[daveysapps]

To cut down on the number of machined components, the thought is to use a table structure that is known to have a relatively good straightness tolerance ie extruded Al, and skin it with a material that is known to have a uniform thickness tolerance to create a planer surface for the rails to fasten to. A steel structure would require machining for flatness or an epoxy pour. I do not have economical access to machine long parts.

Perhaps this isn’t the best approach, but it seams to be the best given the processes readily available to me.

That being said, I would prefer to build the table out of steel...

[daveysapps]

Project update.

Welded base


Laser cut sheet metal



80/20 machined



table assembly

[daveysapps]

FYI, by no means do I consider myself to be a welder.

[daveysapps]

So I am getting ready to install the Y-axis Chinese ball screw under the table ( I am calling my Y-axis the long axis that drives the gantry). I am inspecting screw straightness/run-out prior to install. The screw is a 2525 x 1500mm long ball screw, and will be mounted with a fixed/supported bearing system. I placed the screw's machined ends on V-blocks and measured .0012" of TIR on the drive side of the screw (coupling shaft portion), and .0022" of TIR in the center of the screw. Looking at the specs for a THK screw of this size, they are holding .00078" of TIR on the drive side for a C7 screw. Now I do not expect a cheap Chinese screw to be comparable to a THK screw, but was wondering how many RPM's I might be able to achieve without the machine shaking itself apart? Perhaps the stepper motor RPM's will be more of a limiting factor than any ball screw whip concerns...

My gut tells me that .0012” runout is more than adequate for a DIY CNC router.

Ultimately, I am looking for a stable robust machine. Not trying to set any land speed records.


This is all very new to me, so any insight that others might have would be greatly appreciated.

[daveysapps]

Update


Ballscrew installed


Side plates and guide rails installed


Painted side plates


Installed 5/8" thick fixture plate with tapped holes