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If you have stalling problems then you must start by fixing those, before you start milling or try to figure out the missing steps. It may be the stalling which causes the issues you have. Anyway, stalling can be caused by too high speed and acceleration or some mechanical or electrical problems. Locate the source and fix that.Quote:
Originally Posted by totts
Disable jogging and fix the stalling issues first. You must be able to run rapids repeatedly without stalling. Once you can do that then you can start checking for the rest of the problems.Quote:
Originally Posted by totts
That diagram shows only how to connect an external PSU for the drivers, not the BoB. Anyway, if there is no external +5VDC input to the BoB you can always split the USB cable, separate it from your PC and feed it through those two wires. It is not a good idea to take the 5V from the USB because that is not always able to deliver enough power, or the voltage is too low for your opto couplers. Generally an external power supply is preferred because it is better and more stable.Quote:
Originally Posted by totts
I set up the machine and had no problems with short code but long code I found I had missed steps (after machining that part) so I then ran code in rapidQuote:
Originally Posted by A_Camera
G00X10Y10Z10
G00X0Y0Z0
Repeated this about 1000 times and it went back to 0
After running a few test in jog mode the motor stalls as per video.
I'm hooking up a new computer tonight to determine weather it's the pc or the Bob.
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Quote:
Originally Posted by totts
So you have no stalling at full speed? Run this a 1000 times:
G00X(maximum X)
G00X(minimum X)
...to check X and likewise for Y and Z separately to check stalling. Running as short as to 10 units (inches or mm?) can be too short to test for stalling, but it is enough if missing/extra steps are needed to be checked. Also it is better to separately test the axes because running all three at the same time may result in less speed per axis than the maximum.
I had previously ran the x axis separately. And the y,
Some progress!
I have tried a new computer tonight and all the jerky ness has gone so I'm going to get a new desktop pc sorted and run my tests all over again and hopefully get some parts made!
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Okay right after a new pic, running loads of test programs and the program itself in fresh air and then coming back down to a dti, and it returns to zero, I decided to run a test part.
Run the test part and I had it skip again argh!
I ran the program in fresh air but this time, I ran it with the spindle on!
And it skipped, so I've come down to interference.
Problem is, all my cable is cy cable, all grounded at one end, checked the earth continuity all is well.
But I have a cy cable on the vfd to motor cable which is earthed at one end and wondered if this could put interference down the earth? I've placed vfd at one end of my garage and the control on the other and currently running the program again so we shall see if I get the same problem.
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After a few mystery e-stops I tried putting a filter onto the mains side of the VFD but no improvement. I then ran an extension lead from the other end of the workshop and plugged the VFD into that, instead of the row of sockets for all the CNC stuff (PC, monitor, control box power mains supply). Not a single problem since and has been good for months. Note that the VFD and motor cables themselves are still in the control box, next to all the other electronics. It's just the power lead that is connected remotely and that has solved it.
Interesting, my vfd is on a different socket to the rest of the control, but it is on the same ring main just two sockets apart.
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Well the program has finished and it still moved so I'm going to take the shield off the earth tomorrow
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You haven't earthed the PC to the control box have you.?
Also do you have Earth on the Frame.? I'm presuming all your Earths go to one Star point.?
Nothing can cure a crappy board with poor filtering on the signals / i don't know what that is exactly but i know some boards are good :angel: and have it/ .
I had last week's similar problems, fortunately not with the motor output signals, just probes, switches and PWM output. Neiter filtering of line input, grounding, shielding or whatsoever helped. One of said boards worked well in other machine. All worked fine untill i switched my servos.
But in you case a shielded cable from board to motor drive might help. I have resolved a friends machine similar problem once, changing said cable with a shielded one. Problem solved. In fact his cable was shielded before but wires at end were very large, So i cut them at minimum so all is shielded. Changed cable just to be sure though, as i had a better one at that moment.
Are your cables between this and that shielded?
And by that mean that the shield must be grounded to case
I've tried to make all my signal wires shielded, there are just over two inches long at either end.
Machine frame is earthed via the spindle from one point and all shields are all going to one point. Pc control cabinet is earthed too.
But my pc has a shielded USB cable which means the pc and the control box is actually earthed together and I have had a few false errors at some point saying it was disconnected.
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The case of the pc should not be connected directly to the machine, if it is, try removing that link, I have suffered with this.
is the BOB ground connected to the chassis? pretty certain it should not be, none of my boards were.
