Update Feb 10, 2017
I remixed a version 2 see it here http://www.thingiverse.com/thing:2100690
Read the info here before looking at the new version I reference the ideas here.
Update Nov 15, 16
Thanks goes to doctorjay for remixing the project so that it fits the stock versions of the Robo3D. Here's the link http://www.thingiverse.com/thing:1892658
Update: 03 Feb 16
All up and running, turned out better than I expected! Fit is great and plastic stays in place extremely well. Note that I screwed the back side closed so the back does not open. I had those magnets left over from my 330mm bed upgrade and I dual purpose them for weights to hold the front plastic down, and it clings to the the two screws in the midway position for a "held open" state while working with the hot end. The pic with my finger in it is the "held open" shot. Start printing, it's now a proven project!!! Note: on drilling any plastic retaining holes, drill slow to avoid heat and you get the best holes. Extruded plastic balls up when it is heated, drills well when cool. When cutting the new threads, turn in....turn out,, repeat going farther each time. It avoids plastic cracking, splitting. recommended color is grey as it will mesh well with the color of the plastic. I used orange so that final pictures will be easy to see. Yes I will be dremel cutting off the screws later.
Update: 29 Jan 16
This worked well for me. But so good that the PLA pieces I used for my cable chain slightly melted and I had a mess created by a few uncoupled connectors. Glad I only had 10 PLA pieces and the rest were ABS. I'm reprinting chain links... argh. But hey the ABS piece I was printing at the time was WARP-Free!! and looking fantastic. I've removed "this is a work in progress" as I'm happy with the results thus far. It's time for the remixes or requests for change if you have ideas.
Printing with a .8mm nozzle rather than a .4mm does make the support removal a pain. Other wise a printing speed of 27 worked well. Printing faster causes rounding of the corners and makes fit bad.
I loved Mike's Acrylic enclosure but I wanted my extended bed more. That left me with no options for a heated chamber until now. With $6.76 in extruded plastic, Some clear plastic sheeting, you too can have the heated chamber you want even if you used my http://www.thingiverse.com/thing:1154745 "True 330mm Y rails upgrade". I'm using a 6mil clear plastic that I bought 100' of from Lowes (chain of US hardware stores) to put my hot tub in my basement.
People with stock beds:
If you have the standard stock bed (what's stopping you from upgrading????) you can still use this, you just need to shrink the length of the Extenders to shorten. I was making sure this works with stock the entire design time. If some one wants to help, I just need the full distance the fence should be to support the fully extended bed.
Instead of printing the 2 supports, you can cut a piece of wood (or dowel) and counter drill a pilot hole a tad smaller than 3mm to connect the sides together.
You MUST print solid (100% infill) to get the stability needed AND USE SUPPORTS for all prints except the Supports.
Printing with a .8mm nozzle I had issues with the supports as they were kinda hard to remove.
Comments, Comments..I want to hear what you think about this.