CNC Mill Purchase advice

[sigipa]

Hello All,

I know this question has probably been ask before in various forms, but I was not able to find a post that really answered my needs.

I am looking to purchase a CNC Mill. My budget limit is 15K complete with all necessary items. I've been looking at both new and used machines, but I really have no idea what to look for. I was hoping some kind soul(s) on this forum could help.

I need a mill capable of doing mostly things related to computer case construction. Cutting holes for ports, drilling/tapping case screw holes, various mounting hardware. I guess most of the work would be done with 14-16ga sheet.

There is one exception to this. I have been hired to design and build some long range security cameras. There is a problem with people shooting at these units once their location is discovered. I want to build a stainless steel housing out of 1/2" stainless steel plate. There would be 3 pieces of plate that would form the bottom and sides of a rectangular box. I would need to be able to cut holes for stepper motors, cables, mounts, etc. I also want to bevel the edges of each plate.

I have absolutely no exprerience with any kind of metal working. I am a software developer by trade. I have done a bit of work with embedded devices.

I could really use some advice on the following items:


1. Am I crazy to attempt this project?
2. What are the best machine choices for this application?
3. What is the best software to use?
4. Is their a reputable source for used machines?
5. What are the other 5 million questions I should be asking?

Thanks,
-S

[Zumba]

No metalworking experience? Don't even think about buying a used machine. It'll be like buying an airplane without having ever set foot in the cockpit of one. The salesman will shaft you badly. You'd do yourself a huge favor by first signing up for a machine shop basics class at a local community college.

It sounds to me like you're doing this solely for work, not for personal enjoyment. I'll tell you right away that teaching yourself to become a machinist is very difficult. You'll run into tons of obstacles and the only thing that'll get you past them is passion for machining. Some people have it in them, some people don't.

I have a friend who wanted to join me in my business ventures. Rather than getting into a long drawn-out debate regarding his potential skills, I lent him the first four DVDs of my 14-DVD machine shop training video set... about 30 hours of video total. He couldn't get past the first disc. Too boring for him. Wanna take a guess as to whether he's working with me or not?

[Pres]

Based upon what you described, it seems like you need to be looking for sheet metal machinery - Not a milling machine!
(more like a CNC punch press?)

[StealthDumpKits]

1/2" stainless plate? You trying to stop .50 cal AP rounds?

[sigipa]

Hello All,

Thanks for the feedback. First off let me answer your responses.

Zumba: I was looking at the Tormach, I have ordered some DVDs.

Pres: I have modified my design such that the 1/2" plate does not need milling. I'm going to build a simple box like housing for the internals and drop that into an 18ga stainless enclosure. You are right, at this point I'm looking at a CNC plasma cutter instead of a mill.

StealthDumpKits: We did some testing at 50yds with a 300 win mag. We are not only concerned about penetration, but enough denting that could shatter the lens and the 300 did do that to thinner material. Lenses are 15k each. We feel it would be better to be safe than sorry

So.. as I said previously, I've been looking at a CNC plasma cutter. More specifically I've been looking at Torchmate and Dynatorch. I do have a couple of questions now about that.

1. When stainless is cut with a plasma cutter, does it cause any discoloration in the metal?

2. Can the stainless be finished somehow after cutting this way?

3. I was looking at the Hypertherm 1250 for a cutter. Could anyone comment on it as being a reasonable choice?

My equipment list at this point consists of:

CNC plasma cutter
48" Box/Pan Brake
Drill Press
Tap and Die set
Bench Grinder
Various handtools

Thanks again for your time and interest,
-S

[StealthDumpKits]

1. When stainless is cut with a plasma cutter, does it cause any discoloration in the metal?
A. Yes

2. Can the stainless be finished somehow after cutting this way?
A. I'd suggest sand blasting then powder coating rather than natural stainless finish. Try to pick flat non-reflective colors the same as the environment it's mounted near for camo.

3. I was looking at the Hypertherm 1250 for a cutter. Could anyone comment on it as being a reasonable choice?
A..I like my Hypertherm.

Rather than make a huge investment in equipment, not to mention learning curve, why not sub out the plasma profiling and bending? I have a good low cost source for both in Virginia. Great turnaround time too, usually next day, three at latest. His plasma cutter cost around $79K with very large table and 200+ amp output, also has two oxy-fuel heads.

Couple more items you might need:
Air compressor for the plasma machine, air powered tooling like die grinders.
Free standing belt/disk sander
Electric angle grinder
Manual mill/drill with vise, clamps and tooling.

[DareBee]

Fabrication of computer cases to put on the market - is seriously difficult business.
Punching and forming of sheet metal is best done in a CNC Fabricator - this machine will be less than 1/4 the time to make a case than plasma & forming as well as better quality.

If you are just doing prototyping or making a couple of boxes to play with the plasma is ok but you will still need a press brake (and dies) to do all the forming.

[NinerSevenTango]

You never mentioned what kind of quantities you need to produce, or how many hours you want to devote to this.

More than anything else, this will determine what kind of equipment you need.

I have a Tormach, and it is capable of doing the things you need. But getting things done quickly is another whole deal.

You could also look at waterjet cutting.

--97T--

[Zumba]

For the camera bodies, what quantity do you need? If someone asked me to make one, I'd use a solid round piece of stock and turn it on a manual lathe. Making thick boxes with plate steel is a royal PITA in comparison.

[wizard]

A couple of things that may apply.

1.
The stainless will likely need passivation after handling / forming.

2.
As others have pointed out it sounds more like you are in need of a sheet metal shop than a mill. The only exception I can see would be the construction of very small lot sizes of industrial or military computer enclosures. Even then we would be talking about heavier walled enclosures where a mill could be used effectively.

3.
Others have also pointed out that a water jet is the way to go. For the types of projects you are describing, where I expect that looks mean something, a water jet will get you there faster. For the very small lots you are talking about you could just have a shop cut and bend the stainless.

4.
You may be able to get away from the stainless if you can source some ballistic armor plate. I really don't see how this will solve any problems though as anybody that has a problem penetrating the plate can simply wait for the lens to come into view. As you note you don't even have to hit the lens square. In the end it really sounds like your client needs another solution.

Dave

[NC Cams]

Between lazer and/or water jet cutting, you'd be hard pressed to facilitize your shop and do it as inexpensively.

Farm out the cutting and welding until/unless you plan to make LOTS of them and/or do other fabrication of a like manner. You can probably have a local welder join the parts together for starters and avoid that start-up expense.

The hardware alone (brakes, mill, saws, welder, cutting tools, screwed up parts) could EASILY use up a year's worth of profit - if you're only making a few, you'll NEVER recover the start-up costs alone yet make any money.

Now, if you're trying to do this to buy some "toys" that you "really need", that's a whole another story altogether.