To retrofit or buy new?

[RP Designs]

I have been back and forth with this and am having a hard time deciding. I am looking to purchase my first CNC mill and am really torn. What I would really like is a VMC with a tool changer, but I do run into problems with machine height and garage door clearance and am generally concerned about the weight of a VMC on a residential concrete slab. On top of all that I tend to think that a VMC on my budget may be pretty well worn and I don't think I have the time, budget or experience to go through the machine thoroughly to get it into near new shape. So the VMC is a long shot unless someone can reassure me that if I shop well I can get an older machine that will be reliable, will work well, won't crush my concrete and can be fairly easily moved into my garage.

So my other choices are to just go ahead and purchase a hobbyist machine such as the Tormach PCNC, Michini Mech 1610L or CNC Masters Supra. Based on my research on this site it seems that the Tormach seems to have the most knowledge and reputation for customer support and product quality. The work envelope is decent and would most likely meet my needs I might like just a little more travel in the x direction. I can also get the 4th axis without great expense which is a plus to me.

Other than the hobbyist mills I have also been looking at used vertical mills and knee mills. I have been considering either trying to find an older machine in good shape and converting the controller to a newer PC based system. The advantage to this is that I can probably do this cheaper than the hobbyist machines listed above, but I haven't done this before so there is a bit of apprehension having never done this before. Since most of these machines tend to be 3 phase I would need to get a phase converter also but I could potentially get a bit more robust machine using servo's instead of steppers but it would be older. The maximum speeds seem to be a bit lower and I don't know how that will translate in terms of surface finish but I do get a bit more robust motor. I know there are quite a few people who have gone down the path of buying a used machine and done a retrofit or upgrade. Is it worth it to potentially save a few bucks? Will I end up with a better quality machine or should I just stick with something tried and tested?

[RP Designs]

Anyone have any insight they are willing to share?

[DSL PWR]

What is your budget?

[RP Designs]

around 10K

[Glacern]

Hey RP,

My response here is sort of along the same lines as my reply to the "CNC production lathe for $10,000 or under" thread in this same forum.

We've been building a bed mill that comes close to your requirements. Up until last night, we had not revealed any information, but we're far enough along the development process now that we can leak a few details.

The machine we're using as a starting point is a (new) 10x54 bed mill with Meehanite castings, made in Taiwan. Some details:

5hp, 40-taper spindle
3000 pounds
27" of Z-axis travel
AC servos
32mm ballscrews w/ double ground nuts (choice of rolled/ground screws)
Preloaded NSK Japan angular contact bearings for ballscrew support
Head will lower enough to slide under a garage door.

This particular machine will go over $10K. We've been thinking about bringing a knee mill to market as well that'll likely hit the $10K mark exactly. It would also be a 10x54 heavyweight but with an R8 spindle and 16" of Z-axis travel.

If you can wait a bit, we'll have photos and the final spec available in a month or two. Machines will be ready to buy in 3-6 months. This machine is further along in development than the lathe in the other thread.

Let me know what your thoughts are!

[mc-motorsports]

Originally Posted by Glacern Let me know what your thoughts are!

Leave the chineese junk in CHINA. Don't tell me your going to put a MADE IN THE USA sticker on it when your done.

That's my thoughts.

[integerspin]

I was looking at used bridgeport interacts, seemed better than cnc-ing my mill. One concern was getting it in the door. 69inches with the door open, that sounds wrong but it's not 79. Anyway low door.
Weight, I struggled moving my lathe, CVA like a monarch, so almost 2 tons [the big interact] sounded heavy.

But I really thought a bed mill would be better than a turret. I have an ajax turret mill and at the end of the day it's a wobbly thing if you try using a big cutter, the table postion isn't reliable if you alter knee height. Another concern was limited Y travel on a lot of the smaller machines, I make things now and again with a 12 bolt pattern set on 13.5 diameter, little interacts have ~12 inch Y travel.

Cut a long boring story short I bought a Matsuura on ebay for £500.
I phoned the company it belonged to and asked a machinist about it, he said it was a really well looked after machine bought in for a job that was fairly accurate. The machinists liked it but it was old and management bought them a nice new machine, that wasn't as reliable. He did say it looked pretty much like a new machine. I was amazed when it was delivered. it looked great. I think I had a result.

I would have used it, or at least tried, but it turned out to be a different model to the one I had all the details of from Matsuura, 3.7 tons instead of 2.3 and at least a foot bigger in all directions. So I stripped it for a refit, partly to save on space, justremoving the cabinets make it a lot smaller and to make it a bit more efficient[you should see the heat sinks on all the original electrics].

It was dropped on loose gravel drive and was a right git to get moving. Once on two lenghways scaffold tubes it was as easy to move as my lathe. Took me an afternoon to move it across the drive and rotate it and get it in my garage[inc the bit below].

Height. Well it would go under the door frame[with the door removed] if I removed everything from the columm and skated it with the base on the concrete. I decided it was far quicker to take a saw and chop a section out of the wooden frame above the door!

So what did I end up with. as far as I know a rigid machine with good condition box ways, large ball screws, big servos everything on it is really nice even the old switches and wireing are all good quality.
I haven't ordered my new drives yet but I will have it up and running for a lot less than I probably would have ended up paying for an interact on ebay.


The date is wrong that was taken last year just before I bought it
So all in if you can do the refit I would have thought an old vmc like this was a good starting point.

[helixcnc]

If you are looking for a mill in the 10K range check out a machine that I listed on ebay. It's a Bridgeport with a Centroid control. It's listed to buy it now at $16900. I was planning to accept an offer over $12000 but as time goes on I may go lower.

[Cartierusm]

integerspin, nice find 500 quid, sweet.

Personally with this economy and before it went tits up on craigslist you can find a ton of VMC for 10 or less, I'm not talking Hass VF3 but you can find some decent stuff or at least in my area.

[PhoenixMetal]

Just a little caveat for you if you do decide to go the route of a full on VMC... Unloading it into your garage just might be quite a bit more difficult and expensive then you expect. We recently purchased our first VMC, which we estimated weighed around 6,000 lbs or so. We have a 5,000 lb capacity forklift, but we figured we could lift it anyway (with some extra counterbalance weight on the forklift - its worked before). However, since VMS have a large enclosure surrounding them, this put the center of weight far out on the forks, and our forklift was not able to lift it. So then we tried out neighbor's nice new 6,000 lb forklift. Couldn't even budge it (our smaller, much older forklift was stronger - go figure!). Then we tried picking it up from both sides simultaneously (it was on a flatbed), however we couldn't get the forks to reach properly. In the end, we had to rent a 13,000 lb forklift to unload it - costing $900 for 20 minutes use.

Bottom line is, VMCs can be quite a bit more difficult to rig than most other machinery. So if you don't have access to a big forklift, and all the necessary rigging hardware to lift it safely (straps, chain, etc.), then go with a smaller machine or at least budget for the rigging costs.

Oh, and don't forget about the need for 3 phase power if you go with an industrial machine! You probably don't have that if this is a residential location where you are installing it!