Messages

351

Mach3 under Vista / Re: Use of Embeeded Widows OS - Good, Bad, or Ugly?

« on: January 21, 2014, 11:33:21 AM »

Clarification:

My question is generic and not specifically about Tormach. That just happens to be the path by which the info came to me.

Tormach's reasons are based on information that was current WHEN they made the decision, but that information is extremely dated to the point of being pretty much meaningless.

What I would find interesting is if anyone has experience with Embedded Windows XP or later (I do not) that could shed some light on why one might choose it for a CNC controller  . . . or perhaps a 4th axis controller  . .  (hint, hint) or and ATC controller (more hints), not in 2009, but TODAY.

I don't know enough about it to venture an educated guess on what the advantages or disadvantages might be. There are some savvy people cruising these hallways so I thought there might be some dialog available, but perhaps not. Questions about Embedded Windows OS might be equivalent to asking questions about Pascal or Cobol.  Not so much that nobody knows, but that nobody cares.

So, this is one of those question where no answer . . is the answer.

352

Mach3 under Vista / Use of Embeeded Widows OS - Good, Bad, or Ugly?

« on: January 21, 2014, 07:37:58 AM »

It has recently come to my attention that Tormach uses Embedded Widows XP on their CNC computer (what they call the 'controller').

It is my understanding that the Embedded OS is targeted at purpose build devices with a very limited scope. Examples might be a modem, a router, perhaps a kiosk in the mall, a variety of 'smart' products from thermostats to coffee makers, but certainly not a general purpose PC .

So I am wondering if there are any gurus out there that can provide some dialogue on this. Advantages? Disadvantages?

I have read the Tormach 'white papers' and 'engineering notes' of the thinking behind using Embedded Windows XP on their computers, but the information used to justify the move is far outdated and no longer valid relative to computer timing and interrupt issues.

353

General Mach Discussion / Re: 4th Axis (B) is not homing

« on: January 20, 2014, 08:15:30 AM »

Couple tips on 4th axis homing;

*There is a cat cable that has each pair separately shielded. I don't recall the designation at the moment, but it is not uncommon stuff to find. I have been using it for about a year now with excellent results. You are better off running a separate cable as you did, but the separately shielded pairs is a worthwhile extra expense for anyone buying new cable.

*Consider running home and limit switches at 12V or 24V for a high level of immunity.

*A freebee fix that might solve 'spooky' false triggers is to simply run the signal 'backwards'. In your scenario, likely the home signal wire was picking up enough induced power to trigger the BOB. It may take only 3V and tiny current to exceed the 'high' threshold of an input pin, however, if you arrange for a full 5V signal to be 'OFF' and grounding that 5V to be 'ON' (a.k.a. active low), you build in a great deal of immunity because no amount of induced power will be able to trigger the signal pin and it is not possible to induce ground . . . . so far as I know anyway.

Also pay attention to the debounce setting in Mach, particularly if you are using a mechanical switch.

354

General Mach Discussion / Re: Rigid Tapping

« on: January 20, 2014, 02:00:18 AM »

I was only slowing down the spindles accel  in response to questions asked by Terry in the thread we were discussing this in at the time.

I was reading that stuff and I thought it was actual and not theoretical.

There is no pause at the end and actually Mach itself is not controlling the tapping, it is done totally in the CSMIO and is called via M84 instead of G84.

It was my impression that Mach did not implement rigid tapping at all.

The spindle in these vids is dual speed, ie feed out is set to double the in-feed rpm, can be set to what you want but double seems to work well for me.

Now there is an interesting idea. Why didn't I think of that?

Just to avoid confusion, my spindle is a servo and is controlled by the CSMIO as a servo ie +/- 10v control to the drive and it adheres to the acel I have set in motor tuning, the Z is synchronized to the actual encoders counts and it seems to work very well, the spindles encoder is 32,768 pulses per rev so the CSMIO is getting plenty of positional data to keep things on track.

I guess I better revisit that site. It was my impression the CSMIO was a motion controller. From this description, it is also a servo drive? I may give this device a close look for the new mill I will start work on in a couple weeks. The Kflop is a powerful tool, but getting it to do things takes a huge investment in time.

