not initializing

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nichoce04
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not initializing

Post by nichoce04 »

I have an older DHC machine that won't initialize. After attempting to initialize is comes back with an error message (COULD NOT DETECT LIMIT SWITCH CLOSING ON CARRIAGE GATRY). Have tested switches with an ohm meter and switches perform as designed. Check continuity of wires from switches to the end of the pigtail connector and I have continuity. I am not able to jog either motor in any direction. This machine has been sitting for a few years and am now trying to get it operational again. Looking for help. I am a high school shop teacher who is a novice with this machine but have an extensive background in electrical troubleshooting.
Thanks Chuck
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Re: not initializing

Post by adbuch »

Chuck - you will not be able to jog until you have initialized the table. Initializing zeros out x, y, and z. Check to see that both ends of the gantry are completely resting against the stops when you slowly move the gantry to the home position by hand. If the table somehow got "bumped" and knocked out of square, it is then possible for the right end of the gantry to make contact against the stop before the left end of the gantry triggers (depresses) the Y limit switch. It is also a good idea to unplug, blow out, and reconnect the main harness connectors from the gantry and carriage motors. I assume you are running 3.11 (not Design Edge), but you may still have a diagnostics routine where you can test the limits switches using the computer. The screen shot below is from my Design Edge version.
David

limit switches in diagnostics.jpg

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Re: not initializing

Post by adbuch »

Also make sure the correct branches of the main wiring harness are plugged into the correct. Did the error message indicate which limit switch (gantry or carriage) was malfunctioning? Here are some excerpts from the Video Manual that may be of use to you. If you don't currently have a copy or the Video Manual, you can purchase a replacement Video Manual directly from Plasmacam for $10 plus shipping. You will want to put your machine in Diagnostics Mode (if possible) to conduct some of the tests below.

David

From the Video Manual:

"Check limit switches - Carefully hold the carriage and gantry as shown, and move them in and out of the corner to open and close the limit
switches one-at-a-time. Check that the "X limit" and "Y limit" indicators turn yellow and then white on the computer
screen when the corresponding switch is closed and opened.
If either indicator fails to respond correctly or if an intermittent problem is suspected, turn off the machine and continue
testing as follows:
Verify that the limit switch button is fully depressed when the carriage or gantry is pulled into the corner. If this is not the
case, check the carriage or gantry alignment, and check the gantry timing.
Inspect the limit switch with the problem for visible damage and replace if needed.
Unplug the connectors from the limit switch, prying them off as shown to minimize damage. Hold the digital multimeter
probes to the terminals of the limit switch and verify isolation when the switch is pressed and continuity when the switch
is released. If the limit switch fails to do this, it is faulty and should be replaced.
Otherwise, unplug and remove the controller, then briefly power it back up and reconnect using the Diagnostics. If a
limit switch indicator shows white, the controller is faulty and should be replaced.
Otherwise, check the continuity of the main wiring harness and the gantry wiring harness to see if one is faulty. Connect
the harnesses together and test the continuity of the limit switches through them while gently flexing the connectors, to
find intermittent problems.
If no problem is found in the wiring, the controller may be faulty and need replacement."


"Check carriage alignment - Check the alignment of all the moving parts. Make sure sufficient clearances are present so parts do not scrape
against one another. Roll the carriage back and forth to make sure a gap of about 1/16 inch (1.6mm) exists between
the gear and the gantry tube. Verify that all the rollers are well engaged on the tube, and that the angled carriage roller
rides about centered down the corner at the back of the gantry. Make sure that the loader plate and its springs are not
in danger of scraping against the gantry tube.
Check that the carriage does not easily tilt on the gantry by gently pushing the top or pulling the bottom toward the front
of the machine. Verify that the carriage engages the limit switch near the center of the stop. Roll the carriage to the
stop at both ends to verify that it does not come off the gear rack."


"Check gantry alignment - Check the gantry for clearances in the same manner. Check that there is space between the moving parts, including
the pulley and limit switch as they pass near the leg bolts at the back left corner. And check that the gantry rides clear
of all the rail screws.
The gears inside the rails should ride approximately on the center of the gear racks. Verify that all the rollers are well
engaged, riding about centered over the frame, and not about to fall off any edge.
The gantry should be able to move all the way forward, and all the way to the back, without the gears disengaging from
the gear racks."


"Adjust gantry timing - Carefully check the gantry gear timing by rolling the gantry back until its stops hit the legs. If a gap remains between the
stop and the leg at one end, kick the front legs in opposite directions to eliminate the gap. Recheck the timing to verify
that both stops hit the legs together."
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Re: not initializing

Post by rdj357 »

One of the things in David’s list is pretty common - if the gantry is out of square and not touching the stops at the same time on each end you will get this error so I’d check that first.
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Re: not initializing

Post by adbuch »

Robert - that was my first thought also. But I thought I'd include the other info just in case. I don't know if 3.11 has the same diagnostics screen as Design Edge, but I included some of the other information from the Video Manual anyway.
David
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