[tef9]

Hi,

Ok bit of over kill, but I was fedup with stepper resonance. So I swapped the motors out (for DMM tech AC servo Motors) On a BF30 - wow...what a difference!

Also If I do buy a used bridgeport as the next project I can use them on there!
I just need to make a new enclosure for the electronics.

Heres the video:

https://www.youtube.com/watch?v=y7gOPmVlh1c

Thanks,

Andy

[tef9]

These are Dmm Tech AC servo motors. By tuning the motor and the driver you get a smooth almost noisless running of the motor. It is like silk...I wish now I had decent ballscrews....

A

P.s I did try a bigger motor however it had no effect! I think resonance is in the driver, or thats where it starts.

[LUCKY13]

The A/C servo's will always be smoother/quiter than steppers. Infact you can count on them being smoother/quiter than D/C brushed servo's (some high end drivers/systems can get close to A/C servo). A D/C brushed servo with a high quality drive will run quiter than others, but on average they will have more noice than a A/C servo setup.


You meantioned buying a BridgePort, and using the old motors on it ( I think you ment the old stepper motors). If so, your steppers are no where near big enough for a Bridgeport mill. If you meant you might use the A/C servo you just bought on the Bridgeport then that would work fine.


This may help with your steppers ( hey use them, you have them), if you read through this thread I believe you willl find something that could of helped your steppers a hugh amount.

http://www.cnczone.com/forums/steppe...er_damper.html


Basically it talks about different ways to add vibration dampeners to a stepper setup, and how much it effects the system. I would bet that just adding such to your setup would have cured your problem.


The problem is, now that you have used a good servo system you willl always know how much smoother they are compaired to stepppers (even good running ones). Even though many claim servo's are a waist of money for our hobby mills, the truth is a good servo system that is sized and tuned right will out perform and be smoother than a stepper system. I mean just how sweet is it to watch and use your system now? Even if you would have cured the noise in the stepppers, it simply would not compair.


IMHO the DMM servo system is the best bang for the buck, combined with having a good quality system. Yes they cost more than other systems, but you get a better system. The cheaper systems can be used and made to run well, but there is always comprimizes when compaired to something such as a A/C servo system. Its just like racing, how much performance do you need, and how much money do you want to spend?


Personally I really do not like the sounds of steppers, or deithering D/C servo systems. Tunning and properly designed systems will always help in all cases, but smoother is smoother.

BTW, remount one of your steppers and try the vibration dampeners, it will cure the problem you had. Driver type can effect things a lot, but we have seen them cured of this even with cheap drivers that have zero res control.


Jess

[LongRat]

Nice set up you have there.
Don't know what drives you were using before with your steppers, but I have never had any resonance problems on my BF30 with steppers, on G201 drives. I'd love to see a video highlighting the dynamic performance of your new setup though... how about some fast 3D contouring work, lets say a relief engraving toolpath or something at 2000+ mm/min? That would be cool and would really highlight the AC servo benefit over steppers.

[tef9]

Thanks for the posts all,

Lucky13 - Ok so I was given a large fly wheel which I attached to the back of the stepper motors...this gave me a window of about half an hour before the grinding came back. Also it shook the machine so badly it dislodged the fly wheel...not great! I did have Diycnc steppers on there (nema23) however I then upgraded to nema 34 steppers (as seen in the other video I have). Still no joy...the DMM tech however do not suffer at all...and I really do feel like I have a cnc mill to play with. I would probably go with a belt drive and a 400watt motor next time, however direct drive was quicker for me to get going!

The system can do 5000mm/m without a problem...however I have no limits on there at the moment (due to be mounted in march when I have free time) and well...it makes me nervous at that speed.

Longrat - yes I will post a video of me doing some really cool stuff....but be patient...its taken almost a year to sort this probblem out Sadly I have to work Did you ever build that CNC router you were considering?

A

[TiagoSantos]

tef9, congrats on the DMM servos They are pretty awesome and the company is great! I've visited them a couple of times (they're 15 mins away from me) and Tianyu has been a great help on my build as well.

I went with the 400W servos with a 3:1 belt drive reduction. I've mounted the Z axis and did a couple of tests and it seems perfect. I might end up trying a 2:1 reduction on X and Y, but I don't think I'll need THAT much speed

Are yours the 750W motors? Which drive do those work with?

If I run into a bunch of money somehow, I'd love to use one of their 2kW servos as a spindle motor.

[tef9]

Hi there,

Yup 750 watt!

Dyn2-h driver is the one I used, this is the DC voltage version so I am not using mains....still for machine this size does it matter? I have 3 PSUs wired in Parrallel, 48v with 21Amp.... I will use the mains driver if I upgrade machine...then the motors become 900Watt!!! I got the DMM kit so I have not improvised...it was simple to set up thanks to CNCzone member Mactec54. Just need to make a case!

Not found any piles of cash, but yup I am considering the 2Kw motor for a spindle....looks so tempting....


A

[LongRat]

I did build the CNC router and my friend used it to set up his own sign making business.
It ended up being a real beast, in the end we limited the speed to 7500mm/min because it just wasn't safe going any quicker. Had zero backlash all round and cut metal pretty well too.

[tef9]

very nice build, and good speeds too... I hope business is booming. What sort of metal can it cut? Any good at steel sheet? Is that HWIN rails on there too?!? Awsome!

I was sent this link of a UK user that used the DMM tech on their router.

[ame=http://www.youtube.com/watch?v=LRjfJrrvJwc]DMM CNC Cutting HMW Plastic - YouTube[/ame]

56000 mm/m ... wow!

A

[LongRat]

I used 16mm round section Chinese rails. They were a great, cheap but extremely effective solution on this machine. For a stepper driven ballscrew machine 7500 is plenty fast enough given the modest travel. We cut sheet aluminium and brass on it, and engraved stainless steel sheet but I don't know if he has ever cut out anything in steel. The high speed on the Kress spindle might be a little too much.

[SCzEngrgGroup]

Lucky13 - Ok so I was given a large fly wheel which I attached to the back of the stepper motors...this gave me a window of about half an hour before the grinding came back. Also it shook the machine so badly it dislodged the fly wheel...not great!

A flywheel will do little or nothing to help resonance, and, as you learned, will create a number other problems, while significantly degrading dynamic performance, especially acceleration. What you need is actual damping, to suppress the resonance, and prevent it from growing in amplitude, which is why the dampers Lucky13 linked to have the "slugs" of aluminum round stock "floating" in them. That setup is actually quite effective, dead-simple to make, and does not significantly degrade performance in any way. The electronic damping in better stepper drivers, like Geckos, is also quite effective.

Regards,
Ray L.