[Tkamsker]

I have refurbished an Lathe/Mill combination to do the stuff.
Everything fine (EMC2 2.4.2 i maybe upgrade to 2.5 or whatever is needed)
The Heavy Klippfeld K-10B CNC Umbau - tkamsker
Milling head is having some issues where 3 times the Z values are correct then it seems that 0.3mm in steel are to much and the cutting forces are lifting the whole stuff so the real cut is only 0.1mm ,.
My idea now is to add an digital read caliper (i hope the name i correct in english) and feed the value back to the controller. ( I can do electronics so if i need to make an quad signal or whatevery i am fine)
So my idea is that the system tries to go to value Z1 then measures and if needed does Z1+xyz till Z1 wish is measured Z1 or after x tries it gives an error.
So my question i am getting crazy now ? Does it make sense ?
Any better suggestions ?
i think Servos wont help because the transmission is done by Stepper motor belt drive with 1:3 reduction and then it goes to an spindle which again transmits the power to an ratio. So thats why i want to measure (and be able to use it in manual use )
thanks
in advance
thomas

[CaptainVee]

The issue may be mechanical.

Could it be backlash? Because of not using a ball screw? When you move z to zero and then move it back to 10 you may need to move a bit more because the nut loses contact with the screw for a moment.

If this is the case, try to find out how much there is ( ALSO look at the belt, that may cause some backlash too). You can add a line to your configurations .ini file to compensate:
BACKLASH = 1 #if backlash is 1 mm

[Tkamsker]

Hi,
thank you for the fast answer.
I am sure it is kind of backslash but it is nit the same i varies in the distance from 0 point
Situation pictures Die Maschine und Umbau - tkamsker

thats the reason why i would like to read distance back to emc2 ,..
and then correct the move.
So if that would be possible i would be happy as well
thx
thomas
or if i can change the backslash on distance ?

[109jb]

The problem with doing a closed loop with a stepper system is that if the machine is not going to the position that is desired it means that the stepper is losing steps. If it is losing steps them the torque capability of the stepper motor is being exceeded. There is nothing you can to to increase torque on a stepper motor, unlike a servo with you can simply supply more electrical power to and thereby increase torque. If you are losing steps then you will still lose steps even with an encoder. The likely outcome is that the EMC will stop operation due to a "following error". EMC uses a tolerance between what is commanded and the actual position. If this tolerance is exceeded then the system will stop with one of these following errors. A stepper has its greatest torque at 0 rpm, so the faster you go the lower the torque. This is why steppers are generally run without a reduction drive to the screw. Likely you either need a bigger stepper motor, lower feedrate, you have some binding, or a combination of all of these.

[Tkamsker]

Hi,
Thank you for the fast answer ,..
I know about the stepper and torque thats why i have really strong steppers and they have an gear transmission ratio in 2 Ways.
If you see the picture Fräsaufsatz im Einsatz - tkamsker
where the "golden" miller goes through alu. You see the Milling head so my stepper goes over an belt drive (which of course is flexible ) this goes to an gear on the quill. (i hope the word is correct in german it is called pinole like an Press drill ) there is an 2nd transmission. and when the miller cuts ther is force (depending) on the cut "size". So my idea is can it be possible that the cut forces are putting the machine to backslash ? And if i measure it without cutting forces the wight of the head is backslashing forced by gravity ?
Is this possible.
Or it is also possible that because of 2 gears the gear error sums up ?

Thats basically the reason why i asked if reading back the exact length would be an option ,..

So if there is an good hint how i can isolate the error to fight it would be verry apprechiated.
thx
thomas