Incorrect elstcam dimensions

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This topic contains 23 replies, has 4 voices, and was last updated by  mio 2 months, 4 weeks ago.

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  • #89656

    mio
    Participant

     

    hello, i finished building my mpcnc a few days ago and i started testing on medium but i have two problems
    -The first is that my dimensions are not good at all for example the outer contour of this piece should be
     150 x 50mm while it is 146 x 47.5 so smaller while the inner contour that should be 35 x25 mm is 36 x27 so bigger ...
     I do not understand anything
    
    -The second problem is that I already broke 2 end mill and my cups are not very clean I use these endmill:
    https://fr.aliexpress.com/item/5Pcs-Extra-Long-3mm-2-Flute-HSS-Aluminium-Extended-End-Mill-Cutter-CNC-Bit-Kit-P0/32795794539.html?spm=a2g0s.9042311.0.0.27426c37S3YgdL
    
    and I try these 3 parameters only the first to work but the endmill blackened while my cutout lasted only 5 minutes
     
    
    So if someone could explain to me a little bit I look in all google but I did not find anything
    I just see 50mm/s is to fast for mpcnc 
    I also have these end miill but I do not know if it's better
    https://fr.aliexpress.com/item/High-Quality-3mm-2-Flute-HSS-Aluminium-Durable-End-Mill-Cutter-CNC-Bit-Extended-Incisive-Power/32766661861.html?spm=a2g0s.9042311.0.0.27426c37S3YgdL
    https://fr.aliexpress.com/item/1pc-Tungsten-Steel-End-Mill-Straight-Shank-4-Flute-Solid-Carbide-CNC-Milling-Cutter-2-3/32827988556.html?spm=a2g0s.9042311.0.0.27426c37S3YgdL
    Thanks and sorry for my bad english
    #89657

    mio
    Participant

    i make a mistake for the first picture sorry

    #89707

    Ryan
    Keymaster

    Make sure you are cutting on the proper side of the path and not on the path.

    1 user thanked author for this post.
    mio
    #89712

    mio
    Participant
    thank you ryan i am honored lol
    but i dont understand 
    
    
    you want to talk about the choice of outside / inside contour?
    
    
    #89833

    mio
    Participant
    Okay so I keep looking for my answers and I have advanced a bit
     For the problem of ugly cut I try with a straight cutter 2 teeth 
    a depth of 1mm and a feed speed of 10mm / sec for started and I get perfect results 🙂
    I believe that the endmill that I had sullied were of bad quality (HSSAL) or not adapted
    
    On the other hand I still have my problem with the dimensions
    
     I redid two trial one with elstcam and one with cambam to see if the problem 
    came from the software or possibly my mpcnc etc I put you  picture that's even worse with cambam ...
    
    Frankly if someone has an idea ...
    
    
    
    
    
    
    
    #89848

    Ryan
    Keymaster

    Check your gcode to make sure it is moving the length of your dimension plus the bit’s diameter, if not you are not cutting on the correct side of the path.

    #89849

    Bill
    Participant

    Mio, what size end mill are you using? 3mm, 6mm? Have you tried drawing with a pen instead of cutting? When it draws a square, is it square? Is it the right size? Before diagnosing cuts that have a width it’s easier to diagnose pen drawings because the width is minimal. You could be seeing issues with your build or issues with your CAM.

    #89862

    mio
    Participant
    Thank you for taking the time to help me
    
    I am not an expert in gcode I looked a bit but I would not tell you
     I attached the g code file if that can help
    
    And forgive me for forgetting I use 3mm endmill for my tests
    
    Otherwise I do not think I'm wrong cup side estcam shows the way 
    to the endmill in red so I do not think that's it
    
    Otherwise for now I'm still testing but the squares are after my first tests I would revive tomorrow
    
    I did not do any pen tests I would try tomorrow too but
     the strangest thing is that my perimeters are too small while my inner perimeters are too big
    
    Tomorrow I think sessayed a larger test room to see if 
    the gap increases with the length but it does not make sense
    
    I am surprised that no one is ever having this problem
    
    Unless I misconfigured my endmill in elstcam but what settings?
    
    
    
    
    
    
    Attachments:
    1. test-mp.gcode
    #89866

    mio
    Participant
    By the way when you think about it if the exteriors are too small and the interiors 
    are too big maybe the endmill is on the line instead of being in front or behind
    
    I think that's what ryan meant (I did not understand) but how did that change?
    
    
    
    
    
    
    #89906

    Ryan
    Keymaster

    I am a little swamped today, can you run my crown gcode and tell me how that works.

    #89907

    Ryan
    Keymaster

    Your gcode is not correctly formatted you need to look over my instructions again. For one of the cuts I am getting 32mm x 22mm, which doesn’t match anything you have show me yet.

