Messages

1201

General Mach Discussion / Re: how to go to z without traveling dagonally

« on: April 27, 2009, 04:18:42 PM »

No problemo, guys. I can take a little heat.

This thread really was hijacked badly. On the other hand, notice the number of reads and that tells a story also.

"Heck if that part is all you need to build you can do that with 3 axis"  Brilliant deduction . . how do you suppose I made the one in the photo? I could make if from a block of steel and a file if I had the time . .  that's not the point.

Anyway, fellas, no new thread needed, I got all the info I needed, and today I wrote and tested the macro I wanted to automatically generate the G-code and pass it to Mach to make the threading or turing passes. Works great!

In spite my complaining and some of you guys sulking, in the end there was success and I do appreciate all of the time spent on my issue. I am a very happy camper . . .  except maybe for the sore butt . . lots of teeth marks down there . . . . 


 

1202

General Mach Discussion / Re: how to go to z without traveling dagonally

« on: April 27, 2009, 04:12:48 AM »

Hood you are entitled to your opinion. I participate primarily in professional forums. Hobby forums tend to be more emotional and all about pals and personalities. The Mach forum is an interesting mix of both. I'm here for information, and to help others if I can, not to find a date. Personalities do not interest me in this venue.

If reply A says "green" and reply B says "No, BLUE!". That is a contradicion, in FACT. It is not me creating the contradiction, yet you seem to imply that I am somehow responsible for it, or that it is OK and how dare I question this. Well, every forum has it's "old guard" who have grown to believe that their opinion is law and they don't like to be challenged.  They are going to answer the quetion they think you SHOULD have asked, not what you actually did ask. It happens. It's a forum, it is what it is.

In any event, as I said earlier, someone has already provided the grand hint I needed to get underway. I've tried out the function and it does exactly what I want. I just need to spend the time now to dig into Mach's scripting capability. I have perused it quickly and I see in there what I need.

"Now as for the linear axis, I am taking my life in my hands here again risking you complaining that I am giving you false info again."

I normally do not find it neccessary to kill someone, being annoying is usually sufficient. No one has yet died from my whining and I do not recall saying that HOOD gave false info, quite the opposite I believe.

In any case, thank for explaining the linear thing. I already knew "what has been meant" by that and I'm sure it works well for some. It just does not interest me as I work in azimuth mostly so it would be an unnecessary conversion back and forth, and would compromise absolute positioning that I need.

 

1203

General Mach Discussion / Re: how to go to z without traveling dagonally

« on: April 27, 2009, 02:50:48 AM »

Picture is worth 1,000 words.

This is the current 4th axis mounted on the mini mill table. (I am building a new one now but it will be similar)



As to the Y axis moving, To make the following part, after turning the barrel down. the 4th axis stops, indexes and the mill head cuts the flats across the Y axis



Linear mode is an interesting idea, but I need A to be rotary axis.

1204

General Mach Discussion / Re: Can two 36v power supplies be used in series to get 72v?

« on: April 26, 2009, 07:34:20 PM »

Nosmoking,

My particular problem was resolved in this way:

1) I found the interface schematic published on the Gecko website.

2) I decided to sidestep the whole 24V issue and go with photointerruptors instead of switches. I asked again on the forum for a wiring diagram for that  . .  I got good intentions and promises, but no schematic. I was, however, critisized for even wanting to use photointerruptors on the limits because mechanical switches are 'just as good'. 

3) Peter Homann of Homann Designs was kind enought to review the interface schematic and catalog cut on the interruptor that I sent him and he provided a lot of information on how the schematic could be modified/simplified for use with the photointerruptors.

4) the entire issue became moot as when I totalled the cost of components at retail, it nearly equalled buying a prebuild indexer from CNC4PC, so I bough another of his excellent indexers (I use on on the spindle) which includes both the photointerruptor and the interface. When I get a chance I will install it as the X axis limit and just plug it into the BOB the same as the spindle indexer.

However, the limit switch wiring potentially causeing false e-stops seems to be a fairly common problem, so someone like yourself publishing a schematic on how to bump the voltage to 24V and interface that back to the BOB would be a great service to the CNC commumity here, methinks. If you do come up with something, I will be happy to host it and provide you a link to use for access. I'll even add a copyright notice on the image for you if you choose. That's not much, but it is at least something I can contribute.
 
To answer your question, I have two BOBs, the Gecko specific BOB fropm CNC4PC (C6G, or something like that I think) and the newest BOB from Homann Designs (for which I believe there is no documentation yet). They are just TTL 5v so far as I know. Let me know if there is any information I can procide you that would help with the design of the circuit . . within the limits of 'Electronics for Dummies' level where I am mired.

1205

General Mach Discussion / Re: how to go to z without traveling dagonally

« on: April 26, 2009, 07:01:17 PM »

Wow, awesome replies this time!

I must have finally explained it clearly enough becuse some of you are getting it now. It can be frustating when one askes how to paint their car red and the replies are not how to do it, but that red sucks and you should not want red.


SetMachZero(3) is the magic pill I was looking for. That should allow a program of any length to run.

Someone mentioned I could make a macro to create a 'continuous' run mode. That is exactly what I have been wanting some help with, as I am no Mach guru by any means. Until such time as Mach impliments such a feature, I have to go with work-rounds. I don't know how I can be more clear that swap axis is NOT an acceptable solution for my needs, so I am not going to discuss that any further.


Speed and the mechanics of the 4th axis is not part of the question. That is already worked out, tested and functioning fine. Mach seems to have homing for the A axis, so if that is functional (I have not tried it), then that is a non issue. I would be happy to answer any questions about the mechanical aspects of the existing (currently up for sale) or planned new 4th axis rigs, but I don't want to distract right now from what is at issue, which is the programming.

