Mach3 user thinking about switching over....

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16 Feb 2011 04:46 #7229 by PetefromTn
Hello all,
I am a member of the benchtop forum over on the CNCzone and I have recently converted an RF45 Lathemaster machine to CNC. It is running well and I am enjoying using it on Mach3. However I have been watching youtube videos of other retrofits and many are running this EMC2 software and have interesting capabilities such as rigid tapping and closed loop control. I am very interested in learning more about this. Specifically the rigid tapping sounds very nice. I have a sensorless vector drive on my mill and I am wanting to get spindle indexing done on it and I have a pretty nice optical sensor here that I thought I might use. Can a reasonably accurate spindle encoder be setup with say four white line tapes on the spindle pulley and this one sensor using EMC2 and get the positioning accuray necessary for this rigid tapping as long as I only go like say 150-300 rpm or so? I have my mill setup with a CNC4PC C11g breakout board and three Gecko G320 servo drives and I am adding a fourth axis soon. I understand that you can download the software and load it onto a CDrom or DVDrom and temporarily load it onto your machines control computer and kinda make a test run is this accurate or is there more to it than that? I do not wish to lose my Mach3 settings until I am confortable with EMC2. Is there somewhere I can see the entire interface and perhaps play with it offline somehow? I also have never used anything but windows so I am not really good with linux I am sure.... Would just love to see my machine perform a rigid tap and have full closed loop control. That would really be something... Am I dreaming here or is this possible? Another question is how does EMC2 work with tool tables and my chosen TTS tooling for repetitive Z height datum? I would like to get setup with rigid tapping and be able to use multiple taps in either a quick change tap holder of some sort or individual holders I guess in some sort of 3/4 shank for the TTS system. Any ideas and information on this would be most helpful. Thanks and nice to be here with all of you... peace

Pete

Here is a small video of my machine running I just made...


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16 Feb 2011 08:59 #7234 by andypugh
PetefromTn wrote:

I have a sensorless vector drive on my mill and I am wanting to get spindle indexing done on it and I have a pretty nice optical sensor here that I thought I might use. Can a reasonably accurate spindle encoder be setup with say four white line tapes on the spindle pulley and this one sensor using EMC2

Rigid tapping needs an index as well as position information. That tends to mean that you need three sensors. It is just about possible to spoof it with 2, and for a lathe you can use one. The reason you need two with a mill is that you need an encoder that counts correctly in both directions, which means you need two sensors in quadrature
en.wikipedia.org/wiki/Rotary_encoder#Incremental_rotary_encoder
EMC waits for an index before it starts a coordinated move so you need that channel too. This doesn't make a whole lot of sense, really, unless you plan on doing multi-pass rigid tapping. It ought to be possible to cheat with HAL (Hardware Abstraction Layer) components (a bit of a lash-up of dividers and subtraction on the encoder counts would be possible) to save an IO pin.
You can see an example of a home-made encoder in this video of my vaguely similar machine:

That uses three "gap" type sensors. However the lathe spindle worked fairly well with an encoder made by wrapping a laser-printed pattern of stripes round the shaft and using reflective optical sensors.
You might find that you can use a drive pulley if it is a toothed-belt and the sensors have a short focal length.

I have my mill setup with a CNC4PC C11g breakout board and three Gecko G320 servo drives and I am adding a fourth axis soon.

With 4 axes and a 3-channel spindle encoder I think you would start to run out of parallel port pins. It is possible to use more than one parallel port. (I would be tempted to skip the breakout with a PCI parallel port, though, as they are so cheap) . (The Mesa 7i43, which plugs into the p-port and gives you 48 IO pins and hardware step generation is also worth considering if you do run out of pins)

I understand that you can download the software and load it onto a CDrom or DVDrom and temporarily load it onto your machines control computer and kinda make a test run is this accurate or is there more to it than that?

Booting from the LiveCD should do exactly what you describe. You can run various simulated configs and see how you like it. I think you can also create a config with the wizard to run your machine, but can't say I have tried that when LiveCD booted.

