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Gerald_D
Registered
Username: Gerald_d
Post Number: 741
Registered: 11-2005
| | Posted on Saturday, January 20, 2007 - 05:53 am: | 
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Those grubscrews must be very tight - sometimes I destroy the spanner/key/wrench when tightening them.
The z-axis limits are now described in this thread. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 743
Registered: 11-2005
| | Posted on Saturday, January 20, 2007 - 06:16 am: |
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Fabrica, once your router works, you need to go through quite a process of getting the axes square to each other. This is the time when you will be finally adjusting the x-axis limits and the shims behind the x-axis V-rollers. I will start another thread when you are ready for this. For now, get your router going so that you can cut the top of your table flat. |
fabrica
Registered
Username: Daya
Post Number: 206
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 08:54 am: |
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Ok Thanks. |
fabrica
Registered
Username: Daya
Post Number: 207
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 02:23 pm: |
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Below given is a photo of the first cut I made with the Mechmate. The letters does not mean anything. Gerald, How is the quality of the cut. Do you think the machine is stable and free of unwanted vibrations.
 |
fabrica
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Username: Daya
Post Number: 208
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 02:31 pm: |
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Componets laid out before final wiring and getting mounted onto the box.
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fabrica
Registered
Username: Daya
Post Number: 209
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 02:35 pm: |
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Gerald,
In the baove picture we have pushed the relay (instead of isolator switch)and router relay to the top to isolate A/C signals from the gecko drives. |
fabrica
Registered
Username: Daya
Post Number: 210
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 02:46 pm: |
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Gerald, I have another problem which needs to be solved with your advice.
When the gantry is moving at some points the motors on the x axis is moving very erratically. This is the reason for the Gantry to climb onto the x rail. When you look at the motors from the other end of the shaft you see it not moving at all but making a noise. It happens to both the X axis motors at the same time.
We changed the current limiting Resistors from 2 amp to 5 amp and finally to 1 amp, but the problem did not get solved. What should be the correct resistor.
We connected the second grub screw to all motor shafts and screwed them in very tightly but the same problem continued. It happens all of a sudden. |
fabrica
Registered
Username: Daya
Post Number: 211
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 03:01 pm: |
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Below given is photo of the final control we had. In our haste to get the thing going we had got the main wire which provdes a/c cpower to transformer bundled togethr with the screened running to motors bundled together and running out of the control box together through the same bottom hole.
Do you think that this is causing the erractic behaviour of the motors due to A/C riples being piched by the motor wires. The erratic behavou happens on most times when both the X and Y axis are moving together. This means more power running through the A/C power cord.
 |
Gerald_D
Registered
Username: Gerald_d
Post Number: 745
Registered: 11-2005
| | Posted on Saturday, January 20, 2007 - 03:29 pm: |
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I can't see a problem with cut quality in that photo. Are you happy with it?
Does the erratic behaviour start at a certain speed? The current resistors depend on the motors and how you have wired them
Looking very quickly, I am a bit concerned about how close your big power supply is to the PMDX. That is not a toroid transformer and your power supply is maybe "noisy". The cable from the PC to the PMDX also looks thin - is it shielded? What are your motor wire shields connected to? |
fabrica
Registered
Username: Daya
Post Number: 212
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 03:59 pm: |
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Regarding cutting quality, I am very happy with it.
I have so far noticed any relationship with the erretic behaviour and speeds.
Gerald do you think that this errectic behaviour is noise related.
The transformer which we use were with us we did not bother to do up a toroid. But if everthing fails we could think of it.
The parallele cable is shielded. The motor wire shields are not connected to anything.
Do you think that we should the table as well. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 747
Registered: 11-2005
| | Posted on Saturday, January 20, 2007 - 07:07 pm: |
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Fabrica, glad to hear the cut quality is okay for you.
It is very difficult to diagnose this "erratic behaviour" because I can't see/hear it and it is not something that is common......
The ShopBots were fond of getting the shakes when the speed went too high and two axes had to move together. But you say your problem does not depend on speed. (The ShopBot issue was related to resonance of the gantry structure). Does it look like your V-rollers are bouncing up and down because of mechanical flexibility in the structure? I doubt it. (If this was the case, it would happen only at high speeds and dynamic movements).
Therefore, if it is not mechanical, then we must look for something electrical...and interference is the first thing that we worry about. Everything must be properly grounded. The table, the gantry, the y-car, the z-slide, and the shields of the cables. Only ground the cable shields at one end, the end nearest the control box. Also, the negative of the power supply must be attached to the same ground point as the shields, table, cars etc. If you do all this and the problem remains, we can look somewhere else. But it will not be a waste of time to do proper grounding - especially if you plan to use a dust sucker later. |
fabrica
Registered
Username: Daya
Post Number: 213
Registered: 10-2006
| | Posted on Saturday, January 20, 2007 - 07:54 pm: |
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The v rollers are properly seated on the Rails while travelling from one end to the other (X and Y both).
I too feel that this is a problem created by electrical noise. OK, I will start work the comming Monday and start with concentrating totally on the elctrical side of issues.
