Messages

271

General Mach Discussion / Re: Mach + Smoothstepper and Dwell

« on: October 18, 2012, 10:04:23 AM »

Richard,

Must be a recent bug addition.  When I used a SmoothStepper, fractional delay values worked fine.  Try an older version of the plug-in (I think I last used v05ogx), and I think you'll find it works as it should.  I don't understand why the millisecond mode has never been fixed....

Regards,
Ray L.

272

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 17, 2012, 07:20:35 PM »

I found the alignment pin was dragging on the receiver (the receiver is a crude prototype, and needs to be re-done).  I removed the alignment pin, and added a small, spring-loaded pin on the arm, to help push it away from the head.  It's now working nice and smooth, with very positive location at both ends of the travel.

Well....  Back to trying to "will" the pneumatic parts to show up, so I can finish this bad boy....  I cannot wait to see it working on its own.

Regards,
Ray L.

273

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 17, 2012, 06:20:44 PM »

Terry,

Believe me, I am well aware of the geometry.  The arm needs to rotate 140 degrees, which is a LOT.  Basically, both ends of the travel end up being near a critical point, where it is at the very limit of usable range.  If I move the cylinder further out, then the ATC can no longer retract far enough to clear the table.  Right now, it's going right up to the edge at the quill end of the travel, but it DOES work reliably.  It takes a fair amount of tension in the cylinder to pull it off the quill, hence the "jump", but once it's moved the first 3/4" or so, it's fine.  One simple fix is to just add a very small (<1/2") air cylinder that is fed by the same air line that feeds the big cylinder to retract the ATC.  This small cylinder will pop out, and "push" the arm away from the head to get it started, which will completely resolve this small problem.

I could, of course, also go with a more complex linkage, but I really don't want to go there unless I have no choice.  This simple linkage is close enough, I have no doubt I can make it work perfectly with just a few minor tweaks.

Regards,
Ray L.

274

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 17, 2012, 05:21:02 PM »

Got the pivot arm actuator done.  It's a little "sticky" at the quill end.  It's difficult to make this work with a simple mechanism as the arm needs to rotate 140 degrees, and actually goes slightly over-center at the quill end.  It seems to work OK, but I will smooth it out, to get rid of the sudden acceleration when it leaves the quill.  Worst case, I can add a small "kicker" cylinder to get it started.  Other than that, it seems to work nicely.

http://www.youtube.com/watch?v=whtDRNmo8Sk&feature=youtu.be

Now if only the rest of the pneumatic parts would show up, I could start working on the software side....

Regards,
Ray L.

275

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 15, 2012, 11:08:55 AM »

Most of us are in that boat, I suspect. I did schedule time for the project, so I could work on it *almost* full time for a few weeks, but I did not get it done completely due to pesky interruptions like food and sleep. Now I will be off line for two months with the next scheduled project, so that levels the playing field and makes for a fair contest, methinks.

As for the prize . .  I like Cave Creek Chili Beer . . . .  Just sayin'     

Well, you could be in some trouble then.  I expect to be back on mine in the next day or two.  The only thing holding me back will be I'm missing some pneumatic doo-dads, which are due to show up any day now....

Regards,
Ray L.

276

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 15, 2012, 09:18:09 AM »

Steve,

You forgot one:  Measure with a micrometer, mark with chalk, cut with an axe.

Regards,
Ray L.

277

General Mach Discussion / Re: Mach3 or CAM tool offsets?

« on: October 14, 2012, 11:04:19 PM »

If you're applying the offsets in CAM, you don't need to enter them in Mach3, and vice-versa.  Unless you're doing very high precision work, I doubt you really need to worry about tool diameter errors from nominal, so you can just apply the offsets in CAM - it's much simpler that way.

Regards,
Ray L.

278

General Mach Discussion / Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?

« on: October 14, 2012, 12:43:49 PM »

Unless you're using the worlds worst CAM, rapids will amount to a VERY small percentage of your total machining time - typically just a few percent.  As Hood indicated, higher acceleration is of more value for most applications, especially for 3D work, where low acceleration can increase your machining time many fold.  100 IPM is a perfectly reasonable rapid speed for a BP, and you'll gain little by going much beyond that.  As Terry indicated, you start going too fast, and the machine will start shaking, and walking all over the shop.  Plus, of course, when things go wrong with fast rapids, they can go very wrong, VERY quickly - before you have time to hit the big, red button.  I have servos on mine, and it's quite capable of running 350 IPM, but I run at 200 IPM, because there's just nothing to gain by going faster, and the chances of a destructive accident are much greater.

Regards,
Ray L.

279

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 14, 2012, 10:56:12 AM »

Ray,

You better get a move on, buddy. You have been at this ATC project waaay longer than me so it will be    if I beat you to the punch.

I wrapped up some incidental loose end stuff; intelock pin and solenoid for the drawbar actuator, beefed up the interlock lever on the pod, etc, got the shafts made for the swing arm and the carousel, and ordered the steel to make the mounting brackets for everything . . . . . before putting the whole shebang on a shelf.

You're getting a 60 day window now to keep that tortoise moving while the hare is off on a rabbit trail doing other stuff. After that, I figure about a week and I'll be changing tools.

Contest rules: everything does not have to be powder coated or otherwise 'spiffy',  but the automatic tool change has to be . . well . .  automatic,  and under its own power. No manual operation and no  . .  uh . .  temporary actuators . . . 

However, other  . .  'favored contestants' will be allowed to demonstrate the completed ATC on a totally non functional mock up of the milling machine head . . .  because there is no actual mill yet . .  and because he is making the rules. 

Contest winner is responsible for any and all federal, state and local taxes on prizes, which may include a case of the contestant's favorite beer  . .  and bragging rights.

Tick, tick, tick . . . . 

Steve,

You've had the considerable advantage of actually being able to work on yours....  Except for about 30 minutes to install the flow control valves and make that video, I've been too busy with "real" work to touch mine in weeks.  Hopefully later this week I'll be abve to get back on it.  I think I can finish it off in about a week, once I have the time.

Regards,
Ray L.

280

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: October 12, 2012, 07:14:02 PM »

Ray, you mentioned having a pin and rod arrangement for align the tools and the spindle, IIRC. Is that on the to-do list or am I just not seeing it?

Nice job overall. Where did you get that swing arm actuator . . . 

Steve,

The alignment pin is half there - the pin is on the other side of the head.  The socket on the arm is not yet there - I just got the bushing today, so it's about an hours work to make the holder and mount it.  That will accomodate any minor "sag" that might occur on the arm and it's mount.

You weren't supposed to notice that actuator....  :-)

Regards,
Ray L.