Gantry Upgrade to C-Beam

If there are any aluminum shavings in the cut, they will end up welding themselves to the side or to the bit and causing problems. You’ve got to have constant vacuumage and/or blowage and keep the cut path spotless.

I may be wrong, but I don’t think snagging on burrs would cause problems unless you’re cutting too deep.

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I re-did my cut file so the last mm is a separate file going slower so I can easily keep the chips vacuumed clear.

Just ran across this article in the CNC Cookbook that has some good recommendations for aluminum -

One thing I was wondering about, is your profile cut a single groove the width of the bit? I was watching a video of someone on the forum who makes paintball triggers and it looked like he was always milling a channel larger than the bit.

Thanks for the link.
I reviewing my setting the second bit break was totally my fault. In adjusting the feed rate when switching from a single flute to a dual flute I screwed up and increased my feed rate instead of cutting it in half. :scream:

It was. I have seen other videos of people milling aluminum with a wider channel. I had assumed it was a milling stratagem in Mach 3 or something.

I will look more into this.

Making a outline offset 40% bigger than the profile cut then making the step over 40% produces a wider pocketing cut “channel”, using 2 passes without a huge increase in overall cut time.
I am guessing this makes for easier chip clearing, and it would help if it was a run out issue.

Does anyone know more about this approach? Why it is done and how much wider should the channel be than the bit?

Found a post with more info on profile cutting aluminum:
Aluminum Paintball Trigger Plate(s) - Cut and Anodized

Nice, that’s the one I was remembering (the video of that). Now the question is, does your CAM software have that option?

No, but I can manually make the outline into a pocket with the offset tool. A bit clunky but it works.

I did a quick test of using pocket strategy to do the profile cut in a unused space on the material.

I made a offset outline 40% of the bit diameter around my test object (bat symbol) and did a pocket cut with a 40% step over so it would do it in 2 passes.
Cut at .39mm depth, 1016 mm/min, 18,000 rpm
I wet with WD40 and vacuumed up chips

I did the pocket cut for the first 90% of the material, then switched to a traditional profile strategy with tabs for the remainder. I could not make tabs automatically happen with the pocket cut, but I think I can manual add them in if I want.

It worked fine. No broken bits, no bad “sounds”, Lots of chips and mess.

Now to run the bracket print. That will take about 4 hours so I may wait till the weekend as I need to monitor it closely.


Dude! That looks great! I’m looking forward to seeing those gantry plates.

I finished cutting the plates last night, using the pocket cut approach worked perfectly.
I also re-did the original profile cut on the first bracket as a pocket cut and finished cutting it out as well.

2 of the 4 eccentric spacer holes on the bottom of the bracket are a bit too small. I am not sure why just those 2 are different, I will have to check my cut file and see if there is a reason for that.
But I should be able to drill and sand them out to fit.

Hopefully I will get a chance to bolt this all together this weekend.

I did just realize that I don’t have a spindle mount for the c-beam. The one I ordered will not hold the Makita. :scream:
So I will either have to adapt the XC spindle mount, make one, or order one. More research.

Looks like a beast! Very clean edges, nice. How much did the AL plate cost you?

I am not sure as my local metal supplier sells cut aluminum remnants by weight. I got 2 plates for about $45, This plate was a little thicker so, around $25

I was lucky, the remnants are a lot cheaper if they have one in a size / thickness / grade you can use. Otherwise there is a cutting fee of $10 per cut plus the specific material cost. (The 6061 costing more than then 5052)

Good to know, thanks.

Our cnc machines at work use 20mm linear rods for the sliding doors in a span of around 36 inches. I also had thought about using linear rods so out of curiosity pushed in at about the middle it seems to flex very easy so I decided I will not be converting to rods. Just my experience.

Yes I added wheels. There may be some alignment issues if my bracket is off. Worse case I may not be able to align all of the wheels to be effective, but I figured it was worth a try.
The extra wheels do reduce my total Y axis work area, but the plan is to extend the Y axis next.

I have noticed that a lot of the OX and c-beam designs add additional pairs of wheels to help distribute the load. The Z axis C-beam actual has 16 wheels, 4 pair on the outside and 4 pair on the inside.

You’re also not rubbing the backside of the bit as it cuts a groove.

Openbuilds sells set screw type shaft collars. You may want to use clamping shaft collars. Same with the beam couplers. Set screws can be evil.

The replacement wheels came in so I resumed working on the upgrade.

I drilled and taped (where needed) the plates, and started to put it all together.
It is starting to look like a gantry :smile:

I need to rewatch the assembly videos especially for the Z axis as I am having bit of trouble following the written instructions on setting up the locking rings properly.


I am starting to review my TinyG configuration settings of the upgrade and I noticed that the c-beam screw drive max feed rate is a lot higher than the XC.
6000mm/m Max, 1500mm/m recommended.

For the X axis this will be a significant slow down from 8000mm/min.
But a big speed boost for the Z axis from 500mm/min.

I have noticed that cuts with a lot of Z axis movement were slowed down by this limitation.
I had been avoiding spiral cut smoothing strategies on my profile cuts for this reason.

It will be interesting to see how the increase in Z axis speed offsets the loss of X axis speed.