Which to convert? G0704, RF-45 or Bridgeport?

[bogiestl]

I'm going to need a 4 axis CNC mill for a niche market project. I don't want to reinvent the wheel, and I don't want to buy someone else's problems. Having worked in a shop with a few pieces of older equipment (that only seem to break when they become mission-critical to a run...), I'd really like to buy newer hardware. China's quality has been getting better, so...

I want to use an "off the shelf" controller - By that I mean "a PC," which I know I can easily replace/buy parts for - next time I pay $900 for a monitor, I better be able to see it all the way across the shop... And if I put a picture of a hot chick on it, it better be drawn in more than ASCII...

I'm a little leery of buying a used purpose-built CNC on two fronts - 1) They seem to be REALLY heavy (since they were designed to be able to do BIG jobs at high speed/feed), and 2) by the time they get into my price bracket, I'm worried that I'll be buying someone else's mechanical problem child. Couple that with replacing controller stuff, and...

Looking at the three basic platforms, since I won't be reinventing the wheel (see above...):

I could -probably- get away with the 704 but it'd be limited for larger stuff. The RF-45 seems a bit beefier, with the larger table available, and a full-size Bridgeport/clone is not out of the question.

Money-wise, I'm figuring that the ball screws for the bridgeport will run... oh... about 2x what they will for the others? Motors/drives for the larger mills will cost a bit more, but really, hey, I'm figuring that they won't cost -that- much more.

So... Pros? Cons? What do you guys think? I've spent the past year in a shop, but before that I was a graphic designer and tech writer...

[bogiestl]

Also, in the event of the full-size conversion, I'm considering one of the Bridgeport clones that Grizzly sells that has a horizontal spindle added on - That could come in handy. Not for the primary intended use, but hey...

[LUCKY13]

BP clone hands down, if yuo have the room & the funds its a no brainer. One thing the BP clone will be a much better machine, more versatil, and last much better. You add a horizontal spindle and it gets even better.


One thing I have figured out is it really doesnt take any more room to have a BP compaired to something like a RF-45 ( except for head room). Now I really like my RF-45 but bring me a BP for trade and its yours.


OK cost, it will cost more to covert the BP. BUt thats only if you go cheap on the smaller mill. Most kits for the BP machines are good quality screws & yes you could order up your own cheaper screws but why do something like that on such a nice machine. If you get screws of the same quality of most BP kits it will cost just as much for a RF-45 (atleast very close).


The bP just wins in every way. Only if money and space are a problem does the smaller machines become practical. If a smaller machine is needed the G704 could be the way to go, its a tough little machine for its size and it can be converted pretty reasonable on the money side. The RF-45 is very good for a bench type machine but it takes a lot of working things out your self, making a lot of parts yourself, and then you still have a benchtop machine that cost close or even as much as a compairable BP.



Grizzly has been making some pretty darn good BP clones IMHO. A buddy of mine has one and I love it. The things yuo can do with this style mill are just way beyound the ability of the benchtop machine. It doesnt seem as if this would be so until you see someone who has used a BP for along time and know what there doing.

Now one thing against the BP is controlling coolant if you try to inclose it. There are many different ways of doing this and a few have come up with some pretty easy, and less combersome ways of achiving this. Weight of the machine and having the floor to support it is also something to think about. Plus the hieght of the machine. But if you have the floor support, the celling hight and the funds I wouldnt give it another thought. Get the BP.


Once people start offering CNC ready kits for the RF-45 that are afordable & available then this machine will get more popular. But for now it takes a lot of work to convert, or alot of money ( enough to pay for a BP & convertion). If yuo have sevral months to build the convertion parts and weed through getting the needed electronics then it becomes much more affordable. And it makes a nice CNC machine for the guys with limited funds or shop. But its no where close to being the machine a BP is.

G704 - Buy it, order up what you need to convert it, use it very quick. Cost less, but will handle less ( but its still a very good machine). Hard to beat for the homeshop guy with limited money & shop. Plus easier to convert because convertion parts are out there afordable for it.

RF-45 - cost more, takes lot longer to get converted, have to either make a lot of the parts or pay high prices for the parts. Much more capable machine though. Will handle a lot of different milling jobs & hold bigger parts. Price could be fairly reasonable to complete, or expeincive depending on how you go about it. Probably the best benchtop machine out there (at hobby prices).

BP - Buy it, buy the parts needed, build it, making parts. Cost about the same as high end RF-45 builds but its a quality machine when done, will handle even more milling jobs & also will handle doing specialty setups much better. WIll be more ridged, last longer and have better resale value. Plus there are many attachments that can be bought to extend the ability even farther. The versatilty because of the turret is a hugh plus. And it will be way more durable, and be able to bring money in much easier because it can do most any work (even some automotive type work).


One thing about having a CNC machine, the more you do with it, the more you realize the other things you can/want to do with it. If yuo can afford & support the better machine it will pay for itself easier in time. Being able to take in a wider range of work will make it much easier to support the price of the machine & tooling. Thats another thing, it cost exactly the same for tooling no matter which machine you get.


Jess

[bogiestl]

Thanks - I guess I'm looking at two "turnkey" setups, and one that is sort of... Altho one of the nice folks I talked with at Microkinetics said that they've now got a kit for the RF45... I'm leaning toward Mach for the controller tho, so things are still up in the air... I'm getting ready to move, and depending on where I end up, I may have a basement shop, which will eliminate some options - but if there's a nice big secure garage, the BP's looking interesting - 9x42 would be overkill...

[wizard]

Seriously stay away from Bridgeport conversions if CNC production is your goal. Especially if your business might end up hiring somebody.

If you need to produce parts a turnkey solution is the way to go. DIY will significantly impact time to market. Consider looking at Tormach and other low end CNC solutions. Then move look at solutions from the mainline CNC systems builders. HAAS has some surprisingly low priced machines for a machine tool company. I'm certain that other reputable builders do also.

The big catch with the bigger builders is that PC based controls are replaced with more custom hardware. I'm in total agreement with focusing on PC controls, as the alternatives become hopelessly expensive to maintain.

Thanks - I guess I'm looking at two "turnkey" setups, and one that is sort of... Altho one of the nice folks I talked with at Microkinetics said that they've now got a kit for the RF45... I'm leaning toward Mach for the controller tho, so things are still up in the air... I'm getting ready to move, and depending on where I end up, I may have a basement shop, which will eliminate some options - but if there's a nice big secure garage, the BP's looking interesting - 9x42 would be overkill...

[DSpeck]

At work, we have both a real VMC and a BP clone conversion. The business started with the converison, then the owner bought the VMC. HUGE difference! My main complaint with the conversion is having the knuckle. It will go out of tram - period.

If you can, find a used BP CNC machine, and retrofit it with modern controls/drives/motors (if required). They don't have the knuckle, just table and knee motions. This means the head will not move. It is much more rigid, and was designed to be CNC from the start. Some of them have a QC tool system, which will speed up your production, tool. From what I understand, the iron, ways and ballscrews usually stay in good shape, but the controls need to be replaced with something that will be maintainable with current technology.

Just something to consider, if you have not made a decision yet...

Doug.