Machsupport Forum
General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: BarryB on March 31, 2009, 03:18:34 PM
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Hey folks, go big or go home right? Anyway, I'm building a 6 axis cnc and would like advice and pointers as I order parts and what not. I figured I'll order all the electronics first, make sure they work, and build the machine around them.
For the final machine, it's going to be a moving gantry system with an A/B head from doughty drive. Initially the machine will be 5 axis. The 6th axis will be added later to the table to revolve objects. The cutting surface, I plan on being about 4' x 4' x 3'. I will be primarily cutting wood, soft and hard. Sometimes I'll be cutting metal as well.
Here's what I've ordered so far...
1. USB Smooth Stepper
2. 7 Gecko G203V drives
3. 4 Nema 34 1250 oz motors
4. Mach 3 (of course)
What I'd like advice on from here, would be:
1. Power Supply (I need it to power each drive, which in turn will power the motors, remember there are 7. The gantry will have two drives/motors to move it.)
2. extra switches like limit switches, emergency cut-off switch (how many, and where?)
3. wire (what's the accepted standard, how many colors etc)
4. kit box to store everything neatly (Are there large locking ones? Do we all make them by hand?)
Later on I'll ask questions about the frame. For now, it's only electronics.
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I'm just ordered a B/C drive and about to order the spindle. I do have a couple spindle questions though. What is the difference between S1 and S6? If this is in a home workshop, would that make a difference if you got S1 vs S6? Is one more difficult to use than the other, more testy?
Let me know.
I figure I'm 1/2 way through parts ordering now, this gets a bit pricey huh!
Barry
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Hi Barry,
For your wire - used screened cables for everything except the spindle (this will avoid any possible stray pickup problems at a later stage) and earth them at the controller box end only. For bipolar steppers you only need 4 core, for unipolar you need 5 core, not sure if you will be using encoders. Obviously the cores have to be man enough to handle the motor current. Limit switches only need two core but again make it screened cable.
Hope this helps.
Tweakie.
btw. When it comes to earthing - it pays to have one single earth point and earth everything to this single point within your control box. (do not earth the screen of your LPT connection - this is only earthed at the computer end).
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Thanks Tweakie, I didn't know that about the wire. I thought screened cable was only for audio/video. Good to know! Btw, I plan on hooking up all the electronics first, to make sure that works, and can place it all in a lock box hidden away before making the frame. Does that make sense? I usually see others build their frame first. Dunno, just seemed more appropriate to me this way.
Barry
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Hi Barry,
I just stuck the box on the back of my router frame where it is out of the way and wired to it. If it didn't work first time I knew I would get it working eventually. But as luck would have it first time and rock'n'Roll.
Tweakie.
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Nice organized kit box you've got there. I plan on mine being like yours too. Your power supply is supplying power to everything? How does that work? I was thinking I'd have to get a separate one for each part for some reason. Yes, that's the newbie in me;)
Barry
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Hi Barry,
My machine here is a 3 axis router. Each axis motor is current limited to 2 Amps and the PSU is rated at 24 Volts, 6 Amps. The driver board gets its 5 Volt from the 24 Volt PSU. This setup wouldn't work for everybody but it is fine for my needs.
Tweakie.
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A friend of mine has an emergency stop switch for each axis of his machine. I didn't expect that. I expected one switch for the whole machine. What do you guys do? One switch, or one per axis? Is there a requirement for a commercial setup?
Barry
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I have never heard of having one for each axis. Generally, you need an E-stop (too late button, as I call it) so that you can easily access it wherever your at. Typically, small bridgeport styles have one. The small lathe at work has 3. One at the manual controls, one at the interface, and another close to the door. A machine we're building at the moment has 5. I'm sure OSHA has guidelines.
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Hi Barry,
It is essential that you can reach the EStop at any moment. If the EStop is out of reach then by all means add another. Having one for each axis doesent really make sense as EStop is EStop no matter which one you press it will still stop the process.
Tweakie.
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That makes sense. I'll start with one, and when I decide more is needed, I'll add more. Btw, spindle ordering tomorrow;)
Barry
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What kinda spindle ya getting?
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I'm getting an HSD spindle. It's 2 HP, only weighs 3.5 KG and air cooled. It's the right kind of performance vs price vs weight that I need. Anything heavier would break my design.
Here's the link to it:
http://www.hsd.it/prodotti.asp?co_id=1020&service=
MT1073
Y6162Y0010
I'm told it'll take about 8 weeks to be in though, damn!
Barry
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Be careful with the cut's. Anything above 1Hp will bend that setup. And 1HP is already beefy.
