Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: radioactive on February 18, 2009, 11:48:44 AM
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I've done enough reading to go cross-eyed... Lots of great info though. Getting ready to start my conversion on my mill. Here's the build thread I just started:
http://www.cnczone.com/forums/showthread.php?t=73820
I'm thinking I will need to use the Viper 200 drives for my servo's. What all is necessary up stream of the servo drives?
I thought since my new PC doesn't have a parallel port on the back I would use a smooth stepper board but I just read that it doesn't replace a breakout board and a breakout board is still needed? If so, I do have a parallel port connection on the motherboard I can connect to. It's a new PC dedicated to running the mill so would there be any downside to this? (not using a smooth stepper).
Breakout Boards
So some breakout board choices I've come to by searching are the PMDX-122 shown here: www.pmdx.com/PMDX-122/ for $81.
the C11T shown here http://www.cnc4pc.com/Store/osc/product_info.php?cPath=33&products_id=181 for $124.
The Bob Campbell breakout board shown here http://campbelldesigns.net/breakout-board2.php for $130.
or the Bob Campbell combo board shown here http://campbelldesigns.net/Combo-board.php for $245.
I get alittle lost looking at breakout boards as each manufacturer has about 3 models with little differences...
I plan to run it as a 3 axis machine and add a 4th axis later down the road.
Would like to have a charge pump monitor, E-stop button, PWM signal to VFD, inputs for home switches, end of limit switches, etc. Also like to build a pendant with controls on it as well, but I assume this will require additional inputs (possibly another breakout board for input into the PC)?
Also need to find some encoders for the servos (US Digital?)
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You need to figure out exactly what functionality you need, before you can choose a BOB, or rule out the SmoothStepper. What step rates do you need to achieve to get your target rapid rates? Since you're apparently using servos, your step rates may be quite high - beyond what a parallel port can support. Mine run 20K and 96K steps/inch, so getting reasonable rapid rates means running beyond what a PP can support (the PP usually tops out at 45kHz). You may also get smoother, more reliable operation with the SS - I sure did. If you do use the SS, not all BOBs will work well with it. I know the CNC4PC C11 will not - I had to modify mine to make it work abouve 40kHz step rate (and the spindle speed control is very unreliable....) Not sure about the C11T, but I suspect it uses very similar circuitry. For the BOB, do you need spindle speed control? If so, what kind - Step/Dir or PWM? What voltage range? Not all the BOBs you list support spindle speed control, so you'd have to buy an additional spindle control board, in addition to the BOB. How many relays do you need? Many systems will require at least 3: Spindle CW, Spindle CCW, and Coolant. Some need even more. Do you want/need opto-islolation? If you're using Geckos, you don't need this on the Step/Dir signals, but may still want it on the other signals, to help with noise immunity on limit/home switches, etc.
Regards,
Ray L.
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I use the PMDX122 on all my machines and like them a lot. I also think it is often best to seperate out things like relays, spindle control etc rather than having them all on the one board, especially if mains voltage is involved in such things as spindle relays, but I am sure there are many who would disagree :)
As Ray has said, your encoder count will determine the pulserate you need, I think the Vipers have electronic gearing but again personally I shy away from using that as cogging can become an issue at lower feed rates, so the SS might be the best way to go.
One other thing is the parallel port connection on the mobo may have low voltage so make sure the BOB you get is happy with this, most are nowadays I think, however if you do get a smoothstepper then that is not an issue.
Hood
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I do not know what rapid speeds this machine is capable of? How do I determine the step rates of my servos? They are SEM servos model 30M4-59, 2400 rpm, 142 volts, 30 pulse amps? Or is this strictly a function of the encoder I mount on it?
I do not need spindle speed control to start with, however my VFD can accept 0-10V to control the speed if needed. I figured at some point I might as well get it to work. The mill has a vari-speed pulley setup on it now. I can always worry about this piece later and just select the speed manually for now...
The viper manual shows the step/dir inputs as opto-isolated.
I like the K.I.S.S. principle so keeping everything on their own boards sounds better to me, I just need to figure out what I need.
Hood, the electronic gearing you mentioned, is that related to the "Step Multiplier Select" available on the vipers? It offers 4X multiplier, 6X, and 10X. I assume this is to electronically gear down the servo, meaning on the 10X setting, it takes 10 times as many steps to move it 1" as it did on the 1X setting?
Probably a stupid question (but reveals my knowledge of milling machines). Why the need to reverse the direction of the spindle? Aren't must cutters made to spin the same direction while cutting? What am I missing here?
