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SINUMERIK CNC automation systems

Lathe can't cut thread well

Thread Starter: qx100 Started: 8/2/2012 10:12 AM Replies: 31

8/2/2012, 10:12 AM

qx100

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Dear experts,
I meet one trouble ,our lathe (802dsl system)can't cut thread well .The first cuting is OK,but the second cuting the start position is wrong .Before the lathe never is used for cuting thread.I checked the parameter ,found the encoder parameter 31020 is 2300 ,but actual value should be 2500,that marked on the Simense encoder.I guess the pulse numbers is wrong ,so the CNC can't find the correct position when cuting thread .But when I change the 31020 to 2500 ,the feedback speed is wrong .For example ,S10 ,before abroud 10r/min,but now around 8.6 r/min.And when sp apear 360°，the the spind already run 1.26 circle.If the 31020 set to 2300,the spindle run 1.06 circlel.I also check the encoder 's fixing ,it's ok.Can you help me ?Thanks.

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8/3/2012, 1:52 PM

OvidiuNastac

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Hi
Maybe your encoder is mounted with a demultiplication ratio and they don't used MD31070 and 31080. You must see the exact ratio for the encoder or else you will not be able to do threading. What are the values for 31070 and 31080?
Good luck
Nit

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8/3/2012, 4:08 PM

qx100

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Thanks ,MD31070 and MD31080 both is 1.I also geuss encoder is mounted demultiplication ratio ,the valve around 1.3,but I can't find it.

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8/3/2012, 4:31 PM

CNC600

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qx100 wrote:

...MD31070 and MD31080 both is 1...

Hi,

please check the parameters 31050 and 31060. I guess just the parameters with index[0] are adjusted correctly. But You need to adjust the parameters with index [1] as well in the same way.

Background:

Below Threadcutting (G33/G331/G332) the CNC activates the parametersets for the involved Linear-Axis in the same way with the spindle axis.

spindle in Gearstep#1 ==> Axis ratio in 31050/60 with index[1] becomes effective for the linear axes as well.

All axis-parameters with index [0]...[5] follow this property. More details in Function description S1 (Spindel)

hope that helps,

CNC600

hope that helps
CNC600

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8/4/2012, 6:41 AM

qx100

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Hi,CNC600,Thanks for your help! The lathe spindle is controlled by anolog signal ,the driver is DC motor.The spindle has two gear-shift lever .MD31050 index[0]...[5] is 1;MD30160 index[0] and [1] js 85,index [3] is 21.We are using 21.Now when running ,the actual speed (measured by man ) flow the setting value .But the value show on the HMI is wrong when MD31020 setting corret value (2500).Another hand ,when encoder pulse is set to 2500,the spindle turn one circle ,the spindle angle display value is more than 360°，aroud 450°.if MD 31020 is set 2300, the SP display 390°.How to count the actual speed in CNC system? By count encoder pulse number or Z pulse number?

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8/4/2012, 6:48 AM

qx100

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Another question ,I got the information for manual "When cut thread ,if don't set SF ,the CNCsystem will use thread start angle SD 4200 :THREAD _START _ANGLE),"How to find the SD4200 in CNC system? I think maybe the reason is when the second cutting ,the SD4200 isn't same as first cutting's.

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8/4/2012, 10:37 AM

Pee El Sea

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HI,

It might be the phasing of your spindle encoder reference signal.

When you first power up the control the spindle will not be referenced. Move the spindle by hand and look to see when the spindle referenced graphic appears or when the display resets to zero from a value other than 360.

If the spindle references as soon as you move it then swap the encoder reference signal wires.

Threading starts from the zero pulse or a set angle from the zero pulse.

Pee

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8/4/2012, 12:06 PM

CNC600

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Hi,

First of all You have to check the correct spindle control in each GearStep:

- check the mechanical gear ratio:

program M3 S60 and SPCOF and count the really effective revolutions at spindle side in each GearStep. You need to adjust 31050/60 with the mechanical assembled gearStep-Ratio to get 1 mechanical revolution in 1 sec - independend from display on HMI

- check the encoder response:

pending on the numbers of encoders and the interface signals to activate the encoder make sure one spindle revolution causes 360deg in display (axis diagnosis screen)

usually the first encoder is located directly on the motor shaft and the second encoder is connected 1:1 to the spindle shaft.

For a correct spindle response the 2nd encoder need to be declared as "direct encoder" MD ENC_IS_DIRECT[1]=1. and the ratio in 31080/90 need to be declared as the mechanical ratio of coupling - mostly 1:1.

You have to check the interface signal for encoder activation as well. Do You select the first or the second encoder for position control?

I'm not really sure - but the 802 provides only 1 interface signal for encoder activation. Am I right? If You want to activate the second encoder, You need to swap the encoder activation in MD 30230.

To get a better overview please answer these questions:

- how many encoder do You use at the spindle?

- Where are the spindle related encoders assembled on? what ratio?

- where did You define the encoder data now - encoder dataset [0] or [1]?

result of Your first cutting:

- does the pitch of thread match to the programmed value?

hope that helps

CNC600

hope that helps
CNC600

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8/4/2012, 4:45 PM

qx100

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Hi,CNC600,thanks for your help! Below is my answer
1、the spindle is analog cotrolled.Spindle motor is DC motor ,and driver is 6RA70.Motor speed feedback is by tachogenerator.
2.Spindle encoder on the spindle box,MD31070 and MD31080 is 1:1.MD31040 is 1.
3.because we only use one encoder ,we only fill encoder pulse number in the MD31020 .
4.The first cutting is ok,but the start position is wrong when second cycle begin.And pitch of thread of first cutting is OK.

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8/4/2012, 5:54 PM

CNC600

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Hi,

if the MD 31070/80 and 31040 are below index [0] - the setting in the MD's is OK.

the pitch of the first cut is also (almost?) OK.

But in the MD31020 ENC_RESOL belongs 2500 (I believe Your investigation regarding the assembled direct encoder).

The problem occurs out of the encoder configuration on the SINAMICS side. For a further investigation a couple of information is needed about the SINAMICS configuration.

As I know the spindle encoder is attached at a SMC20-Modul. Internaly the encoder values will be transferred parallel to any other axis encoder signals in an unused 2nd encoder channel.

Now we want to find out the channel of transpotation of the encoder signals:

what is inside in 30220 [0] and 30220 [1] of the spindle NC-MD's? (ENC_MODULE_NR)

I guess You'll find the same number in MD 30220 in any other linear axis – What axis?

Where did they connect the encoder cable from the spindle encoder? to a SMC20-Module?

Hope that helps

CNC600

hope that helps
CNC600

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