Messages

891

General Mach Discussion / Re: What is a good probe to use with Mach?

« on: January 20, 2010, 05:59:20 PM »

The top end of the stylus will be supported by three springs, each with a tension adjusting screw.  By adjusting the spring tensions, the ball tip can be precisely centered to the centerline of the spindle.  The "switch contact" is simply the electrical contact of the ball tip to the work, so there is no "overtravel" - contact with the workpiece activates the Probe input directly.  If pushed beyond the contact point, the springs and spherical bushings allow the ball and stylus to swivel out of the way, so there's no damage.  Once the tip is released, the springs should push it back into perfect alignment.

Ray, your idea gave me an idea.  I'm going to try a couple of things and get back to you on this.

892

General Mach Discussion / Re: Opto switches behaving badly

« on: January 20, 2010, 05:13:27 PM »

If you have Mach3 set up to share homing and limits, you waste whatever the delta is between your trigger point and the actual physical limit.  Speaking for myself, I'm good to go on my X and Z, but I would not give up .3" of my Y.

Opto's are extremely accurate and allow you so set the trigger very close to the actual stop, that is one of the reasons I ditched the mechanical switches. Those with significant travel likely will home at a pretty good clip, so the need to be cautious about messing with the debounce is a real concern in many cases.  The relationship between debounce and homing is something useful to be aware of.

893

General Mach Discussion / Re: Anyone Here Have Experience Milling 6061-T651 Wrought Plate?

« on: January 20, 2010, 04:51:46 PM »

I'm not sure I buy the sharpness argument, as these coatings are literally a few molecules thick.

That said, I agree that sharpness and surface smoothness is key to successful soft aluminum cutting, as I commented previously. The primary reason I like the coated cutters is not for higher speed or production longevity, since I can't cut at what would be considered 'high speed' by today's standards and I do prototypes and not production as a rule.

For those of us who don't have or want a flood system, certain coatings offer a measure of 'anti pick-up' to the tool. So aluminum behaves more like an egg in a 'teflon' coated pan rather than a steak on the grill, often allowing dry machining with only compressed air for cooling and chip evac.  Uncoated cutters always need lube of one kind or other, in my experience. For those with flood cooling, the debate is somewhat academic. Many moons ago I had a bridgeport with flood cooling and you really didn't even have conversations about material 'welding' itself to the cutters . . .  on the other hand, I wan't cutting any soft aluminum back then.

The caveat with uncoated cutters on aluminum is that you *might* get away with a dry cut  . . . . and you might not. The trouble is the way you find out that you didn't . . . which can get expensive in a hurry. I may as well add once again that in my view, mist 'coolants' like Kool Mist that I have tried are no better than dry cutting for soft grades of aluminum, however, something that I find very effective for band saw blades is 'grinder's paste'. This stuff is pretty miraculous at keeping aluminum from sticking to saw blades and grinding belts . . . . . just don't use it for final finishing if you plan to paint the part afterward.

894

General Mach Discussion / Re: What is a good probe to use with Mach?

« on: January 20, 2010, 04:22:55 PM »

Thanks for the comments so far.

My primary want is for edge and particularly circle center finding. I have to do a lot of that and it is tedious, to say the least. The digitizing would be fun to explore if I had a probe, but it not a practical need for anything that I am doing at this time, other than plotting an off angle edge or an edge contour.

So if I could get a suggestion for edge and circle center finding, it would be much appreciated.

895

General Mach Discussion / Re: Opto switches behaving badly

« on: January 20, 2010, 10:49:48 AM »

Be aware that debounce delays the recognition of a 'hit', so you may need to slow your homing so that the axis does not slam into the end of travel while the computer is figuring out if the signal is real or not. 

896

General Mach Discussion / Re: Opto switches behaving badly

« on: January 20, 2010, 06:01:55 AM »

In extreme cases in very noisy environments, you can also opt to run the signal side of the opto at 12V for more noise immunity. You then need to knock the 12V down to 5V be for connecting to the BOB.

I am making a little circuit board for signal boosting and running remote LEDs. It can also be used for the above mentioned task of knocking a high voltage signal down to 5V.

This is a video showing my previous mill routing the little boards. You will see the finished board at the end of the vid. Routing PCBs is new to me and it is really fun.

http://www.youtube.com/watch?v=r9Zf_5yHB1I

897

General Mach Discussion / Re: Anyone Here Have Experience Milling 6061-T651 Wrought Plate?

« on: January 19, 2010, 11:00:59 AM »

That thing looks obscene   

898

General Mach Discussion / Re: Would like opinions on servo motor voltage and PS secondary in series

« on: January 19, 2010, 10:58:44 AM »

The motors don't seem happy  . . very buzzy, so maybe this is the problem. There are two separate rectifiers, so I'll need to check the second one and see if it also is kicking out only 50V. One of these days I will have to break down and buy another scope, I suppose. I had one briefly, but that's another tale.
 
The 105V is on the DC side. I am buying a complete PS.  I'm too busy to build stuff like that, although it seems I may be forced to repair the current one if the rectifiers are fried again. 

Have my hands full finishing up my new mill, building more 4th axises (axii?),  and finalizing the pneumatic spindle lock and tail stock for it . . on top of my regular work.

FWIW, I am advised by a very reliable source that 20% to 30% it the max overvoltage one should attempt. 100% is verboten and can damage the motor coils even without overheating. Antek publishes the voltage drop on some of their units and it seems clear to me that the unregulated PS will not put out the rated voltage while there is a load on it, so I'm confident in the choice. I want 2,500 in the low range and 8,500 in the high, and it looks like I will get that with the new PS, so fingers crossed as I push forward making the pulleys as designed.

899

General Mach Discussion / Re: Would like opinions on servo motor voltage and PS secondary in series

« on: January 19, 2010, 07:44:32 AM »

Interesting,

If I have this right, there are 4 diodes in the rectifier and if one goes belly up (and fails open?), then would you loose 25% of your voltage? That would fit with what I am seeing . .  sort of. The PS is supposed to be 72V and I am getting 50.

Both of the rectifiers in this PS blew up and I replaced them with the identical parts . . .  a bit hard to find as they  are thru hole with one staggered pin.

Maybe I should check the AC voltage coming off the toroid?


On the PS question, after gathering info from a couple of trusted sources, my decision is to go with a separate 105V 800W unregulated linear (toroid from Antek) exclusively for the 90V 7.6A spindle motor.

900

General Mach Discussion / Re: Anyone Here Have Experience Milling 6061-T651 Wrought Plate?

« on: January 19, 2010, 04:30:37 AM »

Amateurs . . 

Real pros buy name brand coated carbide cutters . .  position them carefully . . . get them up to max RPM . . .  and then jog at full speed directly into the hardened vice jaws