So, I feel that there is understanding of the objective now. Just down to discussing the best actual macro code. I am very familiar with programming and the concept of scripts, but I am a novice at G-code and Mach3, so that's where I would appreciate some guidance and assistance.

Actualy I now have enough pieces of the puzzle to complete what I need, but I wuld still welcome some more detailed discussion about the specifics and options if anyone feels so inclined.

One specific that was presented was code that repeated A360 over and over, but while that is valid, it would only work in incremental mode and it does not solve the problem of accumulation of machine coords for the A axis. The function SetMachZero(3) would theoretically solve that. That is the key piece of the puzzle.

So, for the scripting gurus out there, what needs to happen is to create a new command that reads the system variable that stores the feedrate in dist per rev. Then take the commanded X move and do the very simple math to calulate the number of degrees the A axis must turn to accomplish that feed rate over that distance and aseemble and pass the appropriate command to Mach.

The machine coord of the A axis could be zeroed after each move or the accumulation monitored by a brain (I think) and reset to zero upon reaching a specific number.

More sophisticated features would be to distinguish between a turning pass and a threading pass and force multiples of 360 for threading passes.









 

1206

General Mach Discussion / Re: What size motors?

« on: April 26, 2009, 10:39:31 AM »

That's an interesting point.

Certainly with a fast lead and ball tracks that would be the case. With a 5tpi el cheapo ball screw and a crappola asian mini mill like mine, not a problem. It took the effort from intellerable to bearable 

1207

General Mach Discussion / Re: Can two 36v power supplies be used in series to get 72v?

« on: April 26, 2009, 10:34:45 AM »

NOsmoking,

I very much appreciated every suggestion and exactly as you point out, I realistically assesed my ability to devine a doable solution from all those cards laying on the table in front of me. While I can solder very well, if my life depended on my designing a circuit more complicated than a light bulb with a switch, I would be long gone . .LOL!!

As with my question about wiring limit switches at 24v and interfacing back to the 5v BOB, what I needed and could not get was someone to make me a schematic with part numbers. Given that, I can build things electronic. But I assess my ability to design electronic circuits as near zero and my abiltity to fry expensive components at near 100% . .

The last thing I want is to put off people who are sincerely trying to help, but when there is conflicting information, I really have no way to determine which is correct. I was able to repair a variable speed drive by replacing the MOSfets, so I'm simply parrotting that proceedure with the power supply.  I take zero credit for fixing the controller. It was a FAQ on www.littlemachineshop.com that led me to try replacing the MOSfets. I can desolder an huge transitor and solder in an identcally numbered replacment, but I'm not foolish enough to believe I had ANY idea if it would work or why . . . 

Anyway, my ability to run a 72V motor on a 72V power supply is relatively high, so that was the safe route to take, methinks, but I value every response, even if in the end there is no clear solution.

1208

General Mach Discussion / Re: how to go to z without traveling dagonally

« on: April 26, 2009, 10:10:16 AM »

Did they ever have Abbott and Costello on TV or movies in Scotland?  This is just like their famous "Who's on First" routine      LOL!!

I know this is confsusing, but I am at a disadvantage because the conventional terminology does not cover what we are discussing, and I think we are interpreting differently my awkward attempt at selecting the closest reasonable description. 

Please note how I wrote the word thus: 'continuously' meaning this is as close as I can come to the description because of the symantics issue.

Obviously, unless I am just amazed by shiny objects and can't dress myself without help, I have no desire or need to just have the A axis sitting there spining madly away while nothing else is happening . . . 

OK, seriously, in practictice I use feed per rev, so all I need to do is start the spindle and command an x move and Mach calculated the required motion for the axis based on the speed of the spindle. No such facility exists between two axis, that I know of in Mach. 

It seems obvious to this observer that the A axis is not indended to be a 'spindle' and cannot be 'turned on' with Mach calcing the needed axis move to accomplish the feed rate based on the A 'spindle speed'. I'm sorry I can't help but trip over terminology here because there is overlap in definitions, I suppose.

Given that there is no way currently to accomplish the above described scenario, the only practical work-around that I came up with for 'continuous' revolution of the A axis to accomplish the desired cut is to use what is available which is huge azimuth numbers. Fortunately, so far I have not hit the wall with what Mach will put up with in this devious trickery . . .   

Feel free to pick a term for "rotation of the A axis in one smooth continuous movement sufficient to accomplish the desired cut using whatever toolls we actually have to do so" . . and I'll be happy to use that term so that we both know "Who's on first" at the same time.

1209

General Mach Discussion / Re: What size motors?

« on: April 26, 2009, 09:44:29 AM »

I put ball screws on my mill as a prelude to the planned CNC conversion. I still cranked by hand, but 5 turns per inch was SOOOOO much better than 16 . . . 

It is not very difficult (famous last words) to make ball screws for any machine tool.

1210

General Mach Discussion / Re: Problems threading on the lathe

« on: April 26, 2009, 09:38:39 AM »

I have noticed what appear to be rounding errors in Mach on the cutter comp routines. If that is related, it may be a place to look. I've had problems like this as programs age and I am continuously modifying them. Usually it (if I ever find it) the problem is old variables without enough precision that never got updated.

Specifically, in Mach I get a distinct perpendicular axis shift at the tangent of two arcs when I used an cutter comp offset of .008 but changing to .009 eliminated the shift.

FWIW


BTW, is there any tought of adding a continuous rotation capability for servo motors?