Hi everyone!

I recently joined this community and this is my first post. I am excited to start contributing and learning from all of you.

I have recently decided to design and build a CNC-based FCAW welding machine for my workshop. The welding machine´s weight is about 30 kg. The main challenge I anticipate is related to the large working area dimensions (approximately 2 m in the Y-axis, 1.8 m in the X-axis, and 0.5 m in the Z-axis).

Due to these dimensions, I've opted for a gantry-style configuration. However, I am currently unsure about the best drive mechanism and structural approach for the Y-axis.

I have considered four possible configurations:

1 - Dual Motors (Master-Slave Setup):

Each side of the gantry has its own rack and pinion mechanism, driven independently by two synchronized stepper motors.

2 - Gantry with Central Rack Under the Table:

Linear rails are placed on both sides of the gantry for guidance, but the driving mechanism (rack and pinion) is centrally located under the working table, connected to a cross beam attached to both sides of the gantry.


3 -Single Motor with Central Drive Shaft:

One motor placed centrally drives a single robust shaft connected to two pinions, each engaging with racks located on each side of the gantry.

I am planning to use for the Y axis a Nema 34 motor with a nominal torque of 12 Nm. For a maximum acceptable angular deflection, that I thought to be of 0.1°, it turns out that the shafts diameter should be of about 36 mm. Commercial bars of such a diameter are not easily obtainable in my location, making this option less attractive.

4 - Cartesian Robot Style with Single-Side Drive:

A Rack and pinion mechanism and linear rails are placed only on one side of the gantry. The opposite side has a passive support wheel to avoid cantilever effects and reduce torque (around X and Y axis) on the driven side.


The fourth option is actually the one I like the most because of its simplicity.

Given that this machine is solely for welding, it won't be subjected to significant forces along the X or Y directions, aside from minor friction from passive wheels and inertial loads.
Therefore, I expect the momentums around the Z axis applied to the linear rails of the Y axis to be easily supported by the rails.

However, I'm concerned about potential racking issues with this design.

Could you please share your expertise and insights regarding:

* Any potential issues or clarifications needed for these four designs?

* The specific advantages and disadvantages of each configuration based on your experience?

* Recommendations or insights into long-term reliability, precision, ease of maintenance, and overall suitability for welding applications?

Your advice and experience would greatly help me make an informed decision.

Thank you very much!