Jamming conduit in to corner rails

Is it supposed to be darn near impossible to put the conduit into the lower corner hole?

I’ve tried a few different times until my fingers hurt from holding the rail, and I still cant even get close to “in”, let alone all the way.

Yeah, something is seriously off with whatever conduit I got…

I can’t slide the rollers on either, even after loosening up a fair bit. Seems like it’s hitting on one of the wedged ones too, so it’s not one that loosening is going to help much I fear.

I need to go down to my shed and get out the calipers, but a basic mm ruler shows it somewhere close to the 23-24mm mark, so I don’t see why it’s not working…
yet obviously something has gone wrong.

So, with the help of a screwdriver and nearly cutting a finger off in the process…somehow I managed to wedge it into the corner with some pokes, scrapes, and scary plastic sounds.

I also managed to get one roller assembly on, but I basically had to loosen all the bolts with bearings into “hand tightened” and pull the bearings UP to allow the pipe to slide underneath and make contact with the 2 pressed-in bearings.

With some work, the side with 2 bearings will slide back down so that full contact is made on the bar. The bad news is the side with the single bearing now teeters on “barely nut on” because the bearing slides right to the nut and only touches the railing with about 1/4-1/3 of the bearing width.

Should all 3 bearings sit flush with the rail? or should all 3 be slightly off and using the edge to contact the rail?

Not sure if a post disappeared or what…

Anyway, calipers measure 23.49mm OD on the conduit, so that’s not the trouble.

The ID of the corner block (lower) was 22.57…meaning almost a MM to try to wedge open to fit the conduit. A little tighter than I originally expected.

Good news…that rail’s not ever coming loose.

Did you print it in PLA? What nozzle size?

Heh…I have no idea. I got them from you. :wink:

Well we know they are perfect then…hahahaha… at least close. Yup PLA, things should be snug but it should go together pretty easily. All bolts should be loose then snugged up after complete assembly.

Nuts are bearly on the roller bearings. Should all the bearings sit fully on the rail or at a bit of a diagonal.

Eyeballing my bearings, they are fully on and normal to the rails. I use standard conduit from Home Depot. I did need to use a wide screwdriver to slightly wedge open the corner blocks to get the rails in but it was not difficult. Can you include some photos of the bearing problems? I don’t understand “Nuts are barely on the roller bearings.” Are your bolts too short?

What printer and nozzle are you using? Perhaps you need to calibrate your extruder.


Sorry for the dark pic, was taken last night. In this one, the side with 2 bearings are “up” - as you can see lifted off the piece pretty far just to allow the conduit to slide through gently. In this pic, the single bearing side is flush with the conduit.

After taking it out and sliding it back on again, now the side with 2 bearings are down flush with the plastic piece and sit nicely on the conduit, but the single bearing doesn’t have room to be flush with the plastic piece. At this point, only the edge of the bearing actually touches the conduit.

You can kinda see where the nylock nut is on the one bolt. Barely on enough that the nut doesn’t fall off. If the bolt was any longer, the bearing would miss the conduit entirely.

As I mentioned above, I bought the plastic parts from here and didn’t print them myself hoping to save some time.

The bearings are already tangent to the pipe surface there is no difference in plastic flex if you just snug up the nuts. All the parts are meant to flex. Things are going together fine.

Not sure I entirely understand that.

I had to loosen the nuts and pull the bearings up off the plastic just to slide the conduit all the way through, otherwise it would jam on the second pressed bearing. (the ones sandwiched between 2 sides of plastic and using the longer bolt that also holds the motor mount.

In that pic above, there’s about no way those 2 bearings would slide down to be flush with the roller plastic. If I take the conduit out, I can press those 2 down, but then have to lift the single bearing side up like that to get enough clearance for the conduit. Maybe if I wrench down on the nut it will start sliding the bearing around the rail? Being new to hardware like this, I wasn’t sure if that could/would in any way destroy the bearing with too much lateral pressure.

This is Home Depot 3/4" EMT conduit, and the OD was measured above. So I don’t think the rails are a problem.

Maybe I’m being too delicate with the plastic…but in trying to do the screwdriver trick SteveC mentioned, I heard a small bit of cracking noise (nothing visible) just putting the first corner block on.

Will work on it a little again when I get home. Just having a hard time visualizing how it will go together without breaking something.

On the part you took a picture of, roller f, the longest bolt controls the tension. Make sure that is very loose. Then tighten the the 3 bearings. When that is done, only tighten the longest bolt enough so that the motor mount is not flopping in the wind, but still loose. The zinc coating will wear off very quickly after an hour or so of use and allow more room. All of this has to be accounted for initially or the machine would be sloppy.

That middle bolt, plastic on both sides, is on all parts and is the only one you need to make sure is loose.

