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Hi all,
I was wondering if someone could point me in the right direction. I,m looking for an image of what a good & a poor pulse wave form (Mach3) should look like on a scope.
I have been having trouble with my stepper motors making a "Knocking" noise and missing steps and have narrowed the problem down to the computer. Tried everything to fix it, trust me! Also my question is, if my computer can pass the Driver test on Mach3 with a "System excellent" , then can it only leave a "dodgy" parallel port that could be distorting my wave form? I have hooked a scope straight onto the PP with no BOB, driver or stepper connected and the wave form looks very ordinary. And before anyone asks, yes my computer does meet all Mach3 recommended requirements.
Thanks in advance
Regards Julian
How about using a signal generator to feed the BOB in place of the parallel port?Originally Posted by sylvester1073
You can test each axis and see if the problem is caused by CNC hardware or PC software.
"Knocking" is hard to see on the scope because it means 1000-2000 good steps followed by a 1-3ms pause. It's hard to synchronize the scope to see that.
Hi eSilviu,
This is a good idea,thank you. I will see if i can borrow one from somewhere and i will get back to you with the result.
I still would like to know what a good and bad wave form would look like on a scope just to satisfy my curiosity.
Regards Julian.
Back in 2008 I tested four PP cards in a Shuttle computer with Mach3 operating at 100KHz step rate. The best card was a Koutech IO-PP210 (http://www.newegg.com/Product/Produc...-231-_-Product), here is the output;
http://www.pbase.com/eldata/image/127250909/original
The worst output was from the Shuttle onboard PP (super I/O chip);
http://www.pbase.com/eldata/image/127250931/original
And here is 100KHz from a function generator with duty cycle adjusted to match Mach3 output;
http://www.pbase.com/eldata/image/127250887/original
It is the lack of jitter that separates the sheep from the goats. You should ensure that C1E and Intel Speedstep (anything that dynamically adjusts CPU performance) is disabled in your motherboard's BIOS to minimize jitter.
Back in 2008 I tested four PP cards in a Shuttle computer with Mach3 operating at 100KHz step rate. The best card was a Koutech IO-PP210 (http://www.newegg.com/Product/Produc...-231-_-Product), here is the output;
http://www.pbase.com/eldata/image/127250909/original
The worst output was from the Shuttle onboard PP (super I/O chip);
http://www.pbase.com/eldata/image/127250931/original
And here is 100KHz from a function generator with duty cycle adjusted to match Mach3 output;
http://www.pbase.com/eldata/image/127250887/original
It is the lack of jitter that separates the sheep from the goats. You should ensure that C1E and Intel Speedstep (anything that dynamically adjusts CPU performance) is disabled in your motherboard's BIOS to minimize jitter.
Hi Eldata,
This is fantastic! I must be getting close to the cause of the problem. My scope image is similar to your worst image. Also, when i zoom out on my wave form you can see on every second or third pulse that the baseline continues through without breaking. So this all points to the PC not putting out a decent usable pulse stream. Therefore i make my assumption again that; If my motherboard & CPU combination is capable of passing the "Driver test" with flying colors, then the only other thing this leaves is the parallel port? What do you think....?
Julian.
- for sure a serial or usb interface will bring the best from your CNC. Now it depends on how much you are willing to pay for software+controller.
- or maybe you could return to DOS as the real-time, single task OS
- or you could try linux EMC2: download "ubuntu + EMC2 live" iso file, burn-it to a CD and boot from CD. It will run from RAM and CD, and it's easy to work with.
Hi eSilviu,
I was hoping to stay with Windows and Mach3. I'm not familiar with anything else. I guess it's just a comfort thing.
Can i put a hypothetical question to you guys? If a computer is producing a poor quality pulse stream out of the PP, then why wouldn't it also send a poor signal out through the usb or serial port?
Julian.
because:
- with PP, the software you are using (Mach) will controll every moment when stepper must do a step;
- with USB or serial, the software will talk with the controller on the CNC: "do 147 steps on X axis, with 100in/min speed". While the controller will execute those 147 steps, it can simultaneous receive the next command.
