Step 4 Router and Brass

I have a rarely used Step 4 540 router on Mach 3 with the standard Proxxon spindle. Used only occasionally on wood and plastic thus far. I have a fancy to use it to machine some brass model plaques and logo`s.
Before I break it trying!! Has anyone tried it on brass. Slow feed/high speed minimal stepover approach presumably?
Also have a larger Kress spindle. But it looks a bit large for the 540. Anybody fitted one please.
Would really like to make more use of this machine. Your experience appreciated.

Proxxon will engrave brass, but sooner or later the bearings will give up. It also tends to get rather hot at high RPM if you run a long gcode. However it is a cheap solution for a tiny spindle situation.

Kress will engrave brass without any problems at the extra price and weight.

Thanks for reply. Have experimented a little without problems, except as you suggest, the spindle gets quite warm. Since the process time is not important. I will interrupt the program every 20 mins or so to cool. Additionally I will air cool it with comp. air and some cardboard ducting to both cool and blow swarf.. So still working round it.
Going to finish mount for the Kress today.Will see what the little servo`s think of it.
Hopefully I can get some more use from the machine in future

Could you post a link about the router you are going to mount the Kress on?

It is a small Step 4 540 Basic. Do you want further info? I have first part of Kress bracket. Need to make an adapter plate to complete.

Well, according to the photo I found after searching the name of the router, the manufacturer shows it with a Kress mounted on it already. So I expect it should handle the weight of the Kress just fine.
(en.step-four.at/hp2/index.php?action=1482)

Aha! I have never noticed that! I even have that sheet pinned on the workshop wall! So need no more reassurance. Thank you!

Mine is an older machine and was fitted with the small Proxxon as standard. I bought this machine a while back and have not given it much attention until now.

For the current version on their website, I see no spec about the stepper motors. They are also covered by a case, so I can't roughly estimate their capabilities upon their size either. However, it doesn't take a lot of torque to move the Kress around, I would rather worry about the deflection of the 16mm hanged rods instead. Since you already have Kress mount in production, the only way is forward :)

Hello again - Here is photo of the units. As you will observe. I doubt if this size Kress was ever standard on this machine.
But I stand to be informedhttp://www.mycncuk.com/attachment.ph...id=14464&stc=1

Well, your router looks different from what they show on their website at this moment. If those are 10mm smooth rods, there will be quite a lot of flex. Also, Nema17 in the 0.3Nm range I suppose, will have a hard time pushing it around. But like I said, since you are half-way through already, you will have to mount it even just to check how well/bad your axes coop with the Kress weight.

The rods are 12mm dia. I have lightly clamped the Kress to the head and it runs around nice and smoothly. I checked the central deflection on the rods and there is a "no cutting load" movement of 0,03 mm. For what I am doing I think it may stand a chance of being OK.
Will post again once cutting is possible.

Yes, unsupported rails will inevitably have a certain amount of deflection. If the engraving you are doing is rough enough to match those tolerances, it should be fine. Light cuts also reduce further deflection when the engraving bit will meet the workpiece.

If you have access to a decent lathe, you could craft yourself a spindle out of a brushless motor for engraving purposes.

The parts I want to make are for steam engine name plates. So no real tolerance problems. Although it will be interesting to see what it can hold. I will be working on plate sizes no more than 75x75 and will locate workpiece origin close to machine origin. This will also minimise the deflection
A brushless motor setup came with the machine. But although high speed it is not very robust. I never used it. Similarly it has a fairly professional looking vinyl cutting head also never used.

Probably a regular punch set would have been much easier for simple name plates :)

Unfortunately they are anything but simple. Some have 3D coat of arms and fancy foliate lettering.
Reproducing the original cast iron plates.

http://www.mycncuk.com/attachment.ph...id=14465&stc=1
A relativly simple one!!

Going for emboss will mean a lot of material removal, in contrast to engraving the letter path only. Also, the whole area removed will show the endmill paths, it is a natural aspect of milled surfaces.
The plate you showed is more suitable to casting, rather then milling. On the opposite side, if the surface was flat and the letter sunk into it, it was more suitable to engraving.