    #89950

    mio
    Participant
    I'm really sorry to bother you ryan
    I spent several hours searching on google before bothering you but I did not find anything
    
    So today I was going to do several new pen tests, with a 6mm endmill and a larger piece to see 
    if the problem is linear
    
    By cons for dimensions 32x 22 that you found it could correspond to 35 x25 
    of the original drawing of the interior square if we add the 2 x 1.5mm of the endmill
    
    And now that I think about it, it could be the endmill that is not perfectly centered 
    and that eats a bit more than it should
    #89979

    Bill
    Participant

    OK, looking at portions of the gcode:

    G00 X41.0000 Y65.0000 F2100
    G00 Z0.5000 F480
    G01 Z-0.5000 F180 S12000
    G01 X9.0000 F600
    G01 Y87.0000
    G01 X41.0000
    G01 Y65.0000

    This is the first section it cuts. It moves from your beginning to X41,Y65, drops the Z to 0.5mm off the surface, then again slower to 0.5mm deep. Then it cuts along the X axis to X9, turns and cuts along Y to Y87, turns and cuts back along X to X41 and finally turns and cuts along Y to Y65. Remember those numbers match the center of the bit. That forms a box that’s 29mm inside on the X and 35mm outside on the X. The Y size is 19mm inside and 25mm outside. So, if you were starting a hole it will be cutting a hole 35mmx25mm. If you are cutting a part it will be 29mmx19mm. Which are you attempting, hole or part? From your image it looks like you are trying for a hole that’s 35×25. Since the actual hole is 36×26 your bit either is actually 4mm instead of 3mm or it’s wandering in a circle instead of spinning in place. Can you take a caliper and measure to verify the bit is 3mm?

    1 user thanked author for this post.
    #90010

    mio
    Participant
    Thanks Bill and Ryan too for taking the time to help me
    
    You're right bill this afternoon I made a hole in the mdf just to see
    and instead of 3mm it was 4 mm so it was not my gcode but my endmill that made a wrong round
    
    I used this technique (the one with the 100mm tube) on a katsu router and I think it's because of this
    https://discuss.inventables.com/t/makita-er-collet-conversion/139164
    So I put 4mm in elstcam instead of 3 and I now have normal dimensions!
    
    Thank you again I hope it will help someone in the future
    
    Now I only have to buy a second er16 but with a hole this time to test the 
    second method to see if I have less deflection with the endmill
    
    And in small bonus a photo of the machining for which I built the machine (not only ^^)
    
    The first part of an itopie to update my very old mendel ^^
    
    If it interested someone the parameters was:
    
    mDF
    endmill straight 3mm
    15mm / s
    3mm / s (z)
    1mm depth
    and of course a picture of my mpcnc for ryan ^^
    
    
    
    4
    1 user thanked author for this post.
    #90174

    Bill
    Participant

    The ITopie looks like a nice project, I like the way they tuck the power stuff under the platform.

    #90217

    mio
    Participant
    Yes it is a beautiful project that reduces much of the parts to be printed which is very rigid,
    square in addition
    it's been a long time since I wanted to do it
    
    
    And a very important point is that it is customizable (scad file) I modified mine to make a 30 x 30
    And since it seems to please you I put you a picture of the second and last board I cut today 🙂
    
    
    #90264

    BT
    Participant

    I built an iTopie early last year to replace the MP3DP v1 because I was looking for something a little bit stiffer.  Due to workmanship issues, my MP3DP wasn’t as reliable as I wanted and I ended up having to do lots of repairs to it.  The repairs were generally effective, but the sheer number of them plus a fair amount of brute strength and ignorance led to some cracks in the corner pieces.  I could have reprinted them, but I decided instead to just go with the iTopie instead.  Haven’t had any issues with the frame since 🙂

    #90294

    mio
    Participant
    Thank you for the feedback 4BT 🙂 It comforts me in my project
    
    Just out of curiosity did you use trapezoidal screws or conventional threaded rods?
    
    And if not hesitate to give your experience with itopie is always interesting to have other opinions
    
    
    #90300

    BT
    Participant

    I used a leadscrew similar to what Ryan sells in his shop here.  I am not using the threaded rod.  I did end up installing a BL touch for the z-axis end stop and for bed leveling.  It helped with getting the first layer down and making my printing more successful.

    #90326

    mio
    Participant
    ah okay and suddenly if you used a trapezoidal screw (like that of the store ryan) 
    you have changed the X axis which file did you choose?
    
    
    #90334

    BT
    Participant

    You would need to change configuration.h and specifically, the steps/mm for whichever axis.  The specific number would depend on your lead screw, stepper driver, and stepper.  Prusa has a calculator on reprap to help with that calc.  After you’ve done that, you can make actual measurements, like move it 100mm and measure how far it actually moved and then adjust the steps/mm to correct it.

    #90355

    mio
    Participant

    Im sorry my english is not perfect

    it was not my question
    I wanted to know what x end you have printed (stl file)
     for your trapezoidal screws knowing that the original itopie uses "normal" threaded rods
    
    
    #90372

    BT
    Participant

    Got it.  I forgot that I ended up modifying the STLs (iTopie_x_end_motor and iTopie_x_end_idler) to change from threaded rod/nut to the leadscrew.  One of these days, I should probably go back and update the STL now that I’m much more comfortable with Fusion360.  I’ve attached my versions, but as I recall, they required some finish work so the lead screw nut would fit as well as a couple of holes for the nut mounting screws.

    #90433

    mio
    Participant

    Ah okay I thought you had taken a file on thingiverse for example

    Thank you I was watching that I would post pictures if it interests someone!

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