at what RPM on the motors does it stall? is it at the same speed all the time? Do both motors on the X stall even if they are not linked mechanically?
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at what RPM on the motors does it stall? is it at the same speed all the time? Do both motors on the X stall even if they are not linked mechanically?
Both motors stall simultaneously, they are using separate drivers and slaved together in Mach3.. I have tried varying the speeds and accelerations in Mach3 but that makes no difference. It only does this on full rapid, when the x and y are being moved simultaneously.. I can repeat this every time by jogging both axis at full speed, it also does it if I run code that rapids (G0) at 45 degrees...
Steve..
What speed are you stalling at?
What happens if you are moving X at maximum speed and then just move Z?
It is stalling at all speeds.. Had it as low as 500mm/min up to 2500mm/min.. Acceleration from 10 - 120.. Stalls at any speed.. The x axis is completely unaffected by the z axis.. It only happens when the Y and x is both moving at full speed..
Have wired my nema 23 (3Nm) in parallel.. Wow, whizzes along now at nearly double the speed...!
Was re-checking this fault and had the y axis stall as well as the x..! Hmm.. seems the problem is getting worse now.. Spent a good chunk of the morning frowning hard at my PC, its a quick computer but have had some comments about the parallel port that are starting to sound ominous...!
Steve..
Steve, Smooth stepper on it's way this will eliminate the PP completely. . . Remember thou I want the bugger back.:confused:
Thanks Jazz..!
Will pop the bugger back as soon as I have tried it..!
Steve..
Disconnected the X and Y motors from their X-Y table. Unable to reproduce the problem of horrible sounds and missed steps described above when MACH3 jogging the motors at full speed. I'm becoming convinced that, since the X and Y-axis move very smoothly on their own, that the issue - in my case - is related to some resultant force vector in the heavy X-Y table causing table twisting and thereby increased friction and too high loading on one or both of the the motors (even though motor currents seem low). I can't tell by sound or feel whether it's the X or Y motor generating the noise. A mystery that's annoying and puzzling.
Sounds very much like you have some binding then or if it's X-Y table that uses dovetail ways with jib strips then you could have some slop enabling the table to twist and jam.?Quote:
Originally Posted by Karl
If so then I would strip down the table and check for any chips that have got lodged or stuck, clean all surfaces carefully checking for damage or high spots.
Re-lube the ways and rebuild being carefull not to over tighten but still enough take out any slop then try again.
Good luck.!
Steve I'm clutching straws for you here but it may be worth trying another PP cable.?? Will at least be another part of the elimination process.!
I'm pritty sure you have a pulse issue and this where I'd be concentrating my main focus.!
Think you are right Jazz.. Having revved up my y axis by re-wiring it as parallel, I am guessing that there are more pulses/second now and this may be why I am experiencing even more stalling, the y axis did not stall before and it is now... Your smooth stepper will surely prove this one way or another and I will do as you suggest and get another cable..
As we discussed before, I should probably think about a PCI PP but I remember your thoughts on this.. So, anyone out there know a tried a trusted PCI parallel port that they use on their CNC?
Steve..
Look fr cards that contain the 'NetMos' chip on it,a lot of the cheap ones on Ebay do, just fire odd a mail asking them. There has been good feedback on these.
Alrighty..!!!
Finally getting somewhere...! Changed my parallel lead, big difference and stalling was reduced immediately, but not gone... Then dropped micro stepping down to 800 for each axis and then re-sited every wire.. Bingo...! No stalling.. Had it whizzing around the limits of each axis in 45 degree moves for about an hour.. Not one stall.. Gradually ramped up the speed and acceleration of each drive and would have got it up to around 4500mm/min except one of my ballscrews is bent, nearly shook the frame apart..! Just got to remove the dodgy ballscrew as I think the machined (motor) end might by eccentric...
Thanks all so much for your help, wish I had done everything step by step now as I am not certain if reducing micro steps or rewiring it was the cure.. From what I have read on many posts, 800 micro steps should be within easy reach of my PC, so I still think I have a weak parallel port.. Will get a PCI one from ebay (with a NetMos chip, thanks 2eUpoz) and will still try Jazz's smooth stepper (mucho thanks Jazz) as that sounds like a cure all for this type of pulsing problem..
