Restarting a file

[waynec]

I have a PR with the DOS control software. Several times now I have run into problems with my Z axis loosing it place, resulting in a diving bit (arrgghh). I loose the Z location, and sometimes the x and y.

I can re-home the machine OK. But what I'd like to do is resume cutting from the last good line number. How do I get the machine to go to that line number without first going thru all the other steps? I want to tell it to go to that line number and have the machine move to that spot, so I can turn on the router and resume the cut.

If there isn't a way to do that, how SHOULD I be dealing with this problem.

Thanks from a slightly frustrated PR user.

Wayne from White Salmon

[billp]

Wayne,
It's been covered here before, but the command you want is ; " FG" (file go to).Be SURE to make note of both the line number where you have stopped, AND the " X" and " Y" positions. When restarting the file again move the machine so that it is ABOVE the last known X/Y position, and when asked what line to begin with, try to back up a little and start a few lines before you left off.
The purpose of both these moves is to insure that there is some transition between where you left off, and where you will restart. AND by having the machine ABOVE the last known point you will not plow through the entire piece as the machine tries to reach your last known coordinates.

[waynec]

Thanks! I was using the FG command to get to the line number, but I didn't put together that I had to move the machine to the starting point before restarting the file. I guess I was hoping a single command would do both.

So, to restate what you are saying, I need to use the M or K commands to move the cutter to the x/y/z position just before where it 'went bad', and then start the file at the line number, or a few lines before, and then restart.

I assume that if I start a few lines before the line thats tied to the x/y/z position, I'll also have to move the cutter to the correct x/y/z for whatever line I start at. Do I use the position shown in the FG command for each line to locate?

I'm almost getting this. Is this in the manual or programming guide?

Anyway, thanks for the help. I participate in a woodworking forum where we get asked 'what table saw should I buy' over and over. I appreciate that you take the time here.

Will an Alpha machine fix my diving Z problem?

Wayne from White Salmon

[billp]

Waayne,
If you have replaced your bit and re-zeroed everything it should repeat the moves of your first attempt. The " FG" command just allows you to start at a point of your choosing. The most important part of this in my experience is to make sure you have your bit well above the surface of your material, or it may do an abrupt plunge as it tries to go back to the line where you have chosen to resume the cutting process.
All of this should be in the user's manual if I remember correctly.

[gerald_d]

Wayne has been patiently putting up with his diving z for over a year. link (http://www.talkshopbot.com/forum/messages/26/5828.html#POST19358).

[mikejohn]

I always look for the Jog move prior to the file line that I wish to resume cutting, and call up that line, (assuming I have re-homed and have the z above material height).
FG, Line (n)umber, (R)un


............Mike

[patricktoomey]

Wayne, I have had a similar issue that was caused by attempting to raise the Z axis above the limit. When the Z Carriage jumps at the top of the gear track it doesn't get any higher but as far as the computer knows, it's still moving up. Then when it goes back to cut it plunges too deep because it thinks it's higher than it actually is. I don't know if this could be your problem but I thought I'd throw it out there just in case. I ran into this with a drag knife vinyl cutter in the spindle. The cutter is so long that I had to set the safe z to .25. At my normal setting of .5, every time it came up to the safe z height it would jump at the top and then when it went back to cut it was .25 too low and plowed the cutter into my table trashing my blade. After two times in a row I finally realized what was happening.

[waynec]

Hi Gerald. You are sure right about putting up with it. Its really the machines ONLY problem. I thought I had it under control by keeping the ballscrew well lubed with graphite. That helps alot.

In this case, just before the Z dived, the dust collector clogged and had dust flying everywhere. I'm pretty sure that dust got into the ballscrew and caused the dive. I'm gonna try to make a cover out of a pepsi bottle.

Help me to understand the process of'recovery'. I take the carriage back to home and re-zero, then reset the Z axis to run above the surface, and move the carriage back to the last good point by running the program and letting the machine air cut till the correct line number. Then I interrupt the file, insert a MZ command to lower the Z back to the right height based on the line number I'm restarting from, tell it to continue cutting from this new point. Right?

Is this in the PR manual? I have that manual, but I haven't found this info.

Is the PRTAlpha different in its recovery process? Does it have the same Z axis vulnerability?

Couple days ago I was ready to throw the thing in the scrap heap. But I'm hooked on the technology, so I'm gonna give it another try or two.

THanks all for the help.

Wayne from White Salmon

[mikejohn]

Wayne
what I do is
a: Note the line number where the problem occured
b: Re zero x,y and z
c: Move z above material level but don't re-zero
d: FG to the last jog position before the line where the problem occurred,then Run.

In fact you could J2 to the x/y position where the problem occured then restart by FG the line number you ended on.
If you simply go from anywhere to that line position, the bit is likely to plunge down through the material as it goes to the correct x/y/z.

............Mike

[john_david]

Wayne,
I don't know if you "Z" problem is fixed, But here is my experience.
We had the same problem on our PRT and when we called shopbot they recomended we change from the flat spring steel spring to the new 2 extension springs like they have on the Alpha model.We also decided to keep our plunge rates to 0.5 all the time for feed and jog.
This has fixed our loosing "Z" position

Hope this helps

JD

[artisan]

Wayne, pay special attention to what Mike John has said. When you use the "FG" command, if your bit is not already near where you last were cutting, it may tear into your material because the "Z" will begin it's move along with the "X" and "Y" and if your last position was say....1 inch deep....the "Z" will head down for that spot and damage anything in it's way. Two other tips are to (1) drill a small hole in the corner of your scrap if you can for the 0,0 XY position. I have found this to be more accurate than the limit switches. (2) I have a blackboard by the Shopbot to write down the last line of code so I can always find my way back. I do a lot of 3D work and the Shopbot is notorious for losing it's way on very large files....especially if I'm in a hurry....D

[waynec]

Thanks all!

I think I have it now. I was RE-Zeroing before moving to the last good line.

I have the coil springs on my PR. I've been using copius amounts of graphite lube on the ball screw, which really helps. This time I'm almost sure it happened because the dust collector got plugged just minutes before. Dust was everywhere, and notably in the ball screw bearing.

The idea about drilling a home 'hole' is a great one, and I'll start making it habit. On most cab jobs I cut, I can't drill on the sheet itself. But I can make that ref point off the sheet on the spoilboard, or anywhere else within limits, and its still a ref point, right?

Anyway, I'm saving my pop bottles for a new Alpha machine. No one has told me yet- are Alpha's prone to Z axis diving?

Again, thanks all. I'm sure you guys get tired of answering the same stupid questions a million times. I appreciate your patience as I catch up.

Wayne from White Salmon