Re: [CAD_CAM_EDM_DRO] Smallish CNC Miller

Hi,

I'm sure there are some on this list who will disagree with me but here are
my thoughts as I'm also UK based and doing the same job on my Bridgeport
clone.

1) Mach2 is a good choice

2) Forget stepper motors as those needed to move the slides on a Bridgeport
need to be in the order of 1400 in/oz and probably Nema 42 frames, these are
expensive. The ones you have indicated are not big enough. Go with Gecko
320's and servo motors, if you want to say some money and play at making
them yourself buy permanant magnet DC motors and stuff an encoder on the
ends. There has been some discussion about these :

http://www.surpluscenter.com/sort.asp?UID=2005040516484640&catname=electric&
keyword=MBDD

Item #10-1573 but I think item #10-1783 may do as well, anyway I have
ordered the latter.

The encoder could be obtained from a small surplus servo or bought new from
USDigital.

3) Ballscrews are availble at not too much cash, around £50 each, from
ebay.co.uk. There is a company advertising nearly every week selling 25mm x
5mm lead ballscrews of various lengths.

4) My machine does not use the combined leadscrew mounting banjo that the
Bridgeport uses and there is no reason why you could not make the mountings
for the ballscrews yourself before you take your machine to pieces and you
have access to a lathe.

5) I am planning on using the knee as the Z axis but will also ballscrew up
the quill. I bought some plans for doing the quill off the web but can't
remember who from, I think it was Chris Bruno @ Sliderule Racing. It was
only about £10 and worth the money.

Regards,

Terry

> Hi Folks,
>
> Firstly thanks a lot to all the people who replied to my first post.
> I learned a lot from the replies and a lot more from all the other
> traffic in the group, thanks again.
> I may regret this decision but based on the info I have gleaned I am
> going to attempt a conversion of my Bridgeport.
> The strategy is to firstly get hold of some software for a play.
> Based on what I have read and seen I conclude pragmatically that
> Mach2 looks a good choice, the manual alone is a great piece of work.
> Step 2 is to get some servo motors working on the bench. Gecko 210s
> seem to be a good choice for the drives but I could do with a bit of
> guidance on stepper motors. Nema size 34 motors look like the right
> choice for the X and Y motion (might hold off on Z until X and Y are
> installed) but there seem to be options within this spec. I am UK
> based so any suggestions for suitable suppliers and more specific
> spec would be welcome. Radio Spares do motors 2.5V 4.5A with a
> holding torque of 2200mNm (part 440-470), Mclennan have other options.
> What do you think about a break out board between the PC and the
> Geckos? Not strictly necessary I understand but useful?
> With things working on the bench I plan to start work on the machine
> conversion. I have purchased Chris Bruno's (what a helpful guy!)
> manual which looks like a great place to start and like the idea of
> still allowing manual operation. Conversion to ball screws seems
> essential especially as my Bridgeport is a little tired and I am
> following this up with a UK supplier. I have not managed to find a UK
> supplier of a ready made conversion kit and may yet fall back on
> Rockport assuming they are willing to ship at a sensible price.
> So there we are, the journey has started, my data file is filling up
> and the hunt for hardware is on.
> Any other words from the wise would be most gratefully appreciated.
>
> Ian
>
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