Counter balancing Z axis..

[ger21]

Really, and I've mentioned this before, unless you have to run very high microstep rates, maybe you have servos with high encoder count, or have to run the machine at very high speed (i.e. laser engraving) it's likely unnecessary that you'll reap an advantage by using an external motion controller

And on the other hand, I've seen posts from probably over 100 people that couldn't run their machines reliably with the parallel port, and switched to motion controllers.

it seems like lots of users are not having issues so maybe this is just an oddity with my hardware and software that I have running in conjunction with Mach...

From what I see, most people building machines have been using motion controllers for the last 5 years or so.

The majority of people still using the parallel port are the ones buying cheap chinese machines that come with a Mach3 demo, or pirated license.

[ger21]

The primary advantage to using an external motion controller is that it is doing it's own trajectory planning

Mach3 and it's competitors do the trajectory planning in software. The motion controllers only handle the step/direction and I/O.

Controllers doing their own trajectory planning cost at least 5-10x more.

[Jim Dawson]

Mach3 and it's competitors do the trajectory planning in software. The motion controllers only handle the step/direction and I/O.

Controllers doing their own trajectory planning cost at least 5-10x more.

Gerry, you just pointed out one of my pet peeves in nomenclature. If it doesn't do its own trajectory planning, it's not a motion controller but rather a fancy BoB with some on-board processing capability. But you are correct, a real motion controller is expensive.

[louieatienza]

And on the other hand, I've seen posts from probably over 100 people that couldn't run their machines reliably with the parallel port, and switched to motion controllers.

From what I see, most people building machines have been using motion controllers for the last 5 years or so.

The majority of people still using the parallel port are the ones buying cheap chinese machines that come with a Mach3 demo, or pirated license.

Well, that's a hundred over an installed base of probably tens of thousands, if not hundreds of thousands. I tend to wonder how DIY CNC survived 9-10 years ago when USB motion control boards weren't prevalent? I think "most people" is a bit misleading. most people still do this on the cheap - meaning computer with parallel port. I also think that most people that use Mach3 with a parallel port are not "pirating" software. Heck, I invested a lot of money on CAD/CAM.

I have the same Mach3 license, which is a "forever" license, with the MachStdMill free screen set, running through a parallel port. I also own both SmoothStepper and EdingCNC boards as well. Jim's right - I guess the nomenclature is confusing. These are really USB pulse generators not motion controllers technically. Maybe I'll give Mach4 a shot when they decide that the parallel port driver is a necessary "basic" part of the package and not a $20 add-on. Besides, I could get a UCCNC100 and their software for about the price of Mach4, and while the EdingCNC board starts at 219e, the software is free.

[louieatienza]

Louie, while I agree that computer multitasking on a running machine tool is not a good idea, it is possible to do so with an external motion controller. I'm glad to see there is someone else that is crazy enough to run ''lights out''. Like you, I run lights out for much of my router work which generally runs 9-12 hours per run, but normally I don't do that with my mill because the runs are usually much shorter. If I were using a open loop system and/or without an external motion controller that has fail-safes programmed in I would not be comfortable doing that.

The primary advantage to using an external motion controller is that it is doing it's own trajectory planning and on-the-fly position error correction, in addition to taking the load off of the Win computer. This is typically a much more accurate system than running from a parallel port. This is how I manage to hold mill tolerances on my router, typically < +/- 0.001 inch. Buffer underrun/overrun should not be a problem in a properly written CNC program.

That's cool... I don't think it's crazy - just a testament to setting up a stable system I suppose, and not trying to stretch out the performance of the machine. It's all stepper motors, so no closed loop. Not even home or limit switches. But with conservative rapids and acceleration settings, it's extremely reliable. Only bonehead operator errors, like re-drilling a hole where I installed a fixture bolt, or stupid things like black-outs, gave me problems. Luckily these were nested parts and I was able to recover most if not all after getting back up.

Ad to multitasking, that is not as much an issue with writing a CNC program as much as writing a CNC program that's fully Windows compliant - meaning being able to share and allocate resources, run in the foreground or background, run windowed, etc... It would be tough to clog up a USB1.0 interface at 12Mb/s, let alone USB2.0 at 480Mb/s or USB3.0 at almost 5Gb/s... Most WinTel computers from 12 years ago can pump out 40kHz step frequency, so most folks running max 10X microstepping can still use a parallel port and run their machines reasonably well. I came to this conclusion about 5 years ago with the SmoothStepper, which is why I went back to the parallel port on my larger router.

