Messages

1351

General Mach Discussion / Re: CNC'ing both quill and knee

« on: February 11, 2009, 11:37:00 PM »

Thanks, I'll play with it this weekend.  If it looks like it will work, then I guess I will have to get started mounting my servo to the knee.

Vince

Well, it's not quite there yet.  It doesn't work properly if you move the Z axis while doing the tool change.  I'll fix that and re-post.

Regards,
Ray L.

1352

General Mach Discussion / Re: CNC'ing both quill and knee

« on: February 11, 2009, 11:06:52 PM »

OK, I'm sure this isn't the most efficient way of doing this, but I believe it works as intended.  Running it in simulation, it appears to work correctly.  I'm assuming here the quill is the Z axis, and the knee is the A axis.  When you change tools, it over-rides the change in the Z DRO due to the change in tool length, and instead moves the A axis by the difference in length between the old and new tools.  So, the effect is Z does not move, or is returned to its previous position if you moved it during the tool change, and the tool length is compensated for entirely by moving the knee.  The knee is moved minus for a longer tool, and plus for a shorter tool.




Put the following in M6Start.m1s:

REM Get the current tool length, and store it in User DRO 1200 for M6End macro
OldToolLength = ToolLengthOffset()
SetUserDRO(1200, OldToolLength)

REM Get the current Z axis position, and store it in USer DRO 1201 for M6End macro
OldZPos = GetOEMDRO(802)
SetUserDRO(1201, OldZPos)

REM Activate the new tool
tool = GetSelectedTool()
SetCurrentTool( tool )





Put the folliowing in M6End.m1s:

REM Get the length of the current tool
NewToolLength = ToolLengthOffset()

REM Figure out how much tool length changed, and in which direction
OffsetChange = NewToolLength - OldToolLength

REM Get the Z DRO value before the new tool length was applied, stored in UserDRO 1201 by M6Start macro
OldZPos = GetUserDRO(1201)
SetOEMDRO(802, OldZPos)

REM Get the cuurent A axis (knee) position, and apply the new tool length
OldAPos = GetOEMDRO(803)
NewAPos = OldAPos - OffsetChange
REM Move the knee to the new position
Code "G00 A" & NewAPos

REM Return the the position we were in before the toolchange

x = GetToolChangeStart( 0 )
y = GetToolChangeStart( 1 )
z = GetToolChangeStart( 2 )
a = GetToolChangeStart( 3 )
b = GetToolChangeStart( 4 )
c = GetToolChangeStart( 5 )

if(IsSafeZ() = 1) Then
   SafeZ = GetSafeZ
   if  SafeZ  > z then
     GotoSafeZ()
   end if
   Code "G00 X" & x & " Y" & y
   Code "G00 Z" & z
else
  Code "G00 X" & x & " Y" & y
end if



Regards,
Ray L.

1353

General Mach Discussion / Re: CNC'ing both quill and knee

« on: February 11, 2009, 03:06:52 PM »

Am I missing something?  Seems to me, my suggestion of modifying the M6End macro is quite simple.  You have access to the tool offset through the tool length DRO.  So, even if Mach does apply that somewhere, it's a simple matter for the macro to un-apply it by adding/subtracting the offset to the Z DRO, re-setting the DRO, then moving the knee by the appropriate amount.

Regards,
Ray L.

I guess it would be a simple matter for someone who does VB for a living and knows the ins and outs of Mach.  For me, it would be easier to ask me to levitate.  I'm sure there are many who would love to see a post of all the code required to make this happen, feel free to be our hero.  If you ever need a Piller 400 HZ parallel cabinet installed and wired up or autopilot aileron servo replaced or even an Atos hang glider rib adjustment for racing, I'm your man.

Vince

Well, I ain't no VB whiz, but I can learn enough to do what I need to do.  Fact is, I consider VB to be one of the most abominable programming languages ever created.  It's a God-awful mish-mash of about a dozen different paradigms, with more excpetions than rules.

In any case, I think we're talking about all of *maybe* a dozen lines of code:

1) Get the tool offset
2) Add/subtract tool offset to Z DRO, and reset Z DRO to this value
3) If necessary, do Z move to undo automatic tool length compensation, if there is one
4) Issue move command on knee axis, to do the tool length compensation

I'm guessing someone who's familiar with how Mach does toolchanges, and up on VB and all the Mach OEM codes, could do this in about 10 minutes.  If I had a machine to work with, I'd guess I could get it done within an hour.

Tell you what, even though I don't have a machine, I'll try to play with it over the next few days, and see if I can do it in simulation.  Should be pretty straight-forward, I think.

Regards,
Ray L.

1354

General Mach Discussion / Re: My First Mill and first CNC upgrade

« on: February 11, 2009, 03:00:51 PM »

My HomeShopCNC steppers are as follows:

RHT34-1200 oz/in $258.00 For X and Y. Geared 1:1
RS34-2550 oz/in   for Z geared 2:1
RHT34-740 oz/in  for A direct coupled to the rotary table shaft so it's 1:1

Are are run with Gecko G203V drives.

Steppers are the most powerfull at slow speeds so that's the reason for the low gear ratios.

Ray, Are you powering the knee or the quill for the Z axis?

Regards,
Kerry

Kerry,

Right now, I'm using the knee for Z, but I'm in the process of designing a quill drive.  Once that's on, I'll use the knee for tool length compensation, and the quill for the "active" Z axis.

Regards,
Ray L.

