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03-23-2008, 05:33 PM #1
Real cost of Bridgeport CNC conversion?
For sometime I have been interested in a knee mill conversion. I have read many posts about conversions of all types. It seems there many approaches to a conversion but it appears there are basicly 2 complete out of the box kits, Centroid or Acurite. They apparently are complete kits including ball screws. The price for the Acurite 3 axis kit is $15,200.00 and that is if I install it myself. I was quoted a simular price on the Centroid. Are these prices worth the money or is it more worth while to try and piece something together? I recently purchased a new Sharp 10x54 TMV 3hp mill with VFD. At the time I just could'nt swing the added money for a CNC version of this mill. Now I am regretting not coughing up the extra money and buying the CNC version of this mill. So, I have decided one way or the other this mill will become a CNC. This machine will be used for manual as well as prototype low volume work. Thanks for any information or personal experiences any of you might provide!
03-23-2008, 07:19 PM #2
You made the right choice by getting a manual knee mill. Saved a bunch of money that you can use toward a real VMC later on, like the SV-2412.
They're not cheap at $35-40k, but you're getting a whole lot more than you'd get out of a $20-25k CNC knee mill. Twice as much mass, bed mill structure, more horsepower, higher spindle RPM, 40 taper spindle, toolchanger, coolant, enclosure, and a Fanuc control.
03-23-2008, 07:50 PM #3
Also check out the Prototrak conversion kits:
I would only consider a 3 axis conversion, you lose way too much capability with a 2 axis conversion. One potential issue on all these conversions is G code capability, check and make sure they support that, in the past some of these systems only supported the companies "conversational" commands.
As Airborne pointed out, CNC knee mills are in a no man's land in terms of price/performance. They're great machines for some usage, my BP clone CNC machine does everything I need it to for prototyping and small run production, but I'm in a special "in house use only" situation, you generally can't compete with other job shops with this kind of machine unless you specialize in prototypes and very small runs or one offs only.
If you have more time than money and feel comfortable working with electronics and PC's, you can do a PC conversion using the Mach PC based controller from www.artofcnc.com .
Keep in mind though that its a fair amount of effort to get a retrofit done with this approach, I went this way because I had a strong interest in learning about CNC machines from the inside out, and I ended up with a great machine. But econonically unless you have some free time to burn most times you're probably better off buying a turn key machine rather than retrofitting one.
However new turn key CNC knee mills are too expensive for what you get, typically $20k to $25k, and at least around here used ones in good shape don't go for much less than that. For that much you can get a Haas TM1, a much more capable machine, or save your pennies and sneak into a VMC, Sharp and Bridgeport have smaller models for less than $40k.
But if you have questions about doing the retrofit yourself, fire away.
03-23-2008, 09:35 PM #4
retrofit knee mill
At work we recieved a bridgeport series 1 cnc knee mill with a analim control.
the analim had a mind of it's own, it would follow codes once or twice then go to the back field. We replace the analim with the Centroid m-39. I ran it for 3 yrs. and liked working with it. We instaled all motors and control box and rep. configured the control. Had a chance to move up to a Haas TM-2 and traded in old machine. kinda miss it. Like the new machine but taking a while to learn the controls. Centroid does except G Code.
03-23-2008, 09:52 PM #5
there is a big difference between peicing your own kit together and buying one. i bought a kit minus wiring and between running my business and other commitments, getting this mill running has taken about 6 months. luckily i have another mill, but don't forget to add your time into the equation if you need this to make money. if your doing it for hobby work then by all means convert it yourself and you'll save about 10,000. i would also get servo motors as opposed to stepper motors, and mach 3 is pretty good for a DIY controller and runs on PC. the hard thing to come up with really are the limit switches and home switches. now ultimately you don't "NEED" these to run, but for safety sakes i wouldn't run a mill without them.
for a bridgeport i would get at least a NEMA 34 servo motor and to run mach 3 get US digital encoders. also do not skimp on ball screws, i have seen just ball screw kits for bridgeports. and i would drive the knee as opposed to the quill but this may limit you in terms of doing contour work as driving the knee is difficult at speed. its a heavy block of cast iron.
good luck with your project whatever way you decide to go.
03-23-2008, 11:54 PM #6
Listen, I strongly feel you will do nothing but burn cash by buying a cnc conversion kit for a bridgeport. We recently sold our Tree 3 axis Knee mill for a steal at less than 10K! They will straight smoke any converted bridgeport. They are a box way machine with plenty of quality iron. We actually made nicer parts with it than our new Haas VMC!! We had a Tree 250 but you can easily upgrade them with a bigger spindle motor and other goodies. You will get more than just CNC. A coolant system, a production designed machine, A VFD spindle, a quick change type holder, true precision ground ball screws, the list goes on.
Sorry, I am firm that wasting money trying to cnc a Bridgeport it just that. I loved our Tree machine and it was a mistake selling it!! They sell for a song and are BUILT! You would love one compared to a bridgeport. Even against the old series two, I would take a Tree any day. Wish we had room to keep it.