Once I've checked the ballscrew I have a 6 hour job to do so am going to see how it goes with the new settings..
Karl, guess you have tried reducing the micro-stepping on your drivers, if not, got to be worth trying and definitely try a new PP lead as Jazz suggested.. If that does not work, then good luck and please continue the post until you have it working properly..!
Steve...
Good to hear it's work Steve :-)
by the way the last PP card i bought was from this guy. Had to search quite hard but found him.
http://myworld.ebay.co.uk/fullspeedit
Great news Steve. . I've known a few case's of failing or poor quality cables giving troubles, thou I still think it's your PP causing the problem. Thats why dropping the microstepping works.
Bet if you dropped the kernel speed to 25K you will be able to micro step higher.? . . . Give it a try and I think you'll find you can get 2000 M/S.!
Edit: The only reason to run higher Kernel speeds is if you can get higher speeds from your motor/screws than the kernel allows and your if PP is upto the job.
Other wise Mach works best or should say most stable at 25K. . . . If your happy to run at around 5mtr/min then I would leave it at 25K for best stabilty.
good result Steve!
What did you change with ther wiring??Quote:
...and then re-sited every wire.. Bingo...!
Ok heres a post from the Yahoo forum By Art fennerty the genius who invented Mach3 that may may explain something of what I mean and also clear up why Mach likes 25K best.
It's part of a reply over along running issue a guy had and so some of it may not make sense but it's interesting reading and should shed some light.!
Here's the deal with kernal speed.
Lets say you select 25Khz, and then tune your motors. While tuning, you find you have the velocity slider up all the way, but would like to go faster than you can tune.. you then must select the next higher kernal speed, and retune all motors. If while tuning, you find you cannot go fast enough, repeat till the kernal speed is such that you CAN select the speed you need.
The reason is this..
In 25Khz mode, the computer interrupts every 40us.. in 35Khz, every 28.5us , in 65Khz, every 15us , and for 100khz, every 10us.
Now, the time-in-int is the amount of time spent servicing that interrupt. One of the secrets of the printer port driver, one Ive never discussed , is that
all drivers in windows are told to do their thing fast, and get out. My driver breaks that rule..heck it breaks most rules. :) . SO it takes the time it needs to
do 1 step pulse, read input, set outputs, unset the step pulse, jog if necessary, etc.. and then exits to wait for the next interrupt. The time-in-int is the time it takes to do all that.
So lets say your in 25khz, every 40us an interrupt will come along, and your machin has a time-in-int of 15, that means your cpu has 40-15=25us to do its
normal windows activity. Your computer is now 37% a pulse driver, and 63% a windows OS..
Time-in-int doesnt vary from kernal speed to kernal speed, only computer to computer. Lets say yours is 11us. ( a bit high ), if your in 65Khz mode, your now interrupting every 15us.. , so Windows now has 3us every 15 to do its thing, its now a cpu that is 20%windows, and 80% pulse engine.
The windows component runs Mach3, so you now have 20%Mach3 ( plus windows fucntions) , and 80% pulse engine. As the pulse engine % goes higher, the chance of lockup goes higher.
So higher kernal speeds give you higher criticality, which can be defined as your sensitivity to random bad events affecting the computer. The lower the kernal speed, the higher your immunity. As youve noticed, your 45Khz machine doesnt lock up as much as your 65Khz machine. That follows the logic Im explaining. (Im almost willing to bet your machine at 25Khz will never lock up , or would be very very rare, (Im assuming this from your statement about the two machines correlated to hundreds of very similar conversations over the years with lockup victims. Fully 80% of them didnt realize the connection, and tuning lower in kernal speed stopped the problem.
