Phil's linear rail Z axis upgrade

Sorry. Cold medicine.

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Did you bring enough to share? :slight_smile:


This axle mod I am reading about , Would that be running a bolt from the front of the carriage through both v wheels and out the back with nuts in between the wheels to keep them in position? If tubes are used one would need to be dead accurate with the tube length to avoid compressing the sides of the carriage box. (if that were even possible with a bolt that size)

I was actually toying with this idea in my mind while at work but looking at it in person I am not sure what real benefit would be obtained. Thoughts?

I did the linear mod back race this evening with 1/8" steel. swapped out the 2 top motor bolts with longer ones from my local Ace hdwe and once the brace was in place secured it with nyloc nuts. On the top I botched my measurements and ended up drilling and tapping a single hole for top side of the brace into the center of the vertical back plate of the lin-Z and reused one of the socket heat screws from the x axis motor. That Lin-Z is stiff as all get out now!

I thought about the easy route but decided to do it the hard way and I am glad I did, nothings going to loosen up on that part of the build. I also decided to go that route because I’m going to bolt on a Hitachi 12vc to it and I wanted it as robust as possible. I also added two idler wheels on the two fixed wheel axles and it rolls very smooth and true. It also eliminates most chance of belt whip that occurs on the X axis. I am very happy with my efforts up to this point.

Any pics anywhere buy chance?

This is a good idea as long as you are…

A hair long, you are compressing the bearings. A hair short, you are introducing lateral play.

Some time ago I got some long 5mm ID spacers for this exact reason, but haven’t so far attempted to shorten them (and I do not know if I ever will as I started building a stiffer machine). In order to do it square and within a very tight tolerance, ideally you need a CNC lathe.

An alternative little hack could be making a fixture to hold your spacers upright, i.e. by drilling holes with the OD of your spacers. Then, by probing on the fixture’s top face and knowing the fixture’s hole bottom Z, you could mill the excessive length with high precision.

In that case you could be selling kits to people here :slight_smile:

@PhilJohnson - can you elaborate on the powder coating setup? I’ve wanted to do that for some time now, and I just freed up a bit of space in the shop. I think I’ve seen retro-fitted mini fridges or something like that in the forums here, but wondered if you had recommendations…

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I did the axel mod with help from @BenRios and I have not touched them since. So, it works great.

If you are going to go through that much effort you might as well go with the standard axle mod which for reasons mentioned will not work at all because you have no way to adjust the wheel slop on the inside.

Boy, I sure made a mess out of that last post. My axles were a lot harder because I double nutted both sides and didn’t have much room to manipulate the nuts but like everything else once I found a logical, systematic system it didn’t go to bad.

I’m pretty sure McMaster has what your looking for. I’m sure you could find them cheaper but might be worth trying these:

Not sure how their pricing would be, but check SDP-SI.

Misumi was more expensive.

I used a machine made by the MicroCarve owner for several years, and I had to replace the Oilite bearings three times if I remember correctly.

Wood dust acts like an abrasive, and the Oilite bearings, being softer than the hardened shafts, do wear. That’s my theory and I’m sticking to it. :smirk:

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So, why has everyone gone with attaching the spindle mount to the slide piece?

I noticed on the sheet of paper that came with mine it mentions other brands and when I looked at the Probotix pictures, I found this:

On that machine, the entire Z axis assembly travels up and down and not just the spindle mount. It’s opposite what everyone else has done.

What would be a negative of this mounting configuration? It would keep from having to statically support the top side. Might need a beefier motor but I don’t see any negatives myself.


It might need the beefier motor. It would also not be possible to brace it against any flex in the mounting between the carriage and the z axis slide. Not a problem if it is really tight.

It also sets the weight a bit further away from the x slides, which would increase the torsion somewhat. That may or may not be a problem, depending on how rigid the x axis is.

Even with those potential issues, I will probably be looking at mounting mine the same way, once I get to upgrading my z axis.

I’ve got the single piece X axis and I’m thinking of beefing up all my motors as well when I do this upgrade (Xcontroller should be able to handle them).

One potential issue is clearance between the X carriage and X axis for bolt heads. Low profiles/flat heads should fix that though.

Personally, I’m leaning towards mounting it the same way as the Probotix unless there is a compelling reason not to that I’m overlooking. It’d be easy to make a template for the hole pattern and drill the holes into the carriage. No need for tapping as the linear Z holes are already tapped. You’d still need an adapter for the spindle mount but it’d be relatively simple.

I never even looked at mounting it that way but this configuration really increases the mass that is being moved, the router, slide, stepper motor, acme screw etc. putting more load on the stepper. And as previously mentioned, it puts more weight out away from the gantry increasing the load by whatever factor on the v wheels. and if using the original makerslide, flex could be an issue when making aggressive cuts.

I just looked on EBay at the microcarve unit that Phil recommended. It has a big note in the description section that it does not work with the XCarve.

Now I am going to have to go through this whole thread again to see how you modified yours.

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