Rainer
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I just received the B/C drive unit from Doughty Drive. That is one industrial piece of engineering there. I can't wait to use it!
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I'm sure a bunch of you will say, duh, what a stupid question, but this is my first time building a cnc machine, so I'm trying to dot all my i's and crossing my t's.
I just ordered the power supplies, and wanted to verify that these will indeed do the job. It's a lot to think about. I'm using Gecko 203v's and they have a power supply of 15v to 80v, the motors I'm using are two fold. 5 of them are 4.2 v/4 amp, two of them are 3.36 volt/2.2 amp. I'm wiring them all in series to be lower power/heat. The power supply I picked out for these is a tdk lambda sws600 24v, 25amp, 600w amp. I believe this works for all of them, yes? I will just need to add a limiting resistor on the geckos to limit to 4.2v and 3.36 volts on their way out.
The 2nd power supply is for the 5 volt, 1 amp power supply and only powers 1 device. That was a bit simpler;)\
Can you guys tell me if I'm on the money or off my rocker?
The spindle power supply is going to be from the manufacturer of the spindle so they'll tell me which one to get there.
Barry
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You're off your rocker ;D
Take a close look at how the cabling should look like according to the manual....
I have a bad cold, so I will not dare to give you a cookbook here with my stuffed head and smoke coming out of my ears... But here is a list of things you have to check and set accordingly and you are on your way!
1. Check the winding of your stepper. Parallel Bipolar gives the best oompffff and look up that voltage for that type of wiring for both motors. There are two other ways to connect the winindgs and they are not as powerful. Check that!
2. Take the lowest Voltage of the motor e.g. 3.5Volt and multiply that by something between 15 and 20. Till you get a result you can actually buy.... Like 40-50 Volts.
Consider that higher Volts are fine but it also becomes much much unsafer to operate.... DC is worse then AC to touch and be really really careful with anything above 5-15Volts...
Really!
3. Take the highest AMPS like 4amps and multiply with the volts you need. e.g. 70Volts times 4amps is 280 watts. Thats what one motor can pull. I know... that is not correct as it is less because the gecko drive is pulling with 20KHz and bla bla bla but I don;t want to scare the good man.... Soooooooo something like 5-600 watts will heat that flock of motors well.
Considering not all axis are moving at the same time.
4. Switching power supplies are not good. Use a Toroid transformer. Antec.... New Jersey... My Chinese Neighbor... Good Stuff and very affordable. People will try to get into an argument about toroid's and switching power supplies. Tell them I'll meet them behind the gym and show them their split diode!
5. The Gecko's resister does limit the ampere NOT the voltage. You are a tad lost there.... aehhh of the rocker ;).
6. The Spindle will use a VFD Device which will supply the 300 to 400 Hz to drive the RPM high. Do not let the Manufacturer talk you into some horrendous sum. Your size should not cost more than a couple hundred dollars. Check Dealers Electronic with their fabulous VFD's and great service. I have 4 from them, all quality manufacturers like Westinghouse and one fried after a year and a half and I got it exchanged for free and upgraded to the latest model...
So.... check your setup again and the best of luck. And for all.... keep it safe. This is not harmless stuff....
Just in case, give your wife my email address.... I can use that 5th axis head >:D
Again.... best of luck and the best wishes for a un-toasted experience
Lemo
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Thanks for your advice. I ended up ordering a 65v, 1300 watt power supply instead. Based on your advice that's between 15 and 18 times for the large and small motors I have. It should all be good now, thanks;)
Barry
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1300 Watt, wow!
I didn't see you mentioning welding ;D ...
Make sure that this power supply will be on it's own breaker. It will pull a LOT when being switched on and a transformer based power supply.
20Amps slow on 120V would do...
No need to cool it as the motors will not use more than 4-500 of them 1300 Watt's.
But in case of failure you have reserves to run the tool through the floor >:D
Keep us posted.
Lemo
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This one seemed the best value, however, if you recommend another, I'm all ears. I'm choosing from:
http://www.kelinginc.net/SwitchingPowerSupply.html
I was choosing the 65v since that was 15 times the power of the larger motor when set in series (smaller number). Although you are recommended parallel, which I may do as well. I do see they offer a 975w which is only 15A, which may be better?
Both power supplies have a 5v dc output which is great to power the breakout board, smooth stepper.
Barry
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Don't worry. The watt's are fine once you are above or at the demand of the motors. Anything more will cost you copper, money, and weight but that's it.
