Frage Tool changes

I'm a newbie looking to benefit from others' experience.

I've seen comments (from Rory) that "we don't like tool changes" - why not?

If I change tools in a job (say v-bit for end mill) I'm concerned at the pressure I am putting on the portal/Z-axis.

Can this cause problems with alignment of the job? Should I move X-axis all the way to the end switch to change tools? Am I worrying about nothing? I've not yet encountered problems (other than forgetting to re-set Z-zero after tool change - d'oh)

One thing I have found (confessions of a newbie here) is if you don't tighten the collet properly on the bit, it can seem fine until you plunge a few mm when the friction of the bit against wood is enough to cause the bit to rotate in the collet instead of cutting wood - very puzzling when it happens! This is what led to this post - I now exert significant torque with the spanner on the nut when fitting a bit, to make sure it is tight.

Hints 'n' tips greatly appreciated.

Donald

For each job that requires a tool change you should find a point where it is comfortable for you to change the tool. I tend to set this point as park position in WinPC NC, so for a tool-change you simply hit F9 and the SC goes to this position. Forgetting about adjusting the Z null happens more frequently when you are a beginer. When you destroyed some expensive parts like PCB end mills or maybe the machine table you will become more cautious.

When changing the tool no pressure to any axis should be involved! In fact there is no need to use any other than a rotary force to loosen or tighten the collet.
If there is still a little force it will hardly change the position of the machine, because when stopped the motors still are under votage creating a holding force. Additionally the rotation of the spindles is translated to a movement, but a movement won't translate to a rotation as easy as the other way around.

Tightening the collet is simply something you need some practice in. The whole tool-holder parts are made in steel, so you can hardly brake anything there. It's more a question of tighten it that hart that allows you to loosen it again after the job is done without the need of a pneumatic wrench ;o)

Thanks Andreas.

I was concerned that with one hand holding the spindle lock button in (HF350 spindle) and the other turning the spanner, I have no way of preventing torque being transferred via the toolholder clamp once the collet was tight; your reply has reassured me.

Donald

So far I have only used Proxxon IBS/E spindles (2 pcs at the moment) and I take them out of a spindle holder for a tool change. Might be a good idea to have several spindles if one uses the same couple of different bits all the time. Probably not as practical with expensive spindles.

We don't like tool changes as it takes time and you have to re-zero if you have time and patience it does not matter. But a general rule - its good to minimise the tool changes.

I always remove the spindle from the machine in both the proxxon and HF cases. The spanners and torque etc are such that if not done correctly you can put a lot of pressure on the machine. Personally I feel more comfortable removing the spindle and tightening the collet.

Its important to give the collet a good nip with the spanner as the vibration from the cutting can cause the cutter to move out relative to the collet and cause a mess.

Just my opinion - by no means "The best way"...