Another question is how does EMC2 work with tool tables and my chosen TTS tooling for repetitive Z height datum?

You can either measure tool length and type the numbers into the tool table editor, or you can touch-off the tools to the work and have the offset written to the tool table. With a TTS I would be tempted to go for the first option, but there is no reason you can't use both as the mood suits you.

Here is a small video of my machine running I just made...

Unfortunately that seems to be blocked from the country I am currently in, due to content from UMG.

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16 Feb 2011 12:07 #7238 by BigJohnT
PetefromTn wrote:

Specifically the rigid tapping sounds very nice. I have a sensorless vector drive on my mill and I am wanting to get spindle indexing done on it and I have a pretty nice optical sensor here that I thought I might use. Can a reasonably accurate spindle encoder be setup with say four white line tapes on the spindle pulley and this one sensor using EMC2 and get the positioning accuray necessary for this rigid tapping as long as I only go like say 150-300 rpm or so? I have my mill setup with a CNC4PC C11g breakout board and three Gecko G320 servo drives and I am adding a fourth axis soon.


Hi Pete,

As Andy mentioned you need an index pulse and a quadrature encoder. Looking at your video I would mount an encoder to your spindle and not fiddle with home made ways unless you just like to tinker. Encoders are cheap (I get mine from automationdirect.com) and easy to mount when you have a setup like yours.

I understand that you can download the software and load it onto a CDrom or DVDrom and temporarily load it onto your machines control computer and kinda make a test run is this accurate or is there more to it than that? I do not wish to lose my Mach3 settings until I am confortable with EMC2. Is there somewhere I can see the entire interface and perhaps play with it offline somehow?


You can boot from the LiveCD and play with all the sims but as your running from the CD you can't save anything or create a custom configuration. One easy way is to just put a different hard drive in your computer and install Ubuntu/EMC on that to test with. Also I think there is a way to make a bootable USB drive but I'm not sure how to do that. While a servo system it is not as important to have low latency as software generated parallel port step and direction pulses you should check it after you boot from the LiveCD to make sure your PC hardware doesn't have some gremlins hiding in there.

I also have never used anything but windows so I am not really good with linux I am sure.... Would just love to see my machine perform a rigid tap and have full closed loop control. That would really be something... Am I dreaming here or is this possible?


Ubuntu is actually easier to use than windoze and I've used windows since DOS 6.22 went out of fashion. The Gecko site is down so I can't check but as I recall the G320 drives take step and direction? To have a closed loop system you need to connect the encoder to EMC and EMC tells the drive how fast and what way to run.

Another question is how does EMC2 work with tool tables and my chosen TTS tooling for repetitive Z height datum? I would like to get setup with rigid tapping and be able to use multiple taps in either a quick change tap holder of some sort or individual holders I guess in some sort of 3/4 shank for the TTS system. Any ideas and information on this would be most helpful. Thanks and nice to be here with all of you... peace

Pete


I assume the TTS system allows you to get repeatable Z height for tools. What I do on my BP with a QC200 spindle (no tool changer but repeatable Z for tools) is to load the tool then place a 0.500" diameter dowel on the Z0 location (usually my material top but sometimes my vice top) and lower the tool to a point where the dowel won't pass under and as I raise up the Z until the dowel just passes under the cutting edge I stop and enter a 0.500 for the tool table and the tool number. I do this for each tool (using a different tool number) and it takes only seconds to do. Now when you do a manual tool change in your g code with a T1M6 for tool #1 you can have the machine configured to go to a tool change location and a popup prompts you to insert the correct tool. You swap tools and tell EMC to proceed and off it goes.

