Was looking at the Replacing the bed thread ( Replacing the Nomad bed ) , and was wondering as I looked at it whether this is designed only for engraving something on top of material, or also for cutting a shape out of material, all the way through. You’d have to be VERY precise about zeroing if it was cutting out a waterline shape, no? Can you guys give examples of what you’re planning on doing with the new bed?
What are we planning to do with the replacement bed? ANYTHING!
Using spoiler board is entirely up to the machinist. If one KNOWS that the mill is trammed (square) to the bed and KNOWS that the work at hand will never near the bed, no spoiler board is necessary.
If the machinist KNOWS that the mill is trammed and the work can be done using a vise or fixture that is known to be square and accurate/precision (e.g. parallels inserted into a trusted vise) and KNOWS the work will not hit the vise/fixture, no spoiler board is necessary.
If the bed is suspect (or known to be not) square to the machine (as is the case with the Nomad), one puts down a piece of spoiler board and mills it flat to the bed. Now the top of the work surface is known to be flat and square to the machine with a high degree of accuracy and precision.
If the work requires milling through the stock (e.g. drills, ball end end mills, square end end mills used in place of drills) then one MUST have a spoiler to prevent damaging the bed. The Nomad may not have an expensive bed but some mills have large beds that are square and flat to less than 0.0001". Touch that with a milling tool and you’re in serious (and expensive) trouble!
For safety’s sake it is common to ALWAYS have a piece of spoiler board. I do. YMMV.
With a sea-of-holes, the spoiler board is usually cut to the size of your stock.
A) Fixture the stock, milll it flat.
There usually isn’t a semi-permanent spoiler board. A spoiler board is made to fit for the job at
hand, even if it is for a multi-piece job.
The sea-of-holes makes it trivial to grab the spoiler and hold it. One can even cut holes in the
spoiler to fix it (via recessed nylon screws; recommended so a collision - if it happens - isn’t too
Another reason for working this way is the spoiler board materials VIBRATE. They swell,
expand and contract unevenly with humidity and temperature changes. Make the spoiler board on
the spot ensures the best possible accuracy and precision.
The Nomad is a too underpowered for a face mill (rapid flat making tool) but a fly cutter is available
(externally) and should make quick work of milling a spoiler board.
B) Fixture (clamp) the stock AND spoiler and begin the work at hand.
For things like engraving, tape and wax can affix material to the spoiler board. IMHO those are necessary evils, things to be avoided at all costs. I HATE gumming up my expensive end mills! YMMV.
I have an extensive number of fixturing mechanisms - pins, clamps, compressors, vacuum hold (not for the Nomad), pushers, pullers, and such - and can usually find a way to “make it work” without tape or wax. Have a safe place to keep them; start/continue your collection today!
The beauty of a sea of holes is that one can use available fixtures and adjust to their task (via hole choice); make what you need to fill in the gaps. It’s no big deal to machine a custom fixture for a complex or repetitive job - especially if you can’t find it commercially or it is outside your budget - you’ve got a CNC machine!
I don’t think I would ever machine on my nomad without a spoil board. I actually like to cut .01 through my material so I get a nice clean edge on the bottom of my wooden teethers.
Also, the million hole bed means you can use a spoil board that is the same size as your stock. So you can cut something to your needs, and just put a little piece under whatever you’re cutting.
By-the-by, there is an old standby used when working wood that may be useful when one has a machined spoiler board. It helps prolong the life of a spoiler board by reducing the number of times one has to machine it.
Set your CAM with Z0 on the bottom of your object. Now put two pieces of paper on the (machined flat) spoiler board and do a Z0 touch off on the paper. Make sure that the paper can just barely move without tearing.
Now machine as normal. Holes are made using square end end mils… let the machine do the work.
The physical, machine Z0 is shifted by ~3-5 mills off the spoiler board (more than the uncertainty of the CNC machine/Mill). When the work is done, what’s left is “onion skin” - a wood layer so thin one can often see through it - that can be removed with your finger.
Your spoiler board should never have been touched. YMMV.