Good Evening All,
Well things just did not go to plan today at all 
I got three 3ft x 3ft MDF boards thinking that I was being over pessimistic and would only need one ….
So first issue I had was I forgot to set zero after aligning to the model origin on my board. and after about 30 seconds of hilarity as things got very exciting very quickly I hit the big old red panic Button and normality returned!! - Lesson Learnt clear offsets and zero is your friend …
Attempt number two : started contour cutting holes all was going well then heard a clunking / funny noise like I was missing steps. when it went to the next hole to start the plunge it started the cutting in the air about 3mm above the stock and now my depth of hole cuts is off let it run for a few more holes and it happened again, stopped the job at this point and then all hell broke loose again after stopping the job the z axis started to lower all the way down again not stopping until I hit the panic button again otherwise it would have gone through both the stock and the original board.
Attempt number Three - read online about the belts possible not being tight enough , so tightened them, turned power off and disconnected the z power cable and moved carriage up and down freely with no bumps or funny sounds replicated under power.
Ran the job again messed up the alignment and ended up enlarging holes let it run as the board is gone now under no load (small cuts was ok) but as soon as it got into pure cuts did about 10 then started to behave the same this time I noted that it was trying to plunge but looked like it was not able to, started browning the surface of the mdf making the same sort of clunking sound… yip you guessed it panic button hit again.
I must confess at this time I am feeling very frustrated that I cant figure out what the hek is going on so off to the internet I go again
Attempt number 4(board turned over): again tightened the belts as people said the z axis is hard to tighten and needs allot, so I have got the belts as tight as I can get without thinking something is going to break these are now violin pinging sounds (cant describe it better) both at rest and with z axis down. (should this be tighter?)
Long story short same problem got about 11 holes in then same problem clunking sound followed by phantom cutting and loss of steps = button pressed and a walk away from the table as now I am just mad that I cant do a simple thing as cut a 11mm hole…
so had some lunch back to machine gone all over it tightened bolts screws etc (none really needed it but didn’t know what else to do) thought that perhaps my feeds and speeds might be the issue but as I understand it I am at the lower end please see below:
I don’t know what to do next any suggestions - pointers, and could someone comment on my F&S is it ok to high to low (as a side note I tried increasing the RPM on one of my attempts just in case it needed more but that had no effect either)
I have spent all day trying to figure this out but I simply lack the experience / knowledge to resolve this on my own, and my searches have gotten me to the same conclusion belts or Feeds and speeds.
I would love some help, happy to try and give better more info if needed.
Yours Frustrated
Sherpa
