One of the first things I realized after the machine started cutting was the amount of mess created.  Chips were not only flying around the shop but creating a major problem by littering the table X-axis rails and ball screw.  In this post I’ll describe my recent addition to my router by detailing the machine enclosure.  I’ll start with the list of requirement, get into the design, pics and video of build, and then offer some alternatives which I investigated along the way.  "Enclosure" is a term used loosely here as you'll see it's not your typical containment box approach.

Requirements: 

• Material removal is aluminum, therefore I can't simply do a dust boot.  BUT design should allow for the addition of a dust boot in the future.
• Enclosure should not contain/restrict the chips into a small area around the cutter.  
• Work area must be visible at all times from in front of the gantry and both sides of machine.  I need to be able to see what's going on and want the ability to take pictures/video during cuts when guarding is in place.
• Must not restrict FULL access to the table for part loading/unloading operation.  Quick removal can be an option here but best is to have full access to table without removing anything.
• Protect the linear rails and screws from contaminant during ALL cutting situations and cleanup activities.  "ALL" is a key point here and you'll see how this drove different design approaches combined together.  
• Enclosure should not prevent quick cleanup of area INCLUDING some in-process shop vac or compressed air use during the cut.  Quick removable partitions for access is an option here.
• Provide some level of protection from broken bits flying off.
• Can not restrict current cutting footprint.  ie - I considered simply boxing in the cutting table with ~4" side shields on the ends but this would take away from the available table length for mounting (along with create a nuisance for part loading)
• Should not extend current router footprint.  ie - I considered extending bellows or guards to the end of the table to protect linear rails and screws but this would result in a larger shop footprint required during the table end of stroke.

OK ... enough of that.  It's just that this list proved extremely helpful for me to write down as I found myself struggling to come up with a sufficient design for my specific router build.

Design Details:
Below you'll see the complete CAD design.  It's a bit unconventional for a "Machine Enclosure" as it's split into a combination of multiple approaches.  The design can be broken down into three main sections:  1) The 'conveyor' protection for the table linear rails and ball screw, 2) The rear guard/shielding, and 3) The front/spindle shields.

"Conveyor" Protection
The protection for the X-axis Table is the odd ball design here.  I haven't seen this approach used yet and as I write this post, although I'm parts complete and ready to assemble, I've yet to verified it works (fingers crossed).  .... well, just ran the table with conveyor attached - works much better than expected for first try.  Will post a video at the end of this post - kinda cool.  

You may say, "why not just mount 4 walls directly to the moving table"....  First, the Y-axis gantry motion is allowed to move the spindle beyond the extent of the table which would then crash into the side walls.  Ok, then make the side walls static by attaching them to the base and only attach the end walls to the moving table.  I played around with this design for awhile but the drawbacks were.. a) obstructed part loading with the walls, b) used more material $ then the 'conveyor' approach, c) I didn't think I'd like the looks of the end wall on the table moving around, d) I didn't really think it wise to mount any guarding to the moving parts.

So the result is a 'conveyor' design using.... ready for it.... PVC schedule 40 pipe and a window shade.  A 1-1/2" PVC section makes up the two end rollers and are mounted to the base table.  They don't actual roll but I'm expecting the window shade to slide freely over the PVC.  As my linear rails on the X-axis table extend about 1" over the extent of the table (I was trying to utilize every last bit of material to maximize stroke), I needed to make some cutouts for the rail and truck to move to the end position.  I think the roller end position will actually 'clean up' the visual appearance of the table end.  A 1" PVC section is then 'slipped' into position utilizing a slot in the PVC together with the Base 1/4" leg sections.  I'm expecting this sudo-mount to be enough to retain the 1" PVC in place (again does not 'roll').  As for the conveyor material, I simply had the hardware store cut a cheap $10 window shade to width and will attach 2 pieces to each end of the moving table, wrap around the rollers, and connect them with a spring for tension.  Four (or more) things can go wrong here.... 1) acceleration of the table causes the conveyor belt to buckle and flap enough to cause issues, 2) the conveyor does not ride straight and possible slips off one side, 3) the tension of the belt causes too much friction between the PVC and window shade, 4) the window shade material does not hold up to the abuse from aluminum chips and continuous rolling back and forth.  Time will tell.

