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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE
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  1. #41
    Join Date
    Jun 2011
    Posts
    692

    Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by tapirath View Post
    Is there a reason that you went with brakes for the Z axis instead of gas spring? I'm planning a similar build and brakes just seems to be not necessary.
    If using linear rail, ballscrews and servos, there's almost no friction to keep the head in place. A brake is needed even with a well matched gas spring or counterweight.

  2. #42
    Join Date
    Aug 2015
    Posts
    2

    Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by skrubol View Post
    If using linear rail, ballscrews and servos, there's almost no friction to keep the head in place. A brake is needed even with a well matched gas spring or counterweight.
    I'm planning to use AC servos so this worries me a little bit. Can you elaborate on that or maybe point to a thread where it was discussed? To me, logic says a well balanced head will stay where it stays if the counterweight/force is good enough.
    I have never done this though so probably I'm missing something. I have seen threads where it's bashed and threads like this where it's recommended so I'm a bit confused.

  3. #43
    Join Date
    Jul 2018
    Posts
    10

    Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Update: I reached the point of no return: I cut the base and thus voided the 3 year warranty. Though I think I already did that by dismantling the PM30-MV.
    I posted a new YouTube vid linked here. This is where I cut 56 mm out of the base for an 11.5 in Y travel. I also cut a larger clearance hole for the 20 mm Ball screw that is Flipped in the Y -Direction. Finally, I cut a lower hole in the base for clearance of the 20mm ball screw and nut. Check out the Cad YouTube Video few posts back for reference.

    https://www.youtube.com/watch?v=9Z_CdX3md8I

  4. #44
    Join Date
    Jul 2016
    Posts
    41

    Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    What are your thoughts on the servo driving the spindle? Suppose you need to run a large face mill or something and need low rpm, how well does the DMM Servo perform at say, 75 rpm vs. 1500 rpm as far as torque is concerned?

  5. #45
    Join Date
    Jun 2011
    Posts
    692

    Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by tapirath View Post
    I'm planning to use AC servos so this worries me a little bit. Can you elaborate on that or maybe point to a thread where it was discussed? To me, logic says a well balanced head will stay where it stays if the counterweight/force is good enough.
    I have never done this though so probably I'm missing something. I have seen threads where it's bashed and threads like this where it's recommended so I'm a bit confused.
    Sorry, missed your response way back when.
    Head weight will vary a bit between having no collet or drawbar in it vs having a big face mill installed. Also, depending upon the type of spring, the spring rate won't be constant over the Z height and may change over time (an air spring may push up as the air in it heats up, or will lose force as some air leaks out.) I guess a counterweight shouldn't have any of the spring issues, but still may have an issue with different weights of the head.

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