[sebastian502]

Bob,

Were you bale to find a solution with this? I just installed Teknic servos and am running into the same issue. Thy are actually a little oversized and I have ran Auto tune with various settings but cannot get rid of the spongy feeling. Like yo, at rest I can move the carriage 1/4" each way but if I push gently with force it engages quickly.

This was part of a change out to Masso controller.

Any insight you have since would be appreciated.

[mactec54]

Bob,

Were you bale to find a solution with this? I just installed Teknic servos and am running into the same issue. Thy are actually a little oversized and I have ran Auto tune with various settings but cannot get rid of the spongy feeling. Like yo, at rest I can move the carriage 1/4" each way but if I push gently with force it engages quickly.

This was part of a change out to Masso controller.

Any insight you have since would be appreciated.

One of the main problems with these servos is the cost and that they are only 3 Pole, most servos of the same class are from 6 to 12 Pole with the quality servos being 12 Pole so it does not matter what you do they are not going to hold the position very well, no amount of tuning can solve this problem

When you look at what is available for the same price and cheaper today these servo's don't stack up to be suitable for CNC machines no matter what the tec. guys say they can't solve these problems

[bobmagnuson]

Bob,

Were you bale to find a solution with this? I just installed Teknic servos and am running into the same issue. Thy are actually a little oversized and I have ran Auto tune with various settings but cannot get rid of the spongy feeling. Like yo, at rest I can move the carriage 1/4" each way but if I push gently with force it engages quickly.

This was part of a change out to Masso controller.

Any insight you have since would be appreciated.

Going with the larger servos helped. I also had Teknic remote into my machine and assist with the tuning. It helped quite a bit.

[EZ1]

So I am in the selection phase for a servo to drive a lathe. I would like the chuck to lock fairly absolutely for milling operations. Do you think given all the feedback so far that the difference between direct drive vs pulley drive and ratio, or the addition of a jack shaft to multiply/divide output rotation to servo rotation would be effective? Are any of the servo models better than others at locking position? Just throwing this out there. I want to buy once and set up once. Thanks.

[joeavaerage]

Hi,
the ability of a servo to resist deflection under an externally applied torque is exactly the same as the servos ability to produce torque against a load when commanded
to do so.

For instance my Delta servos have a rated torque of 2.4Nm, and an overload torque (10 sec) of 7.2Nm. Thus I would expect that the servo might resit deflection, in short
bursts, of torques up to 7.2Nm or 2.4Nm continuously.

You might consider a braked servo. Again using my 750W Delta servo as an example its rated brake holding torque is 2.5Nm. It seems quite common in industrial practice to
design a servo brake having a holding torque somewhat in excess of the rated servo torque.

As Matec pointed out multi-pole servos often have higher torque than a similar sized three pole servo and will do a better job of resisting deflection under applied torqe.

All-in-all I agree with Mactec, Clearpath servos while good quality and well designed for ease of use for new-comers are rather more expensive relative to their performance.
Delta and DMM are Taiwanese and Canadian brands respectively, both manufactured in China. Both are good quality and well supported at fair prices.
Yaskawa is deservedly the worlds leading servo manufacturer but are 150% and more the cost of Delta and DMM. Whether you can justify the extra cost depends on you,
or perhaps your wife...lol.

I would say that any gear or belt reduction between the servo motor and spindle will improve the holding capacity within the torsional rigidity of the gears/belts. Any torsional flex will
result in angular displacement of your workpiece.

Craig

[EZ1]

I agree with everything you said. On my lathes jackshaft, which I had hoped to eliminate, is a drum wheel brake. It utilizes a lever actuated shoe and locks rotation absolutely. As a conundrum when you engage the shoe it rotates the jackshaft about 1 degree. Unfortunately I think that would cause the servo to begin to oppose the position change. To what effect I don't know. An absolute lock would appear to be illusive. My purpose/goal is machine turning. Absolute division is mandatory. I think I need to take another look at the original dividing head machines. Perhaps the chuck rotation is not the correct application for servos but the pattern cutting where position is mechanical and movement is a glancing cut. Thank you. Your insights have been helpful for me thinking this through.

EZ1

[Teknic_Servo]

Hi everyone,

I’m an engineer with Teknic and I ran across your thread. I just wanted to comment on some statements that have been made and provide some support recommendations.

ClearPath is a high performance servo drive integrated with an 8-pole, 3 phase brushless servo motor with encoder. It is designed, built, and supported in the USA. When the motor is properly tuned for your load and mechanics, it should not feel “spongy”.

As bobmagnuson mentioned, you can get an idea of the performance you should be getting by watching the YouTube video he recommended (https://youtu.be/n33fCmUu9A8?t=875) where a guy using ClearPath on a CNC machine demonstrates the disturbance rejection.

If you look at the ClearPath diagnostic display, you’ll see that by leaning hard into the gantry, he only deflects the servo motor about 40-50 counts. (That deflection amounts to about 2.8 degrees on the motor shaft on the model he is using. The rest of the movement you see is compliance in the mechanics.)

Our experience is that the auto-tuner does a good job creating a robust motor file for over 90% of automated applications. That said, it is very difficult to create an algorithm that can perfectly automate this complex process every single time. An automation engineer has the advantage of being able to look at the mechanical design and listen to the customer describe the application objectives in order to create the appropriate tuning file.

In order for the auto-tuner to create a tuning file, it has to create motion and then look at the resulting encoder and torque data. This data is analyzed using FFT analysis and adjustments are made to the various gains up and down in an effort to optimize objectives such as low tracking error, quick settling, and minimal vibration. Sometimes a compromise needs to be made between factors such as audible noise and stiffness due to details like reflected inertia and the mechanical design.

Fortunately, we have a path for users to follow to help optimize performance:

1. MSP Fine Tuning: In MSP under Setup/Tuning/Fine Tuning, you can select “Apply Fine Tuning” and adjust the slider bar. If your axis appears to be “spongy”, you can move the slider bar to the right (or “stiffer” side). If the axis is stiff enough but has some audible noise, you can move the slider bar to the left (or “quieter” side).

2. Re-run Auto-tune: In MSP go to File/Save Configuration File and save your existing motor file (.mtr file) with a unique name. This will ensure that you can revert to the existing tuning file if needed. Then make sure that the axis is fully loaded for the worst case load scenario (e.g. if your load varies between 120-160 lbs, use 160 lbs). Make sure that the load is fully secured. Run the auto-tuner again. During the auto-tuning process, check to see if you have limited the torque of the motor. Limiting the torque can negatively affect the results of the auto-tuning process. Now repeat the tuning process and after the auto-tuner has finished running, adjust the “Fine-Tuning” slider if needed.

3. Free Direct Support: If you are still not getting the performance that you expected, you can always contact Teknic for factory direct support. Our engineers will discuss your application design and performance objectives with you and then use advanced manual tuning techniques to help optimize the tuning file.
If you have additional questions or need technical support, please give us a call at 585-784-7454 between 8AM-6PM EST, or use the "Contact Us" form on Teknic’s website:

https://www.teknic.com/contact/

Best,

Aaron B. - Teknic Servo Systems Engineer