Fit too tight

Something has gone awry with my assembly process as the printed parts that hold the conduit are printing too small for the conduit to fit. I ended up breaking an F roller and all the flex foot parts trying to force the conduit to fit. I printed off reference parts to see what it was actually doing and when I measure the ID of the flex foot I get exactly 23.5mm which leaves zero clearance for the conduit to slide in. I also printed a calibration cube and for a 20mm cube I mic it out at 20.01 which is pretty good. To get the conduit to fit without a hammer I had to scale the parts up to 104% which mics out at ~23.8mm. Can anyone tell me what the design ID of the flex foot and bottom foot is supposed to be? I am not sure what is going wrong for me but something isn’t right. Also, I checked my conduit and it is running between 23.5 and 23.58.

Any help is appreciated.

Not sure what his username is on here, but someone on the facebook group had the same issue. But he printed in ABS at lower infill densities as well.

Those dimensions are good. Did you try and fit the feet without the screws in them?

In what direction did the roller f break? That is hard to do unless you over tighten the roller lock and split it that way.

assembly of this should be done with all the large bolts extremely loose, like nuts don’t even need to be more than hand tight.
And the small screws aren’t really needed until the end if at all.

Yes, I tried the feet without the screws, no go. The Roller was so tight that I could barely get the screws for the lock started. As soon as I was able to get them started it split along the z axis (as mounted on the machine) just inside the bolt for the bearing. See attached pic. The split was wider, but relaxed after removing the lock screws.

A few things I found so far. I used 3 brands of filament. Printrbot (blue), Filament Outlet (White), and Hatchbox (blue). The Printrbot filament was the best. The parts came out almost perfect. The conduits fit snug with no modification. Some of the small holes needed to be drilled to size. The Filament Outlet filament didn’t look as good, and I had to sand quite a bit on the conduit holes for the conduit to fit. The Hatchbox looks good, but the conduit holes all needed to be enlarged using a half round file. Hatchbox also seems to be a bit brittle and will split if over stressed. The brand of filament made a difference on how much post printing work I had to do.

I spend a lot of time test fitting, drilling, sanding and filing to make sure nothing was too tight and all bolts and screws slid easily into the holes. All the parts with bearings I test fit on the conduit with nuts finger tight (not past the nylon bushing) and snugged them up after they were on the conduit.


So this happened to me too. Calibration cubes and other stuff I’ve printed has come right right on the money and I have some mpcnc parts that are too small. I use cura and I wonder if that is a factor. Filament is Foxsmart 1.75mm pla clear. Machine is Hictop Prusa i3.

So I printed the 2 corner blocks at .2 layer height then in a effort to cut down print time I lowered the other two and the rest of my parts to .3 layer height and left all the other settings the same.

The ones printed at .3 are almost perfect for the US 3/4 conduit. They fit super snug but fit. The feet are the same deal printed at .3 they fit.

The .2 roller blocks I needed to take a good amount of material out to fit the conduit. Now with the .3 Flex foot on the .2 roller block I can see the roller block is a little over 2mm less wide than the flex foot. The .3 corner block is exactly the same size as the flex foot.

My Corner Block locks printed at .2 layer height are the correct size.

All my rollers are tight but if I slide them back and forth slowly it look enough of the galvanized coating off for them to slide smooth. There is two types of conduit a thick walled one and a thin walled one. I have the thin walled one.

I find the whole thing crazy and shouldn’t have happened. I blame it on some crazy cura bug on not on the design or my printer. Changing the layer height should not change the scale and if It did then my corner block locks would be off.