Hi Ash
Thanks for the thumbnail of your sketch.
I don't think there will be much to gain as the edge finder will self adjust from way out as started to nearer and nearer to alignment as true centring is approached.
The final tweak causes the finder to jump / kick into alignment indicating centring is as accurate as the device is capable of. The operator skill is in slowing the speed of the feed as centring is approached to get the best feel for the snap / kick.
However I am pleased that I am not the only one who thinks DTI or lasers are better as they are not reliant on operator skill.
My preference is always for DTI as visible laser alignment is difficult and relies on secondary reference to the work piece / machine datum as a supplementary action.
In view of the questions you have asked in other threads I suggest you take an overall view of the way the part is machined and the way the surfaces produced relate to the reference points of both the cutting tooling and the 'zero' for each axis. My approach would be to use an accurate DTI to measure from the machine 'zero' or 'home position' to derive the offset of the work piece's reference edge and from there to compute the tool cutting edge position. This means that all the accuracy is provided by the DTI. The DTI being checked and calibrated against a known standard such as a slip gauge.
You must in addition take into account all the other factors that degraded accuracy. There are a lot of other factors that relate to temperature and tool wear as well as basic positional accuracy of the lead screw and its drive mechanism. I strongly recommend a cold towel to the head and a quiet room when you check the tolerance spread (+&-) from the perfect placement. Production spread tolerancing is a difficult subject and needs to be take into account with the percentage reject rates and the fit required to other components. Obviously the other components would have their own tolerance profiles. Whilst rejects can be reduced by selective pairing of parts - this is at the expense of interchangeability and spares provisioning problems at a later date. This will be a problem that needs to be addressed at the initial design stage if you are considering a production run or runs..
Regards
Pat  |