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  1. #37
    Member Khalid's Avatar
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    Quote Originally Posted by dertsap View Post
    I agree , i absolutely despise plunging end mills , ramp and helical entry are faster and are less abusive
    because of the amount of slop helical would be the better choice in keeping a constant (or somewhat consistent) pressure on the tool , inconsistency of tool pressure will affect the cuts
    overall most cast is like butter compared to most other materials , so under the right conditions you should be able to be extremely aggressive with it as far as speeds and feeds , depths and engagement

    hI cURT,
    Thanks for answering.. I am new in Metal cutting so lot of problems i will face... However with the help of this community and metal cutting gurus will help me...

    I am attaching the picture.. The round circle is a pocket and this pocket is spiral... The table rotates CW and tool rotating Anti-clockwise.. Is this right?.. Or i have to move the tool along the table i.e. both Anticlockwise ?

    My Spindle motor is 2.2KW 3Phase and drive the spindle with gearing mechanism... So far i never see my tool is stopped due to less RPM or very high load on the cutter...

    Attached is the Gcode for the Aluminum Impeller..

    Attached Thumbnails Attached Thumbnails Milling Cast Iron-cutting-direction-jpg  
    Attached Files Attached Files
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/


  2. #38
    Gold Member dertsap's Avatar
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    Quote Originally Posted by Khalid View Post
    I am attaching the picture.. The round circle is a pocket and this pocket is spiral... The table rotates CW and tool rotating Anti-clockwise.. Is this right?.. Or i have to move the tool along the table i.e. both Anticlockwise ?

    ..
    reverse the cut direction in the impeller g code that you created , for cutting inside of lets say a pocket your cutting path should be clockwise and for outside it should be counter clockwise

    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........


  3. #39
    Member Khalid's Avatar
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    Hi Curt..
    Also can you tell me whats wrong with shifting the impeller in stock? You have seen all the pictures and i have not found what was the problem?..
    Is it problem of loosing step?
    Is it problem of wrong calibration?
    or What?

    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/


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    Gold Member dertsap's Avatar
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    to be honest its hard to say , it looks like missed steps but it could also be a result of the part being jerked around because of the backlash , i'd suggest cutting a circular pocket with conventional milling then cut another circular pocket with climb milling and compare the results , better yet try a pocket with a small island in the center
    it may take some experimentation to figure out where your machine will be temper mental and then you can possibly compensate from there

    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........


  5. #41
    Gold Member dertsap's Avatar
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    after a better look at the code and at the picture i'd say its missed steps , either that or your part has moved ,
    try dialing up your part dead nuts , try a few cuts then redial the part and see if it has shifted again

    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........


  6. #42
    Registered M250cnc's Avatar
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    Well i think i will upset a few people with this statement.

    Backlash compensation works in theory but not in the real world cutting difficult materials.

    Why do you think quality builders put so much effort in to an engineering solution to backlash.

    When conventional milling the axis motor power is being used to drive the cutter in the cutting process.

    In climb milling the axis motor is being used to prevent the cutting axis being drawn into the workpiece

    So when you are climb milling with the backlash hidden with compensation the cutter is being drawn into the workpiece unexpectedly this results in a sudden overload of cutting depth which results in you going off the toolpath appearing to be lost steps. This is probably why you broke a cutter.

    So the answer is simple to fix your problem fix the mechanical backlash.

    Phil



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    Member Khalid's Avatar
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    Hi Curt,
    Tomorrow i will test both methods (Climb and Conventional Milling) for a pocket ... I will also measure the Clamps from some reference with a dial...

    Lets Suppose If I have Missed Step, then should the simulation results matches with the real part? You see i have the machining shifted but the results comply with simulation... The problem would be solved if i never stopped the machine and let it to finsih the part.. If the machined part matched what i required with a little shift then the phenomena would be much strange... I guess if i not stopped the machine, i would have deviation in the machined part...

    I also think that the Axis which carries most of the load may have missed step.. In my Case Y-axis may be the culprit...but:
    1- In CASE of CAST IRON Machining, I got deviation across Y-axis.
    2- Incase of Aluminium Machining, My part is Shifted toward X-axis, which is the most Free axis i have.. Having very little load as compare to Y-axis..

    I also ran the Y-axis Motor and pulled the Y-axis slide against the motor and i couldn't stopped that axis by hand...even i couldn'd slow it down. and i have no observation from the motor change of noise!!!...

