I have read through a lot of the polymer concrete thread and have done searches but cannot come to a consensus as to if what I want to try will have a chance of working. I have read of other people wanting to do similar things as well as how machines used to be built using similar methods of casting concrete. The information might be here somewhere, vbut I cant seem to find exactly what I'm looking for.

I have a 4x4' Gerber router and want to start on a 4x8 (maybe a 5X8) self built machine. Being that I already have a router, I would like to utilize it for the new build. I could build a mdf router pretty easily but really need a machine that is more capable. Cost is a factor. I just looked into buying a Chinese machine but have decided that there was just too much risk in getting it here.... too many if's! I actually have a second build which is on the back burner, a cnc woodworking lathe using an old Hardringe lathe. I have a cabinet shop and am in the process of getting a semi custom product into stores that are mostly cnc'd. The 4x4 machine works great, but is a pain to have the limits less than the sheet stock being used. That and I am concerned about down time when the machine needs repair and would like some redundancy.

Here is what I propose:

The machine will be a moving Gantry router. I am better designing as I go with things so am just putting this together in my head right now before designing parts in Cad.

I would like to build a shell out of mdf, or more likely Extira board (if it remains permanent) so I can use the existing router to map everything out precisely. I would like to use this as a form to pour a fortified concrete (not polymer concrete). I would reinforce the concrete with both rods as well as tensioned cable as they do on bridges and decks, but on a much smaller scale. I did concrete work years back so have the concepts down for large scale stuff! I would like to do this for the gantry as well as beams to support the y axis. I could either remove the shell or keep it so the machine could be finished easily. I was thinking of embedding 80/20 t slotted beams into the concrete for not only a straight reference point to build from but for ease in assembly and adjustment during the final build. I've contemplated doing a build entirely out of 80/20, but feel it will not poses the build quality and rigidity I want. Overall the gantry would weigh between 375 and 450 lbs depending on the final design with a 5X10" main beam on the Gantry.

I want a heavy machine to cut down on vibration and increase rigidity over what most other methods people are using. I wont be rolling it around the shop! Though I cut mostly wood, I would like the ability to cut non-ferrous metals at a normal speed. High speed is nice, but I rarely cut at over 200 ipm as it is and am fine with that goal with the new machine with maybe 400 ipm rapids.

The Gerber I have is driven by 1" cog belts which work extremely well. After pricing them against rack and pinion, I find it is more cost effective and will make for a simpler build overall, so am leaning towards that and either a gear box or timing pulley system to get the best torque curve from the steppers.

What do you guys think about the direction I'm going with the concrete? Should it work?

Here are some links while reading various stuff trying to brainstorm I came up with this line of thinking:

Machines That Make | MtM | An MIT Center for Bits and Atoms Project

The Multimachine $150, 12" Swing, Metal Lathe/Mill/Drill

Looking forward to hearing your opinions!

Thanks, Jay