[bp092]

LOL it's probably distributed here in the US and you're getting the end of things with all the taxes, shipping internationally and customs for merchandise.. we all have our disadvantages and advantages. I think woodcraft ships intl?

[Mike F]

At long last, I have a motor spinning under control :banana: :banana: :banana:

But for the patience of my electronics wizard, I would still be puzzling over some non movement. I thought I had meticulously wired everything correctly but there are so many, I suppose it was inevitable I would miss something. It was just as well I took the wizard's advice and only wired one drive. As you can see from the photo, the wiring is not exactly tidy but my excuse is that I was told to wire it first, in any way I could, test it, then worry about tidying everything up once working correctly.

To be honest, there was only one wire misplaced and even the wizard did not spot it before many heads were scratched - well two actually but many times It turned out that that the wire that was supposed to be in pin three of the breakout board was in fact wired to ground (on the CNC4PC breakout board the connectors are labelled 2, Gnd, 3, 4, Gnd, 5, 6, Gnd, 7, Gnd, 8, Gnd, 9, Gnd - not exactly logical, to me anyway)

Once that was solved, it was plain sailing. Everything worked as it should and the motor responded accordingly.

Well, after all that, I just had to put the X axis motor through its paces and loaded the ubiquitous 'Road Runner' program in Mach and pressed 'Cycle Start'. It was magic just watching the motor spin up and down and changing direction - boy, I'm easily pleased Now I suppose I had better stop watching this thing and get on with the other axes.

You just don't know the weight that is now off my shoulders - my hat is off to all those who understand the black art of electronics.

Mike

[bp092]

Mike, what's the tiny monitor up on your tower for? Seen them used for car stereos to be mounted on the dash, never seen them for cnc

[Mike F]

Brian,

That tiny monitor is a very clever device that enables my wife to keep in touch with her beloved soaps --- it's a TV set LOL

I set the thing up in the kitchen as there is no room in the workshop at the moment and the PC just happened to be in front of the small shelf that holds the very small TV set.

I will be taking the controller into school tomorrow just to see if the motor is man enough for the machine. Going to have it move the gantry in X only for the road runner. Should get the enthusiasm levels up somewhat.

Mike

[bp092]

heh, you mean you have that all in the kitchen? God speed Mike, that's a line you don't cross in this household, I'm limited to the basement

[MrBean]

If you do cross the line like I did, you had better be ready to run. Trust me. I know.....

[bp092]

oh man, MrBean, you gotta good lawyer or just a really cool wife? lol

[MrBean]

oh man, MrBean, you gotta good lawyer or just a really cool wife? lol

Yeh I guess I do have a cool wife. She puts up with a lot.
Okay enough messing. I don't want to become a thread hijacker.

Hey mike I notice you're running the Mach screenset that SantiniUK and I designed. How do you like it?

[Mike F]

Brian & Mr Bean,

I'm sure we could start a new thread on 'where not to set up your machine' - could get some interesting replies. I have promised, she who must be obeyed, that the PC and collective bits will shortly be removed, problem is I can't yet determine how long, short is

Mr Bean - only just started using Mach3 but your screen set seems just fine. I like its logical, clean and well organised layout with all buttons and features lined up. Having done a little programming myself for school administration, I am well aware of how important the user interface is. However, I did come across one anomally and I don't know whether it's down to you or Art but when I changed the scaling factor, the toolpath was accurate on the 'Program Run' screen but not the others. It looks like the scaling was not applied to the other graphics objects.

I managed to hook up the X axis to the controller this morning and took great delight in watching the gantry trundle up and down to the tune of 'Road Runner' The drive faulted a few times before I got the acceleration sorted out but now it's just fine. It looks like I can get about 3600mm/min or 60mm/sec at the moment with Mach3 set to 25000Hz. Not as fast as I would like but the motors are limited to 1700 rpm and if my calculations are correct, 25000Hz will give me 1500 with a 250 line, quadrature encoder.

Can't wait to hook up the Y axis now.

[Mike F]

I have been playing with the X axis and its settings in Mach3 and it does not seem to make any difference to the speed whatsoever if I have the pulses set to 25000Hz, 35000Hz or even 45000Hz. Can anybody explain this or is it that the servos are internally limitted to 1700rpm?

I have a licenced version of Mach so it's not that it's stuck on 25000Hz.

Mike

[MrBean]

Are you just altering the pulse engine frequency, or are you entering the motor tuning section, and increasing the velocity setting for X too?

Just altering just the pulse engine will not do anything in itself. It will only give you more headroom in the motor tuning > velocity settings.

Regards Terry.

[Mike F]

Terry,

Thanks for the reply.