03-24-2008, 01:53 AM #7
Here is a brand new knee mill with heavy box ways and Centroid control for $15,000. I have seen that exact machine in person as I just took a road trip to Vegas and bought a new cnc gang lathe with Centroid control from this same fellow. Just a thought, I wouldn't spend that kind of money on a retro unless I just had lots of money burning a hole in my shorts.
03-24-2008, 03:17 PM #8
I agree much with many of the sentiments in here about a 3-axis kneemill conversion. It's NOT money well spent. The money needed for that would be a good downpayment on VMC or a more rigid bedmill.
03-24-2008, 04:11 PM #9
What viper says is why I paid $5K for my working 325 Tree instead of converting my low hour (I bought it new in the early 1980s) Taiwanese knee mill. I then sold the manual mill and the tooling to a friend so it is available if I ever need a turret/moveable head for some project.
Also, having the CAT40 tooling makes setting and keeping tool lengths a breeze. You do spend more money on the holders, but you don't have problems with having tool lengths changing as you move them around in the R8 collets.
03-01-2011, 06:12 AM #10
I just signed up for this forum, and I really like all the useful comments. I just picked up, literally a few days ago, a bridgeport series 1. I thought that the cost of retrofitting would be much less, but I'm not too concerned with time. I didn't have the capital to fork over on a used CNC mill off the bat- so I'm basically stuck.
What are my options at an effective retrofit? I took a look at southwestern industries. It sounds like I bit off way more than I can chew now...
03-01-2011, 06:25 AM #11
I looked into doing a retro and it seems like a losing proposition you can buy older cnc mills for nearly nothing I just bought a Shizouka for a 1000 and granted the mill is old and the operatiing system is antique but it already has servos and ball screws all I need to do is change the computer it is much cheaper to do that than to convert a manual mill. I am using it like it is for now but will do something in the next year to up grade it. I have seen ton of older cnc mills sell for cheap even when they are very low hour machines, from what I can figure is they didnt know how to run it and let it set for decades and them got modern ones to replace the old ones that no one knew how to run.
03-01-2011, 06:57 AM #12
I bought and old 4 axis cnc knee mill for scrap prices and converted it to mach3 for under $2k. Used the old servos and ballscrews.
03-01-2011, 07:43 AM #13
I have a Hurco KM3p looks like new. Bad servo control board. Cost as much to keep fixing it as a retro costs.
Bought it real cheap.
How's everything going? Is there anything you would do different?
I am waiting on Larken to come out with the "new improved" Viper 200 drives. Supposed to be ready in 2 weeks.
03-01-2011, 09:08 AM #14
:: CNC4PC :: iNtRo and there's a link from there back to the mfgr's page where you can look at the specs. About $180 for a drive rated 35 amps and 160 volts. Macona may know more about them since he seems to be very knowledgable on these sorts of things.
03-01-2011, 10:06 AM #15
I had a bridgeport V2xt, boss 3 axis control. Iron and ball screws in as new condition. I spent 1000s on the control and servo motors over the 3 years I used the old control. In the end I just gave upon it and replaced it with a centroid control. The kit came with all the electrical parts except the spindle motor and the limit switches. I put it on, it was easy, 1 day, the only thing I had to make was adaptor plates for the axis drive motors. Bill Meyers, from cnc services east (724 622 5661) stoped by and got it going. He was amazed at how tight the iron was. He said the ball screws were as tight as any new ones. It was less than 1/2 the cost of a new cnc knee mill from MSC. The centroid control is super easy to program, for what I do the machine is fine
03-01-2011, 01:52 PM #16
I looked at the Dugongs a few eeks ago and they were out of stock @ cncdrive.com.
Now I see that CNC4PC has them. They also have a breakout board that connects to the Dugongs with RJ45 connectors ( just a plain network patch cable).
I may have to see if Arturo @ CNC4PC has a package deal or something.
03-01-2011, 02:03 PM #17
The only thing I can think of that I would do different is buy the jog pendant during the initial wire-up.
03-01-2011, 02:16 PM #18
Someone e-mail me yesterday ( From the ZONE), and said:
"Since the new edition Viper is coming out, there would be bugs and glitches in the hardware & software, that might take a while to work out"
This has me thinking that it might take even longer to get it going.
03-01-2011, 03:37 PM #19
AJAX is the DIY version of the Centroid. Same hardware (same company) and you can upgrade to the Centroid software later if you want. I think it starts about $5000.
03-01-2011, 04:15 PM #20
Sorry, 15 minutes left in the shift and the engineer that totes the man-purse shows up and plays 20 questions. "Will you have problems getting the 6" round bar inside of the 7" square tube?" I don't think NASA has this cat on speed-dial.
I should have bought the pendant from Bob Campbell. Now I'm used to using the virtual pendent and will probably never upgrade. Also, some of the "canned" cycles in mach3 are pretty cool, I wish I had spent more time learning Mach3 at the start.
Larry at Larkin has been VERY good to me on that project. Call him and talk to him about your concerns. I'd buy from him again in a heartbeat.
Last edited by i_r_machinist; 03-01-2011 at 04:22 PM. Reason: didn't finish