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m1ptr
27-03-2012, 02:04 PM
Hi Everyone,

I have been making home made PCBs for some time and feel its time to automate the drill process with a small homebrew CNC machine.

I have the mechanical design in hand using a 10" x 10" table, I've bought 3 x 1.8 degree NEMA 23 1Nm Steppers from AstroSyn and am now looking at a suitable controller.

As its a PCB drill rather than a mill, with 0.7mm holes being the most common size I'm drilling, I thought I would get sufficient resoltion if I were to buy / build a controller that supports half step drive. While it sounds interesting to develop I don't think microstepping is needed.

I've looked at TOSHIBA TB6560 3 axis controllers on ebay, and also looked at schematics using MOSFETS and Driver chips.

Any advice, items to avoid and info on recommended designs to build is appreciated.

Regards
Pete

Lee Roberts
27-03-2012, 02:40 PM
Hi peter, have a look at the units from Roy over at www.diycnc.co.uk/html/drv30_s.html (http://www.diycnc.co.uk/html/drv30_s.html), they are 3a drivers and very cheap. I think these maybe a good starting point for such a machine.

Stay away from the TOSHIBA TB6560 units from ebay, if you do a search on these forums you will read about the problems these units have.

Good luck with the build and welcome to the site.

.Me

JAZZCNC
28-03-2012, 12:07 AM
As its a PCB drill rather than a mill, with 0.7mm holes being the most common size I'm drilling, I thought I would get sufficient resoltion if I were to buy / build a controller that supports half step drive. While it sounds interesting to develop I don't think microstepping is needed.

Really you should look to get the resolution you want from the pitch of the screw not the drive stepping. Higher Micro stepping(10x Max) does help but more for motor smoothness than resolution.
What you need is a low pitch ballscrew say 4mm or less, I recommend you don't try the cheap route and use threaded rod or cheap Acme screw and nut.!!
Because of the nature of what your wanting to do you'll need repeatabilty has much as resolution and threaded rod and cheap Acme which usually come with rubbish nuts which just can't give you what you'll need.

m1ptr
28-03-2012, 01:42 PM
Hi peter, have a look at the units from Roy over at www.diycnc.co.uk/html/drv30_s.html (http://www.diycnc.co.uk/html/drv30_s.html), they are 3a drivers and very cheap. I think these maybe a good starting point for such a machine.

Stay away from the TOSHIBA TB6560 units from ebay, if you do a search on these forums you will read about the problems these units have.

Good luck with the build and welcome to the site.

.Me


Thanks for the advice on the TB6560 they do look like they have a reputation as smoke emitters!

Cheers
Pete

m1ptr
28-03-2012, 01:53 PM
Really you should look to get the resolution you want from the pitch of the screw not the drive stepping. Higher Micro stepping(10x Max) does help but more for motor smoothness than resolution.
What you need is a low pitch ballscrew say 4mm or less, I recommend you don't try the cheap route and use threaded rod or cheap Acme screw and nut.!!
Because of the nature of what your wanting to do you'll need repeatabilty has much as resolution and threaded rod and cheap Acme which usually come with rubbish nuts which just can't give you what you'll need.

Useful info thanks, In my current design based on a http://www.rockcliffmachine.com/ plan I'm using 6mm stainless machine screw with a nylon nut. I'll plan to run some tests to check repeatability now I know what to look for. I should be able to upgrade to a ballscrew if its an issue. Cheers Pete

m.marino
28-03-2012, 03:47 PM
I have a DIYCNC system 4 set with 4 of the 3A driver boards and the case. If you are interested give me a pm and we can chat. Also have four of the ext module cards that can go with it if your interested.

Michael