1. #1
    Hi. Thought it might be useful to share my experiences with the Heiz T-720 mill after 3-4 years on.
    I've not had a CNC machine before. I thought long and hard about the purchase, and (obviously) decided to go with a manufactured unit rather than going the DIY route. My main interests were in the production of printed circuit boards - but have dabbled a bit in cutting wood and plastics. Never went near metal cutting of any sort.
    Although I can't make an informed comparison, I think it's a great machine. Accuracy seems good, and I've produced hundreds of boards over the years.
    Prior to the purchase I read much around the issues of FR3/FR4 not sitting flat on the cutting bed, so opted for the floating head to go with the machine. This proved a big bonus, and slight curves in the board were never an issue. On the most part, I just stuck the pcb down on the bed with double sided tape. I think there were only ever 3 occasions where this didn't work well.
    I also opted for winpcnc-pro, so the machine came with a separate controller that takes the cpu load off the attached PC. Never had issues with timing Etc.
    You'll probably have noticed I'm using the past tense in what I say?
    Recently, the machine started to loose accuracy on the Z axis. I've been talking to Prototools (I bought it from them) to try and resolve the issue. They are very helpful, but at the end of the day the only real solution offered by them is to send the machine back to Germany for a refurbish. That's all pretty costly!
    Now, as far as I'm concerned the most important issue here is, you can't replace the Z stepper motor outside of the factory (I've had a go). For me, that's a killer fault. It would seem that unless I'm prepared to ship the machine back I've got a load of scrap metal sitting in my workshop
    I see no option now but to get another machine.
    I'm adding the question "can the stepper motors be replaced at home" to my list of questions before my next purchase!

  2. Quote Originally Posted by damian_uk View Post
    ...
    Now, as far as I'm concerned the most important issue here is, you can't replace the Z stepper motor outside of the factory (I've had a go). For me, that's a killer fault. It would seem that unless I'm prepared to ship the machine back I've got a load of scrap metal sitting in my workshop
    I see no option now but to get another machine.
    I'm adding the question "can the stepper motors be replaced at home" to my list of questions before my next purchase!
    ok, begs the questions:

    a) why would the stepper motor be the cause of loss of accuracy - is it losing steps or what?
    b) why can't you replace it?

    nothing is insurmountable...

  3. #3
    Well from the pictures i've seen of that machine there's nothing special there.?

    Do you mean you can't replace Like for Like as in manufacturer of the stepper or you can't actually remove it from machine.?
    You don't have to replace like for like and any stepper make provided it's sized correctly and matched to your drive will work fine.

    That said I'm 99% sure it won't be the stepper causeing your lack of accuracy but more likely a worn ballscrew/nut or bearing with play in it, could be as simple as worn motor coupling. Carefull examination of Z axis will show any signs of play or movement from ballnut/screw.

    I certainly wouldn't call it scrap or even close to being scrap and if it is then I certainly wouldn't be buying another from same company after only 3yrs and lite duty usage.!

    Unfortunatly your a little to far away from me otherwise I'd gladly look it over for you.

  4. #4
    Quote Originally Posted by irving2008 View Post
    ok, begs the questions: a) why would the stepper motor be the cause of loss of accuracy - is it losing steps or what? b) why can't you replace it? nothing is insurmountable...
    Yes. It's loosing steps. I can't replace it because it's fixed to the screw thread, and (quoting Prototools) is something that can only be done at the factory. I can kind of confirm this, because I couldn't manage to get it off... If you feel this is surmountable, then please do feel free to tell me how..

  5. #5
    The stepper motor is standard, and easy to obtain. I've carefully examined the screw thread. I see absolutely no signs of wear - as is reflected by the machine's light use. I can't remove the stepper motor because of the apparent way its been bonded to the screw thread itself. I can't remove the motor and the screw thread in one go because if it's length. The only way I can envisage getting at it is by removing the gantry sliders so I can drop out the whole of the Z drive mechanics out. The gantry slider rails are an interference fit, and I see no simple way of removing them. Your quite right. I would not consider buying another machine like this if you can't swap out stepper motors. That's why I chose to make the forum post.

  6. #6
    Hi,

    Chances are you won't see signs of wear on the screw thread it's self but you will feel any movement or Backlash and this is what your looking for.

    I think your going to have to provide some good quality pictures of the problem area for us to help more.

    I very much doubt they have built them not to be disassembled so chances are they are just securely bonded with some form of compound and fastening method.?

    Post pics and lets see.!

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