John

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16 Feb 2011 15:17 #7240 by PetefromTn
Yeah the Geckos are step and direction based servo drives, does that mean you cannot use them? That would suck as I spent some considerable time getting them installed and properly tuned up. I would love to put an encoder on the millhead instead of the single sensor but if you watch the video you can see that it might be difficult, I do not have toothed (teethed) pulleys I have vee belt and pulleys so that too might be a problem? I am sure I could put the encoder on the motor somehow but would that be adequate. I do not think I could put it on the spindle pulley because I am working on a power drawbar setup for it and I am not totally sure what will go where with it just yet. I am not so much concerned with the UBuntu learning curve, I am sure I could trudge thru it. That video was pretty cool watching that spindle tie in directly to the fourth axis even when the fellow turned it by hand. That is cool right there I don't care who you are... The major reason I would want to switch over from Mach3 to EMC2 really is for the rigid tapping, anything else would be a bonus. I also am using a CNC4pc C11g Board and it has limited outputs and inputs. I am using several for my Industrial hobbies style home/limit switches. I do not wish to add a bunch of complexity to the wiring of my control unit either so I wanted to be able to minimize the additional hardware for the sake of reliability. It does not sound like this is gonna be possible if I need three sensor inputs just for the spindle.... Is that correct? What would you fellows say is the easiest simplest way to arrive at a rigid tapping setup for my belt driven milling machine and use the least amount of hardware and complexity of wiring? thanks for the input here I need it. Also that video apparently will not run only in Germany which I have never run into before. I am not quite sure why but it may have to do with the soundtrack I chose which is the Love theme from the movie Blade Runner by the master Evangelo Pappathansou.... Peace

Pete

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16 Feb 2011 16:08 #7242 by BigJohnT
Hi Pete,

I missed the fact that you are using a drawbar, that does complicate putting an encoder on the spindle a bit. Can you add a small timing pulley to the v belt pulley on your spindle with a through hole big enough to handle your draw bar and put the encoder on the side out of the way?

You can combine all the home and limit switches on one input with EMC to save inputs. The only thing you loose when doing this is when you set up your homing sequence you have to home each axis separately. You still press the home all button once to home. The other thing you loose is the knowledge of which limit switch is tripped but doesn't seem to be much of a problem on a machine like yours where you can see the axis. You do need to do the math and figure out what your maximum pulse rate is so you can pick the proper encoder count. The encoder needs three inputs A phase B phase and Z (index).

The Geckos are fine you just don't have closed loop back to EMC with them. You just set it up like a stepper drive in EMC. The spindle will be closed loop back to EMC with the encoder feedback.

John

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16 Feb 2011 16:22 #7244 by PetefromTn
Yeah I am using a drawbar and it is soon gonna be a power drawbar with pneumatics. Dunno how large an encoder wheel you can get but it would hafta be pretty huge to fit over that spindle pulley nut . mounting the encoder would not be a problem. Is it sensible to put it in the motors shaft? Is there an array that comes as one piece like a typical encoder? It would be nice to use a premade encoder that has index pulse built in and only have to mount one item to the millhead. I would suppose the wiring would be easier as well. That sucks that you cannot get the true closed loop benefits of the EMC2 software with Geckos, they are great little drives and the customer support is second to none. I am already fixed up here with the Geckos so I cannot see changing over to another drive just to get feedback to the controller since it has never been a problem for my parts so far. I can of course get my spindle reversing setup properly and do semi rigid tapping with Mach3 using a tension compression tap head but I really was interested to get true rigid tapping setup on this mill. It would be really cool. I have serious torque down to around 100rpm or so and the belt drive when properly tensioned does not slip especially on the low speed tier. Is anyone on here anywhere near Maryville, Tennessee... peace

Pete

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16 Feb 2011 16:46 #7246 by BigJohnT
With a belt drive you would want to get your encoder feedback from the spindle unless you had a timing belt drive then the motor would be ok I think. Looking at your video (and it's not really clear to me) it looks like you could take a timing belt pulley and bore out the inside and fix it to the top of your v-belt pulley. Do you have a photo of that area?

Looking on the user map there is another user located at Lenoir City and quite a few in Nashville. I'm located in Swamp East Missouri...

John

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16 Feb 2011 17:15 #7248 by andypugh
PetefromTn wrote:

Yeah the Geckos are step and direction based servo drives, does that mean you cannot use them?