Yes, I am altering the velocity too but not seeing any difference in speed. Maybe these servos cannot go any faster. Am I right in assuming there is nothing to be gained by a faster pulse train if the motors cannot go any quicker?

Mike

[MrBean]

Yes. That's correct. If your motors will only go so fast, there's no benefit in going with the higher pulse rates. I'm not familiar with servo's, I've only ever used steppers. I had to use the 45K pulse engine setting, as I geared my motors down and used 16* microstepping, therefore I needed the extra to get enough pulses for reasonable speed.


Terry...

[ger21]

In 25Khz mode, you'll be limited to 750rpm. 25000 steps per second divided by 2000 steps per rev X 60 seconds per minute.
1050rpm in 35Khz mode, and 1350rpm in 45Khz mode.

You must restart Mach3 after switching modes for them to take effect. If you didn't restart, you wouldn't see any difference.

[Mike F]

Thanks Gerry, I didn't realise I had to re-start for the change to take effect. I won't get the chance to try it today but will report back tomorrow.

Mike

[Mike F]

I re-set Mach3 to 35000Hz then re-started Mach and there was indeed an increase in speed from the motors - thanks Gerry :-)

However, although the motors worked well on the bench, the one attached to the X axis struggled to achieve any greater speed, faulting as the speed increased no matter how slow the acceleration was set. What I concluded from this was that there was an upper speed limit above which the servos could not keep up with, once loaded.

The upshot is that at 25000Hz Mach would let me achieve 3750 mm/min and at 35000Hz the motor limited itself to 3900 mm/min. This all equates quite well with the motor manufacturer's figures of 1700rpm max, my 250 line encoders and 2:1 reduction driving my 5mm pitch ballscrew.

I just needed to know if I could drive them faster - now I know. I assume the only way of getting more speed would be to swap the servos for higher rpm versions? I don't suppose I really need to go faster than 3900mm/min - but it would be good :devious:

Mike

[ger21]

If my math is right, you have 400 steps per mm. Is that what you have in the Mach3 motor tuning? Again, if my math is right, 1700 rpm would require 28,333 steps per second. 1700*1000 steps per rev/60 seconds. If indeed your motor was turning at 1700 rpm, that would be 4250mm/min. 35Khz mode should be good for 5250mm/min, but that would exceed the motors top rpm, so you're limited by the motor. A little higher voltage might squeeze that extra few rpm. 3900mm/min is 1560 rpm.

So, I see three options. Differrent motors, different scres, or different gearing. Different motors would most likely require a bigger power supply (higher voltage). I'm guessing you don't want to go there. Different screws = $$$$. Probably don't want to go there, either. That leaves different gearing. 1:1 would double your speed, IF you have enough power to do it. 1.5:1 or 1.75:1 might be something you want to look at.

As for your percieved lack of power, it might be a matter of tuning the Geckos. Never used them, though, so can't really help you there.

[FPV_GTp]

Hi

Very nice work Mike and well documented thread

keep up the good work

cheers

[Mike F]

Gerry,

I've been away for the weekend so apologies for not replying earlier.

Numbers add up to the same both sides of the pond so I must be doing something right.

Different gearing is probably the easiest solution to the speed issue, though I think I will wait and try the machine out before making any changes. The other point you made, about the current adjustment, is also valid but I am not sure of how to go about optimising this setting. Do I need to measure the current under load, while the machine is running? I appreciate you do not use Geckos so if anyone else knows the answer to this, please chip in.

Mike

[Mike F]

Well, it really is beginning to look like a CNC machine!!

The controller is all but finished - only have to put in the charge pump and auxillary relays for spindle etc. However, there was a problem that I am sure others have come across and were it not for my electronics friend, I would still be staring at an imobile lump of hardware. We were getting all sorts of oscillations on the oscillascope instead of a solid high or low signal when operating the toggle switch to arm the system. It was tracked down to the fact that the mini power supply, giving 5v for the boards, and the main supply giving 40v to the Geckos did not share a common ground. The fix was simply a piece of wire from the main supply ground to the mini power supply ground - job fixed. This goes back a few posts when I queried the apparent 'floating' Geckos.

Got everything wired up in a temporary fashion just to see the X and Y operating in unison. Of course, as with many projects here, I just had to put in a pen and test something. You can see from the photo that it seems to behave just fine. I used the roadrunner program and ran it twice. I was very impressed to find the second run went exactly over the top of the first. WOW!!! this thing looks like it might perform OK. I realise there is a world of difference between pushing a pen round and actually cutting something, but hey, it's progress. Because I have no Z yet, there are some stray lines where the rapids would be.

I also drew some squares and circles and as far as I could check, by eye, everthing was just fine.

Oh well, I suppose I had better get on with the Z axis rather than playing with the pen.