Oh and regarding 316, I think nothing of it as it is what I use day in day out being that the vast majority of my work is done for fishing boats.

Yes, I remember. And you work on big stuff with big machines. That's why I was surprised to see M3. Figured the only use you'd have for that might be as a toothpick 

355

General Mach Discussion / Re: Rigid Tapping

« on: January 19, 2014, 08:58:56 AM »

I do enjoy the 'Hoodisms'. You phrase " . . . .  'ONLY' gone as small as M3 in 316 . . . ." as if this is still in the realm of easily doable. If I had to hard tap M3 in 316, I'd need a couple shots of Jack Daniels first . .    Plus I would stick to the 50% thread hole size as a minimum. Just thinking about 316 makes my eye start twitchin'.  

And that tool changer . . . man, I'll never get tired of watching that thing! Hopeless. Deer in the headlights     Anyway, did you find any advantage to using the slow accel on the spindle or were you just testing? The mill seemed to do fine both slow and fast, but if you had 100 holes to tap, there would be a massive difference in the part cycle time.

Theoretically, if you have the Z accel higher than the spindle and a fast computer, Mach should be able to coordinate the Z movement to the spindle regardless of the spindle acceleration, slow or fast. What I would be wary of is the tapping speeds you are going to transition thru and the period of time spent there.

Tapping tends to be SFM critical (in my experience) so I prefer the tap to cut at the correct speed and stop quickly to minimize the possibility of binding if and when it passes thru an SFM that is nasty bad for the particular size/material being cut. Also, I am a speed freak when it comes to CNC and I am not one to wait around while a spindle (or anything else) comes up to speed. I tend to think in terms of MRR for general machining and Seconds Per Hole for drill/ream/tap and anything else to do with holes.

Speaking of seconds per hole, I can't tell from the videos if you have a pause in the tap sequence between directions.

Considering that the accuracy of the Z stop is the Gorilla for VFD rigid tapping, did you find and difference in accuracy or consistency between fast and slow spindle accel? It would be interesting to see the results of tapping a row of blind holes with fast accel and the next row with slow accel and compare the depth and consistency and quality of the resulting threads. Then do the same with and without a pause between directions.

No hurry on that. You know, whenever you have some free time . .  









 

356

General Mach Discussion / Re: Rigid Tapping

« on: January 18, 2014, 09:30:30 AM »

Just as an FYI, I found a significant improvement in thread quality (and less broken taps) by adding a pause at the end (bottom) of the tap cut.

Some Systems have this and some don't, but if you have the option, try putting dome delay to let the torque settle down before the reverse juice kicks in. Even 1/4 of a second can make a significant difference even with an AC servo.

Also, in my experience, even with ball screws, it takes longer for the spindle to accelerate than for the Z axis to start moving. Also the spindle accell is effected by tap size and material being cut, sharpness of the tap, etc.) while the Z movement is not.  Compensation for this can be found in putting a delta between the Spindle and Z axis to give the spindle some bias in acceleration.

357

General Mach Discussion / Re: GROUNDING - what is the correct way to ground a CNC machine?

« on: January 18, 2014, 09:14:50 AM »

There is a lot of difference between inexperience and laziness. 'People like me' have a great deal of patience for inexperience. We also are often the inexperienced ourselves as no one person is expert at everything. Laziness is a different animal.

Since you have put in some effort, I will fill in some blanks for you. You have already figured out that you do not actually 'convert' 24V to 5V, so no need to cover that.

You do not need a diode unless you are driving a load that will create a surge that needs to be dumped. Mechanical relays have coils which generate surge when they are shut off and the field collapses.

You will encounter diagrams that show a device identified only as a 'relay' with a diode installed around it. This is typically not necessary with solid state devices.

The IMPOTANT current spec to design to is the MAX load on the DRIVE I/O and to be aware that some drives list max PER pin and some list a TOTAL for all pins. Obviously, do not exceed either. At 20ma, undoubtedly you are below the max on your drive, but be aware of the total if that is how your drive is rated. The LTV can handle enough current to fry most drives, so just limiting enough to protect the chip is not enough. Your choice is very conservative so you are good to go.

