Re: [CAD_CAM_EDM_DRO] Skipping steps, avoiding resonance and the importance of being grounded

Randy,

I missed your progress update post - glad to hear it was a wiring/level
problem.

Cheers, Peter

Randy Gordon-Gilmore wrote:

>At 10:35 PM 12/1/02 -0800, I wrote:
>
>>I finally got the thing running this weekend, and it is not running
>>reliably.
>>
>
>Chris L and Jerry J, and Tim G replied with helpful posts about double
>checking each axis on its own, systematically varying one parameter at a
>time and starting slow and inching up in speed and acceleration, etc.
>(Thank you both for your thoughtful posts!)
>
>A first problem I realized, was that I still had "rapid" speed set at
>300ipm from when I had been playing with the limits of speed. Sometimes it
>was working OK, but some G0's did not work as advertised! :-) I set G0 to
>60ipm for X and Y, and 30ipm for Z (I don't have counterbalance springs
>installed on the Z carriage yet, and the Sherline milling head plus adapter
>plate weigh 12 pounds, so I'm taking it easy on Z for the time being.)
>
>A clue for me came when I was "air cutting"--no spindle motor running, no
>tool, no noisy shopvac sucking chips. I was running through the 3D gcode
>file and watching the display while the gantry was running. On a move that
>was purely X, the Y and Z steppers would take random, varying steps (or
>several steps at a time) when they should have been motionless.
>
>I took Tim's suggestion to try another software program. I had played with
>TurboCNC in the past, so I downloaded a fresh copy and set it up for the
>gantry. It was an eye-opener! X axis would jog, but Y and Z would just
>vibrate the motors but not move the axes. I played with the pulse width
>along with speeds and accelerations, but could only get one axis to move
>with TurboCNC.
>
>I began to think that my problem was electrical. I opened the case of the
>controller and noticed several things I had not before. The first one was
>that the signal grounds to the three single-axis controller cards were
>daisy-chained. I removed them and brought all three grounds to a common
>point on the chassis. That solved the problem maybe 75%. But the
>"inactive" axes were still taking random steps. I also noticed that the
>wires from the DB-25 connector to the step and direction inputs to the
>cards were long, thin and maybe not-too-well soldered.
>
>Caudlet posted in another thread at that time:
>
>>One of the areas that gets overlooked is the enemic drive from the
>>parallel port of most PC's I highly recommend a buffer card for
>>
>
>I am already using a good Belkin 6' double-shielded parallel cable, so
>after some Web reading and searching I ordered an Aten CB-140 parallel port
>booster/buffer from Computer Gate:
>
>http://www.computergate.com/products/item.cfm?prodcd=WDECB140
>
>It was the best price I found, $24.95 plus tax and shipping (includes the
>wall wart power supply)
>
>While I was waiting for the booster to arrive, I gutted the wiring in the
>controller case. I relocated the DB-25 to the side of the case near the
>input terminals for the driver cards, and grounded everything to a single
>stud in the case. The CB-140 came yesterday, and I tried out the system
>this evening. Rock-solid!
>
>Wiring problems aside, I can only assume that the Dragon Driver cards are
>more picky about the TTL level of their input signals than Dan Mauch's 2A
>driver board, which has always worked reliably from the start.
>
>I am happy to have both the Sherline mill and the new gantry up and running
>reliably.
>
>Thanks again for the helpful suggestions, guys!
>
>Best regards,
>
>Randy
>
>Randy Gordon-Gilmore ,----.___________ ______________ _________________
>ProtoTrains // = = === == || == == == = || == == == = == =|
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