Now sometimes you NEED higher kernal speeds, ( high step count machines typically), but fully 90% of people who have set high kernal speeds
dont really need them, they do so simply as a result of the very human instinct to have the highest possible speed selected. ( "Yeah boys, my engine has triple hedenstock carbs with dual-hemi semi-octagonal rebuf cyclinder hose accessory packs!".. :)
You may wonder..why the heck dont I tell people this more forcefully, since it will stop most lockups. Fact is, higher kernal speeds DO have a smoother
motion just as a result of granularity, and Ive found the vast majority CAN use higher speeds with no problem. ( I am limited here to 65K ), I use 25K though for reliability. With over 25 thousand machines out there, the number of overall lockups is extremely small, and thats including the tendancy people have to select the higher speeds,so as a result, I try to keep my nose out of their selections, unless they have trouble.
The final question you should be thinking about now is.. "Why didnt you ask me this when I complained about lockups.. :) ), the answer is that the
subject comes up so infrequenctly now that even I forgot to ask this basic question about the kernal speed. I used to post it periodically on this group,
but stopped quite a while back. In retirement I guess Im getting forgetful is my only excuse. Hopefully, youll find 25K never locks up.. Im suspecting this is true in your case. I hope so.
For those that want maximum reliability, I suggest this, use as low a kernal frequency as you can live with. On many machines maximum cutting speed is easily achievable in 25Khz, the only sacrifice in using 25Khz is perhaps a slower rapid speed. Rapids are nice, but not as nice as perfect stability, so I tend to give up some rapids to put their power into stability. Look at kernal speed as a trade-off, you can go real fast, or real stable.. (This is only if you have a lockup problem, many can have both and use higher kernal speeds. )
My own suspicion, again based on time and numbers, is that many people would have lockups, but most leave the kernal at the install speed of 25Khz.. I rarely hear form them. I hear most from 65Khz, and Ive heard quite a bit from 100Khz.. this is because those that can run 100khz are a rare breed, very fast clean machines with extremely stable operating system installs. For 65Khz, you better have a nice fast computer. 45Khz isnt bad, lockups on those indicate a computer suffering some periodic problem that slows the time-in-int too much..
None of this incidentally explains a random move. The driver is pretty much incapable of it, it canot move unless commanded, and it takes quite a sequence normally to command it. Youd have a better chance of winning a lottery than getting uncommanded motion.....unexpected..yes. :), that happens to all of us.. usually at our unknown request, but uncommanded...near impossible in the drivers context.
Let us know how 25Khz works.. do you have to sacrifice much speed ( or any ) to use it? And what IS your time-in-int number?
My average time-in-int is 5-7us by the way, which is pretty normal for a 2Ghz machines, by dual core is only 3-4us, meaning it will take much higher
kernal speeds without reaching any high level of criticality. My 1.2Ghz was around 15us.. ( pretty bad, but ran fine..)
Sorry for the ramble, I guess it was time for one anyway, for some reason there are some that actually like my rambles. lol
Thanks,
Art
Steve has hopefully already reduced the kernel speed as I mentioned it early in this thread (#17). Perhaps not I was not forceful enough.
If it's 800step/rev then on 25kHz with 10mm pitch screw and direct drive the maximum feed is 25000/800*10*60=18750mm/min ... so plenty. Clearly half that with 1600, which it sounds like is still a lot more than your machine will currently do.
The only time I've used more than 25kHz is experimenting ... when I got 1m/s feed on Y-axis that was with a higher kernel speed. I've also monitored the port at 100kHz with oscilloscope and interestingly it seemed fine.
Seem to remember Steve saying he was running 35K thats why mentioned running 25K.! . . . Obviously it's the bent screw thats now Screwing him..:cry:Quote:
Originally Posted by Jonathan
Well yes those figures are right in Theory regards what Mach could actually put out in pulse's but in actual practice 1/1 direct drive on 10mm pitch then a realistic usable figure is 8000mm/min 10,000mm/min Max due to running nema 34's which 800rpm is about the norm and 1000rpm would be about max.Quote:
Originally Posted by Jonathan
Steve was getting close to half this lower figure with bent screws so when every things running straight and true I'm sure he will reach these figures. . . . I'd also wager at higher M/S as well if he was indeed running 35K not 25K.?