I use a 400 ohm power resistor on my Mitsu interfaces. You may want to consider the type of resistor you are using as it will probably get very hot. Power resistors can handle the current indefinitely, provided you space them up a bit off the PC board.

Take the 5V + and the 5V ground off the BOB. Do not use the PC power supply or any floating source for the 5V signal source.

Check the BOB inputs for the presence of pull-up or pull-down resistors and  choose your active high or active low appropriately. This info will be in the documentation that came with your BOB. Often you can choose the state with jumpers. You can wire the 5V side of the LTV for either.
 
If that last statement is not clear, just call 1-800-KnobHead and I'll see if anyone can help you . . .  



 

358

General Mach Discussion / Re: GROUNDING - what is the correct way to ground a CNC machine?

« on: January 13, 2014, 10:05:29 AM »

Brilliant thanks - any idea how to wire it for 24v control?

thanks

Actually, yes I do.

What I do not have is patience for questions asked in layers with zero effort in between.

Good luck with your project.

359

General Mach Discussion / Re: Rigid Tapping

« on: January 13, 2014, 08:44:23 AM »

Hopefully without jumping into the frey, I just wanted to point out a detail that is missing on re-tapping the same hole.

In addition to having the spindle at the same starting point (not necessarily azimuth 0 or index, but the actual starting point from which that particular hole was tapped). you need to have the Z at the starting point for that particular hole also.

This is not too bad if you have only a few holes at the same elevation, but can get complicated with a lot of holes at different elevations or a string of holes done with relative moves.

In my 'rigid' tapping macro, the retract amount is also a consideration because I allow any retract value (to clear obstacles in moving to the next hole) as a parameter passed to the macro. Since the retract can be any value, the macro has to determine if the current  Z is at the retract height and accommodate that space in the next Z move prior to starting the next tapping motion.

In my setup, I have the choice of homing the spindle before each hole, but I found the cost in time to do this is too great in contrast to the benefit of being able to re-tap old holes. holes tapped too shallow are typically discovered at assembly and in practical terms it is much cheaper to hand tap the hole deeper or spec a shorter fastener (if possible) than to run the part back thru the CNC process.

Whether there is a tool changer and whether the tool holders have drive dog also plays into the 'sync' equation. Assuming the spindle homes before each tool change and the tapping routine returning to the starting azimuth for each tap sequence, the spindle will retain it zero reference during any tapping run regardless of how many holes are tapped.  With dogless systems like Tormach, your options would be greatly reduced and you could only reliably re-tap (assuming a spindle home is done after picking up the tool) until the next tool change. When that tool is retrieved again, there is no guarantee the azimuth will be the same , so homing the spindle again will NOT necessarily return the tap to the same starting point.

I think everyone agrees that blind holes are the Gorilla in hard tapping. In practical terms it is often doable to simply drill the hole an amount deeper than the required threads to accommodate the variation posed by tapping heads, VFD's and perhaps even the occasional programmer screw-up, but it is undeniable that exact control of the Z depth is the holy grail and the only method (other  than thread milling) to provide safe 'bottoming' type tapping. My tapping macro stores the current acceleration parameters and then maxes them out for the tap operation and then restores them to the original settings. My experience has shown that normal acceleration settings (and mine are already much higher than most) are not adequate for rigid tapping with small taps. 'Stop-on-a-dime' performance has been mentioned. Taps smaller than 1/4" or M6 need 'Stop-on-an Insect' performance . . .  and a small insect at that.

Love the clutch idea, but it seems that would defeat any ability to go back to that hole for a re-tap. To prevent broken taps (my nemesis, incidentally), my plan is to use the torque control I/O on the servo drives to set the max torque below a certain threshold depending on the tap size. In this way, the drive would stop prior to snapping off the tap and would fault the system allowing for a change to a new tap without having to then dig the old tap out of a hole. This method would also protect against a spiral tap from becoming a permanent part of the workpiece if it snaps off due to being bottomed in a blind hole.  

A lot of the above comments would not apply to the high end machines being debated, but considering the typical machine running MACH software, I'm hoping the information may be useful to the few who have servo powered spindles.    

 

360

General Mach Discussion / Re: GROUNDING - what is the correct way to ground a CNC machine?

« on: January 13, 2014, 07:38:54 AM »

Opto   LTV847