I have a few questions to ask from you about this microstepping issue which I will ask you later. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 748
Registered: 11-2005
| | Posted on Saturday, January 20, 2007 - 09:33 pm: |
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Did you adjust the trimpots on the gecko's for the lowest mid-band resonance? |
fabrica
Registered
Username: Daya
Post Number: 214
Registered: 10-2006
| | Posted on Sunday, January 21, 2007 - 05:32 am: |
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No. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 749
Registered: 11-2005
| | Posted on Sunday, January 21, 2007 - 06:08 am: |
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It must be done. See the gecko instructions. |
fabrica
Registered
Username: Daya
Post Number: 215
Registered: 10-2006
| | Posted on Sunday, January 21, 2007 - 06:53 am: |
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Gerald, In a earlier mail I could remember you asking me as to what model of motor I am using and also the way that I have wired it. You aked me these questions in order to advise me on what value of resstor to use on the driver.
The motor I use is PK296A1A-SG3.6 and I have two pairs of wires going into the two coils A and B.
TOday is a day off for us. But I would like to gather as much info and advice possible so that things would be easier for me tomorrow to see as to where I have gone wrong. |
fabrica
Registered
Username: Daya
Post Number: 216
Registered: 10-2006
| | Posted on Sunday, January 21, 2007 - 07:41 am: |
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To adjust the midband resonance you have set motor speed to 1/4 rev per second and adjust the pot until you hear a distinct null in the motors vibration. Am I correct? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 750
Registered: 11-2005
| | Posted on Sunday, January 21, 2007 - 07:52 am: |
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That motor is specified as 1.0 Amp when wired bipolar or 1.5 Amp when wired unipolar.
It has 6 leadwires - only 4 of the six wires are ever connected:
- if yellow and white are not connected then you have it as bipolar 1.0 Amp
- if other colours are not connected then it is unipolar 1.5 Amp (In this mode you only use half of the windings)
Set the resistor according your choice of wiring (it doesn't make a huge difference for a CNC router). Get the wiring wrong and you kill the gecko... |
fabrica
Registered
Username: Daya
Post Number: 217
Registered: 10-2006
| | Posted on Sunday, January 21, 2007 - 09:13 am: |
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Gerald, Do you have to provide a good earth to the table as well. At the moment it is not earthed and its sitting on a concrete floor. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 751
Registered: 11-2005
| | Posted on Sunday, January 21, 2007 - 09:58 am: |
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Yes, that is how to adjust the driver/motor resonance. Remember you have gearbox on the stepper - the 1/4 rev/sec is for the motor only.
The ground/earth issue is illustrated here. Use the earth point in the control box |
fabrica
Registered
Username: Daya
Post Number: 218
Registered: 10-2006
| | Posted on Sunday, January 21, 2007 - 06:01 pm: |
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Gerald, As you assumed I too feel that this so called erratic behavior of the motors is due to electrical noise.
One final question the earth point (what you have reffered to in your earleir posting) in the control box is the alu plate onto which the Gecko drivers are mounted. And also the negative wire of the power supply (connected to the transformer) should also be connected to the same alu plate. The earthing leads comming from the table (x,y,z) should be connected to the same alu plate.
Please correct me if I am wrong. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 752
Registered: 11-2005
| | Posted on Sunday, January 21, 2007 - 06:19 pm: |
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Yes, I use that plate for all the grounds/earths. Also the cable shields connect to the plate.
The table x,y,z earth wires are not separately coming to the plate - they are connected in series. If you start from the alu plate, a thick copper wire (+6mm2) goes to part 1010307, from there to 1020456, from there to 1030422 and finally from there to gauge plate in the z-slide |
fabrica
Registered
Username: Daya
Post Number: 219
Registered: 10-2006
| | Posted on Monday, January 22, 2007 - 02:25 am: |
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Thanks Gerald. |
Manjeet Singh
Registered
Username: Manjeet
Post Number: 23
Registered: 11-2006
| | Posted on Monday, January 22, 2007 - 04:35 pm: |
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Well done Fabrica,
credits goes to your courage, promptness and hardwork which braught you a success. though I am having all the facilities yet I could not comple the work. I had got all the material today and I will be starting the table very soon and start the new thread within few days, as I got inspired from the Great Mr.Gerald and you I hope I will be the next one to complete the "MechMate Beast" Soon.
..Manjeet |
fabrica
Registered
Username: Daya
Post Number: 220
Registered: 10-2006
| | Posted on Monday, January 22, 2007 - 06:11 pm: |
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Manjeet Happy to hear that you are making some progress.
Gerald, After doing everything that I promised to to do today I still have this erratic behavoir on the motors.
I gounded all wires running from the Gecko's to the motors to alu plates. Connected the negative of the power supply to the same alu board. X,Y and Z were grounder in serise to the same alu board. Tuned the pot on the Gecko's to the minimum humm levels(to overcome midband resonance).
The symptoms on the final run I made in the evening were as follows.
While jogging (with only one axis working) the steppers were running without any problem on all three axis. When you run the machine on a programme where all three axis start to work together we get some motors to miss their steps and direction specially at the accelataration stage of moving.
We took the router wiring completly out of the control box. Even the on/off switch was disabled and was done manually at the router point. Still nothing changed. We closed shop at 7.00 pm today. Tomorrow out first job would be to take the transformer out of the box and see weather this component is the culprit of undue noise generation. At this point we are almost sure that what we are encountering are noise related problems.
Even after taking the transformer out if the problem still persists I would replace the PMDX card to see weather this unit is diffective. |
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