He said 45kHz, so even worse.Quote:
Originally Posted by JAZZCNC
Yes obviously I was just stating the limit...clearly those motors are not going to get anywhere near that with the current setup.Quote:
Originally Posted by JAZZCNC
Tension the screw + rotating ballnut = no whipping ? Since that requires a timing belt could gear it up to go even faster anyway. As this is (I think) an 8x4' machine it would help...
Sorry Jonathan should made it clearer.!..I was refering to a telephone conversasion I had with Steve.Quote:
Originally Posted by Jonathan
Seriously don't get your fasination with speed jonathan.?. . . The ONLY thing it's usefull for is Rapids and seen as 85% + of the time a machine spends is cutting why go to all the trouble of rotating nut, esp on a machine with twin screws .? . . . I see the bennifit of rotating nut to allow long screws but not extra speed and 10mtr/min rapids is good enough for most machines even an 8 x 4.!Quote:
Originally Posted by Jonathan
Let me ask you this.? What do you CUT above 10mtr/min.?? . . .Not much if anything I bet.! . . Also out of the last job (other than mass drilling, which high rapids can help) you cut how much of the overall job cycle time consisted time wise of rapid moves.? . . bet it was easily less than 10% of total cycle time.?
Thats an awfull lot of extra work and expense incorparating 2 rotating ballnuts into a DIY machine just to gain a few percent saving on cycle times, the Key word being DIY machine where cycle times are usually not an issue. . . .Yes in industry every little bit helps but in DIY it's not worth the expense and trouble just for a few percent.!! . . IF . . normal screw setup can be used.
Said this before .!!. . .It takes a substancial machine with a powerfull spindle using high quality tooling to cut at high feed rates. . . . High rapids are only usefull on very small percentage of jobs other than that they are just used for bragging.!!
Also seen as most DIY builders use modified routers usually of the cheaper quality range or spindles like Kress then high cutting feeds with any reasonable depth are simply not achievable anyway.
Jazz,
At last a man after my own heart. All this 10,000mm / sec is just dick slapping. Think about it your part is programmed to run at say 600mm / min the only time this high speed comes into effect is on rapid moves and unless you are belting 4 holes into the corner of an 8 x 4 board any long rapids usually means you are not cutting / programming efficiently.
Even when you ar look at the sceen and see if the actual speed ever gets close to what's' allowed for rapids given that it has to accelerate to speed then slow.
Most time it never gets close to max rapid given the short distance it has to travel.
All insane rapids do is wear a machine out, put undue stress on parts probably not capable of handling them and more chances of loosing steps.
I say dick slapping because a beginners reads all this on here, CNCZone etc and thinks that's what he has to do, most are on small machines that can never, ever reach these speeds and even if they get close how fast can someone get to an Estop ?
When we were first doing the X3 CNC conversions we tried to see what the max they would run at before loosing steps and it was nearly 5 1/2m /min.
We then dropped this back to 4 m/min but it was still scary on such a small machine so finished up at 2m /min.
As a test the machines were sent out with a Sieg Logo badge so the punter could engrave a plate to cover the defunct Z axis handwheel hole as a first job.
There was 4 seconds difference in running at 4m /min and 2m /min
Exactly John and just the reason why I ALWAYS jump on this, It's false and miss leading to new comers and can be very costly and wastefull in both time and money.Quote:
Originally Posted by John S
Unfortunatly like you probably do, I see too much of this miss guided route being taken.!!
Jazz,
The same with over rating components because of bad advise. Following a conversion at the moment on another form of a Taiwanese 636 milling machine.
The guy is using 25mm ballscrews and 1640 oz in type 34 motors, unless he can hit that with 10,000 volts it will crawl but bigger is better - yes ?
End of the day he'll get as much 'useable' power as a 600 oz/in motor and probably twice the speed.
I agree entirely that 10m/min is more than enough and that the difference in machining time between 10m/min and greater is often negligeble. My machine will do at least 15m/min on X and 60m/min on Y, but I leave it at 10-12m/min as it's less likely to go wrong and more time to react should something go wrong. I think the most I've actually cut at is 8m/min.
