lost step

[David White]

Ok I have a 2008 prs standard 4x8 4hp hsd.(Geco drives)no problems until know. I am loosing steps on the x axis on some of my pw files 3.5 insec. This will happen with an air cut as well as with a regular cutting operation . It dosent matter where on the table the file is . I have removed the y car steper just to be sure. Also I only loose steps when both x car stepers are engaged .If i air cut with only 1 steper (either one) no lost steps .speed test 76.5%. yes the bot is grounded to death.

Things i have done to try to solve the problem.
Swaped the z and y stepers for the x stepers
Replaced the x car cables.
Replaced the x car geco drivers.
Replaced the usb hub and cable.
Replaced the computer.

Any one want to take a crack at it . Thanks Dave White

[Brady Watson]

Are the X pinions too far inboard & rubbing on the table sides?

-B

[beacon14]

If you drop the motors (disengage the pinions from the racks) does the gantry roll freely and uniformly the entire length of the rails?

[David White]

The gantry rolls free and the pinions are not rubbing on the rail.

Thanks for your reply
Dave

[bleeth]

Check your gantry for squareness and your rails for equal distance and make sure they are still straight and level. Grease your racks. How long since you changed pinions? Tighten all the gussett and endplate bolts. While your'e at it tighten all the frame bolts.
Does your machine "creep" on the floor after a while? this can mess up squareness.

Since this happens with both motors on it sounds like at some point they are not moving in the same direction at the same time so there very well could be an alignment issue somewhere.

[Gary Campbell]

Check for X motor cable/connection malfunctions by making a long slow X move and wiggling both cables during move.

[David White]

The racks are greased the gantry is tight and not racked and as Gary sugested i wiggled the hell out of the cables. I think it can only be the board or the power supply. I have got at least 20+hr and 500 dollas in trying to figure it out.

Thanks for all your hellp.
Dave

[Brady Watson]

Where are you in NJ?

-B

[MogulTx]

David,

I have a 2008 48 x 96 also. The only time I have lost steps and had the machine REALLY act up is (1) when I loaded new software and the machine acted up for a little while (2) I didn't have a good connection with the USB from my computer to my control box ( I stepped on my cable- I went out and got the X E-Chain to clean things up and this solved my jumble of wires so much that I have not had any further trouble.) (3) When I installed the E-Chain, I moved my ground wires and had them just loosely hanging on the machine. When I put them under a bolt and snugged them down-- the rest of my issues went away.

So, if you have loaded new software- check to see if the SB software has a later upgrade that you can run. Check all your stepper connections as well as your ground and your USB to your control box and maybe one of these will get your problem fixed... (Haven't read ALL the posts above. I hope these steps have not already been covered- but I didn't see them in the last few posts.)

Best of Luck to you.

Monty

[David White]

Thanks for all the input . I am about 1mi from six flags off 195

[David White]

I cut about 300 round parts with out a problem today.Then i tried to cut a cursive name (all parts out of foam) and lost a step. It seams to have the most problem with small (JAGED) moves. I reset the ramping back to the defalt setting still no luck . went back over all the mec. posibilities and found nothing, pinions are good rack and table are squre.Any one have any other ideas. am i missing something obvious .

Thanks
Dave

[adrianm]

The only thing that springs to mind with the two scenarios you describe is that the circles would be one command for quite a large move (the arcs) whereas the letters would be lots and lots of commands each comprising one tiny move.

Sounds like a line of data itself might be dropped every now and again when streaming lots of commands rather than mechanical. How you prove that or fix it is another matter entirely though!

[Brady Watson]

It seams to have the most problem with small (JAGED) moves. ...

If the vectors are dirty & jagged, then yes - you could lose steps if the move speed is sufficient enough & the ramp settings are not set correctly.

BTW - The default VR settings are best suited for cutting cabinet parts, not small detailed parts with a lot of detail.

The path of least resistance would be to cleanup the artwork and adjust the VR.

-B

[David White]

I have adjusted the ramping but still i get the same result . It will some times lose a step just cutting a clean radius but this was a once in awhile occurrence and I used to just think it was something I did but know it is to the point of making the machine completely unreliable. I am back to out sourcing my radius parts .

Thanks to all who are trying to help me with this.
Dave

[Gary Campbell]

David...
Have you tried cutting them at 2 ips? This may be a suitable workaround until you can solve the problem.

[David White]

This is another odd thing that I have noticed just today Gary. If i air cut the part first and i get a lost step and then change the cut speed up or down by .5 it will cut fine. In the words of Jim Cary "god is just a mean kid with a magnifying glass trying to burn my feelers off "

[David White]

Once again thanks to all who are trying to help. I have found the problem but don't know what the cause is. If I run the gantry back and forth across the table (0-96) I put manual steady pressure against the gantry as it travels it will lose steps say every 3-4 feet . After it loses a step the steppers then pull strong for another 3-4 feet. and then become weak . Also if I drop out one of the x steppers and drive the gantry there is no soft spot . It appears that both steppers have to be engaged for this to happen . The voltage from the power supply is 61.5 and drops to 60 when a the gantry is traveling.

Thank Dave

[ken_rychlik]

David, It kind of sounds like one stepper is being told to go faster than the other. I don't think thats possible though.

If the gantry is not square, it will act the same way though.
You may try to loosen the gantry brackets that go in from the bottom bracket and into the big aluminum part. There are 6 on each side. If you loosen these this is how you adjust for square. Anyway run it with them loose and see if it looses steps. That will eliminate if it is in a bind.