Below are some more details of the CAD design for the conveyor.​

Rear guard/shielding
The rear guard is a nylon conveyor stip brush (74405T9) from McMaster Carr with a compatible holder (8813T52).  I'm not concerned about visual in the rear so decided to try a brush.  It's a 4" long 3/16" width with diameter 0.014" general purpose nylon bristles.  It's a bit stiff and I'd probably choose the 0.010" diameter if done again.  Mounting is simply to the backside of the uprights and allows 2 positions of mounting, one which allows brush to lay flush with table and another 3/4" up to accommodate a thick spoiler board.  The bristles will allow about 1/2" part interference to go thru the entire length ok but any higher than this and I think it may bend the aluminum mounting strip.  So it will probably allow a 2" tall part at a reduced width (~4") thru without issue as the overall force from the bristles will not come from the entire length.  

Front/spindle shields
The front shields are made up of Impact-Resistant 1/4" Polycarbonate sheet (8574K43 - blue in pics) & 0.04" thick Chemical-Resistant PVC Type I Film (87875K61 - yellow in pics) both from McMaster-Carr.  The side shields have 4 magnets bonded in to allow mounting to the steel upright and post and allow quick removal.  It also has a cutout where a single piece of film is bonded which allows the spindle to pass.  The main front shield film is mounted to a 3/8" rod which is then attached to a vertical 1"-3/8" post mounted into the table with a 3/8" universal clamp to allow adjustment and quick removal. I should be able to remove all the front shields in <30 seconds for cleanup etc.

Below slideshow has some pics of the final results and in process manufacturing ....... and below that is a youtube video of the 'conveyor' in action.

Update 4/1/2016:
I have cut multiple parts and below is some observations and things I might change if doing again.

•  One benefit which was a pleasant surprise was that I can loosen one of the universal post connection, lift off, and simply pivot it out of the way and the opposite post keeps the rod and film hanging in the air in any position - gives full table access very quickly.  
  
• The thin 0.005" window shade is holding up very well and moving great along the rollers.  When I do eventually replace due to wear I will go with thicker 0.012" but still simply buy a window shade.  I've looked at all kinds of "professional" film/conveyor material and just can't justify anything which cost more as the shade does a fine job for cheap.
• The location of the side shields and front plastic guard is a bit too close to the spindle - I'll likely re-position to allow some more room.
• The gantry rails and ball screw are still getting some aluminum chips flying up onto them - not too much but enough to drive me crazy.  I will likely add a strip of the plastic film around the spindle mount plate which hangs down about 1-2" to try to contain this issue.  Kind of a partial boot.
• During cuts chips were being contained well with the guards but a considerable amount of chips were migrating below the cutting table and collecting very near the linear rails mounted to the base.  I solved this by adding two aluminum angles along the length of the base which completely enclose the rails.  This can be seen in some of the photos.

Added a Mist Coolant system:
I absolutely needed to add a mist system - spraying wd-40 from a can was not fun.  I just happened to have purchased 2 Wesco mist systems at an auction some time ago on the cheap to I went about to use as much hardware as possible from one of these units to make a custom mist to fit my router build.  
The Wesco mist unit works by delivering compressed air and mist to the nozzle tip with two small separate tubes which run through the braided sleeve.  The mist is then mixed with compressed air only after it exits the nozzle tip - this can be seen in photo below - focus on the brass tip end of the nozzle.  A flow valve controls both compressed air and fluid independently with a manifold block which I mounted onto the z-axis.  The close proximity of this flow manifold to the exit nozzle allows fast response to flow changes.  
To position the nozzle I opted for a small Noga model NF1033 articulated holder which has 51mm and 56mm arms.  At $75 bucks this is not a very economical solution for holding a mist nozzle but I've wanted to pick up one of these small Noga arms for the shop anyway, so "two birds".  The unit comes with a 360 deg fine adjustment base attached with a dovetail to a permanent magnet which is all removed to expose a simple M6 thread to mount directly to the spindle column mounting bracket on the router.  The NF1033 also comes with a 3/8" clamp holder on the business end which fits the Wesco misting nozzle perfectly.
Below are some in photos showing the original Wesco mist unit and the modifications to adapt this to the router.