The servo's have tachometers on them now so I will have to purchase encoders.
Thanks for all the replies!
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Yes pulse rate is determined by the encoder count, most encoders give you the line count, so for example an encoder that has 500 lines will be 2000 pulses for one revolution.
Yes the step multiplier is electronic gearing, if you have 4x then one pulse from Mach will be 4 as far as the drive is concerned, this allows you to get faster rapids from the parallel port than you would without the multiplier as 500 pulses from Mach would be 2000 as far as the drive is concerned. The downside of course is at slow speeds you will get cogging, how noticeable depends on the resolution. With a SmoothStepper however you dont have to worry about that as its pulse rate is max of 4MHz so keeping the multiplier at 1x will not be an issue. If you decide on the parallel port then probably best to stick to a 500 line encoder, if using the SmoothStepper then probably 2000 or 2500 line encoder would be best.
Spindle may need to reverse for a few reasons, often mills have backgears and although some like my Beaver mill have true gearboxes that will keep the spindle rotating in the same direction mills like my Bridgeport will reverse the spindle direction when in backgear so you need to be able to reverse the motor. Tapping also requires reversal of the spindle and at this point in time you will need a floating holder however in the future the SmoothStepper should support fully synced spindle/axis so true rigid tapping should be a possibility.
Hood
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Now that you mention that, the previous owner did say when in low or high range on the spindle it does run it in reverse. I had forgoten about it until now. I don't plan on doing any tapping with the mill until I've got some more experience under my belt.
Since it seems that smooth stepper would potentially make it a smoother running system and does allow for a wider range of encoders to be used, it may be the way to go... Then I would only need to add a breakout board for additional inputs/outputs to the SS board.
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Some people dont use breakout boards with the SmoothStepper, but the power out is limitied so you can not really use the outputs to switch relays etc.
Hood
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You mean to attach it directly to the pins on SS board with the appropriate connector? I just read thru the SS manual again, here's some specs:
6 axes of coordinated movement plus a spindle.
Spindle control may be Step & Direction, PWM, or discrete on/off.
Maximum Step Frequency is 4 MHz
I/O: Port 1: 12 Outputs and 5 Inputs
Port 2: 12 Outputs and 5 Inputs -or- 4 Outputs and 13 Inputs
Port 3: 6 Inputs (3 differential and 3 single-ended)
Grand Total: 24 Outputs and 16 inputs, or 16 outputs and 24 inputs, depending upon
configuration.
All outputs are 5V CMOS logic.
Port 2 pins 2-9 have CMOS thresholds (input and output).
All other inputs are TTL, except for 3 of them that are differential and are intended to be used with an
encoder. Except for Port 2 pins 2-9 and the differential inputs, all other inputs are Schmitt Triggers.
All outputs capable of sinking or sourcing 32 mA.
32mA isn't a whole lot for controlling some relays, so I may have to do something there. Easy enough though.
Thanks for the help, makes alot more sense now...
I sent an email to www.warp9td.com asking about availability (I got on the waiting list a week or two ago just incase). If they are still 4 weeks out, do you know if they have any dealers that sell their products for them that may have some in stock?
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There are some pics of a connector a guy made up so that he could wire direct to the SS, I will see if I can find the link.
Not sure of any dealers, think Peter Homann in Ozz is one but for the USA I am not sure.
Hood
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http://www.warp9td.com/index.php?option=com_fireboard&Itemid=33&func=view&id=930&catid=7
Hood
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http://www.warp9td.com/index.php?option=com_fireboard&Itemid=33&func=view&id=930&catid=7
Hood
Very nice... thanks
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Just talked to Greg and he reckons a week and he should have some SS to ship out.
Hood
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Excellent news, I hope to get alot done in the next few weeks...
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Just got my paypal money request from Greg for the smooth stepper board. He must be close to shipping them out like you said.
Can't wait :)
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:)
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i'm using the smoothstepper with viper servo drives.the vipers already have optoisolation..i have drives are connected with no bob.have 500cpr usdigital e6d encoders to 5 tpi ballscrew. separate soundlogic board for inputs and relay outputs.large sajo vertical mill 7" gettys
fanuc motors directly coupled to the axis screws. i have never encountered cogging.it can take heavy feeds with 6 inch facemill .the vipers are a little difficult to tune. the latest version of firmware protects the drives from blowing. one thing about the vipers is that you can set encoder count following error and output to mach estop.
