Re: [CAD_CAM_EDM_DRO] Gecko ERR/RES Handling

Dan,

My son, Dave told me about this thread on Gecko faults, so I am tuning in
again for a couple of days.

I seem to have had excessive (in my humble opinion) faults on the G340's as
long as I have tried to use them until about two weeks ago. I use PC's
running at 700 mhz and faster. Is that what you would call a fast PC? I
use fast ones to get the step speed up.

The software I am familiar with usually puts out negative going pulses, by
default. In some software the polarity is selectable and some not. Has
this been your experience?

The first Gecko I ever recieved was defective. It took time for me to be
convinced that it was really bad, however, as I was almost brand new to
servos, having only installed one JR Kerr servo system. The drive was
cheerfully replaced.

My next Gecko experience seemed to be related to noise and grounding. There
was a time that I believe I was having faults because of encoder and other
types of noise. Not lately. You could review the list, I think in July,
and see the emails relating to noise and grounding with Geckos. I tried
everything I could think of, and seemed to be able to get past most of these
problems, but still had more faults than I thought I should.

Presently, my son is using two G340 drives we bought probably in February of
last year. They still have the bugs in them related to the times two
multiplier. I think I was the first to discover that bug, but Marris did
not duplicate it until someone else ran into it too. At least that is the
impression I have. Dave is using the * 5 multiplier, and both drives seem
to be working ok in that mode, with Supercam software on his plasma cutter
machine which is driven by motors that only draw a couple of amps at the
most. The motion is still not as smooth as he would like, but he has
learned much about the mechanics of rack and pinion servo driven mechanisms,
and his machine cuts ok as long as he keeps a hand on the gantry to dampen
the jerkyness some.

Marris had sent us a new drive in October, I think (boy how time flies). It
was one of the ones that did not hum when idle. It was a free drive, sent
to compensate us for all the trouble we had had. I was helping Dave at the
time, and that drive was nice, while it lasted, which was about a couple of
days before it started to act up in a way that seemed to be related more to
receiving step pulses reliably than with the PD motion loop. Since we knew
the last bugs were in the multiplier boards, and we had just unexpectedly
received "fixed" multiplier boards from Marris to install on the "old"
drives with the *2 bugs, I recommended to Dave that he try swapping out the
multiplier board on the new drive. We were excited about the quiet nature
of it, and the higher gain we were able to set on the new drive, and wanted
to use it. The new multiplier installed on this drive lasted about 20
minutes of running on Dave's machine. He was trying to get his plasma
cutter to move smoothly (no plasma cutter attached). He was trying to
figure out why the motion was so jerky-- Was it software? or inertia?, too
low a gear ratio? or what?! I was too busy to help him, and he worked on
this problem for many days and many hours. He finally replaced multiplier
board again, on the new but now very suspect drive (I wouldn't have done
this), and it too failed after a short while. So he gave up on the new
improved drive and went back to using the older two 340's with the * 2 bugs
in them that hum annoyingly while "at rest".

The dead "new drive" sits in a box of other broken Gecko parts. I suppose I
should send it back to Marris, but I have lost much enthusiasm for the
Geckos, particularly after we received a box with a packing slip in it
which said that the two promised replacement drives were enclosed, and there
were in fact, no drives in the box. The only satisfaction I received from
this was a mild rant from someone in Gecko's office. They told me that
three people packed the two drives in the box and that they were sent. When
we returned from a two week business/vacation trip, Dave opened the box
which was received in good condition from UPS and told me as soon as he
opened it that the drives were not there. I don't know how this kind of
situation can be resolved.

Since then, I ordered two new drives and they seem to be running ok since I
reversed the step polarity like you did, Dan. In this experience, I battled
the negative going pulse thing about two weeks ago. I am not as experienced
as you are (seriously), and the solution did not come as easy for me. I am
so thankful I have a good O'scope, and know how to use it, or I never would
have made it to this point. I hope more light gets shed on the positive
/negative step situation by Marris at least in the documentation.

I don't claim to have a lot of experience in the motion control field. I
have only been programming and retrofitting for about three years, and most
of that experience is with steppers. But have sold a few machines that are
working out there every day with my software and control on them. I only
have about 25 years of electronic technician experience too, so I realize my
frustration may be due to my own limitations.

I see that Marris has offered an improvement in the error handling hardware.
Marris is very bright, and a hard worker. I expect that eventually he will
get all of the bugs worked out, and the documentation updated.

Tom Eldredge

----- Original Message -----
From: Dan Mauch <dmauch@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, December 18, 2001 12:39 PM
Subject: RE: [CAD_CAM_EDM_DRO] Gecko ERR/RES Handling


> The only documentation that I know exists on the positive going steps
> issue is what I replied to. I hadn't run into the problem before I
> switched PC's out in my shop. The faster PC brought the issue to the
> front burner as I was testing, prior to shipping on one of my milling
> machines, a newly assembled G320 servo unit. It worked fine on my old
> computer during bench testing but was quite prone to faulting on my shop
> machine. Then I started trouble shooting because I hadn't run into this
> before. After a logical process of elimination I concluded that it had
> to do with the opto coupler and signal type and proceeded to change the
> type pulse and it cleared it right up. I called Marris a few weeks ago
> to let him know what I discovered so if other customers ran into this
> software problem he could advise them of the solution.
> Myself I don't use any pull up resistors on the step and direction lines
> and have had rock solid performance on a the GX0 amps/drivers. The only
> other issue that I know of with the Geckos' G320/G340 is the question
> about the encoder noise when using HEDS type read heads. But I have run
> my own tests with 100 ft of cable and no line drivers and no added
> capacitance and also found rock solid performance. But noise and
> faulting are two different problems and show up differently.
> I have had excellent support from GeckoDrive. But as one that also
> provides support for the Geckodrives that I sell, I can understand that
> it is difficult for a customer to isolate a problem when there are so
> many factors that could cause the problem. Doing it by telephone or my
> email is challenging.
> That is what is so good about CAD_CAM_EDM_Dro group is that there is
> always someone that can help.
> Dan
>
> -----Original Message-----
> From: David Eldredge [mailto:techdave@...]
> Sent: Monday, December 17, 2001 5:33 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Gecko ERR/RES Handling
>
> Dan,
>
> I think you are onto something regarding the positive going step pulse.
> Dad
> and I fought the geckos for a couple of days a couple of weeks ago,
> faulting
> all over the place, trying to get acceleration ramping right etc. It
> was so
> frustrating. Dad is growing to have a strong dislike for the Geckos,
> after
> having so many problems in the past with the earlier bug ridden drives,
> and
> another bad experience he had with the Gecko company.
>
> Finally Dad did just what you did and flipped the direction of the step
> pulses so that they were positive going and then things seemed to clear
> up.
> We were both so exhausted, I don't think we thought it all through,
> since
> Dad was focused on another problem relating to this in which his control
> was letting the step line float with only a 10 k pull up resistor on its
> input. Earlier drives he used in his system did not load down the step
> input line. He suddenly realized that the 10 k was not enough to pull
> up
> the input to the Gecko and so he reversed his whole scheeme and then
> reversed the step pulses so that they were positive going. Things then
> started to work better, and we finally got things working.
>
> Is there anything documented on this? Our Gecko experience has been
> very
> frustrating all around, and I don't know if Dad will go back to them
> again
> or not.
>
> I am glad Marris fixed the error/reset line problem.
>
> We were trying to get real fast rapids (not machining) and we did not
> care
> much about the error then. Of course .01 " of error would have been
> unacceptable machining.
>
>
> Dave
>
>
>
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