Messages

731

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

« on: January 20, 2010, 07:41:04 PM »

BTW - Here are the bushings I had in mind:

http://www.vxb.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=bearings&Product_Code=Kit7218&Category_Code=GE_Type

Regards,
Ray L.

732

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

« on: January 20, 2010, 07:39:31 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.

Simpson,

OK, but if you come up with something that works, you gotta share!  :-)

Regards,
Ray L.

733

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

« on: January 20, 2010, 04:57:59 PM »

Well, here's the conclusion I reached.  I've used a rigid probe for most of the last year.  But, Mach3, flaky thing that it is, *will* periodically screw up, and break the probe.  I've been through at least a half-dozen in the last year.  So, a probe with some "give" is, to me, a requirement.  But, the typical Renishaw-style probes have several drawbacks, when used for machine setup:  First, they have some travel after contact, but before switch actuation, and this travel is different at different angular positions.  Careful calibration is required to minimize the effects of this.  Also, they are very delicate, and difficult to calibrate.

I have a design for a contact probe with "give".  The probe itself will consist of a slender stylus with a 5mm ball bearing bonded to the end.  This will give a very precisely spherical tip.  The stylus will be supported by a spherical Delrin bushing about an inch above the ball tip.  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.

This has no sensitive mechanical or electrical design aspects, so should be easy to build.  The *only* potential downside I can see is "stiction" in the spherical bushing can prevent the tip from self-centering.  But, with a little lubrication, and adequate spring pressure, this should not be a major problem.

The other option I've considered is simply making an insulated holder for a "wiggler" edge finder, but that would have to be manually centered after each contact, which would be very inconvenient.

Regards,
Ray L.

734

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

« on: January 20, 2010, 04:25:24 PM »

I don't know what you mean when you say "coated carbide", but I've learned that the usual coatings like TiCN, while good for extended tool life, interfere with the flute sharpness. Any coated tool I've seen had a less sharp edge than that of an uncoated tool. For aluminum you certainly want the flut to be as sharp and smooth as possible to reduce the friction and heat. Thus not coated mills are better for aluminum.

Here is a good article http://www.moldmakingtechnology.com/articles/030401.html , see second paragraph from the bottom.

May be you mean other coatings, designed specially for aluminum? That make the surface smooth?

Daniel

That depends on whether you're looking for ultimate surface finish, albeit with limited tool life and/or machining rates, or good surface finish with longer tool life, and/or faster machining rates.  Coated tools can last much longer than uncoated tools, and often enable MUCH higher feedrates.  In a production envinronment, time is money, and tools are money, so surface finish will often take a back seat to tool life and throughput.

Regards,
Ray L.

735

General Mach Discussion / Re: Mach3 Customization/Macro Programming Documentation

« on: January 20, 2010, 04:22:10 PM »

Any status on the new manual?

It was published several months ago, here:  http://www.machsupport.com/forum/index.php/topic,12730.0.html

The v4 manual is still not started, since the v4 VB interface is still undefined....

Regards,
Ray L.

736

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

« on: January 20, 2010, 11:42:14 AM »

Simpson,

For surface probing, the "Arnie probe" (the one made by lister Arnie Minear, now sold by www.wildhorse-innovations.com) works great - it's very accurate and repeatable.  Though, like all such probes, it's a bugger to get calibrated accurately.   If you're looking for something to use for edgefinding, etc. for machine setup, I don't find that type of probe to be a good choice.

Regards,
Ray L.

737

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

« on: January 19, 2010, 11:44:52 PM »

Hi all i got a nice speed and feed calculator from cnc cookbook .com its in beta testing ive been using it for a while works real well and it also has a lot of other useful gadgets on it and its free.I run production runs in 6061 exclusively and this calculator has worked fine for chip load calc. and feed rates might be worth a try gives you a great starting point and seems to do very well with end mills .I use accupro end mills and i usually use three flute end mills carbide coated on 6061 it gives a better finish smaller chips and no welding i use flood rustlic coolant works great in aluminum .

Yeah, I'm using G-Wizard to validate my own numbers.  It's a VERY nice tool.  I'm now cutting the "gooey" T651 at 100IPM, *without* coolant, and getting a pretty nice finish!

Regards,
Ray L.

738

General Mach Discussion / Re: mach 3 and servos do you gain any accuracy

« on: January 19, 2010, 11:23:10 PM »

I have been thinking of going to servos and i am a little confused or just stupid one of the two. Anyway here goes as i understand it mach is not a closed loop system am i correct ?second if this is so then what would be the advantage to servos over steppers is there a way to update position for accuracy or not ?
I know you would gain speed in rapids that is fine but what i am really looking for is finer accuracy in repeatable positioning .I have ball screw and know backlash that i can measure with a indicator anyway could some one please kind of explain this to me it would be really appreciated .


Thank You Woffler

Servos will give you no better accuracy than a properly designed stepper drive.  In both cases, when the motors are properly sized, and operated within their limits, positioning will be accurate 100% of the time.  Steppers are inaccurate only when under-sized, under-driven, or operated outside their capabilities.

Regards,
Ray L.

739

General Mach Discussion / A Really Exceptional Vendor....

« on: January 19, 2010, 11:20:09 PM »

It's relatively rare these days to come across a truly exceptional vendor, so when I do, I like to give them a plug.

Several months ago, I bought several very inexpensive ($25 ea., IIRC) 1/2" 3-flute carbide endmills from CNCToyBox.com  (http://www.cnctoybox.org).  When I finally got around to actually trying them, a month or two later, I used the same RPM, feed, etc. that I'd been using with Accupro 3-flute carbides for months.  Unfortunately, it turned into something of a disaster, with several of them getting broken very quickly.  I contacted Curt at CNCToyBox, just to see if he had a recommendation for better parameters to use.  Instead, he made what I thought was a remarkably generous offer - He sent me a couple of very good, and very expensive, "Ferocious" hi-helix endmills (http://www.cnctoybox.org/store/page18.html), at no charge.

Well, a few days ago, I discovered that the broken endmills were really my fault, so I contacted Curt and told him I had scerwed up, I wanted to pay him for the Ferocious endmills he sent, and he refused to accept my payment, just saying "stuff happens"!

Needless to say, I will be ordering from Curt again!  In fact, I just did!  :-)

Regards,
Ray L.

740

General Mach Discussion / Re: Couple of questions about loading GCode

« on: January 19, 2010, 12:22:48 PM »

In Config->GeneralConfig you can define an M-macro to be run on start-up.  That macro can load a G-code file.

Regards,
Ray L.