First Build 5 x 12 Steel Frame CNC router

[Davek0974]

I got my servos from BST too so likely the same, I think the thing with the drive number setting the drive up is that it has no idea what load the motor has - its just a ballpark setting. The downside is the manual is written Chinglish and unless you know exactly what parameter does what, then its all guesswork.

I spent hours and hours tuning, its made harder as you also need to test each tune at multiple speeds, I test at 3, 13,23,33,43 and so on as % of full speed - its easy to tune so that it runs great at say 60-100% but oscillates badly below 50%

In the end i tweaked in the order P - D - I until the following error was as low as possible, then added some kVff if needed.

I'm still not happy with it though but at least the mill is running now. No doubt an expert could tune it in minutes but I don't know any mobile servo experts ;)

[Scott Damman]

Made a tiny bit of progress last night. Got one of the Y axis limits and also the homing prox installed.

Chinglish and unless you know exactly what parameter does what, then its all guesswork.

Dave, This is exactly what I was worried about when digging into the servo itself. I think if I get a bit more understanding of servo driver tuning I will have a better chance of understanding the Chinglish... I hope.

Boyan, that is a very good point, I never checked the max acc and decc in the servo drive. Likely that is the limiting factor. I didnt think about it until now but as I increased the acc I didnt notice an increase physically so probably the servo drive is limiting. I will have to take a look tonight.

Which by the way is well described on many places around the web, but i still fail to comprehend it entirely .

I totally agree, seems like each spot that describes how to tune a servo does it slightly different, making it more confusing for those of us just getting into it... Like Jazz said Black Magic

Thanks for the help!

[Chaz]

Let us know how you manage with the PID tuning.

I have done 3 machines with CS Labs and it's been hit and miss with all of them.

The first was my Denford. If the settings are 'weak' the machine is slow and cumbersome. If too aggressive I get PID errors although I have found a happy medium.

In all cases I have tried auto PID tuning (the controller, after tuning the drives themselves) but limited success.

Even the manual indicates its better to do manually in most cases.

For another machine I retrofitted, we managed to get a nice speed / rate on the machine but its small and doesnt carry a lot of weight.

With my Concrete machine (Thor), it will be interesting. The design is fixed gantry, Y moves a table of around 100kg and I am looking at speeds of >10m/min using a Panasonic 1.5 KW Servo and very beefy ballscrews.

The drives have an auto tune feature which tunes all the time. How this works in reality, I dont know. I will have the Y running again this weekend, just need to do some alignment and will see what I can get from the machine.

I have a video of the machine doing slow movements of I think 4000mm/min. I have had one servo run away (my own fault, made a mistake in config) and I can confirm that the table can move a metric fuckton faster.

https://www.youtube.com/watch?v=5sMb4XmzuXc

[Davek0974]

I have a video of the machine doing slow movements of I think 4000mm/min. I have had one servo run away (my own fault, made a mistake in config) and I can confirm that the table can move a metric fuckton faster.

https://www.youtube.com/watch?v=5sMb4XmzuXc

LOL ;) nice unit of measure :)

[Chaz]

LOL ;) nice unit of measure :)

Ye, fairly standard UOM.

[Chaz]

LOL ;) nice unit of measure :)

Sorry, I know see what you were referring to (not the mm/min). Yep, very fast indeed.

[Scott Damman]

Made a bit more progress over the weekend,

Got one of the X axis screws mocked up

Here I am machining the spring loaded brackets that will act as X ballscrew mid supports. These will support the screw and when the gantry goes by will move out of the way on the pivot. I need to get some shoulder bolts still for these and do a bit more machining for clearance of the ballnut as it passes (to ensure that it cant get hung up on a change of direction).





I also got a air valve block installed on the gantry for all the air that the Z axis needs, also put a terminal block on the gantry in order to reduce the number of wires that needs to make its way back to the control. I ordered some 20 conductor shielded communication cable to go from the control to the gantry terminal block. Gives me a few extra wires incase I need any future expansions or additions.

Im getting excited as its closer and closer to cutting. I am waiting on new toothed pulleys for the Y and X as I made a mistake when ordering, once those are in it will be time for truing and squaring then cutting.

More to come....

[Scott Damman]

Some more progress made, I got the ballnut mount made and installed and also finished one of the ballscrew mid supports. I made a video of one of the ballscrew supports in action, I am just pushing the gantry back and forth. I pushed the gantry from one end to the other as fast as I could and this one support seemed to damp the ballscrew frequency. Im hoping to finish up this side tonight and then do it all over again on the other side.










I need to do some learning on tuning 2 X axis servos at the same time, if anyone has any suggestions im all ears.