I use a 900Watt power supply for 4 1KW servo's. I limited the current in the drives so I won't kill the power supply. With the pulsed characteristics of the drives I never exceeded 800 Watts.
Don't worry, you'll be fine. And yes, Bipolar Parallel has the best torque for your application.
It's all good.
Lemo
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Thanks, it's all so complicated the first time building, I'm sure you'll agree. I did send a note to keling to change to the 975watt. That saves me 5 amps too, which works better I think too, less dedicated wiring.
Barry
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I buy my power supply here:
http://www.antekinc.com/PS-10N63R.pdf
Take a close look at the 5V power supply section. if it's only regulated with a 7805 or similar chip then it's garbage.
Go get a couple of those: http://tinyurl.com/d7c7k2
They are switching power supplies with superior noise levels compared to the cheaply regulated ones.
If you would connect an oscilloscope to the simply regulated power supplies then you will see noise which can lead to steps or direction switches which will be all but impossible to debug later. The switching power supplies linearity is dead flat. That's where the switching power supplies lead. And for a BB you do not need power. A single amp usually is enough. aving 12 V as well is nice as some breakout boards also allow you to controll the spindle speed and for that you need the 12V to drive the VFD of the spindle from 4 to 10 Volts. aprox 7-18000RPM....
PS:I am not sure... but this might be Kelling's source ;)))
Lemo
PPS: Spindle VFD's with great service http://www.dealerselectric.com/
And yes, i bought those power supplies from China. Two weeks later a fun little box arrives with all sorts of cool stamps on it. No sweat and for $3.... I don;t even get the shrink tubing from the local electronics store for that amount...
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Thought I'd show some progress. Here's the start of my control box. The breakout boards aren't in there yet, nor are the two other geckos, but it's coming along. I've modeled the machine too, and will soon be ordering parts for the frame. Wow, these things really add up!
(http://www.3dmation.com/images/ru_cnc/cnc_controls_1.jpg)
Barry
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If the Gecko's are just sitting on the metal cabinet sheet metal, then you will need a heat sink on the back. They do become warm and hot is a bad thing.
With gecko's I do not use a Breakout Board as the Gecko's are already opto insulated. What Software are you planing to use to generate the 5 axis toolpath?
Are you planing to 5 axis index machine or 5 axis continuous machine?
Rainer
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I've got a box of heat sinks that I can add to the back. Thanks for the suggestion. I'm not sure what you mean by index vs continuous. I'm still learning the stepper lingo;)
I'm planning on using Mach 3 initially for path generation. It does do that, doesn't it?
Barry
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Yes, you need a heat sink.
Mach3 is the trajectory planer not the path generator. All Mach3 does is translate movement Commands into step pulses. You need so called CAM software to create the movement commands from a drawing or 3d model.
And you need modeling software (CAD) like Rhino3D or similar to create the model or drawing.
5Axis indexed means that your work piece is rotated in 5 axis into place and then machined in three axis. Imagine a cube with an engraving on each side. The machine would rotate a cube face into position and then the machining will take place in 3 axis. 5Axis continuous is when all axis are moving at the same time and describe a rather complex path.
5Axis Cam Software is at least as expensive as the hardware you are building. MasterCam or Mecsoft's RhinoCam (I use the later one with good success) are the only ones I know which allow 5axis generation
Both charge extra for custom post processor development for a 5 axis machine. Add another bundle...
There is a highly experimental set of routines out there which utilize 3d animation packages to generate a 5 axis toolpath. But that requires that animation package which is not cheap and probably a year to get familiar with that...
Nothing is ever easy! Best of luck and keep the cutters sharp ;)
Cheers
Rainer
PS:Here's a simple example of a 5 axis system using a trunion table as an alternative to 5 axis router heads.
http://www.youtube.com/watch?v=w0-tXDEvAqg
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Hello,
Well, actually no... Mach 3 cannot generate paths. It can with wizards generate 2D and 2.5D toolpaths, and with Lazycam too, but not 3d toolpaths certainly not 5 or 6 axis.
Mach 3 will do what you tell it to do, so you need a CAM package to do the toolpaths,
5 axis CAM packages are expensive since they need to calculate tool offsets in 5 axis, there are a few out there. A freeware cam plugin is available for 3DS MAX, GMAX and Autodesk VIZ, it is called CNC Toolkit
http://groups.yahoo.com/group/CNC_Toolkit/
It works but it has a steep learning curve but it does work.
Now Indexing vs continuous:
Indexing refers to having some axes still while machining with the remaining ones. One example would be a 4th axis rotary table. you machine with 3 axis while holding the rotary table still, then turn the rotary 90 degrees and then machine again in 3 axis, then turn it another 90 degrees and machine again etc..etc..
