MadModder

Sometimes I'm just not as smart as I think I am...

I got the Z axis leadnut plate drilled and tapped in the appropriate places, I also managed to snap off my M3 spiral tap in the process. While running the tap in far enough to be sure all the chips were cleared out of the threads, I ran the spiral tap through the plate. While trying to start the tap back into the hole I managed to get it started crooked, and snapped it off. Fortunately there was plenty of the broken tap sticking out of the back of the plate that I could grab onto and thread it out. I had one other M3 tap, a 4 flute tap, and wanted to chase the threads - but I didn't want a repeat of the previous disaster. So I drilled a clearance hole in a piece scrap plastic and made a simple M3 tap guide. I used that to chase the threads, and also to tap the one remaining M3 hole on the Z axis leadnut plate.

I then set about assembling the anti-backlash leadnut, and getting it adjusted. The process I used to assemble/adjust the Y axis leadnut is identical for all three leadnuts; the only thing that varies is the shape of the leadnut plate. So... Onto installing the leadnut into the spindle slide.

Anddddd... it doesn't fit. Oh, it fits into the pocket alright, it's just that ALL of the leadnut doesn't fit into the pocket. The top of the leadnut plate is still 1-2mm proud of the surface and it should be flush.

The cause of this evil deed? When assembling the Y axis leadnut I discovered that when using the M3x35mm bolts as originally designed, if the two halves of the leadnut weren't clocked properly, I either couldn't assemble the leadnut halves or the nylock adjusting nuts wouldn't lock. My leadscrews are T8 2 start screws, with a 4mm pitch. With the Y axis leadnut, the only way the M3x35mm screws would work was if the 2 halves of the leadnut were threaded so close together that I couldn't remove the backlash in the threads. Clocking the 2nd half of the leadnut to the other start moves that half by 2mm, which allowed me to adjust out the backlash. Unfortunately, that also moved the adjusting nut by 2mm, far enough that the nylon locking ring wasn't doing its' job. I had M3x40mm screws, which solved that problem. What it didn't solve was that the pocket the leadnut fits into on the spindle slide had 2mm of clearance - when using an M3x35mm screw.

Sometimes I'm just not as smart as I think I am.

I got the X axis leadnut block printed along with the new Z carriage, and the heatset inserts have been installed.  I thought that I had assembled the Z carriage for the final time, but I was mistaken.  I haven't greased the linear bearings yet, so I'll have to partially take it apart to grease it.  One of the things I did during the design for my upgrades, was to make sure Future Don wasn't going to curse my name when it's time to service this thing.  I'll need to remove the rails to grease the bearings, but it's possible to do that and not lose the alignment.  By removing the stepper motor and the two screws retaining the upper end of the rails, it's possible to pull the rails out the top of the carriage.  The spindle, spindle clamp, and the bearing block can then be removed as one unit.  Since none of the bolts holding the critical alignments in place need to be loosened, the alignment shouldn't change.

I've got the carriage roughly aligned to the bed, meaning that it's as square to the bed as my square and my Mk1 eyeballs can make it.  The final alignment won't happen until I've got this thing moving under it's own power.  Then I can use a DTI and a 123 block to really dial things in.  This is the current condition of the Z carriage.


The X axis leadnut is currently bolted to the bottom of the bed, I kind of got ahead of myself when I did that.  I guess it's a good thing that I made it easy to remove the bed to work on the bottom of it.  Just remove the four bolts holding the endplate on and the bed can be slid off the rails - bed alignment is not affected.

I need to get a measurement of the distance between the top of the leadnut block and the bottom of the bed, with the leadnut block assembled on the leadscrew.  If I did the "Plottin-N-Conivin" right, that distance should measure around 3mm.  BUT,...  I can't measure the distance until the leadnut block is assembled on the leadscrew.  That can't happen until the anti-backlash nut is assembled and adjusted.  And THAT can't happen until the leadnut plate is fabricated.  And since the X axis and Z axis leadnut plates are very similar, I might as well do them at the same time.  That'll be happening next.

OK, time to Fess up, I make-da-nuther-boo-boo. For some reason I designed the mounting bolts for the Z axis NEMA17 stepper motor to use heat set M3 inserts. Normally that shouldn't be a problem. HOWEVER, the NEMA17 motor mounting locations are M3 threaded blind holes. Something tells me that four M3 threaded blind holes facing four M3 threaded blind holes just ain't gonna work to hold the motor in place.

The Z carriage was printed with 80% infill so you would think that if I could just drill the blind holes through with no problem. That actually would work for the two holes closest to the rails. The other two holes however would still be buried in the upright section of the carriage. That's probably what caused the brain-fart of thinking I could get away with using the M3 threaded inserts in a blind hole. Nope, I need to redesign the Z carriage. It's nothing serious, I just need to move the rails, leadscrew, and everything associated with them about 10-12mm farther away from the upright section.

The X axis leadnut block is printing now, by the time it gets done I SHOULD have the changes ready to go. The plan is to get the carriage reprinting by the time I go to bed.

Hi Folks!
A mish mash of phone and camera this week, which never works well as my editing software  does not like phone ! Will it start? of course it bloody will! A great relief to all involvedfootage! Commando gardening, bramble eradication, dead tree removal, and starting the Fordson after two years in't hedge bottom!
Phil, in pleasantly warm East Yorkshire

Yipes, a string of bad luck! I'm sure you'll get it working soon.

This is what I hate about trying to program absolutely everything in advance, as opposed to measuring and cutting during fabrication. Not that fabrication isn't also subject to errors, but with work in hand, often times you can try pieces against each other, or mark from each other, or quickly measure a fastener and the drill bit you are planning to drill it with, etc.

Some people work better one way, others vary from that. I find I make fewer errors in manual work than I do in additive machining, because the latter demands advance perfect location of all features or a part is often ruined. One frequent problem in an imperfect initial rendering: since infill is usually partial to save material and time, relocating or even resizing a hole or other feature is often not feasible.

Nevertheless, I admire anybody who makes the effort by this or any other means and manages to create something in our hobby. I'm sure this mill project will provide rewards when it starts machining other parts!