Aluminium CNC build (TEP mill converted) by Craynerd

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raynerd:
Phil...
--- Quote ---Alternatively, it's the ideal job for a 4th axis using a 60 dovetail (or fly) cutter.
--- End quote ---

The last time I saw your machine I`m sure you demo`d the 4th axis in motion and you were just looking for the ideal project to really test it out !!! :whip: :dremel: :ddb:

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OK, just to quickly clarify how this wheel is being used... it is the count wheel. The pawl attached to the pendulum drags it around and equally the back stop jams up against the teeth lower down to step it around.

The reason I want to change this wheel is because it takes too much drive and lift from the pendulum to step the count pawl OUT of the teeth. The pawl is only 1/32" so actually in theory the teeth only need to be 1/32 deep to catch and lock the wheel and drag the wheel forward. I`ve said 3/32" to give some tolerance but it certainly doesn`t need to be 1/16 as per the plans. The issue is not actually with the 1/16" teeth...it is because the 1/16" tooth FORCES the "deep tooth" to be even deeper and consequently, if the clock stops (which it does infreqently!) it is because it just hasn`t quite got the momentum to slide the count pawl up the hypotenuse to escape the deep tooth. Having 3/32" teeth and a 1/16" deep tooth will mean that the "effort" to escape the deep tooth will be massively reduced from what it is now. Escaping the deep tooth will be mill escaping a normal tooth on the current wheel. This will make a massive difference. The angles that the pawls (count pawl and backtop) are set at also mean this small difference in the normal and deep tooth, it takes a real extra bit of momentum to escape it! Unfortunately, the way this clock works means that the deep tooth comes around right at the end of the cycle when the momentum of the pendulum is at its lowest!!

So after that little rant and explanation, I don`t think either of the two wheel with the circular roots will work as the hypotenuse must be a clean slope for the pawl to slide up to escape the wheel. Actually, I have no issue with the radius at the bottom of the tooth as this will allow the pawl to slide nicely to its escape...however, will this radius cause the pawl to jump over the tooth and not engage against it. It is the pawl dropping into the sharp root of the tooth that drags it forward without popping up over the top.

Not ideal, but perhaps if I just went ahead with the radius at the bottom I could go around the wheel with a needle file and just sharpen it up a bit...however, it does defeat the CNC somewhat!

I hope that has given you some more info in what I am trying to achieve...truth is, I`ve read your posts and now I`m still not sure of the way forward.

My only cutters at present near narrow enough are the 15deg engraver or a 2mm endmill.

philf:
Aha! Alles Klar! :thumbup:

So the big clearance on my drawing wouldn't work at all. I was picturing a solid pawl.

John's radiused root should be fine - particularly if the rad is smaller than the diameter of your pawl wire.

The slope would also be better going to a point then it's not as steep.

I've just been grinding a 0.5mm cutter:

The end looks like:

I've ground enough parallel to cut about 1mm.

The trouble is that (according to GWizard) you ideally need a spindle speed of 77,716 rpm at a feed rate of 468mm/min.

Do you know what the maximum spindle speed you can get is?

You'd need to reduce the feedrate proportionally.

You're welcome to try it if your engraving cutter doesn't work.

Cheers.

Phil.

raynerd:
:doh:
Damn, Vcarve won`t let me plot a toolpath that it knows it can not fit! I`ve taken Phil's attachement and selecting my 30deg inclusive engraving bit set at only 1.05mm in 1mm material depth and it tells me "Error: Check tool can fit into selected vector at machining depth" if I try and cut outside/right. If I try and cut on the line it will create the tool path so I`m guessing it is doing this because it knows it can`t get into the corner...fair play to it, but that is a pain. If I choose to cut on the line it`ll make my wheel smaller than desired

I`m thinking that 4 axis is the only way to do this properly.

Chris

John Stevenson:
Try it at 0.5mm then file the rest, you will have a pattern to follow and that bit of brass will file out easily.

philf:
Chris,

I've just done the preview in Cut2d with a 0.5mm cutter and it's come out OK.

I've attached another 'clean' DXF the previous one had some arcs left on the points of the teeth from a previous incarnation. (That may have been the problem or maybe Cut2d doesn't worry about fitting into the corners.)

Good Luck.

Phil.

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