Looking for Direction on Retro..

[stang5197]

We have a 1J Bridgeport I am going to retrofit with CNC (steppers, geck drives, Mach2 software). I have been doing alot of ready for the last two months and here are couple of questions I can't find answers too:

1.Are NEMA 34 size motors adquete for the table and quil, or are NEMA 42 more suited for this type of application? (Mainly cutting Aluminum and Cold Rolled Steel). There is a decent price drifference and was wondering if NEMA 34 1200oz/in motors would be strong enough? I see that CNC Master is using NEMA 34 motors, we plan on using steppers rather then servos.

2. Has anyone used the plans from www.campbelldesigns.com for building the power supply?

Thanks for any help.

[Hood]

I have Nema 34 916 oz in on x and y with 2:1 reduction and they are more than adequate. The Original Series 1 CNC motors were only around 600 oz in I think.
On the quill I have a 240 oz in with 3:1 and have not had a problem with it so putting 1200 oz in all round should pose you no problems at all.

Hood

[stang5197]

Thanks for the info. it is much appreciated.

[jdelaney44]

Might want to post the power supply question over at Yahoo on DIY_CNC or CAD_CAM_EDM_DRO of you haven't already. Or at the Gecko site on Yahoo.

I have a power supply circuit that is working pretty good. I still need to reduce the resistance of the in rush resistor. I have a BP conversion Blog thread on this board if you are interested.

Best,
-jd

[titchener]

The 2:1 geared 1200oz. steppers will probably be ok, as long as you're not planning to set any speed records. With that setup and Mach your maximum table speed will be 60 ipm (1 inch per second). That would bug some people, but I've got my machine set at that max speed now and its ok for what I do, prototype work and small runs.

My machine came used with large Nema 42 steppers geared 1:1. I'm running them in "full winding mode" at only about half their rated voltage so they're only putting out about half power and I've still got plenty of power. If you run your Nema 34's at the full recommended voltage and gear them 2:1 I would expect you'll probably have as much power as I do, which I believe is plenty for a BP sized mill doing prototype and small run work.

If you're trying to compete with the table speed and metal removing power of a commercial machine its a different story, but if you don't need super speed those motors should be fine. I'm using Gecko G202's driven by a SoundLogic board with my machine with Mach3 as the controller and its all working well.

I like the stepper based system a lot, when I shut the machine down the table and quill hold their position and Mach remembers that position when I fire it back up. Servos would give me more speed but I don't think I would gain any accuracy as the lead screws on my machine are only good to a thou or two anyway, so for this machine the steppers work really well. If I was starting from scratch on a new machine that had really accurate lead screws I probably would go servos though.

Good luck-

Paul T.

[stang5197]

Thanks for the help. My project has been put on hold for another month do to some other things that came up.

From everything that I have read I think I will go ahead and use the NEMA 36 motors rated at 1780oz/in.

Has anyone heard of or used logitrol control www.lowcostcncretrofits.com/ for there projects. I am considering using one of there setups with the motors listed above.