[Reinier]

I would use thicker wall tubing so you have more threads for your rail bolts.

Thanks, I will consider this. I am also looking at the option of flowdrilling, since I do not want to make the machine overly heavy

[wizard]

Thanks, I will consider this. I am also looking at the option of flowdrilling, since I do not want to make the machine overly heavy

I'm not familiar with flowdrilling, can you explain that for us?

As for making the machine heavy, there are advantages to being heavy and certainly a few with being light. Heavy though will help contour vibration and resonance. It is up to you obviously but I'd lean towards heavy instead of light.

As far as the design goes there are only two things that really bother me. The gantry saddle arraignment with the ball screw on the back side doesn't inspire me. Along with the rails on the top and bottom I'd be very concerned about being able to properly machine the beam and get those two rails into alignment. The ball screw itself should be closer to the saddle too.

As for the second item, it was already mentioned above but 3 mm is pretty thin for screw holding. This is an example of where part sizes are often dictated not by the machines structure but rather the ability to hold screws. You can always buy linear rails that are tapped and use through bolts to fasten them in place. With 3 mm stock you will barely have 2.5mm worth of screw holding capability once you counter sink or in some way debar the mounting side of the holes. Generally you want at least one diameter of thickness for the bolts you need to mount the rails. So rails mounted with 6mm bolts should be fastened to stock at least 6mm thick. Yes this is counter to your desire to control weight. There are other options including welding on stock upon which the rails will be mounted, but you then get into serious machining costs.

When I say minimal thickness it is probably better to being yourself an allowance on top of that. The reason is the the beam may require some machining to eliminate distortion. This of course depends upon the exact meths you choose to address the problem of less that perfect materials. Epoxy leveling can greatly reduce the need for machining but might not completely eliminate it.

Overall though it looks like you are off to a great start.

[louieatienza]

I'm not familiar with flowdrilling, can you explain that for us?

As for making the machine heavy, there are advantages to being heavy and certainly a few with being light. Heavy though will help contour vibration and resonance. It is up to you obviously but I'd lean towards heavy instead of light.

As far as the design goes there are only two things that really bother me. The gantry saddle arraignment with the ball screw on the back side doesn't inspire me. Along with the rails on the top and bottom I'd be very concerned about being able to properly machine the beam and get those two rails into alignment. The ball screw itself should be closer to the saddle too.

As for the second item, it was already mentioned above but 3 mm is pretty thin for screw holding. This is an example of where part sizes are often dictated not by the machines structure but rather the ability to hold screws. You can always buy linear rails that are tapped and use through bolts to fasten them in place. With 3 mm stock you will barely have 2.5mm worth of screw holding capability once you counter sink or in some way debar the mounting side of the holes. Generally you want at least one diameter of thickness for the bolts you need to mount the rails. So rails mounted with 6mm bolts should be fastened to stock at least 6mm thick. Yes this is counter to your desire to control weight. There are other options including welding on stock upon which the rails will be mounted, but you then get into serious machining costs.

When I say minimal thickness it is probably better to being yourself an allowance on top of that. The reason is the the beam may require some machining to eliminate distortion. This of course depends upon the exact meths you choose to address the problem of less that perfect materials. Epoxy leveling can greatly reduce the need for machining but might not completely eliminate it.

Overall though it looks like you are off to a great start.

Uses a tool, usually ceramic, that drills with friction (heat) and pushes material inward, that which could be threaded, eliminating the need for adding thickness with a plate to drill and tap.

[awerby]

The process is pretty interesting; the spot gets red hot, and is pushed inward so there's a collar that's much thicker than the wall thickness. It would make sense for a project like this. Here's a FAQ: Formdrill: F.A.Q.

[wizard]

Thanks guys! Never heard of it as flow drilling.

The process is pretty interesting; the spot gets red hot, and is pushed inward so there's a collar that's much thicker than the wall thickness. It would make sense for a project like this. Here's a FAQ: Formdrill: F.A.Q.

It might make good sense but having never used the technique I'm not sure I'd go this route myself. I have seen the results of this technique but never on something that calls for a lot of fine workmanship.