1355

General Mach Discussion / Re: CNC'ing both quill and knee

« on: February 11, 2009, 11:31:29 AM »

Am I missing something?  Seems to me, my suggestion of modifying the M6End macro is quite simple.  You have access to the tool offset through the tool length DRO.  So, even if Mach does apply that somewhere, it's a simple matter for the macro to un-apply it by adding/subtracting the offset to the Z DRO, re-setting the DRO, then moving the knee by the appropriate amount.

Regards,
Ray L.

1356

General Mach Discussion / Re: My First Mill and first CNC upgrade

« on: February 11, 2009, 11:27:48 AM »

Kerry, Ray,
  Mind to say which model motors you used for the X,Y and Z....and the ratios ?
Thanks,
RC

RC,

I used the HomeShopCNC 850 oz-in servos, with 500 line encoders, Gecko G320s, 70V/20A power supply.  X and Y have 2.5:1 GT2 belt reducers, Z has a 4.8:1 XL belt reducer, all of my own design.  Were I doing it over, I'd use the 4.8:1 on all three, as I can't get the motors up to full RPM with the 2.5:1.  There's more than plenty of power with the 2.5:1, but max rapid speed is >400 IPM, which SCARY fast for a machine this size.  I normally run 150 IPM rapids on X/Y, and 75 nIPM on Z.

Regards,
Ray L.

1357

General Mach Discussion / Re: My First Mill and first CNC upgrade

« on: February 11, 2009, 12:19:50 AM »

Well said Ray, I couldn't agree more!

I run a Lagun knee mill, (Brigdeport clone) every day powered with steppers and it works absolutely great! The knee is powered for the Z with a rapid speed of 25 IPM, X and Y rapids are 100 IPM. That's plenty fast enough for the milling we do so selling me the idea servos are needed for big iron would be tough, especially when I watch that super heavy knee zip up and down.

I purchased my steppers from www.homeshopcnc.com after Rick LaLonde, who i think may be the owner there, advised me what sizes to buy. Like you I was really unsure what to do since that was my first conversion but decided to trust Rick's advice and I am 100% satisfied. Matter fact I just recently purchased steppers for my upcoming lathe conversion based again on his advice.

As for drives, again I agree with Ray. Gecko G203V drives have been happily powering my steppers and I have yet to have even one problem.

My suggestion would be to contact Rick and see what he recommends for your application. Bet you won't be sorry.

Good luck on your conversion.

Kerry

Yup, I bought most of my stuff from HomeShopCNC as well.  I did go with servos this time, and don't regret it, but also don't see a clear, practical advantage.  With the SmoothStepper, I can get 400 IPM rapids on X/Y, and 75 IPM on Z, but seeing that big sucker flying around at 400 IPM is downright scary!  So, I backed it off to 150IPM for actual use.

I agree with everything you said about Rick.  He was a huge help in my first conversion (an X2), and on this one.  Great products, great prices, and great support.  What more can you ask?

Regards,
Ray L.

1358

General Mach Discussion / Re: CNC'ing both quill and knee

« on: February 10, 2009, 06:20:29 PM »

I am wanting to add a stepper to the knee on my bridgeport (Quill now used a Z) just for applying tool offsets.

Did anyone get this working?   How did you get mach to handle the extra motor and apply the tool offsets?

Thanks much!

Mach supports up to six axes, so you'd just assign the knee to one of the "extras".  I think you'd then modify the M6End macro, to take the tool offset, and move the knee by the appropraite amount.  Should be pretty straight-forward.  I'll find out soon, as I've already servo'd my knee, and am about to servo the quil as well.

Regards,
Ray L.

1359

General Mach Discussion / Re: My First Mill and first CNC upgrade

« on: February 10, 2009, 06:18:00 PM »

I am about to buy a Milling Machine, I have selected which one I want however due to its lack of CNC I plan to convert it almost immediately.

It is an Eastern Mill so I was planning to replace the leadscrews for ball screws and then fit ... servo motors on each axis.

Two questions:

1)  I am only looking at Servos due to our 'workshop guy' at work recomending them over steppermotors...is there a real gain?

2) Can mach3 controll Servos?  If not what would be a good set of stepper motors? (I am in the UK)

Thanks,

Andy

Mach is perfectly happy with either steppers or servos, as the interface between the PC and the motor driver is the same for either.
How big is the mill?  For small (table-top) machines, steppers are every bit as good as servos, and generally a bit cheaper.  For large machines (knee mills) servos *may* make more sense.  But, really, outside a production environment, it's more a religious question than anything else.  Up to and including a Bridgeport-sized machine, you can get perfectly acceptable results with either.  There are pros and cons to both, but the functional differences are generally rather minor, and often not good for much more than bragging rights (My mill will rapid faster than your mill!).  By far the most important things, no matter which you use, are to size them properly, gear them properly, and power them properly.  Most beginners tend to start with steppers, and grossly under-size them.  Then based on the poor outcome, they decide steppers are inherently no good, and will always lose steps.  This is simply not true.  Mariss Freimanis, the owner of Gecko (www.geckodrive.com) has a good rule of thumb:  Up to 100W, use steppers.  Above 200W, use servos.  Between 100W and 200W, use either.  You'll find some good information on stepper sizing, and power supply spec'ing on his site as well.  Whichever you decide on, I'd strongly recommend Gecko drivers - they are first-rate, reasonably priced, and well supported.

Regards,
Ray L.

1360

General Mach Discussion / Re: Motor Tuning not Updating

« on: February 10, 2009, 01:59:52 PM »

Ray,
 Think Toms sorted by doing just that, see post 6, it says

so I put the Y outputs to different pins and all is fine now.

Like you I suspect its the BOB that the problem lies with.
Hood

Yup, that post showed up while I was composing mine. 

I wish I could say I'm surprised, but some BOBs seem to create more problems than they solve....

Regards,
Ray L.