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i'm using the smoothstepper with viper servo drives.the vipers already have optoisolation..i have drives are connected with no bob.have 500cpr usdigital e6d encoders to 5 tpi ballscrew. separate soundlogic board for inputs and relay outputs.large sajo vertical mill 7" gettys
fanuc motors directly coupled to the axis screws. i have never encountered cogging.it can take heavy feeds with 6 inch facemill .the vipers are a little difficult to tune. the latest version of firmware protects the drives from blowing. one thing about the vipers is that you can set encoder count following error and output to mach estop.
Are you using the multiplier (electronic gearing)?
Hood
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hood, when i had parallel port only , had the electronic gearing set to 2:1 as the computer was a little slow. went to the smoothstepper. now have set to 1:1.
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I had the gearing 2:1 with my lathe when on the PP and cogging was not really noticeable unless I feed at 1mm/min and had a dial gauge on the sadlle, I could just see the needle twitching as it moved where at 1:1 it was very smooth. Where I really noticed it was when I tried at 10:1, you didnt even need a dial on it to see the jerky movement at very slow revs. I settled for 2:1 while on the parallel port and that restriced my rapids to 3500mm/min but at least it was useable, when the SS got threading I put that on the lathe, set the gearing 1:1 and could easily do 20m/min but settled for 10m/min as its quite frightening seeing a 400KG saddle hurtling towards the chuck at 20m/min ;D
Hood
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Well I received my smooth Stepper board and my three Gecko drives (320's). I've gutted my old controls off the machine and rewound the existing transformer to give me 77 VDC to power the Gecko's. Just ordered a Sound Logic encoder interface board from Rogersmachine.net to work along with my smooth stepper. I believe these two should handle everything I need right now.
;)
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Well I received my smooth Stepper board and my three Gecko drives (320's). I've gutted my old controls off the machine and rewound the existing transformer to give me 77 VDC to power the Gecko's. Just ordered a Sound Logic encoder interface board from Rogersmachine.net to work along with my smooth stepper. I believe these two should handle everything I need right now.
;)
Well I received my smooth Stepper board and my three Gecko drives (320's). I've gutted my old controls off the machine and rewound the existing transformer to give me 77 VDC to power the Gecko's. Just ordered a Sound Logic encoder interface board from Rogersmachine.net to work along with my smooth stepper. I believe these two should handle everything I need right now.
;)
I wonder if 77V isn't a bit aggressive? If you don't have a good energy dump system, that could shoot up on sudden decel, and cook a Gecko. You might want to check that with Mariss at Gecko, before you let the smoke out.
Regards,
Ray L.
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I asked that exact question on another forum (awaiting reponses) and am drafting an email to Gecko right now, it's easy enough to remove a few more turns from the transformer if needed...
What does an energy dump circuit look like?
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I asked that exact question on another forum (awaiting reponses) and am drafting an email to Gecko right now, it's easy enough to remove a few more turns from the transformer if needed...
What does an energy dump circuit look like?
There are a number of ways of doing it, basically providing somewhere other than the power supply capacitor for that energy to go - typically a large power resistor. There's an app-note on the Gecko website giving one example:
http://www.geckodrive.com/upload/returnedenergydump.pdf
Regards,
Ray L.
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Here's the response I got from Marcus:
"You will be fine with 77VDC. The G320 is de-rated to 80VDC and its absolute break apart voltage is around 112VDC. We did this to take into account the line voltage variations as well as component tolerances. Back EMF is not a problem as it gets passed right back into your power supply’s filter capacitor. If you have any more questions, please let me know."
So it doesn't sound like it will be an issue...
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So the current REV (7) G320's have an energy return system built into the circuit?
Bill C.
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Here's the response I got from Marcus:
"You will be fine with 77VDC. The G320 is de-rated to 80VDC and its absolute break apart voltage is around 112VDC. We did this to take into account the line voltage variations as well as component tolerances. Back EMF is not a problem as it gets passed right back into your power supplys filter capacitor. If you have any more questions, please let me know."
So it doesn't sound like it will be an issue...
Cool!
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Here's the response I got from Marcus:
"You will be fine with 77VDC. The G320 is de-rated to 80VDC and its absolute break apart voltage is around 112VDC. We did this to take into account the line voltage variations as well as component tolerances. Back EMF is not a problem as it gets passed right back into your power supplys filter capacitor. If you have any more questions, please let me know."
So it doesn't sound like it will be an issue...
Cool!
Cool Beans!