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Messages - derek

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131
Right now I have a relay that turns the vfd on and off through Mach. If I routed the air valve in a way that when that relay is energized there would be no power available to the air valve so even if the output was turned on in mach the drawbar would stay put.
Basically a variation of what angel tech suggested a few posts back. I think for my purposes this may be the best route.

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ah i see it's the need for the spindle to be stationery for the drawbar to operate you'tre worried about. Add a tacho to the spindle and use this to operate a relay that disables the drawbar.
Ultimately you would want this as a separate entity from Mach. Then at some point you have to decide what do you trust more. Mach or the circuitry your using to monitor the tach and activate the relay.
Not slamming your idea just trying to draw it to the next conclusion. Ultimately I like this idea if it was safe.

133
Well I was planning on using pokeys to run the ATC so it looks like I'll be in the same boat as you! On this machine I'm not running the smooth stepper so that should remove one area of uncertainty. I'm running a smooth stepper on my router and have experienced some quirky actions for sure.


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The only reasonable thing I've been able to come up with is making the ram button on the end of the air cylinder rotate. Then have a wire that the 24VDC that runs my estop system run through it like it was another estop switch. If the ram comes down while the spindle is turning then the button will turn break the wire or contact and kill the 24V. My estop system is totally separate from Mach. when you kill the 24V you kill everything. Servos, VFD,coolant and the air valve for the draw bar. The air valve is a spring return so when you kill the power the default is up.
Not elegant but for an electronics ditch digger like me it will get it done. I've been working with Mach daily since it was master5 and never witnessed it activate an output on its own.
Having said that it wouldn't surprise me at all if it happened tomorrow. That's why my estop has nothing to do with mach.

Speaking of drives what are you running? I'm looking at the Delta VFD-M series. it's in the right price range , takes single phase input and has simple indexing to align the drive lugs.


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You may want to consider that you'll need to move the x axis to one end when you're changing tools to avoid the tools striking the job. Unless you have sufficient z movement to allow this.
Hi
I'm driving the knee so I have a fair amount of travel. I also noticed that efficient tool changing depends entirely on the job your running. Tool length, Height of work etc. So that being said I figured using a macro for the tool change that picks up the tool change position DROs. I would then specify where I needed the table to be in order for the tools to clear. Why move the Z 12" if only moving it 6 will get the job done. At least that's todays theory Check back with me in a couple of hours and I may have a different take  :D

Derek

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The pull stud is the only scary part of the mechanism as a whole.
You know I've thought about this a lot. If we only have 1000 lbs of up force then 1001 pounds of downforce is going to start to move the tool into the work. But more than that it's going to let the tool holder wobble which in most cases will be catastrophic to the tool. I can understand the concern about pull studs in regular VMCs that are running 2-5K pounds of force but I just can't see it being a problem at the levels we're working at. Feel free to punch holes in this theory as I'm wondering about all this as well!

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I watched your video. Very clever indeed. The opening lid was really a surprise!  You should spice that up just for fun. Paint it green and put some big teeth and some crocodile eyes on it. I have to build the spindle and the pneumatics, which are fairly straightforward tasks, and then attack the ATC. I have looked at a lot of arrangements. Mohammad comes to the mountain and vice-versa. Somewhere between ideal, realistic and practical is where It will probably end up.

I was thinking of running a MIDI that went "Bwa Ha Ha Ha" every time it opens and closes! It reminded me of the toy bank coffin that lifted and the hand popped out to grab the coin.

Before I started this maching job I was convinced that mounting my carousel on the end of the table was the best way to go. Keep it simple. Well after watching all of the unnecessary  X axis motion with my tool tray I saw the value in flying in the carousel. I think I've settled into the best choice for me which is  the ATC is positioned to the left of the spindle and up high enough so my longest tool will be above the spindle nose. This is 8.5". The motion is down 8.5" to bring the fork level with the BT30 groove. Over 8" to engage the fork. Down again 3.5" to clear the pull stud to the spindle. Rotate carousel. Up to engage and then reverse out. Bimba makes a nice 3 position round body cylinder. I used their online configuration tool and it was only $75.00 for a 3/4" cylinder.

Now I just need to find the time to make it!



137
Looks great!
It seems you were able to fit a goodly amount of Bellevilles in there so your ejection force won't have to be as large as mine.

Just a FYI I'm running the same setup as you except all my parts are heat treated and tempered A2 ( I seem to recall your using A2 and S7). I just finished a run on a bunch of castings with over 400 tool changes and it never missed a beat. I have another set to run and after that I'm going to do a tear down and see how everything is looking.

Switching to the BT30 was one of the best things I've done to this mill in a while. I'm loving it!

138
Modbus / Re: Good VFD for Mach 3
« on: August 11, 2012, 10:10:22 AM »
Check out the hitachi x200.
Works with modbus through Mach. I hooked one up and it was fairly simple. Do some searching here and CNC zone and you'll find plenty of info.
Derek

139
Probably a slight difference between the timing pulleys.

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right now they are just sitting in holes I pocketed. I'm designing a really quick and dirty cover with an air cylinder that pops open to expose the tools.

The end game is to have a 10 tool carousel. I'll be using a traditional spring loaded fork arrangement on that. It's all designed and ready to build I just don't have the time. I'm using an old servo motor and spare drive I have to run it. Trying to keep it as simple as I can and work with stuff I have on hand.

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