot of the computer and is your FPGA (generates steps instead of the computer) the 7i76 is a breakout board and connects to the 5i25 through a db25 cable(not the computers parallel port). Really not much difference between the two setups but you will see more 5i25/7i76 in the hobby community.

1. LiCHUAN offers both a two and three phase motor design option (not to be confused with the phase of AC power). I assume the three phase is better, but is it worth the extra cost?
   
2. I have read that it is very important to choose the correct size motor for the application (not too small, not too big). The HOSS plans suggest a 570 oz-in motor for X and Y and a 906 oz-in for Z. I have also read that hybrid steppers have a different torque curve than standard steppers. Should I go with lower torque motors for the LiCHUAN hybrid steppers or just get whatever is closest to the HOSS plans?
   
3. These motors look like they have a 5 or 9 pin serial cable for the encoder signal. Do these just connect back to the appropriate driver for that motor, or is it more complicated and I would need a MESA daughterboard or something that I would need to hook them up to the 7i76e board to close the loop?

JJ

The 2 and 3 phase will have different torques and more importantly they have different number of steps per revolution. Stick with 2 phase and you will be fine as they are 1.8 degrees per step and that is what Hoss's plans call for. The 3 phase are 1.5 degrees per step and you would need to rethink your ball screws.
As for torque the Lichuan are rated in Nm so you will need to convert those numbers to find one that works. It looks like they have a nema 24 that is 4.5Nm which is 637 oz in and a nema 34 that is 6.5Nm (920 oz in). The encoder on the motor goes to the driver which will track the position. The driver will send the breakout board (7i76e in your case) a fault signal if it does not perform the move commanded. To get it all working you will have 3 sets of step/dir signals out of the 7i76e, one for each driver. And the drivers will each send a fault and move complete input signal back to the 7i76e that will go into one of the input slots of the card. There is no need to read the actual encoder values in Linuxcnc, you just need to know if the motor did not do what it was supposed to, the driver will use the encoder to achieve the move on its own. The closed loop will be a bit harder setup then the open loops but its manageable and if it gives you trouble you can leave the fault and move complete signals alone until you become more familiar with Linuxcnc hal files.

All good questions though and I know how you feel about your time constraints. I have 5 kids and sneak my cnc obsession in whatever block of time I can find. For linuxcnc this is a good set of documents to read to get you started, just remember that with a mesa card some of it does not apply. LinuxCNC

Mike

[JJ0704]

I think I have found a candidate eBay cheap-o PC with a J1900 processor that might work. It is impossible to determine the details of the specific motherboard in it since I don't have the serial number of that particular machine, but I'll assume that whatever it has it will be possible to isolate down to a single core. Hopefully using the 7i76e Mesa card should make whatever latency it has acceptable.

Intel D525MW Dual Core Atom CPU D525 1.8Ghz Mini ITX Motherboard Intel | eBay

Plus, I'm going to buy one of these, just because they are so darn cheap...might come in handy someday if I decide to convert to an all-in-one enclosure.

Why woud you want the C35 also?

Only because it makes the driver wiring easier and 'cleaner' looking (and its only $38). You just plug this C34KL adapter into your driver, then just hook them up with a short RJ45 patch cable.

Next step is getting a quote for the closed-loop hybrid steppers and drivers.

JJ
p.s. - thanks for the links...very helpful!

[ger21]

My single biggest 'gripe' about LinuxCNC is that the development community has not spent enough time to simplify it for the general public to consume

Imo, it's because they think it already is. I've read numerous posts from the Linux faithful claiming that it's no more difficult to use than any of the windows controls.