Building a CNC Router

[Tim K]

I remember when we first discovered chip loading. The theory is easy to understand once it's explained, but we found the recommendations to be counter intuitive. The size of chip required to carry away the heat is always a surprise. I would say that most hobby woodworkers run their routers at feed rates that are half or less of what's required to be at the correct chip load. Even 15 years into it, I'm constantly surprised at just how fast our CNC runs when we have the chip load calculated correctly (which is 100% of the time since it's programmed into the software). The only time we deviate from recommended chip loading is when we're unable to hold the workpiece solidly enough to withstand the lateral cutting forces. Invariably when we do that we get burning on the cuts.

[Grant H.]

I remember when we first discovered chip loading. The theory is easy to understand once it's explained, but we found the recommendations to be counter intuitive. The size of chip required to carry away the heat is always a surprise. I would say that most hobby woodworkers run their routers at feed rates that are half or less of what's required to be at the correct chip load. Even 15 years into it, I'm constantly surprised at just how fast our CNC runs when we have the chip load calculated correctly (which is 100% of the time since it's programmed into the software). The only time we deviate from recommended chip loading is when we're unable to hold the workpiece solidly enough to withstand the lateral cutting forces. Invariably when we do that we get burning on the cuts.

It is interesting watching CNC wood video's and seeing how many seem to burn the edges when they are doing profile cuts.



More progress!

Gantry to Riser Plate bolted onto the end of the Gantry:
20210106_221355 by ARNEWB, on Flickr

Quick test fit of one of the risers:
20210107_155552 by ARNEWB, on Flickr

Gantry with the rails and plates installed:
20210112_205054 by ARNEWB, on Flickr

Since the gantry is going to be supported by t-slot nuts and bolts, I decided to go a little over board...
20210112_205753 by ARNEWB, on Flickr

And.... It's starting to look like a CNC router. The gantry is actually surprisingly heavy (more than I was expecting).
20210112_213051 by ARNEWB, on Flickr


I can grab one riser and slide the entire gantry back and forth without any noticeable binding, or drag, so I am not concerned about the ability to move it with smaller steppers to start with.

Some may notice that the upper riser-rail block has changed. I was originally shooting to have bolts on both sides of the block, but given the ball screw mounts I have, there isn't enough clearance with the bolts in the middle.

There are some squareness issues that I have to chase down, so that should be fun...

Given that I ordered some other rails for the Z-axis build, while I am waiting on those, I am going to continue working on getting the ball screws on the x/y axes, motors mounted, and then I'll start on the power supply, stepper drivers, wiring, and motion. I assume the rails will be here before I make it through that whole list, but at least I have enough to keep me busy until they show up.

Ball screws for the X axis (gantry support - we can argue about axis designation if you really want, but that's how mine is designated) are going to be a little goofy to start with. The ball screws that I have from my original parts buying are only 800mm long, and I likely need 1000mm or 1050mm for the dimensions that I have decided to build this for now. So, they are a touch short for the moment, but I am going to make them work and ensure that the design is functional, and then use it to rebuild some parts for the final version.

[Great-Kazoo]

It is interesting watching CNC wood video's and seeing how many seem to burn the edges when they are doing profile cuts.



More progress!

Gantry to Riser Plate bolted onto the end of the Gantry:
20210106_221355 by ARNEWB, on Flickr

Quick test fit of one of the risers:
20210107_155552 by ARNEWB, on Flickr

Gantry with the rails and plates installed:
20210112_205054 by ARNEWB, on Flickr

Since the gantry is going to be supported by t-slot nuts and bolts, I decided to go a little over board...
20210112_205753 by ARNEWB, on Flickr

And.... It's starting to look like a CNC router. The gantry is actually surprisingly heavy (more than I was expecting).
20210112_213051 by ARNEWB, on Flickr


I can grab one riser and slide the entire gantry back and forth without any noticeable binding, or drag, so I am not concerned about the ability to move it with smaller steppers to start with.

Some may notice that the upper riser-rail block has changed. I was originally shooting to have bolts on both sides of the block, but given the ball screw mounts I have, there isn't enough clearance with the bolts in the middle.

There are some squareness issues that I have to chase down, so that should be fun...

Given that I ordered some other rails for the Z-axis build, while I am waiting on those, I am going to continue working on getting the ball screws on the x/y axes, motors mounted, and then I'll start on the power supply, stepper drivers, wiring, and motion. I assume the rails will be here before I make it through that whole list, but at least I have enough to keep me busy until they show up.

Ball screws for the X axis (gantry support - we can argue about axis designation if you really want, but that's how mine is designated) are going to be a little goofy to start with. The ball screws that I have from my original parts buying are only 800mm long, and I likely need 1000mm or 1050mm for the dimensions that I have decided to build this for now. So, they are a touch short for the moment, but I am going to make them work and ensure that the design is functional, and then use it to rebuild some parts for the final version.

Igf (key word) IF there's issues with the stepper motors ability to move the gantry, smoothly. Have you thought of a Plan B now, if that does occur?

[Grant H.]

Igf (key word) IF there's issues with the stepper motors ability to move the gantry, smoothly. Have you thought of a Plan B now, if that does occur?

I have. It's noticeably more expensive, but it solves a number of issues in one shot.

Clear Path Servo's. I can get nearly double the torque values compared to my steppers in the same body size (Nema 23), and I eliminate the possibility of missed steps, as they have built in encoders to validate the motion. Beyond that they also simplify my control cabinet, as I don't have to have stepper drivers to run the servos. I can feed the step/direction signals directly from my control board to the servos, along with ~75VDC and it's all done.

If that's not enough, something is likely wrong, but I can always step up to Nema 34 frames. Going to better gearing in the ball screw is also noticeably expensive, but it doesn't solve any of the other potential issues, so it isn't really a great solution either.