Re: Z velocity

[Jon Elson <elson-at-pico-systems.com>]

Richard wrote:

>Hello Jon,
>
>Saturday, November 23, 2002, 6:43:35 AM, you wrote:
>
>JE> I think you should think about this and calculate the linear force this 
>JE> system could deliver
>JE> before going any further.
>
>One of the first things I did Jon. It's 44kN at 3.5Nm given 100%
>effeciency. I'm aware it's high. It's the only motor I have but
>I really would like to know typical speeds used for the Z axis.
>At a maximum of 1"/sec approx you could argue that there's a
>good chance of seeing a crash coming - maybe :)
>
>  
>
Yes, as long as you limit the top speed to 60 IPM.  Although, I've 
crashed a drill 1.5" through
a workpiece before I could hit the stop.  I forgot to reset the Z axis 
zero for the different tool,
and instead of a rapid feed at 45 IPM to .1" above the work, it plunged 
the drill into the work
at that feedrate.  The drill broke off in the hole.  the hole was in the 
right position, and the
particular part had two blind holes exactly opposed.  So, when I turned 
the part over to do
the other side, I drilled that particular hole deeper until the new 
drill bit hit the point of the
broken off drill point to point.  I then drove the broken bit out with a 
punch.

I also did this same mistake with a 1/8" solid carbide end mill.  It 
plunged all the way through
a 1/8" aluminum part and then started plowing through the plate at 45 
IPM.  It left a rough-
sided slot, but it did not harm the end mill at all.  The part, in that 
case, was trashed, as there
was supposed to be solid material at that spot.

So, in a case where you are expecting the tool to rapidly approach the 
work at 45 IPM, then
slow down, you won't be able to react in time.

Jon