Milling - Longitudinal Traverse

I am wanting to buy a milling machine and I'm looking at the Warco VMC Turret Mill. Whilst most of what I want to do will be within its longitudinal/cross traverse capabilities (370mm x 152mm) some will not be. How practical is it to stop & move the position of a piece during milling to allow a longer piece to be worked and can an acceptable finish & accuracy be achieved doing this?

Ian R

Ian,

"Possible, but very tricky" would be my opinion.

Just how tricky will depend upon

1. The acceptable accuracy
2. The shape of the workpiece
3. How it is clamped
4. The meauring equipment that you use

If [for example] you are milling a flat edge, and a 0.1mm step would be acceptable; then it's relatively easy. But if you need 0.01mm; then you will soon be wishing for the long table !!

Could you please let us have some indication of what the oversize workpieces might be. ... Then I'm sure you will get plenty of good advice.

MichaelG.

P.S. Welcome aboard!

Ian,

Perfectly possible; here's a picture of the rear wheel rims for my traction engines being machined to width in stages:

The rims are a bit over 6 feet in length, while the milling machine table is 4 foot, with 790mm of travel. I also machined a V-groove down the middle of each rim using the same clamp and shift routine.

I have machined parts on my CNC mill that exceed the table travels. With careful jig design, tool setting and attention to cleanliness, ie, no trapped swarf, it was possible to achieve sizes appropriate to the accuracy of my machine, about ±0.03mm.

Of course, as we all know, bigger is better, but that will depend upon budget and space.

Regards,

Andrew

Tap tennon blocks into the Tee nut slots and simply advance the work piece along the table, ensuring that the job is tight against the tennons when re-clamping

Firstly, thank you for the replies to date - much appreciated.

Milling flat edges and longitudinal slots [round and square] on [say] 1200mm lengths of Mild Steel/Stainless Steel/Aluminium flat. Milling a 1200mm long rack. Being flat, the pieces should be easy to clamp and advance against guides but will simply stopping and starting show in a milled face? A good visual finish will be needed for many pieces - which includes aluminium parts that are to be anodised.

Ian

I'm not sure a milled finish will ever be the best for anodising; it therefore could be worth taping a large sheet of very fine silicon carbide paper to the bench and cleaning up the surface on that. This should remove any very minor discontinuity mark on the finish. Won't remove a palpable step, but with care you shouldn't get that.

David

Ian, all what you want to do is possible with care! I found It is best if you can do a portion of the workpiece and then swivel the turret so you can machine another portion etc, but of course sliding the workpiece will work also. If you want a machine that has 1200mm of X travel you are looking at a serious piece of kit.

Tony