No bob ground/neg isn't connected to earth, will remove the earth from the USB cable tonight
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So disconnected my USB shield from one end (control end) ran a program only moved 0.3mm instead of the 1.2mm, but found the resistance was high in the earth, the continuity on my multi meter was struggling to pick it up, I checked continuity through my control cabinet earth, which in turn is connected to earth ring main, pc and the USB again, managed to my continuity back, will run a program agin and hopefully will get that 0.3mm back!
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Today i cured all my problems by connecting my VFD ground directly to metal box with electronics inside. Incredible but yes.
As i read that Dean suggested no ground from box to PC, i remembered that when was desperate i did exactly that. Took off ground from PC side and spindle started rising and slowing speed. I said to myself that things are getting worse like that, but as the ground to box was still connected i started touching it around. Touched to ground on socket and was better, touched to PC box- better, then accidentally touched to VFD ground and voila, all was fine. They have common ground at socket, but cable between boxes cured all problems.
So you have USB shield earthed at box end and the vfd earthed there too? Have you a shielded cable from ur vfd to motor?
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I have all earthed at box body -PC, all Transformers inside, etc. The VFD is outside, just near the box. Yes it has screened cable to the spindle connected both ends. So it's connected to machine. Machine is also connected to box. So all also is grounded together at socket. Go and figure then why problems disappeared when i connected VFD box with big box. In other words- they were grounded at socket and machine prior to the bypass cabling that solved problems.
I could only say that my stupid persistence lead to a result. I was many times at point of taking my big hammer and ...
All this talk of Grounding and Earthing, is making me even more confussed!
Is Grounding connecting to 0V dc and Earthing to a Star earthing point or am I missing something, or are we mixing up the terms?
Grounding and Earthing often creates a lot of confusion and to some extent depends how old you are. But you don't connect your DC ground to the Star point which is the point where all the screens connect to and then that is connected to the AC earth. The reason for the Star point is to get rid of earth loops (or ground loops if you are old).Quote:
Originally Posted by nairepooc
Sometimes you have more than one DC power source and again somtimes you have to connect the various DC power -ve together. Hope this helps a bit.
Sorry, my mistake then. In my mother language -ground and earth is the same word, not 2 different. So when i say Ground or Earth, i mean the same. Stick 2m long in the ground that is connected to all grounds in house line electricity, mind not the 0 or phase. If we are talking for DC i say Negative or Common ground. I am not sure that's right, but as English is not my native language ...
Dictionary wise both are same.
But in electrical engineering context both words differ in scope. Ground is a general term that refers to a reference potential against which all voltages are measured. Earth is same as ground but used in context of power systems because the ground here is implemented by burying copper conductors deep down into Earth.
Since Earth has minerals, moisture and it has practically infinite volume, the current flow is only limited by contact resistance between ground/earth conductor and soil. Because of this, on the distribution side, the neutral is connected to earth. On receiving side, fault current from one of the phases can flow into the local earth conductor and make its way to the neutral at distribution side. Apart from being a sink for fault current, the Earth conductor also serves as a return path for instrumentation systems.
:)
Look who swallowed a dictionary.....nice clarification, cheers Dave 😊Quote:
Originally Posted by Davek0974
Yes Dave good clarification one of the problems that has been highlighted is that different disciplines treat the words different such as in electronics PC boards often have a ground plane that is not connected to earth but to DC ground or signal ground in this case ground is not earth.
Yep, it's a thorny subject, don't forget the chassis ground, signal ground, RF ground - there are loads of grounds but they do not have to be connected to earth :)
My head hurts! Haha think I'm going to come back to it when I have more than half an hour to play!
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Keep on the good work mate
Can you post more pictures
Hello all, i had found that disconnecting the shield connection to the vfd to motor wires cured the problem, hence why i haven't been on here as i have been playing with the machine :) now i have a bit of free time where the machine can make some bits for itself!
I might actually finish it as intended! Hanvent come across any other problems apart from that!
I have been looking at getting a trough made up for it, so i can get some coolant running, as this seems to be the limiting factor of pushing its machining capabilities.
Also im not wanting to stand around for 2 hours with a bottle of coolant :)
Hello,
Bit late to the party but i'm new to the site and new to building CNC machines. Would be really interested to know roughly what your eventual budget for this project was? It's been suggested to me on here that i consider converting a manual milling machine rather than starting from scratch and i'm curious as to roughly how it weighs up in terms of cost.
Thanks!
Alex