Help choosing a precission CNC router for aluminium

[erdabyz]

Hello,

I work for a research group in microwave and RF structures and we design and manufacture complex pieces in different metals. We usually get them made at local machine shops and such. Recently we're working in a new and very promising research line with structures that require precisely cut aluminium sheets, and we're thinking about purchasing a CNC router to make them in-house. Its main task for the moment will be cutting aluminium sheet, no thicker than 5mm, and we require high precission and repeatability. Future usage could be 3D milling aluminium sheets or cutting plastics and fibrous materials (ceramic fiber composites, fiberglass composites and such), but it will mainly be used for metal. As for cutting size, 300x400x80mm or so is fine, even smaller would do.

These are our main constraints:
-Price below 5000€ incluing spindle
-Working area size about 300x400mm or so. Z travel above 50mm.
-As high precission and repeatability as possible (rigid sructure, low TIR collets...). Good mill tower to table paralellism very important.
-Compatible with standard mills (no need for auto tool changing, ER11 collet is fine)
-Available in distributors within the European Union

I've done some research and for now the best thing I've found is this:
https://www.cnc-step.de/en/cnc-router-machine/
Concretely the 400T model. However I'm not sure if the spindles they offer for it are any good or if there's any better alternative. Do you have any suggestion? Thanks in advance

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[ger21]

Imo, what you are describing that you need, and that 400T machine, are two completely different machines.

I'd consider the 400T a lightweight hobby grade machine for woodworking.
I'd be looking at a mill, but your budget may not allow it.

[Jim Dawson]

First you need to define what ''high precision and repeatability'' means to you. Is that +/- 1mm, 0.1mm, 0.01mm, or 0.001mm? Then you might look at the machines that the local machine shops are using to make parts for you. Buying a used milling machine might be the best way to proceed.

In looking at the specifications of the 400T, concider that the accuracy and repeatability are theoretical values based on the absolute specifications of the leadscrews and stepper motors. In actual practice, the accuracy will not meet those specifications.

[erdabyz]

First you need to define what ''high precision and repeatability'' means to you. Is that +/- 1mm, 0.1mm, 0.01mm, or 0.001mm? Then you might look at the machines that the local machine shops are using to make parts for you. Buying a used milling machine might be the best way to proceed.

In looking at the specifications of the 400T, concider that the accuracy and repeatability are theoretical values based on the absolute specifications of the leadscrews and stepper motors. In actual practice, the accuracy will not meet those specifications.

Well, some of the stuff we do requires single-digit micron machining accuracy, but those jobs are always sent to professional machine shops. For the stuff we would like to do witht this machine, 0.05mm or so would suffice I think. The whole idea behind purchasing this machine is that we need aluminium sheets cut to size and with internal cuts and drills to support 3D printed structures. It's only a 2D machining job and we are trying to see if we can get both a suitable 3D printer and something to machine the aluminium sheet for a low enough price to make sense for us to have. I mean, the stuff we design for this paricular project is very cheap to manufacture but it's something innovative and we're making many prototipes, so we though it might make sense to be able to manufacture it ourselves if the machines are cheap enough. So let me rephrase my question,

Does a 400T or similar sort of machine suffice for 2D machining aluminium (say an easy to machine alloy) with good precission or are we going to waste money? The only reason to try to manufacture this ourselves is for prototyping cycle time reduction.

I'm actually not involved a lot in that particular project, I happen to be the guy who has a chinese CNC3040 machine that happens to know a forum with people that know a lot about machining. I'm going to ask my colleagues about the accuracy/precission they actually need and give you more proper information.

[ger21]

This type of question comes up weekly here, and is almost impossible to answer.

The answer depends entirely on your expectations, regarding cut times, finish quality, and final precision.

Just about any machine can cut aluminum plates, into just about any shape. The difference between a $500 machine and a $500,000 machine is cycle times, finish quality, and precision.

What's acceptable for one person, won't be for another.

While I know that things are much more expensive in Europe, I wouldn't spend that kind of money on a machi8ne that uses bronze bushings for linear motion, and has a Kress "spindle". You'd likely be replacing the Kress rather soon, and I'm not sure that machine can handle a larger, more suitable spindle?

[erdabyz]

This type of question comes up weekly here, and is almost impossible to answer.

The answer depends entirely on your expectations, regarding cut times, finish quality, and final precision.

Just about any machine can cut aluminum plates, into just about any shape. The difference between a $500 machine and a $500,000 machine is cycle times, finish quality, and precision.

What's acceptable for one person, won't be for another.

While I know that things are much more expensive in Europe, I wouldn't spend that kind of money on a machi8ne that uses bronze bushings for linear motion, and has a Kress "spindle". You'd likely be replacing the Kress rather soon, and I'm not sure that machine can handle a larger, more suitable spindle?

But you were very helpful, at least now I know that bronze bushings aren't the best and I confirm my suspicion about the kress spindle, which I wasn't going to use anyway because it doesn't seem to have speed adjustment. Let me again rephrase my question. What are the features I need to check for to see if a machine is any good or a toy? Now that I look closely at the 400T, some things look better on my CNC3040 than on it. My CNC3040 uses ball bearings for linear motion with dust seals and has thicker aluminium overall, looking more solid. I opened this thread to see if someone could point me to a good and dependable european manufacturer/distributor of CNC routers suitable for aluminium.