My Momus build

**hedgehog23** · 08-17-2011, 05:59 PM

updates?

**TeslaFreakshow** · 08-22-2011, 08:31 PM

Yep few updates, I still haven't made the router clamps or bought the router yet. But I did get the belts and pulleys installed finally and I made a stand for the whole thing. I'm probably going to have to dismantle the whole thing and locktite it because I didn't have any when I assembled it. I also finished the bottom and poured the epoxy. Its just made form 3/4 inch plywood.

I got the wrong shaft coupler the one I ordered is 1/4" to 1/4" I needed the 1/4" to 3/8" I also need to figure out how to arrange everything in the garage so the parallel port cable will reach the machine.

**TeslaFreakshow** · 10-04-2011, 01:03 AM

Alright well ive finally finished the router clamps. I had a few problems. I widened the clamps to fit the r2401 router and the clamps ended up hitting the acme threaded rod so i cut two notches out of them which im not that happy about.

So everything is pretty much good. i made some test cuts with a .310" diameter somewhat dull single flute router bit. I'm having a problem with the z axis shifting a little one direction after a few cuts. I was cutting some 3/4 inch poplar at about 15 ipm at about .250" depth.
I suspect that my spacer blocks are exactly the same height. I'm thinking of making new ones threading them and then welding them to the z axis carriage blocks. Anyone else have this problem? I can't seem to figure out what IPM is reasonable for this type and thickness of wood

**momus_cnc** · 10-04-2011, 10:14 AM

It sounds like what you are describing is the problem of the carriage racking/shifting out of square? This shouldn't be happening, especially at that feed rate in poplar. With a good sharp bit, and that depth of cut, you should be able to push through poplar at 10x that feed rate with no problems with the machine. (not saying that is the correct feedrate for the material, just that the machine should withstand the cutting force with no problems)

A few others have had this problem, and it has been mentioned in a few threads. Basically, the 4 main studs holding the carriage together need to be VERY tight. I'm working on a design change that will provide positive locking between those parts, so they don't rely on just clamping force. But in the meanwhile, the fix is to first make sure the nuts on those studs are as tight as possible, and if a problem persists, then change them out for 5/16” studs or bolts. I took my own machine apart to see just how much difference the 5/16” would make, and it is substantial. You can get them a lot, lot tighter. I also swapped out my homemade spacers for some purchased ones to make sure they were as flat as possible and have parallel faces. I bought them from Quality Aluminum Spacers - Largest Selection on the Web for $1.20 a piece. They are 11/16" long, 5/8" o.d and 3/8" i.d.

Attached are some photos of the upgrade to 5/16” bolts. I was hoping I could do this one bolt at a time without tearing half the carriage apart, but unfortunately that is what I had to do in the end.

First photo is the “before” shot of the original spacers and studs.

Next photo is of the new parts. 5/16” grade 8 bolts, nuts and washers.

A testament to the strength of the loctite. One of the studs snapped while trying to remove it. This meant I had to remove all of the bearing from this piece so I could heat it up with a propane torch to soften the threadlocker. Luckily there was just enough stud to grab onto it with a pair of vise-grips. Once the studs were out, I just drilled out the holes through all the parts for the larger diameter bolts.

Last shots are the new bolts and spacers in place.

With the new 5/16” bolts I can drive the collet of the router sideways against a block clamped to the bed of the machine, and the steppers will stall before the carriage shifts. And that is with my Gecko G540 drive and 381 oz/in motors, which have gobs of power.

-Bob

**GTFreeFlyer** · 10-04-2011, 11:38 PM

Awesome, I just bought those spacers. That'll save me some time. Any news on when to expect the plans update to come along?

**SpeedyDad** · 10-04-2011, 11:40 PM

Yeah, I just ordered the spacers too. Figured I might as well upgrade my carriage since I haven't aligned it yet.

**TeslaFreakshow** · 10-04-2011, 11:57 PM

Sweet, better than trying to make new ones. I was going to borrow someones mill and do them that way but this is much easier.

**momus_cnc** · 10-05-2011, 09:39 AM

Any news on when to expect the plans update to come along?

It won't be for a while. Many months, most likely. There are enough changes that I will be needing to construct another full machine to test them all out. My plan is to post many of the changes here first, as I work on them one at at time. Many of them will be things that are backwards compatible and can be retrofit to the existing machine, and in those cases I'll post new drawing sheets and any other needed info (like the limit switch info I posted a couple of days ago, which even included G-code). That will also help me get some feedback on the changes before I incorporate them into the plans.

-Bob

**Festus440** · 10-05-2011, 01:37 PM

Originally Posted by parallel__lines

It won't be for a while. Many months, most likely.

Any chance of having updates and corrections put into a sticky?

Thanks,
Bob

**OCNC** · 10-16-2011, 10:05 PM

Originally Posted by Festus440

Any chance of having updates and corrections put into a sticky?

Thanks,
Bob

I saw this thread and thought I'd throw in my two cents with the idea that it might help someone using the Momus plans.

I built my Momus router last winter. I was expecting that the plans had been proofed by the designer but I subsequently found out that they weren't. It's a WIP using plans purchasers as Beta Testers. Needless to say I was a little bit disappointed. Anyway apart from the errors that cost me in time as extra handwork and in materials as other more suitable small parts the most discouraging item was the crappy Z-axis. It was prone to racking and difficult to tune plumb and square. I ended up scrapping the original one and redoing it to my own satisfaction. The basic difference is that there is a 1/4" thick square aluminum plate that spans and secures the upper and lower y-bearings and the right and left z-bearings. The bearing carriage is therefore located, made rigid and aligned square without those ridiculous spacer blocks of the original design. The smaller holes are for #10 flat head screws with the 3/4" square stock being threaded to receive the screws while the 1/2" x 3/4" stock has clearance sized holes for a tight fit up. The four larger holes are for 5/16" bolts that pass through the whole 'sandwich'. The other related bearing blocks need to be re-dimensioned to fit this change. As you may be able to see in the photos my machine is larger than the original design. I used 3' lengths of flat ground stock for the x rails. I found the cold rolled stock to be of disappointing quality. The Y rail is about 31" and this gives me a working area of 26(x) x 21(y). You should also note that I have a thrust bearing on the Z lead screw. Relying on the stepper's bearings to carry thrust loads is poor practice. I'm also using Roton's Hi-Lead Screw for the Z axis (.250 lead per rev). This provides excellent transport rates. The drive nut is the stock product from Roton and is easily secured in a standard shaft clamp. I would also recommend that the 1-1/4" rail angles be reduced to 1" angles (unless of course you like the grinding that the 1-1/4" rails will require). I used a piece of 3" PVC pipe to fabricate the router mount. The hose clamp holds the two halves of the pipe securely and allows very quick changing of router bits and zeroing to surfaces. I drive the unit with Geckos, Mach 3 and a Smooth Stepper. It works quite well for what it is...but I wouldn't build another one this way...too many parts.

Chris