Author Topic: X axis problem  (Read 18306 times)

arvydas

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X axis problem
« on: September 07, 2015, 07:07:59 PM »
I think my RV1S has a problem with the X axis. I can definitely hear a different sound when I manually move the machine in X direction (technically when I move more for the X motor rather than Y). Y movement sounds very smooth, but X has this grinding sound Mike mentioned in one of the other posts. I've seen Mike's video about fixing the hybrid module, but before I go that path does anybody have suggestions on how to diagnise the actual fault?

phonoplug

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Re: X axis problem
« Reply #1 on: September 07, 2015, 07:11:22 PM »
When you say 'move it' do you mean under machine control, or move it by hand (eg with the e-stop switch pressed)?

arvydas

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Re: X axis problem
« Reply #2 on: September 07, 2015, 07:35:12 PM »
In RVPlace I use the control menu to move the arm.

phonoplug

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Re: X axis problem
« Reply #3 on: September 07, 2015, 07:39:32 PM »
How does it feel when powered off? Is it nice and smooth like the Y? This should rule out mechanical problems. Somewhere else in an old thread there is a picture of someone who had a shreadded drive belt -I think this is uncommon but clearly it has happened before.

arvydas

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Re: X axis problem
« Reply #4 on: September 07, 2015, 08:06:42 PM »
Can't tell right now as I'm out of the office. Will check this first thing tomorrow morning. Is it safe to move the arm when the machine is turned off or should I diconnect the arm connectors first before moving it just to be a bit more safer?

phonoplug

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Re: X axis problem
« Reply #5 on: September 07, 2015, 08:33:22 PM »
Its fine to move things when its off. Just be careful not to bash the head into anything as it will be in its lowest position!

arvydas

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Re: X axis problem
« Reply #6 on: September 07, 2015, 09:31:49 PM »
Thanks for the info. Will try to make a video if possible to show what I mean.

Mike

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Re: X axis problem
« Reply #7 on: September 08, 2015, 12:07:48 AM »
You need to move the arm slowly  - the steppers generate voltage, and if you move too quick they start trying to power everything - you can sometimes see the illuminator LEDs coming on!

You do get some difference between motor noises. something that may be worth trying is doing a lot of very small steps  & see if some are noticeably rougher than others. Position the arm so it's mostly one motor moving.
The issue I had was one motor phase not being driven due to an open contact on the D connector at the base.
If you measure the motor resistance at the stepper driver board, you should see the same resistance (a few ohms) between each adjacent pin and the 2 outer ones - the motors have 5 coils, connected as a ring. 

arvydas

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Re: X axis problem
« Reply #8 on: September 08, 2015, 10:49:03 AM »
Made a video of everything discussed:

https://www.youtube.com/watch?v=uOUajRDRBQM

Video is in three parts: moving by hand, warmup and moving using the controls on the RV place. The last bit hopefully will show what I mean. It's not quite grinding, more like buzzing sound, but I don't get the same sound on the Y axis.

I can't tell the exact difference when moving the arm by hand. It sort of feels slightly different, but I can still move it freely.

Measured the resistance and I do get a few ohms as suggested. Tested both X and Y motors.

Mike

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Re: X axis problem
« Reply #9 on: September 08, 2015, 04:27:15 PM »
That does sound a bit rough. If cabling is OK, could be a dead driver output.
Unplug the motor and use diode test on meter to test both ways from ground to each output pin and supply to each pin - all channels should read the same.
Or look at the outputs on a scope - again each output should look similar.
Don't connect or disconnect motor when powered as back-EMF can cause damage. 
I have some new driver hybrids.

arvydas

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Re: X axis problem
« Reply #10 on: September 08, 2015, 05:03:33 PM »
Mike, thank you very much for your help! I think it was a dodgy power extension lead I used to connect the machine. Replaced it with another high quality one and the machine runs a lot smoother now. The machine is placing the components a lot better now too! There is still buzzing on X axis, but only at higher speeds and a LOT less noticeable. Still bugs me though! I'll contact you directly about hybrids. Would like to have some spares just in case as they seem to be not easy to get a hold of.

I now highly suspect that the issue may be with power. Changing the extension lead has proven to be a significant improvement. Don't have a clue about power wiring in my office, but will try to buy or make a beefy power cable to connect the machine from a power outlet on the wall. It's currently connected to power socked on the wall between the two rooms in the office and I suspect that it may be not up to the requirements for the machine.

Had a look at the internals of the power control box. Would like to eliminate the issue with the stepper driver module. Is it safe to swap those modules around for the machine or are they calibrated for the axis?

Mike

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Re: X axis problem
« Reply #11 on: September 08, 2015, 06:03:31 PM »
I wonder if it's your smoothing caps going bad - stick a scope on the DC rail while running. Also a meter on the AC mains to see if you get any variation when running - if it's on the low side it may be an issue, though I'm not sure why it would only affect one axis. If voltage is marginal the symptom you'd probably expect is missing steps at some coincidence of all motors moving.
AFAIR the stepper drivers are identical but the Z axis has different  switch settings as it keeps the motor on all the time to stop the head dropping.  Make a note of all settings!

If you want to experiment, the rotation axis is the safest one as it won't break anything by hitting endstops.

Also remember that if you have a short that has blown a driver, swapping could kill another one!.
Worth checking that when unplugged there is no measurable conductivity between the motor pins and ground. Test while wiggling cables etc. to check for intermittent issues.

I don't know why the hybrid on mine went - it doesn't seem to be a common problem. Best guess is a wiring short to ground but I checked everything pretty carefully. As a precaution I've put fast-blow fuses in the supplies to all of the boards but not had any issues since.


phonoplug

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Re: X axis problem
« Reply #12 on: September 08, 2015, 09:24:14 PM »
Just seen your vid. I had exactly the same problem. Is your motor box the older type with a couple of parge toroidal transformers in it?

Its the connections going on to each of the motor drive cards. They are IDC and a bit crap, possible not crimped with the proper production tool, and if they have been taken of and put back on a few times they come lose in the IDC 'fork'.

I replaced them all (5-way motor one and 10-way power/control one) with better connectors which crimp on the wire properly (not IDC) and make contact to the pin on at least 2 sides and its been absolutely fine ever since. These are the connectors I used but you could use others:

http://www.toby.co.uk/content/catalogue/products.aspx?series=1900-TGB-L

With the machine off, try unplugging both connectors on each of the 4 drive cards and re-connecting them. You may find the problem disappears (for a little while) or possibly gets worse.

arvydas

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Re: X axis problem
« Reply #13 on: September 09, 2015, 01:13:58 PM »
Mike, will do the tests you suggested. Thanks!

phonoplug, I'm not sure about the motor box type, because I haven't seen any other types apart from mine. It does have a huge toroidal transformer in it, but just one. The connectors are indeed IDC and I will replace them with crimped ones. Did you use crimp housing for the connectors? Would be great to know the part number.

arvydas

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Re: X axis problem
« Reply #14 on: September 09, 2015, 01:56:17 PM »
phonoplug, it looks like you were right :-) For some reason didn't notice this yesterday, but probably because I didn't look thoroughly as this is right on the side of the bottom of the case! This is the very first wire that comes from the board with a huge cap. Would be very grateful with any suggestions on what would be the best course of action next :-) The connectors now have to be replaced. Probably have to check if the board is OK too.

http://agileinnovative.co.uk/other/rv1s-control-box-failure.jpg

http://agileinnovative.co.uk/other/rv1s-control-box-failure2.jpg

http://agileinnovative.co.uk/other/rv1s-motor-controllers.jpg

http://agileinnovative.co.uk/other/rv1s-toroid.jpg