No, that's no problem, EMC2 is perfectly happy with step/direction drives.
You possibly have the option of using the drives in velocity mode, and closing the position loop in EMC2, but that would need a whole lot more IO and encoders on each axis. Probably not worth the trouble and expense. If what you have now is working, then it will carry on working with EMC2.

I do not have toothed (teethed) pulleys I have vee belt and pulleys so that too might be a problem?

No, absolutely no problem, but it does mean that the encoder absolutely has to be on the spindle and not on the motor as the belt ratio is indeterminate with a V-belt.

It does not sound like this is gonna be possible if I need three sensor inputs just for the spindle.... Is that correct?

I think that you could possibly manage with just 2. Either two sensors and a once-per-rev pulse using one of them as the index too (ideally you would have half the spindle black and half white, and the sensors at 90 degrees to get the quadrature). Better would be multiple pulses per rev with the sensors offset by half a pulse to get the quadrature. One simple solution which might work would be an encoder and 1:1 belt drive, as used here (This is another EMC2 installation, with a power drawbar):

If you look at his other videos you will see a 1" tap rigid-tapping.

What would you fellows say is the easiest simplest way to arrive at a rigid tapping setup for my belt driven milling machine and use the least amount of hardware and complexity of wiring?

Not wanting to sound too much like a Mesa salesman, I think that freeing yourself from the parallel port pin limit would be useful. For $80 you can buy a 7i43, plug it into your parallel port and then you have 48 IO pins, megahertz encoder counters, super-smooth hardware step generation etc. (There is no reason you can't wire your existing BoB to a subset of the pins)
That would be rather a commitment to the "EMC2 side" though. As a first step I would be tempted to experiment with a laser-printed encoder disc or strip and a second optical sensor to use just two pins. The index could possibly be a software button, I think, but creating a fake index in HAL ought to be possible. The p-port has 5 input pins. It is possible to have all the home switches and limits share one pin, so it is probably still doable with the full three channels.

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17 Feb 2011 02:01 #7268 by PetefromTn
Just got my Spindle reversing setup with the Teco Sensorless Vector drive and it is working well. It reverses very quickly and has really good torque. I am anxious to try the rigid tapping feature but I am just not sure about the best way to get spindle positioning. The homebuilt encoder/index sensor setup looks like it should work from that video but I gotta think about the mounting and wiring as the head travels of course. The reality is I am trying to decide if I want to change systems and go with EMC2 and take advantage of the features available or just purchase a tension compression tapping head and do semi rigid tapping under Mach3 without worrying about spindle indexing. Either way I am gonna add another parallel port emulator for other sensors and things to add to my machine things I want to add. This is a work in progress of course but I am using it to make some money now and that is kinda cool. I want to be able to eventually rig up a power drawbar, simple toolchanger, and a fourth axis for a relatively complete machining center on a benchtop machine frame. Should be pretty cool.... If there is anything that I should consider when it comes to this that I have not realized please let me know so I can make the best decision. What are your thoughts on the servo tuning setup for the Step and Direction in EMC2 with the Geckos? Peace

Pete

Oh yeah here is another video... sorry for the crappy cell phone quality... peace

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17 Feb 2011 08:14 #7272 by andypugh
If you remove the front cover on the spindle casting, can you see the spindle shaft? It might be possible to clamp a 2-part encoder ring round it (or even use a paper encoder wrapped round the spindle, like I did with my lathe)

I assume you have seen the video of the Tormach power-drawbar? If you need to do belville-spring calculations you might find this spreadsheet useful:
www.bodgesoc.org/DIN2093DiscSprings.xls

I guess you are thinking in terms of a rack-style toolchanger? Currently the support for those in EMC2 is not especially good. There is a project underway to introduce G-code-as-toolchange for toolchange variants which require coordinated axis movement (rather than simple quill-up). Conversely, for more complex toolchange systems the availability of Classic Ladder in EMC2 may be an advantage over Mach3.

I am a bit concerned about the phrase "Parallel Port emulator". What do you mean by that?

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