The goal of all the parts is to flex them to get them to edge of there plastic deflection to minimize flex when in use, flex by design to pre-load them or they will be springy and loose after your break in. You are using my parts, that I printed, on the exact same conduit I use. You should be fine. I admit the corner blocks are too tight but they work fine, They have to be this way because of peoples poorly calibrated printers. In the beginning there were complaints of them being too loose. If I was printing all parts they would all fit perfect.

Will check it out later tonight. I know those longer bolts are less than “tight” but probably not nearly as much as the other 3.

Well, it’s got an assembled frame and the gantry is on. Need to make feet for it tomorrow so that I can sit it down nicely without fear of smashing the laser mount.

Did manage to crack one of the screw holes for the lower end of one corner bracket. Will see if it holds down, but based on how tight it’s in there without screws…I imagine it will be fine.

I ended up taking a file and cleaning out a good bit and ramping the “entry” side of the corner bracket lower holes to make things go in. I had to do the same to the Z axis top piece.

Rails are on. Took the bearings, spacer, and fender washer off and backed the bolt out to barely keeping the motor mount on. After cracking that one piece, I got into “f-- it” mode and figured it would go together tonight or break in my hands. Most of it stayed together so we’ll see how it goes from there.

Once I get the legs on, will square it up and start running wires and doing some basic movement tests. There’s little catches here and there, mostly I think due to needing to move back and forth and work out any little kinks before a good final tightening down.

If I were to rewrite the instructions, I’d say to wait on the belt tension bearings until the very end and just thread the bolts through until they’re on the rails. Same goes for the corner block top-hole holdown screws. Ended up having to pull them completely out to lift the gray hold-down lever enough to wedge the rail through.

What’s the actual procedure for the Z lock nut? In the middle Z build, it has one putting it on the first pair of triangle things…but on the Z axis it has manually placing the lock nut on the threaded rod.

Tomorrow’s to-do list:

  1. Stop whining like a pansy. These are big boy rails and big boy bolts…you aren’t going to break it. It aint held together with m3 screws.

  2. Cut the last 4 legs. Not going to buy a pipe cutter for just this last bit, so gonna muscle through it.

  3. Mount legs, and get it semi-squared on the table.

Friday will probably be wiring and belting day, and Saturday may be the first laser tests.

Thanks for talking me through it guys. I panicked about the same way putting the X-Carve together. I’m not super handy in the whole “lets build” thing.


It’s coming alive…

Legs on, everything still loose to be squared up once I get the table ready and the machine down to the basement to my new “office”.

I’m hoping to get it “close” on level/square up here so I can hook the motors up and test electronics before I run too much cabling.

Then to let it sit on some rectangle cuts. I’m thinking something like a 12x20" pocket at ~1mm depth per pass, maybe 15 passes. That should make it go around the rails at least a few hundred times.

Don’t know why it imported the picture upside down. Looks normal in my desktop…but whatever.

It’s still coming together like the beast it is!

Better get those stickers of the rails before they gum them up. I learned the hard way.

Stickers are a WIP.

Anyone have an easy way to get them off? WD40 no work. Might try wife’s nail polish remover, she says acetone will do it.

Anyway, today’s progress so far:

  1. Installed and configured Repetier-Host, and started playing with the Ramps.
  2. Didn’t realize that the cool thermistor thing in the wiring kit baggie was required, but did remember the “error” with temp being something about a blog post, re-read it, and found the thing. The one that comes included with base-kit doesn’t seem to have a plug, so that would have sucked. So, thanks for including that in the wiring kit!
  3. Wired up all the motors just to verify axis on the boards and see if the motors turned nicely.

Am noticing a slight issue with the Z movement though. Might because I didn’t use any lube on the threaded rod though. Or something in the rails is catching on one of the bearings. But it comes and goes, like it fights through it a little. It’s down to a point where I’m just about at what I expect the optimum focus height for the laser is going to be, and am only planning to go ~3-5mm (3 down, 2 up as a safety height for clamps and such). Will see how it runs on a test piece once I mount the pulleys and run the belting later.

I can’t do much until I bring my table down to the basement to sit the MPCNC on. I’m not going to try mounting the laser on it while laying on a concrete floor with the tool mount a mere inch or two from the ground.

Will undo the wiring, tape up various points where it may come in contact with pipe. And get it back into a somewhat workable order.

Instead of using a fancy drag chain, I’m thinking about using some flex pipe like for a vacuum cleaner or drain pipe and feeding wiring through that. Particularly if I can get some that I can also run through the X/Y pipe for some added security on the wiring.

I’ve seen some videos of MPCNC sitting on a floor with kids sliding it around with ease. Will have to double check all bolt tightness and see, but mine doesn’t just slide like magic yet.

All told, a lot of frustration (this is my 2nd ever “build” of a cnc device, so I’m still a noob)…but I’m happy to see things coming together a bit.

Still hoping I can turn the laser on tomorrow and see some burning!

What laser are you going to use? I am thinking of using the JTech Photonics unit.