pncconf Clearpath SDSK settings

I have my new 7i96s and my machine is - almost - ready to be powered up. As I run pncconf, I am looking for a little handholding to make sure I get the entries right. I have four Teknic Clearpath SDSK CPM-SDSK-3411S-ELS, one on each axis, with a paired Y gantry, found here: teknic.com/model-info/CPM-SDSK-3411S-ELS/ . All are powered by an IPC-5 75v power supply. I have a second ps in case one isn't enough, but I think it is.

The maximum acceleration I calculated as 49800 mm/sec^2 is WORLDS away from the default 750, and pncconf doesn't allow more than 10000. That's just the tip of the iceberg! I can't be the first person to use Clearpath SDSK servos on a LinuxCNC machine; where can I find examples of settings someone else has already proven out?

Additionally, I think I have the wiring correct for HLFB, aka drive alarm, but I am still in pncconf and I don't even know how to assign the pins there. The only options that seemed like they would make any sense were "digital in 0", and so on. Does that sound right? If not, what should I use?

You can edit the ini file directly to set the accelleration.
Read the docs on ini file configuration
But I think you will find more than 3000-5000 will shake your machine apart,

rodw wrote:

You can edit the ini file directly to set the accelleration.
Read the docs on ini file configuration
But I think you will find more than 3000-5000 will shake your machine apart,
 

This was a general question about the settings for very common servos, not specifically about maximum acceleration. That was simply to point out that I can't even enter a calculated value.

I am looking for examples of known good settings for a Clearpath SDSK servo, for all of the entries in pncconf.

tommylight wrote:

Unless that is a very small 3D printer, 49800 mm/sec^2 is way, way, way to high.
 

Okay. I am looking for known good values for Clearpath SDSK servos on an Avid router, specifically a Benchtop Pro. There is no way that I am the first person to set up this specific configuration.

Pncconfs 10000 limit is about 1G. I would consider this super fast for routers
with more typical values in the .5 G range.  49800 mm/sec^2 is about 5G
which is crazy for almost anything except some 3D printers and perhaps laser
cutters (with linear motors)

Higher accelerations will excite vibrations and cause position errors due to
machine flex (especially when you are accelerating something heavy like a spindle)

Lower accelerations will cause slowing on sharp curves. One way to look at this is to
calculate the minimum radius possible before the machine needs to slow on corners.
This is V^2/A so at a acceleration of 10000 mm/s^2 and a max cutting velocity of say
100 mm/sec, you can cut a 1mm radius without slowing down.

Another way to get a feel for this is to calculate the time needed to reach full velocity.
at 10000 mm/s^2 and 100 mm/s full speed, its only 10 ms from zero velocity to full velocity.
That's what I call starting with a bang!


 

PCW wrote:

That's what I call starting with a bang!
 

Understood, and thank you for the reply. I calcluated 49800 mm/sec^2 from the data I had available to me . If 10000 mm/sec^2 is still too high, then what is a known good value for this motor? How does the max. accel. entry factor into the behavior of the software? As a dummy check?

From my limited time on planet Earth, I have learned that if I include more than one thing in a forum question, the one that matters the least will be casually non-answered and the important one will be completely ignored. My dilemma is that I feel the need to include background information to give context, and this context is usually where people latch on. That's what happened here.

Again, I need to reiterate that I am not hung up on one specific data point. I want to enter the correct information in pncconf in its entirety before I power on the axis motors, and there are many other variables to consider, for the motors and beyond.

We already talked about HLFB, but no one has ever explained how to assign the inputs in pncconf so I can use them for this purpose. I currently have the machine wired exactly as shown, based on the limited amount of information here :

To put into perspective the limited information available about this topic, this post is already the top Google search hit, and there aren't many more. So Teknic, please, if you're reading this, I am looking for SPECIFIC settings I need to make this work with LinuxCNC, including HLFB.

tommylight wrote:

No idea where or how you got those numbers, but utmost respect for effort in getting things right.
Start with 300mm/s/s, do some tests, then go higher, but most probably 750 will be to much for short fast movements like Fusion360 does.
I am refraining from further "muddying the waters" for now as:
1. i have no idea what "HLFB" is
2. -deleted-
 

HLFB "high level feedback" is many things, but it can work like a drive alarm and that's what I will be using it for. There have been a couple of posts on it, but they all go nowhere and the OP never comes back and says "I did this thing exactly like this, and it worked. Here is how to recreate what I did."

For examples of dead ends, here you go:

forum.linuxcnc.org/49-basic-configuration/41375-clearpath-hlfb

and

forum.linuxcnc.org/10-advanced-configura...with-hlfb-mesa-7i76e

and

forum.linuxcnc.org/10-advanced-configura...ervo-with-mesa-7i76e

I just want to know what to enter into what box, and move on. I am at the pncconf step, so any talk about ini files or HAL or anything past pncconf is not yet relevant to me. I need to know what to tell pncconf what to do with the inputs I connected the HLFB circuits to. And I need to know if I have connected it properly in the first place. I don't know what I don't know.