The articulating arm of course moves the nozzle into position with ease and locks to exact location.  The reach of the arm allows the nozzle to be located around the spindle about 270.  I opted to replace the original Wesco SS coolant tank with a simply 2 liter plastic bottle which is located on the base and out of sight behind the gantry. The elevation of the coolant for this style mist unit must be below the nozzle outlet to avoid dripping when compressed air is removed and I also found that placing the tank too far below the nozzle (on the floor of the base) created too much lag time to get the mist flowing and operation was sporadic. 

This post will not be about the electrical details of home and limit switches but rather on my choice of hardware and how I incorporated them into my fixed gantry design.  Due to lack of experience in limit switches and the unknown accuracy they give for repeatable home position I decided to include in the X & Y axis both a set of limits and a separate (more expensive) home switch.  An overview of the added hardware and location is shown in the below CAD picture.  Note that v03 on the download page now includes this design. ​

The Y-axis gantry limit switches are button depress style switches from CNTD, model #CZ-7110.  I chose this style due to the lack of space between the Z-Axis assembly and the gantry rails for a toggle style and the fact that I could 'hide' the entire switch inside the gantry rectangular beam.  The button of the switch is the only part exposed into the moving path of the Y axis gantry and is actuated by a toggle ramp mounted to the back side of the rear z-axis plate.  One drawback is the limited adjustability of the switch location due to the hole restriction in the tubing; therefore, adjustment is made by carefully locating the elevation of the button to the toggle ramp. ​

The home switches are higher quality precision contact switches purchased from Misumi (model #MSTKD-EL) at a cost of $60 each.  I wasn't certain of the repeatability of the cheaper limit switches (~$7) so decided to use both on the X & Y axis and compare them.  The home switches are mounted onto a simple mount made from 1" steel round machined to include both the switch and a stop screw to insure I don't damage these expensive units.  Unfortunately at this time Mach4 together with my ESS (smoothstepper controller) does not fully function with both home and limit switches so I've yet to have a comparison for you - I'll update when software is fixed.  At this point the limit switches seem to be very repeatable leading me to believe I don't need the separate home switch.

You'll notice that the home switch (and one limit which currently acts as home) is located directly at the fixed end of the ball screw.  This is because the ball screw incurs significant thermal expansion in operation therefore for the most precise repeatability is obtained at the fixed end of the screw shaft.  I was surprised to learn that ball screws typically see about 2-5 deg C thermal change in operation and this results in an expansion of 0.02-0.06 mm (0.0008-0.0023") at my maximum extended position.  Also of interest is that precision machines avoid this thermal error by 'stretching' the ball screw to the estimated maximum displacement from the thermal expansion and fixing both sides of the screw shaft.  This shaft now loaded in tension will simply reduce the tension load as the temperature increases and have zero overall length change due to thermal expansion.  They also adjust for that stretch of the shaft by manufacturing the pitch to incorporate that stretch... Neat!  They talk about how to load the shaft in tension preload and set into the fixed ends but I was discussing this with a colleague and we came up with a simpler (more diy) approach.... all you have to do is heat the shaft to a set temperature (maximum expected) and then mount 'hot' into the fixed ends and when it goes back down to 'shop' temperature it will be in tension.  Just need to make sure your end supports are directly connected together with a stiff enough connection to accommodate the tension load.  Oh and then have a special pitch manufactured.... ok, definitely not a diy item typically considered.
 
Some pictures below of the manufacturing and build (slideshow format)
Cheers.