First case is equivalent to "I will write on this forum one letter/post"
second case is "I will write on this forum one sentence/post"
In wich situation do you believe we will better understand each other?!
Sticking with windows and Mach + necesity of performance will make you buy Warp9 SmoothStepper adaptor USB/CNC. (about 170 Eur without taxes)
At the same price or even lower there are other solutions, but you must give-up on Mach3.
eSilviu,
I understand your logic...I think
I have just got back from the shed and think i have found a problem. I put a meter across pin 2 & ground on my PP & i am only getting 2.6 volts out. My Gecko 251s require 3.3v minimum. After 2 months of head scratching and making changes, i never bothered to check what my PP voltage was. I just assumed it was ok because my motors ran and ran well even at thier highest speed allbeit with this knocking noise. If the Geckos minimum is 3.3v, then how are they working at all?? What are your thoughts on this?
Julian.
Q1. What else is running on the computer?
A1. See Mach3 notes regarding this. I'm assuming you are not using a laptop.
Q2. What maximum step rate do you need?
A2. Whatever, set the Mach3 kernel speed to the lowest setting higher than your desired max step rate.
Q3. Have you ensured that C1E, Intel Speedstep (or AMD equivalents) are all disabled in the motherboard's BIOS?
A3. Note that the driver test results are misleading when it comes to this and some other requirements. You can pass with flying colors but still have issues.
Q4. Are you using a dedicated PP card or onboard PP?
A4. Some dedicated cards and onboard PPs are subpar.
Q5. Does your BOB buffer inputs or output 3.3V or greater based on any input voltage (later you mention your PP output voltage is only 2.6V).
A5. If not, then get a decent PP card if the motherboard allows. I mentioned a decent card previously with 5V output.
I recall a particular Mach3 (non-lockdown) version that had a problem with output. However, it was quickly addressed. Make sure you are using a recent release of the software.
Finally, it is mainly servo setups, needing more than 100KHz step rates, that require more than PP capability under Windows. Mission critical production environments are another exception.
Hi Eldata,
Here is part of a post i submited in an earlier post
I have made a homemade CNC router/mill. All works well except for this persistent problem with the stepper motors locking up on me and missing steps. It is okay at the slow speed settings, but even then you can hear it occasionaly making a "knocking" noise. From mid range to full speed it makes a constant "knock'' or "ticking" noise at about one second intervals, followed by a " lockup" every 20-30 seconds of run time. Apart from this the motors sound nice and smooth.
I have disconnected the stepper motors from the machine and still the same problem, so it is nothing to do with friction etc.
I have tried everything i have read in these forums but to no avail!
My computer is desktop 1.8Ghz Pentium 4, 1 Gig ram, 16meg plugin video card, Windows 2000 pro. running Mach3 and absolutely nothing else. No antivirus, internet, or any other program is installed.
I run 3 x Gecho 251s on heatsinks through a Opto-isolated BOB.(not cheap Chinese stuff), with power supply and motors to suit. All cables are shielded and ground appropriately. I have tried the following:
1) re-installed Win. 2000 and latest drivers.
2) reinstalled Mach3, and tried the latest version.
3) Installed Windows XP. & service pack 4.
4) tried optimization, special driver, 1/2 Sherline mode, various step/direction pulse widths, enhanced pulsing, turned watch dogs off/on, tuned plug-ins off, played with Dir low/active etc. kernal speeds and everything else i have read in these forums.
5) I am an electrician by trade and have checked all connections and ground everything that needs to be.
Also i went into systems and disabled that many things it is a wonder the computer even runs.
I couldn't find C1E or intel speedstep in device manager but i will get my local computer geek to have a look today.
Now i'm sure the main problem is low voltage on the PP and possibly a poor pulse stream.
I've just got hold of a EPP PP card PCI plugin, so i will try that today and see what voltage out i get from it.
Thanks for your reply, i will let you know how i get on
Regards JUlian
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