Continuous is when all axes are moving at the same time.
Now with your control box, heatsinks are a must if your steppers are above 3 amps i think, but it is a good idea to have them even if its under that. you have 5 geckos mounted on your box, and you say you still need to mount TWO geckos more? that would be 7 geckos, and mach can only handle 6 with dual parallel ports.
Regards
Fernando
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Also consider mounting the heatsink outside of the box to prevent heat build up in the box. Or push filtered air through the box to vent it.
R
PS:Just curious... not counting labor or software, what's your estimate on how much the system will cost you?
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Yup, I'm using 7 geckos. Two of them share the same signal but send out their windings oppositely to balance the load of the x axis. A close example to what I'm doing is:
http://www.cnc-toolkit.com/gantry_router.html
My build is a bit more beefy than this one, but the principals are the same. The 6xth axis will be a rotary table that I mount to the table. I'll add that sometime later this year.
Heh, you don't want to know the price. It's way more than I expected it would be;)
Barry
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If you drive two steppers for a X-axis then build a torque dependent e-stop in case one goes limp. You do not want to destroy your setup while one stepper is locked for some odd reason (pick one of 10,000) and the other one is happily pulling things apart. With a setup like the machine pointed out but more robust you will be in servo territory. Expect to switch form steppers to servos at one stage. I know... this is just what you want to read lol.
Rainer
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yeah, not what I want to read at all. If I do go servo it'll be a long time from now. Already invested in all the stepper hardware.
Hmm, torque dependent e-stop. Do you have a link for that kind of part?
Barry
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I'm curious too. Just what is a torque 'dependant estop' and what would you use to trigger it ?
Tweakie.
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uhhhh i think my roland operates on similar principal for finding its home.. its controller board registers a high peak in the motor "voltage/ampage/wattage??" when it slams the table into a stop.... basically measuring when the stepper stalls and sends a signal to stop driving it and then marking that position as "home" thats good for about 0.3mm accuracy as a "home" position measurement... i hate my roland...
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What made me curious is that from my experience stepper motors (unlike dc motors) do not draw any more current when they are stalled than when they are running (assuming that the driver is still sending current to the windings). Now I wonder how Roland detect the stall.
Tweakie.
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lemme ask my guy.. who likely is on this forum too as he has mach controlled mills too.. hmm lemme serach my other forum.. may find info there too.. hang ten
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ok .. he calls it "current sensing"
i post a quote .. excuse me mark for quoting you here without checking with you first :)
Quote
"Current sensing, used by Roland to indicate a MDX-15/20 limit has been reached, is a recognized method, but is widely thought to be a poor trade-off in performance for economy. If you do accept the trade-off, then the rough design of the stops is still ... ermmm ... stunning" and "When they collide, the stepper current goes skyward, the MDX electronics sense this and shut down the homing cycle. Then the MDX moves off the stop (a different Y amount by a matter of 4mm depending on whether it's acting as a mill or a scanner) and says to you "I'm in the VIEW position!" so you can then UNVIEW the unit and watch it go an exact distance to 0,0."
and this from Ken .. mwaaaaaahahahaahaha
Quote
"If I am understanding things right, are you saying the "faux limit switch" is actually two hard metal pieces that crash into each other and stall the motor out?
If so, why in the world didn't roland invest a few pennies into some cheap micro switches or even a few dollars into some proximity type switches to avoid homing and zeroing problems?"
so basically i went from a mill that crashes 2 plates into each other and registers a motor stall as a homing signal to a Minitech with 1 micron accurate Omron switches... you think im happy???
Betcha Ass I am!!
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Thanks for going to all that trouble Chris.
Tweakie.
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no trouble dude.. i used to have a life, regular sex and party and all that stuff.... but then i bought a mill.. now i have a keyboard glued to my fingers and wax dust in my hair.. and i look a little like a deranged mental asylum escapee with bad dandruff...
no trouble at all!
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Heh, I'm right there with you Chris. I'll post some more picts this weekend.
Btw, a question was asked before what toolpath generator to use. After some research and talking to friends, I think I'll use linuxCNC for toolpath, and Mach3 for controlling.
Barry
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I had to do homework all week/weekend till today. Here's progress though, I've wired power to everything. I didn't mount the breakout boards yet, since the standoff screws were the wrong size. This week will be a lot of soldering, not looking forward to that.
(http://www.3dmation.com/images/ru_cnc/control_box2.jpg)
Btw, the frame gets ordered tomorrow, finally!
Barry