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Thread: Wrong coordinates at the end of machining

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    Default Wrong coordinates at the end of machining

    Hi all,

    I recently purchased cnc router from china it's a machine with ncstudio v8, stepper motors (nema 34), fuling inverter 7,5 kw and yako drivers. I tried to machine simple rectangle 480 x 780 mm on 40 mm HDF material. I made toolpath in artcam to be machined inside the rectangle with 12 mm endmill straight bit. I loaded the file in ncstudio and made an simulation, everything seemed alright (the coordinates are all ok) so I started with machining, the start is ok, right coordinates (x, y), but as soon as it gets to the point diagonally from the start point x and y are -20 mm off coordinates. Can anybody tell me why is this happening, why is shrinking the rectangle for exactly 20 mm at the end of machining. Thanks in advance.

    Sent from my HTC Desire 620G dual sim using Tapatalk

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    Default Re: Wrong coordinates at the end of machining

    Question: Does SPU (steps per unit) could cause this? Btw when I manually jog, in ncstudio, on axis the spindle goes exactly as much I write. For example if I write 10 mm on x axis, the spindle goes exactly 10 mm, etc. So from that point I am confused if SPU has wrong parameters. What could be other thing to cause this shrinking for 20 mm?
    Any suggestions, please?

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    Default Re: Wrong coordinates at the end of machining

    gjokos,
    Does your software handle cutter compensation. If you draw a rectangle then you tell the software to cut outside the line, inside the line, or on the line. Cutter compensation needs to know the diameter of the cutter and typically subtracts half the diameter. Make sure that is not what you are seeing.
    Russ



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    Default Re: Wrong coordinates at the end of machining

    I did the file in artcam, I told to cut inside. When reading the code all seems to be ok, in the trace window of ncstudio, when I run the simulation all is ok, right coordinates as it should. When I cut there is a mistake of exactly 20 mm on the far right x and top y coordinates.

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    Default Re: Wrong coordinates at the end of machining

    Is it some parameter in ncstudio, is it wrong SPU, I am confused.

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    Default Re: Wrong coordinates at the end of machining

    If steps per unit are wrong, then if you tell the machine to move say 1" then it will not move exactly 1", this should be tested on each axis.

    G1 X5 F50 Issue that command and the machine should move the X axis exactly 5", if it does the Steps Per Unit for X are correct
    G1 Y5 F50 Then try the Y axis the same test, again if steps per unit are correct it will move exactly 5"
    G1 Z-2 F30 Then test Z which is given negative number to move the Z axis down exactly 2", if so then steps per unit are good.

    You can issue these commands on the MDI line. Home your machine first so the origin will be 0,0,0

    Russ



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    Default Re: Wrong coordinates at the end of machining

    Thanks Russ, will try this, I only tried by manually jogging the machine, not with written command.

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    Default Re: Wrong coordinates at the end of machining

    I think steps per unit solved the problem, my mistake was that I only tried it with small movement, like 10 mm, so the mistake was small. When I tried with bigger movements of the motors the mistake was more noticeable then before. The SPU was 0,0125, now it's 0.0120. The formula for calculating the SPU I found on the net was too complicated to use, so I used trial and error method, so this could be still work in progress. Anyways, thanks Russ.

    Sent from my HTC Desire 620G dual sim using Tapatalk



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Wrong coordinates at the end of machining

Wrong coordinates at the end of machining