The reason I tested the Y-axis up to 60m/min was an experiment to verify my modifications to Irving's motor calculation spreadsheet to include pulleys. I was ascertaining how accurate the calculation was by trying different ratios and comparing the limit to the calculated value.
I meant that comment to be just pointing out it is probably possible to get round the vibration problem and the feedrate gain is a bonus.
Ah ha ye and it was probably the supplier who told him he needed that.!! . . .. . . . The same someone who sold a guy I know 12.5Nm for his Z axis.:whistling:Quote:
Originally Posted by John S
Nah much better to replace the bent screw IMO because after you have gone to all that trouble and expense for what amounts to a very costly and mostly un-usable bonus the screw is still bent.:exclaim:Quote:
Originally Posted by Jonathan
RE 60M/min Y axis out of interest how much pulley ratio did you have to use and what sort of accelleration did you achieve.? . . . If you don't mind me asking.!
Hi All..
Been out the loop for a couple of days but I note some fascinating posts from you cnc guru's.. Love the one about Mach and kernal speeds, have popped mine back down to 25KHz and it seems fine..
The sort of speeds you guys are talking about seem more than fanciful to me at the moment.. Have been running my machine at 1.8mts/min max during all these other problems, now that I can achieve more, I still dont dare go above 2.5mts/min due to the bent ballscrew shaking the machine so much.. I did try 4mts/min which the motors seem to easily achieve, but shaking was so severe I thought something was going to rattle off the machine.. Am going to try straightening the ballscrew today, will let you know how I get on..
Steve..
True it is quite costly having already bought the bearings etc for rotating the screw. If the nut is rotating and the screw is tensioned (ideally a lot) then the bend should not matter much. As long as the ballnut is precisely on centre (which admittedly is tricky) then there's no radial force on the screw. If the screw is bent and spinning there is a large cyclical radial force which causes it to vibrate... No doubt there's more to it than that but I bet it would be a lot better.Quote:
Originally Posted by JAZZCNC
I'm guessing it's a 25mm screw, what length is it?
It was 42:14, but I accidently put 42:12 on the video. See here, post #136:Quote:
Originally Posted by JAZZCNC
http://www.mycncuk.com/forums/showth...outer-building...
I can't remember what the acceleration was... think it was 2m/s^2, might have been 3. Either way it only hits 60m/min for about 200mm... except if you smash it into the side :whistling:
Hi Mate, are you using Mach3 with a parallel port? If so what kernel speed are you using and what is the maximum velocity for the X and Y axis.Quote:
Originally Posted by fasteddy
Mike.
Ok...
Seems my run of bad luck is continuing..! Got an EP002G1 psu from a fellow forum member, but I have measured 58.8v output unregulated..! I know this is much higher than it should be (42-46v on the spec sheet).
This is too much for the drivers I am using which are limited at 50v (already blown one of them).. I know there are many out there that have these psu's and am wondering if there is anything I can do to 'dial' down the voltage? Will pop the cover off a bit later and see if there are any pots but this is like letting a road digger perform brain surgery and I would prefer some advice before rummaging around in it..
Steve..
Are you just putting mains in and taking pos and neg out ?
Reason I ask is I have used quite a few and done it this way and they have put 42 volts out, rock solid.
If you feed a voltage into some of the pins you can vary the voltage but only higher. I just use 4 wires, two in, two out.
See that red glow on the southern horizon? Thats me blushing with embarrassment.. Turns out the 'budget' pp3 battery in my multimeter is only kicking out 6v so it was making all the readings out... Sigh... New battery and voila, all the voltages measure as they should do..
Sorry for flapping, will get on and bugger summat else up now...
Steve..
I wondered why the sun was out in Swindon? LOL
Clumsy bugger
did you actually blow one of the motors??
Hi Mocha..
Did not blow a motor, just an old driver that was only rated at 35v, and I put 43 into it.. Bought a Gecko g250x to replace it, but seems my luck is running consistently and this driver is dead.. Just waiting for a replacement now...
Steve..
Why a 250?Quote:
Originally Posted by fasteddy
Surely a 251 with terminals/heatsink would be a better choice with less risk of it dying due to not installing it correctly?
How do you install one icorrectly?
Steve..