[109jb]

If you really want to eliminate real-time issues with the OS, without having to buy an external motion controller, you could download the shareware TurboCNC which time in good old DOS. My first machine I started for a short time with turbocnc and it worked great. I shortly after switched to LinuxCNC(free open source) which has a modified Linux realtine OS that LinuxCNC monitors for excess latency. I have had no problems other than a few warnings that did not result in errors at the machine. As I said, my machine runs 200ipm on all axes.. just a few more options.

Sent from my Z958 using Tapatalk

[OlfCNC]

These are really USB pulse generators not motion controllers technically.

They are mostly not just "pulse generators", most of them have their own built in functionalites for example the THC control, spindle PID control and things like that which functions have to be optimaly realtime working.
Some others even closing the loop inside the motion controller running the PID loops on the controller.
Generating pulses is only a part of the job of motion controllers, most of them doing many other tasks too.

[OlfCNC]

If you really want to eliminate real-time issues with the OS, without having to buy an external motion controller, you could download the shareware TurboCNC which time in good old DOS. My first machine I started for a short time with turbocnc and it worked great. I shortly after switched to LinuxCNC(free open source) which has a modified Linux realtine OS that LinuxCNC monitors for excess latency. I have had no problems other than a few warnings that did not result in errors at the machine. As I said, my machine runs 200ipm on all axes.. just a few more options.

I gave both a try, but I'm the type of guy who likes to see what is going on and TurboCNC unfortunately do not really show that with it's outdated DOS text type graphics.
With Linuxcnc I had difficulties setting it up and once I thought I managed to set things up it started loosing steps ... yup I used no motion controller, only parallel port.
My plasma machine now runs fine with a UC400ETH with 20m/min (about 780 IPM) rapids without problem.

[109jb]

I gave both a try, but I'm the type of guy who likes to see what is going on and TurboCNC unfortunately do not really show that with it's outdated DOS text type graphics.
With Linuxcnc I had difficulties setting it up and once I thought I managed to set things up it started loosing steps ... yup I used no motion controller, only parallel port.
My plasma machine now runs fine with a UC400ETH with 20m/min (about 780 IPM) rapids without problem.

A 780 IPM plasma and the OP's router which he already stated has less than 100 IPM Z-axis are totally different animals. I admit they are not for everyone, but they worked well for me on my machine at about 27 kHz stepping rate. If you have to have a backplotter then TurboCNC doesn't have this as OlfCNC mentioned, but I learned to operate cnc's back in the 1980's when not even the industrial machines I ran had backplot. I don't really view having a backplotter as a necessity.

TurboCNC and LinuxCNC are presented simply as options for the OP. If anyone doesn't like them that's OK, but my 200 IPM 3 axis milling machine has been running on LinuxCNC since 2012 without a hitch on an old Pentium III desktop that was salvaged for free.

Another possibility if the OP likes to tinker and experiment is Grbl. Grbl runs on an Arduino that you can purchase a clone of for about $5. The Arduino can be connected to the existing BOB, or can take the place of the BOB. All of the realtime step generation tasks are performed on the Arduino and the "host" can be any USB equipped computer. The USB communication is not required to be real-time in any way whatsoever. The Arduino running Grbl, as simple as it is, is really a motion controller. It accepts G-code via simple text stream over the USB serial connection and interprets it and acts on those commands generating stepper pulses, PWM for spindle, actuating relays for coolant, etc. If the "host" can't supply the g-code fast enough, Grbl doesn't care, it just runs the commands it has received and waits for the next one to arrive. This is not really a concern, as I have run test codes with up to 3-million lines of g-code using a atom N270 powered netbook and it keeps up fine. The command set is limited but very functional if using CAM. Fusion 360 has a Grbl post-processor, so you can do just about anything you want. As mentioned, the "host" computer can be any USB equipped computer. I run my user interface on an old HP mini netbook running Windows 7.There are user interfaces for Windows, Mac, Linux, etc. I made an adapter for my previously mentioned milling machine to connect the Arduino to the existing BOB for my LinuxCNC setup and can run Grbl using this adapter. The step generation is limited to about 40 kHz (30 kHz officially), and at least on my machine I can run as fast with Grbl as the LinuxCNC setup (about 27 kHz). I have examined the step pulse on an oscilloscope and it is a just about perfect square wave all the way up to 30 kHz. This option will probably only appeal to those who like a new adventure, or the cheapest penny pinchers out there. I fit both of those descriptions, and have enjoyed working with Grbl. It isn't "plug and play", and does have limitations, but works well. I have a second machine that runs Grbl exclusively and has performed flawlessly. If interested or intrigued, here a picture of the "adapter" i originally made for my machine. This one used an Arduino nano, but I would only recommend a UNO or Mega 2560 with a Atmel 16u2 USB to serial chip because of communication issues with the import CH340G USB to serial chips found in some of the clones.



