Machine for engraving brass

Hi,

New to this forum and CNC. I am looking at options for a CNC machine which I would like to use for engraving brass. Specifically it would be for clock and watch dials. The depth of the graving for me doesn't need to be very deep as I wax fill and silver the dials. The machine would be used for very low volumes of dials, but due to the nature of what I'm making I do seek very good accuracy and clean cuts; especially for watch dials. So I'd be etching anything between 30mm diameter to 300mm diameter.

I'm aiming at a budget of £1500 ideally (if realistic)!!!

Looking around ebay etc I can see lots of Chinese 6040 type machines such as this one:

https://www.ebay.co.uk/itm/3-4Axis-6...gsNXV_ZScwYOng

It certainly looks the part with ball screws to ensure accuracy etc. It also has the benefit of having a fairly large table.

Question is, will the machine be suitable for engraving brass? For the very best dials I'd be using CZ120.

Any thoughts would be appreciated. Also any ideas on alternative machines if I'm being unrealistic about these nice looking Chinese machines.

Thanks!

I've read a few other threads about this machine and it sounds like the supplied electronics (stepper drivers etc) are poor and would need replacing quite soon.

I have seen that the machine is available in a frame only option:

https://www.ebay.co.uk/itm/free-ship...kAAOSw52tbYXq-

Would this be a good starter for making my own machine, or are there better options? It comes with ball screws so at least feels like I might be able to make an accurate machine out of it.

Failing that are there better kit options or suggestions on parts suppliers for making my own machine.

Hi,

As you have started to find out these machines have lots of electronics issues. However, they also have mechanical issues that are less known.

Yes, they have ball-screws but how the ball-screws are connected to the machine is poor which defeats the point of ball-screws.
They mount them using non-angular contact bearings which are machined into the endplates(poorly) and allow the ball-screw to float. Which results in back-lash.
(Look closely at the pics and you'll see the bearings and single ordinary nut sticking thru gantry sides.)

There are other less than ideal design features like how the gantry flimsily fastens to bearings but they are not so much a problem as the ball-screws.

That said for occasional use in soft materials and learning these machines are Ok. But if you want high accuracy in harder materials like brass and prolong use then I'd give them a miss.

Unfortunately, while many low priced kits etc exist, none of them are any good or what I'd recommend to anyone wanting to cut anything harder than balsa wood or whipped cream.

Bottom line is that there isn't any machine out there at low price that is any good and thats simply because it's not financially possible. The only way you can have a Good and accurate machine at lowest price possible is to build it yourself.
Even then £1500 is very tight and will require you buying correct components from the right suppliers, most of who will be in China.
Then you need a good design and have the time, tools and skills to build it. Along with lots of research to fully understand what you're taking on and how the electronics etc impact the machine.

My advice (From helping many Chinese 6040 owners) is that if you don't want to undertake to build your own then don't buy one of these cheap machines and save up for the better machine. Either second hand or custom-built for you by someone like me or others on the forum. It will save you money and lots of frustration long term. (not to mention money in wasted Brass)

+1 on everything Jazz has said.

I've been engraving a bit of brass recently (pics attached below) - and you really do want something that's accurate and robust - particularly squareness and accuracy on the Z, as just a bit of variation can spoil the line (too thick or too thin). The good news is that you can build something that'll do the job at a decent price. It'll last you and you'll learn something and have fun in the making of it.

Wal.

Attachment 26653 Attachment 26652

Thanks for your replies - this is all good information which will save me wasting money on an inadequate tool; although it looks like I need to extend my budget.

In terms of sturdiness I had considered a machine like the Sieg SX3 Mill from ArcEuro Trade, but for my dial making needs it wouldn't be able to cut a large enough area. I'm looking to engrave items up to 300mm x 300mm.

Is there a potential machine/model make I should be looking at which might give me an idea of budget or ideas for a design to make one?

Wal, what machine have you used for your work above?

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Originally Posted by Wal

+1 on everything Jazz has said.

I've been engraving a bit of brass recently (pics attached below)

Wal.

Attachment 26653 Attachment 26652

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Nice work there pal (or should it be Wal? lol) - what sort of cutter did you use for that?

>Wal, what machine have you used for your work above?

This was done on my self built 3 axis mini mill - there's a bit more info on that here.

The fixed gantry design means you end up with a fairly big machine footprint for a relatively small work area, but you do get a bit of added rigidity on the Z. If I was making this again I'd change a couple of things which would drastically improve the design - 1. hi-win rails, 2. an assured way of mounting rails and bearings so that they're perpendicular on the opposing faces of the intermediate plate which carries the machine table, and 3. swapping bearings/rails on the machine table so that they resemble the way that the Z axis is configured (ie. machine table underside has the rails bolted to it and the bearing blocks are mounted to the intermediate plate..) Drop me a line if you'd like more detail - if you're near Stockport you're welcome to stop by for a look at my set up.

>what sort of cutter did you use for that?

Standard four flute carbide, 90 degree chamfer mill. The cheap engraving tools aren't sharp enough for this level of detail. I also tried the super sharp engraving tools that you can pick up for around £8 a go - a waste of time - the tips break off within seconds of starting the job..!

EDIT - in addition I also used a 0.6mm square end mill to clear the larger areas of the design.

Wal.

Maybe a mill supplemented by a 5th axis which is a rotary table would be a good approach. Mills normally have a good X travel but more limited Y travel which limits the size of dial you can do, but if you can rotate the dial most of the cutting could be kept withing the Y envelope while you rotate the dial blank to cover the full circumference.

It's only a 5th if there is a 4th too ;-)
A rotary table on a 3 axis mill is still a 4th, it's just it's the C Axis rather than the A Axis or B Axis :D

Oops! Can't count.

Quote:

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Originally Posted by JohnHaine

Maybe a mill supplemented by a 5th axis which is a rotary table would be a good approach. Mills normally have a good X travel but more limited Y travel which limits the size of dial you can do, but if you can rotate the dial most of the cutting could be kept withing the Y envelope while you rotate the dial blank to cover the full circumference.

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That would be a neat approach. Would you run into any difficulties/ limitations with configuring commonly used software going this way? (Obviously, anything's possible - just wondering how well this approach is supported..)