    For next test I put 200lb of weight on the top of X-axis slide and commanded Y-axis to move 4 inches and it went exact 4-inches+- 0.01... No Missed step...

    Is there anything wrong with the shuttle acceleration or Backlash compensation?

    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/


  8. #44
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    Quote Originally Posted by M250cnc View Post
    Well i think i will upset a few people with this statement.

    Backlash compensation works in theory but not in the real world cutting difficult materials.
    I am really a newbie in Backlash compensation.. I have a router and doing woodworking for the last 5-years with it and never used backlash compensation...
    In my view, Backlash compensation only works at the time of change of direction of motor rotation...A lot of peoples here using backlash compensation with their machines and getting perfect results including Bobwarfield...

    Quote Originally Posted by M250cnc View Post
    Why do you think quality builders put so much effort in to an engineering solution to backlash.
    Because they sell their machines for good.. and they provide the quality product to the users that don't know how to compensate for the backlash time and again ..and they get Handsome amount of money from their sellings...
    I know nothing so kindly pardon me in this...
    Quote Originally Posted by M250cnc View Post
    When conventional milling the axis motor power is being used to drive the cutter in the cutting process.

    In climb milling the axis motor is being used to prevent the cutting axis being drawn into the workpiece

    So when you are climb milling with the backlash hidden with compensation the cutter is being drawn into the workpiece unexpectedly this results in a sudden overload of cutting depth which results in you going off the toolpath appearing to be lost steps. This is probably why you broke a cutter.

    So the answer is simple to fix your problem fix the mechanical backlash.

    Phil
    Thanks for the informations... i learn daily something new from you guys.. From above statement i understand that i should use conventional milling?..Am i right...

    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/


  9. #45
    Gold Member dertsap's Avatar
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    i wouldn't worry about how much weight your table can carry , but I'd be interested in how much weight it can pull
    i agree the sooner or later you should deal with getting rid of the backlash because it will make your life easier , but in the meantime you'll have to learn how to work around it , I know how clever you are so with some experimenting with cuts you'll figure it out .
    you need to eliminate all of the possibilities of failure so scribe a line at the head and the column and make sure the heads not moving , if you calculate you chip load you may be taking a heavier cut than what your setup can handle so try knocking your chip load in half and do some testing as to how much you can push your tools ,
    your aware of the size of motors that I've got setup on my router and I dragged my boy half way across the table when I asked him if he thought he could hold the gantry back , but when I take too heavy of cuts in aluminum then I'll run into the same types of trouble . the last was doing 3d profiling on ally and found a problem with the way the y axis was mounted (whole new problem ) , point is that that you need to eliminate all possibilities for disaster

    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........


  10. #46
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    Quote Originally Posted by dertsap View Post
    if you calculate you chip load you may be taking a heavier cut than what your setup can handle so try knocking your chip load in half and do some testing as to how much you can push your tools ,
    The same i think the stepper motor stall or loose steps.. The attached picture shows another PEN plotted with the same machine..The Gcode provided by RICH at machsupport forum..

    The moves or IJK and started for different Z-moves.. I amazed to see how start and finish point coincide with each other.. Again i am in 0.01mm range..

    I have to increase the voltages to my stepper from 36Volts to 48Volts... My stepper can withstand Voltages upto 80Volts DC with 4.2Amp/Phase.. Currently I am supplying 3.8Amp with 36Volts.. will it increase its strength by increasing the voltage?

    Attached Thumbnails Attached Thumbnails Milling Cast Iron-untitled-jpg  
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/


  11. #47
    Registered M250cnc's Avatar
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    Quote Originally Posted by Khalid View Post
    Because they sell their machines for good.. and they provide the quality product to the users that don't know how to compensate for the backlash time and again ..and they get Handsome amount of money from their sellings...
    I know nothing so kindly pardon me in this...
    There are lots of users on here who built their machines with zero backlash "Me Included OK 0.03mm" because that is the best way when you want to machine difficult materials.

    It is not a case of knowing how to use backlash compensation, that may work on soft materials or cutting AIR

    Try running you gcode with no tool in the collet centre on the part as normal check at the end that you are back on zero

    You will then know if the code is right

    If the code stays on zero then you will know that the machine is at fault

    Phil



  12. #48
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    In above case no-load condition, The machine started/stopped at Zero.. and the results are within 0.02mm range...

    So , In my point of view i am just loosing steps at high load on Y-axis..and thats my finding

    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/


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