Here is a video of my first machine running the roadrunner g-code program using Grbl.



Again, these are just suggestions from my personal experience. I enjoy tinkering with my machine just about as much as making parts with it. If you want to just plug and play then the UCXXX controllers are probably a good bet, but if like me you like to tinker, then these other suggestions may appeal.

[adam_m]

I'd like to stick with Mach3 since I own it and am a bit comfortable with it.. but by no means an expert. If I didn't already, I probably would be talking about the Linux alternatives for my CAM software.

I've noticed that the pulse output is mentioned a bit in the external motion controllers, SmoothStepper is 4Mhz, how does this impact the performance of the machine and how does it compare the parallel port on most motherboards?

Also, does the Mhz rating also impact Mach? Meaning is it compatible and more acclimated to some than others?

I think my game plan at the moment will be to try an older PC and see if the problem abates. If so, then I'll know what I'm dealing with after which it sounds like I'll need to decide on whether I want to muli-task on the PC which will dictate the long term solution.

Adam,

[ger21]

I've noticed that the pulse output is mentioned a bit in the external motion controllers, SmoothStepper is 4Mhz, how does this impact the performance of the machine and how does it compare the parallel port on most motherboards?

The original Mach3 Kernel frequency, and still most commonly used, is 25Khz, or 25,000 steps/second. 4Mhz is 160 times faster.
Note that the pulse rate is configurable in software. Good thing, because you won't find any stepper drives that can receive pulses anywhere near that fast.
Better quality stepper drives have will have a 200-250Khz maximum. Cheaper servo drives maybe 500Khz max.
At 4Mhz, the drive needs to see the step pin change state 8 million times per second (on-off 4 million times)

Also, does the Mhz rating also impact Mach? Meaning is it compatible and more acclimated to some than others?

Not sure what you mean here. If the motion controller has a Mach3 plugin, then it will be able to run at any frequency it's capable of.

I think my game plan at the moment will be to try an older PC and see if the problem abates

Your earlier post would indicate that your current PC was fine. You said it ran for 30-40 minutes with no problems, until you started doing other things on the PC?

Two things you should do with your current PC before switching.
1) Run drivertest.exe in the Mach3 folder, and watch the pulse rate at the top, and see how steady it is.
2) Open Task Manager and monitor CPU usage while Mach3 is running g-code.

If you have a steady pulse rate, and CPU usage under 50%, then your PC is probably fine.

[louieatienza]

There's actually another thread on SmotthStepper issues in the CNCRP forum, which brought up some good ideas for "cleaning out" your PC which are even more important with CNC parallel port use (as well as some I'll add):

- Use msconfig to remove unneeded services and startup programs
- Keep the PC offline
- Disable or remove any antivirus software.
- Always run Mach3 maximized. Resist the temptation to leave other windows running in the background.
- Turn off any power saving features
- Turn off CPU throttling in BIOS. While your there, it's a good idea to check and make sure your parallel port is set to EPP mode.
- ArtSoft also recommends a dedicated GPU with at least 256MB RAM.

[A_Camera]

I gave both a try, but I'm the type of guy who likes to see what is going on and TurboCNC unfortunately do not really show that with it's outdated DOS text type graphics.
With Linuxcnc I had difficulties setting it up and once I thought I managed to set things up it started loosing steps ... yup I used no motion controller, only parallel port.
My plasma machine now runs fine with a UC400ETH with 20m/min (about 780 IPM) rapids without problem.

...and I am running my CNC with 8000mm/min (315in/min) on each axis with the UC300ETH. Linux is fine if you are a Linux fan or a computer geek. For "ordinary" people, Windows is better, easier to use and much more flexible, especially for hobby use.

[adam_m]

So, after purchasing a smoothstepper and making as many PC changes as possible I'm still losing steps in my Z axis. I'm very disappointed...

The steps in this case were lost 17 minutes after the job started, I had previously ran the job for an hour + before stopping for the evening and then restarting the job today.

After I realized the steps were lost I re-homed the Z axis and finished the run.

Could this be a driver problem since only appears to be happening on the Z axis? I currently run a G540, so I would have to purchase an additional unit... suggestion on that??

So a recap -

- switched cables
- switched motor
- installed smooth stepper
- closed applications on PC, but with a smoothstepper I was under the impression it would not be a problem.


Any other ideas?

