Z setting problem

[rej]

i had to buy a different board for my 2001 prt because the old drivers went bad due to me moving the carriage while plugged in.

so i got a board including the cabinet from a friend.
the board is version 2.07
my motors are all 3 the same - 296a1a-sg3.6 .5 step

i called shopbot and was told to set my x, y to 1466.772

x,y seems to work fine
but my z is the problem. they told me to set it to 1833.465 this shoots it like a rocket.
when i put it to 355 it seems great, for vcarving.
but when i run 3d, the z climbs up.
anyone got any suggestions?
thanks

[ron_moorehead]

If all your motors are the same and the drive grear and rack is the same then your unit value should be the same for all three on the x, y and Z. I had mine all the same until I changed out my motors to 7.2:1 for the x and y and 1:1 for my z then my unit values changed. The only reason to have difreent unit values on your machine would be if your Z drive grear was differnt.

Hope this helps.

[rej]

how do i tell if the gear is different?
are you talking about the number of teeth on the sprocket?

[ron_moorehead]

Mine are diffent sizes. The X and Y gears are 1.5" across and my Z gear is 1" across. Larger gear has more teeth.

[rej]

well, i ran the program again with my z at 356.
for 2 hrs all went great.
so i shut the lights off in the shop and let the machine carry on. went back out 40 minutes later and the z had gone up about 3 or 4 different times.
then i remembered that last night i shut the lights off, went to a dinner and when i returned the z was off.
so, i have re-started the program again and i'm leaving the lights on. hope this solves it.
do you think that the lights, which i believe are on a seperate circuit, could be the problem?
some sort of spike or something.
i'll post at about midnight when i see what happens.

[ron_moorehead]

Check your grounding. Do you have a dust collector? Make sure it's grounded.

[rej]

i didnt have to wait until midnight.
the z started raising after about 49 minutes.
i am hoping it is how the 3d file was put together.
i did not group the components, i just selected all the indv. ones and put them in the working model. then after some sculpting, i made that a component, then made a squre vector for the parts i wanted to cut, selected that vector, and ran a rough and finish pass.
my other files are put together different and have ran fine so tomorrow i will run one of them again and that will tell me if the bot has trouble. tomorrow i will post the results.

[adrianm]

I'd be very surprised if it's the way you made the file. I've done several just like that and not had an issue.

Even though the file is a lot of lines it should be pretty easy to look at the M3 commands and see if the Z is rising.

[rej]

adrian,
how do i do this?

[ron_moorehead]

Hi Robert,

The control software has a file editor id you go to programs and Shopbot and look for SbEdit you can open your 3d file, shopbot code and review the file by scrolling down through the file. I would look towards the end of your file and look at the. lines starting with M3 like this M3,0.000000,2.750000,-0.100000 The M3 comand is a comand to move in 3 dementions the first is the X the second is the Y and the last is the Z, in the above the location to cut is X= 0.0" the Y= 2.75" and my Z = -0.1" cutting depth. If your air cutting about the 3D part your cutting out I would see something like M3,1.1,2.75,1.111 constitaly towards the end of the file, you will also have moves between cuts so it my be commoun to see the Z go postive once in a while betwen cuts.

[bleeth]

Ron: You don't say whether you are running a router or a spindle or what material you are cutting. The most common cause of this is collet not tight enough. This can be caused by not enough torque when tightening or a worn collett. It is also possible that the shaft on your 3-d bit is a bit undersized and therefore you can't grip it tight enough , but more likely it's time for a new collett. Also, make sure your bit is still sharp. If it is getting dull, then it could be having trouble cutting and bit by bit losing steps in Z.
When it is cutting "high" are the z readings on the screen correct? If you pause when it is up to safe z is it at the correct height physically?

[rej]

it had a collet adapter. i used it for extra length. also, the bit was a cheap one.
i changed the collet to a 1/4 collet and used a 40.00 bit and would'nt you know it - problem solved.
learned my lesson the hard way, pay more and get quality.
thanks to all who responded. i appreciate your help.