Pro's Con's, what to choose?

[GalaticDan]

Hi,

Ok, this is a stabe in the dark and depends upon application but....

If you were making a CNC machine and it's fairly large and used bridge port parts and THK sliders, a new 50mm square steel frame constuction for y-axis and a 2.2KW spindle drive. Gantry travel 1080mm by 900mm. What positioning drives would you choose?

a). the 3 brand new NEMA42 stepper motors (12mm shaft dia.) I've got in the corner of my garage with gecko drives, still to purchase?

b). the 3 used bridge port servo motors (16mm shaft dia.), now fitted with 5volt 2048PPR TTL encoders and using the rutex drive system, still to purchase?

I know it's very much machine and application specific but I guess I'm after replies from people who's used both drive techologies and who would be kind enough to share there experiance with me. Cost wise the servo motors using the rutex drive system (75volts, 20Amp) will be about £650UK and the gecko's £450UK, all complete in switch gear cabinate. I did spend some time sourcing the servo and stepper motors, also the time I put into mounting the industrial encoders on the servo motors.

Thanks for your time,

GalaticDan

[kong]

Is this a router table? If so, then both of those systems could be overkill. Just stabbing in the dark at present, but look at www.homecnc.info and see what Jeff used on his miller and router table.

[GalaticDan]

I agreed to some extent. The basic idea was initially to get the bridge port working but there's 2 much missing so I decided to use parts off the mill. My initial idea was to build a simple milling machine and I've looked at other peoples ideas. Since I started I noticed that alot of people seem to build machines out of box section type material. I have a friend who works at a local FE college who's offered to make my large y-frame out of 50mm solid mild steel, shoulder bolted together and if I'm prepaired to pay for the difference he'll be happy to make the double y-frame out of stainless 304. This got me thinking about a fairly large general purpose machine.

Cost wise, I've already got the motors, most of the axis parts but no table to support the machine and given the size of weight it's likely to be one of the two driver solutions I use. The problem is until it's built and I try out different on materials drilling, milling and routing I will not know if the machine will be suitable. I've look at so many machines on the web. I would want to machine only metals for this project. 2" deep moulds from various metals for my plastic injection machine and sheet stainless 2mm cover most of the gantry travel.

GalaticDan