knee mill vs bed mill, brimingham, enco, jet other

[allenpnx]

Hoping to get a little guidance.

We produce an optical glass material from which we sell round blanks (diameter and thickness). We presently use an acramil knee mill with an old anilam CNC. We use core drills to core from 24" x 12" plates of our material. Our CNC programs are very simple drilling programs -drill depths .25" -1". Exisitng setup works well, but the machines are old and failing.

We need machines that can run 16 hours a day -yes that is a lot of cores.

Is a bed mill better for us than a knee mill?

How is the reliability and accuracy of any of these machines or any other recommendations brimingham, enco, jet ? Can they run up to 16 hrs/day?

Thanks for any insight you can provide.

Steve

[ironDigit]

any mill can be ran 16hrs. a day ,leaving the question of "how may days'" do you want it to run ?

thats why all/most all established machinetoolbuilders quote their maintenance/lasting? periods in hrs(sometimes couple a million hrs) and you can use your hrs. as you wish.

but i guess if you replace this puppy by something like a haas ,hurco , MORI SEIKI it won't be running no 16hrs. a day to keep up anyway.

almost forgat that if you aren't machining heavyweight workpieces a bedmill is the way to go since a knee will slow you down.

i prefer x-y bed and Z on the bridge.

[davo727]

Hi, Knee mill design is from 1938. OK for hobby use now but not modern production. Here are some trak bed mills.






http://www.southwesternindustries.co...bedmills.shtml

[NC Cams]

With todays equpment, you might be better off with a VMC.

The speed and accuracy of the VMC's are phenomenal. The controls. too have GREATLY improved.

Example: Haas TM1's offer VMC control in what is/was essentially a small machining center.

Before I bought a machine based upon a preconcieved notion, I'd look long and hard at what/s out there. You might find something with a bit more capacity and capability in a more friendly package.... Especiallly one that can be programmed to run by itself as can be done with a VMC.

[toastydeath]

A VMC is certainly more versatile, but it's going to be hard to beat the cost effectiveness of a cheap knee mill if you're only drilling 1" deep holes. That's quill turf, and you're never going to touch the knee if it's a dedicated machine.

If that one machine is serving you well and you don't see a need for tremendously increased volume in the near future, sticking with a couple of those machines is fine.

However, if you have a need for increased production, I see two options:

You could look at a used HMC (horizontal machining center). They can be had with multiple pallets (a table) that swap out. You load your parts on a cube, and it can machine four groups of material at once - one for each side of the tombstone (what they call the workholding cube). Since the tables swap, the spindle is always cutting even when the operator is loading the machine. If you use something like double sided tape to keep the glass on the tombstone , the cores shouldn't fall out until you go to unload the pallet and pull them off forcibly. They can be had with anywhere from two pallets on up, so you can load a batch of glass up before the 2nd shift leaves and have a full 24 hours of production if you buy a machine with multiple pallets.

The other option is something like a converted CNC planer mill or maybe a CNC router. Huge worktable is the main feature for both. Routers usually have a high speed spindle and a 4'x8' table, meant to hold sheets of wood or aluminum. A planer mill is a whole different, bigger beast. Common workspace sizes are something like 40" to 80" wide, 14' to 30' long. They're planers converted over to mills, so many of them use bridgeport heads - exactly what you use right now, except with a massive table.