Adam,

[ger21]

Did you ever try reducing the acceleration below 15, or checking the temps on the G540? I just looked through the thread again, and didn't see any mention of it.
The fact that it doesn't happen right away sure seems like a heat related issue.
Do you have a heatsink or fan on the G540?

The drives in the G540 are replaceable. to check if it is a drive issue, I'd swap the Z drive with one of the other 4 and see if the problem moves to another axis, or stays on the Z.

[adam_m]

I did check the temps on the G540 and I didn't think they were extreme and it was pretty consistent and it does have a heat sink on the back of the unit.

I would think if it was experiencing heat issues that I wouldn't have been able to get an 1 hour + worth of cutting in the other night without issue, today 17 minutes. With electronics I realize that can be a crap shoot..

I also did turn down the acceleration on the drive but set it 15 from 20 I believe.

I'm leaning towards the G540 z axis having a problem. In order to make the swap on the axis how would I do that? I'm assuming that would be only on the ports and pins menus...

If I wanted to purchase another driver for the Z axis in addition to the G540, any recommendations you could make?

Adam,

[ger21]

I'd set the accel to 5 or 10.

The simple way to test the G540 is to swap the two cables, and swap their pin numbers.
You can call Gecko and get a replacement drive for your G540. That's the simplest option.

[wizard]

These sorts of things can be tough to diagnose!

Are you 100% sure that there are no mechanical issues?

As for electrical issue there can literally be hundreds potential causes. I once had a Parker drive that we thought was defective and spent days after swapping the drive out trying to figure out why we would loose step rate from time to time. ( the stepper in this application had to run at a fixed and precise speed). Come to find out it was one of the connectors plugging into the drive that was intermittent. Sometimes you have to go over the system from start to finish too make sure everything is 100%. I'm in the habit now of giving every wire I terminate and connect a little tug to make sure it is secure.

One thing I don't see indications of here is swapping your steppers from the Z axis to another and running that way for a bit. (yes major code changes but only temporary). The idea of course is to try to isolate what exactly is causing the problem. Also considering swapping just the steppers if the swapping of electronics rubs you the wrong way. Steppers can fail thermally if they heat up enough for the rotor to drag on the stator. Clearances in stepper motors can be extremely tight so a little heat, a bad bearing or something not concentric from the factory, can cause all sorts of problems that don't show up immediately.

I did check the temps on the G540 and I didn't think they were extreme and it was pretty consistent and it does have a heat sink on the back of the unit.

I would think if it was experiencing heat issues that I wouldn't have been able to get an 1 hour + worth of cutting in the other night without issue, today 17 minutes. With electronics I realize that can be a crap shoot..

I also did turn down the acceleration on the drive but set it 15 from 20 I believe.

I'm leaning towards the G540 z axis having a problem. In order to make the swap on the axis how would I do that? I'm assuming that would be only on the ports and pins menus...

If I wanted to purchase another driver for the Z axis in addition to the G540, any recommendations you could make?

Adam,

If you think you have a drive problem go to Gecko for a replacement if it is under warranty if not still go to Gecko for a replacement. As far as I know they are still maintaining quality and are a reasonably good value. You should be able to run the drive at or below its rated current with no problem. The trick here is make sure you actually have a driver problem. That requires that you isolate the Z axis driver from the rest of the Z axis. One option was described above but you could also swap drives. Frankly swapping drives is a time tested method of isolating weird problems in a servo system.

[adam_m]

Thanks for the posts.

I'm pretty sure Wizard that this is an electronics problem and not some type of binding issue - but as you say tracking this down is difficult and its really starting to annoy me.

I reached out to Gecko this morning and I'm sure I'll get a response.. I'm thinking that maybe for the cost of a driver it may be worth it to just replace it, that would at least in my book eliminate the driver as the problem.

Gerry, I assume this is the screen you're referring to as for switching the pins..



I've switched out the motor already thinking that was the problem but had similar results.

In the short term I may try the cable switching and the pin change.. what will a Y axis missed step look like something that should be round looking like an oval?

Adam,

[adam_m]

I just thought I would close the loop on the issue I've been having.

I found a video on youtube for swapping out the axis drivers on a G540 so that was my approach since I had already tried everything else.



I disassembled the G540 and swapped the Y axis for the Z axis and immediately I noticed that the Z drive was quite as a mouse and the Y drive was having problems moving. So I ordered a drive after speaking with Marcus at G540 and sent in the old driver for repair, I haven't had a missed step since I replaced the stepper driver.

I've been dealing with that issue for years, rebuilt the Z Axis, etc. I'm glad that's finally gone.

Thanks for all the suggestions and help with this one.

Adam,