320's and switch mode PSU

[kong]

Time to make myself look daft again. The Gecko-drive manual states I need a capacitor on my switch-mode PSU. Now I have come to tune the drives, I understand why, or at least I hope that's the problem. My PSU is without the cap at the moment, and I just can't get the servos to run at full jog speed. I have been concentrating on one axis today, adjusting gain/damping all over the place, and also chnging acceleration settings in EMC. So, if the missing cap is the problem, please advise on what type I need! I am confused by the array of electrolytic caps, but will a standard aluminium electrolytic do it? If someone has a minute, could they go here and do a quick search for 339-7903 it would be appreciated! PSU is 24V 24Amp and that cap is 40v 10,000 uF as recommended in the manual.

[balsaman]

Why cant you go full jog? they fault out? It may be that you are over the limit of the motors....or you are over the current limit. Make sure that is all the way up on the pot.

How fast is full jog speed?

I have a tranny rectifier setup and the cap is too small and I don't have a problem so far.

Eric

[kong]

Thanks for the reply Balsaman, I ordered the caps shortly after I posted that last night, in order to get them delivered today.
Yep, the geckos fault out when I approach 3/4 speed. Top speed is 4500mm/min which is roughly 170 IPM, but I can't get them over 3500. The current trimpots are all the way up, and I have played with damping and gain for about 4 hours yesterday. I have altered acceleration only a couple of times, but mainly coz I remember you saying yours was something like 10000 accelleration. So that leaves the PSU. I have fuses between Gecko and PSU, which I am fairly sure would have blown if the PSU was not the problem, but they are fine. The only other thing I noticed was the use of a smaller cap across the gecko psu inputs if you are using fuses. These were missing also, so should be coming today. Where is that delivery man.....

[HomeCNC]

Kong,

What is the encoder size on your servos?

The reason I ask is because I remember a guy posting something about having very large encoder (a 2000 cpr) and the Gecko drives fault out easy.

[kong]

They are 250 CPR, so they shouldn't be the problem. I haven't recieved my caps today, so can't test them, but I bought a spare power supply on ebay last week which has just been delivered. I need to get some larger crimps so my cables will fit it, but I should be able to hook it up tomorrow. At least I can rule out the power supply if it still doesn't work.
edit - As I'm just gonna sit here all night wondering about it, I'm gonna grab the kids and take them to the auto-parts store for christmas crimp shopping and get that thing tested tonight. I'll let you know how I get on.

[balsaman]

What makes you think you should be getting 170 ipm? There are a lot of factors involved. Just cuz the motors are rated at a certain rpm doesn't mean they will get there with your setup. If the drives fault it's because to motor doesn't have what it takes to get where you are telling it to go. The drive keeps raising the voltage until you reach the motor rated voltage (ps voltage) and then there ain't no more.In other words if your motors are 1/4 hp and it takes 1/3 hp to go 170 ipm then your not going to go 170 imp, regardless of the motor nameplate rpm.

Eric

Eric

[kong]

Problem solved guys. It was a dodgy power supply. I just hooked up the new one and hit the max speed no problems. I got the old one off ebay too, I guess sometimes you ghet a bargain, sometimes you get stung. Thanks for the help anyway!
Balsaman, I understand about the geckos keep raising the voltage until there is no more, but surely this is why we fuse things? I don't understand enough about electronics to start an argument, so don't think that's what I'm doing, I just like to understand things as best I can.

[balsaman]

I am just glad it's working. Here's to success! (lifts his glass up).

Eric