[routalot]

I’m not sure I buy your argument that side plate deflection isn’t an issue. I’m not trying to argue the point just that I’ve spent decades in machine repair and build and if I had $10 for every time my first course of action was wrong I’d be retired by now. You could be right of course but it is pretty common to have to reboot ones thinking when it comes to diagnostic work.

As for your question it won’t be easy to hit the $$ mark you have with a suitably stiff DIY build. The one big advantage you have is a well defined working area. That small area makes it much easier to build a stiff machine at a low cost.

The first thing to consider is used equipment. A working industrial router will likely be too expensive for the budget but a machine with a dead controller might pop up cheap. Depending on your location you might be able to pick up used machine bases. Often these end up being sold by the pound. The goal here is to start out with a good foundation to build upon.

Beyond that the only way to control costs is to find parts and materials at rather huge discounts over list. Unless you are extremely lucky hitting $2000 for a DIY machine that can handle these sorts of cuts will be difficult. The other issue is that you need to do some fine machining to build a very rigid machine. What you can accomplish with the tools at your disposal is unknown. This in any event the higher your expectations the greater the likelihood you will need access to a machine shop.

I have to agree with all of the comments from wizard.I also think that pictures of the current machine would be helpful as it might be possible to suggest improvements.It seems a peculiar approach to consider buying a slightly better machine with a view to doing work to it in order to make it acceptable when the existing machine might be capable of matching the result with less expenditure.To give just one example,we don't have any idea whether the current machine might be susceptible to gantry skewing as we haven't seen it.

Have you looked at the cost of replacing the timing belts with ballscrews?I would guess about 15% of your budget for the replacement machine-prior to upgrading it.You might also be able to stiffen the current machine by bolting some angle in strategic locations.