Alternate belt tensioning method (Page 2 of 3)

That is a great design! Any chance you could also please share the extruder, hotend, and fan carriage stl files?

Here is my take on the cooling fan duct.  It's small, detachable and quite efficient.

It is designed around a 30x30mm fan, and it attaches to the front of the extruder by means of magnets embedded on the mount.  I used 6mm neodymium magnets, which are very strong, yet if the duct were to hit something , it will just come off without doing any damage to the print or the machine.

The duct is was sliced in two parts so that it can be printed flat.  Simply glue the 2 parts together.  The magnet mount offsets the duct from the hot end, and provides a good gluing surface for the duct.  The duct can be rotated about 35-45° in either direction before gluing.  Just make sure that you don't have anything in the way (like the heater wiring).

One note:  I usually use black anodized steel screws, but the last batch of screws I bought were stainless steel.  Depending on the type of stainless steel used, it might not be magnetic, so you need to make sure the screws you use on the extruder are magnetic or the whole concept fails

Finally Finished.

Yesterday I finally got my GT2 sprockets, and I assembled everything and ran a couple of tests.  I was able to tighten the belts pretty well, so I didn't need the tensioning springs I bought.  After adjusting the steps in the configuration file and saving them in the EEPROM, I ran my calibration piece and it looks nearly perfect.

I also seem to have gotten rid of the Z ribbing, although I need more testing on that.  When I was replacing the Y rod bushings with the flanged bearings, I noticed that the right side bushing was really loose and wobbly, so that may be what was causing the ribbing.  We'll see after I run a larger print.

So, without much ado, here is the final product...

...and here is what the whole printer looks like.

Mods List:

• RAMPS 1.4 w/ DRV8825  Extruder stepper driver (1/32).

• 750W Server PSU w/ front, lighted Power Switch.

• Graphic LCD controller.

• Ball Screw and nut for Z drive.

• Aluminum Print platform w/ full Copper Print bed and MK2A Heater.

• GT2 belts, sprockets and idler pulleys.

• Chrome hardened 8mm shafts.

• Chrome hardened 6mm "Y" drive shaft w/ flanged bearings and Pillow Block.

• Side opening wire Chain carrier.

• Custom "X" carriages w/ linear bearings.

• Custom extruder carriage w/ linear bearings.

• Custom "Y" motor belt tensioner.

• Larger Extruder motor (Kysan 1124090).

• 40W Heater cartridge for Hot end.

• G-Code controlled Cooling fan & duct

I saw it late last night.  I'll take a look at it later this evening.

How would a wobble in the Y axis cause Z ribbing? However this does explain why you witnessed such slop in the Y stepper belt on your machine and it is no doubt the reason you have had such a bad time with circles. Those bushings are mechanically sloppy as hell even if they are tight.

Well... it didn't.   I did a larger print with smooth vertical surface, and while it does look better, the ribbing is still there.  I'm really at a loss on how to get rid of that.

I don't think it's temperature related. The bed itself is not an issue, it only needs to be hot enough to hold the piece in place.  Nor do I have any large fluctuations in extruder temperature, my temp curve looks pretty flat throughout the print job.

Then there's the fact the error is extremely periodic, there's exactly 4mm between the "rib peaks".  That corresponds to the pitch of my ball screw.

I've been going back to check some of my early prints, and they didn't have this.  Best I can narrow it down to is during the time frame when I made the change to the RAMPS board.  I wonder if that has anything to do with it. 

Don't know, maybe some day the solution will present itself.

Since I'm using the stock SD4 extruder, I think I'll just edit the mesh to be screwed on the bottom screw holes of the left side of the extruder aluminum holder, where the side fan currently is. That won't get in the way of anything on stock SD4.

So earlier today and last night I tore apart my printer to do the first major rebuild since I first installed the Lawsy carriages.  I went direct drive externally mounted motor on the Y (accousedmonk's piece), dual pillow blocks and new 6mm Y drive rod, all GT2 belts and these new carriages.  I kept the Lawsy center carriage and still using the E3D V6 mount I made.  One picture here, then see imgur album for several large photos:

http://imgur.com/a/VRoPE

A couple comments:

• I also used your (Pirvan's) adjustable Y belt idlers that you posted in my other thread.  These were awesome!  The carriages seem to hold the belts very tightly but I still felt I need just a little more.  With just a couple turns of the wrench, I had great belt tension.  It was easy enough to knock out the PEM nut, just take your scraper and tap down on the front of the nut and it pops right off.  Then just hold the part of there as a template for where to drill the adjacent hole.

• Nylon was an excellent choice for the belt clips.  Its slightly flexible and it helped to not have a brittle ABS piece that would crack easier.  But ABS will also works, but if you've got nylon then go for it.

• The bearings are VERY tight in the holes.  I printed them at 0.3 layers in nylon.  I actually had to tap them in with a hammer.  Nylon does not sand as well as ABS.  However, the nylon is less prone to cracking with I shoved the nuts into the traps.  I was not able to get a good alignment between the two bearings and when I had two bearings in there I broke two of them by grinding and several balls fell out.  So I put a single bearing in the middle and there was no alignment issues and it still works great.  So if two bearings do not glide smooth, just use one.  Or get a better print and/or sand the carriages to get a good alignment.  It is less forgiving than the Lawsy carriages, which leave slight wiggle room between bearings for them to align on the rods. 

• I wanted to use bearings on all the idlers but the ones I got were too big on the outer diameter an hit the walls, so I'll look for some smaller ones.

After installing and changing steps per mm, I threw on a calibration cube and it came out good!  I just also did a vase with 80 mm/sec perimeters and it seems to have no problems going that fast.  All the belts are nice and tight.  Overall, I think this is the best mod since the Lawsy carriages.  Thanks Pirvan!

Interesting.

I doubt many users here used these anyway, but here are few "rebuttal" comments on mdrVB6 review.

1.  Loosing 10mm of build space.  That's interesting.  I don't use Lawsy's printhead (X) carriage, so I don't have this problem.  Is the 10mm lost from both sides (5mm + 5mm), or all on one side? Which?

2.  I did use Lawsy's "Y" carriages at one time, and I simply wedged some pieces of folded paper (from a business card) under the bearings to prevent play. 

On these, it's true they are tight, but the idea is to keep them tight.  To keep the 2 bearings aligned, I put them on a rod, then pushed them together into carriage.  Your idea of using a single LM8LUU long bearing works too.

Alternately, we could print the hole slightly lose, then use a set screw that aligns with the groove in the bearing.  That would probably be the better design, as it would also make installation and removal of the motor easier, since you could easily remove the bearings.

3.  I personally never noticed the bearing noise, probably because I have nothing to compare it too, other than the "X" carriage noise, and they both seem to be about the same.  Once it start printing, I think I hear the motor itself more than the carriages sliding on the rods.

Anyway, I've had these installed on my printer since the day I posted this, about 3 months now, and they seem to be working pretty good.  The belt tension is also good, and doesn't appear to have slackened any.

I've been toying around with replacing the standard hot end with the all metal one I got.  I even have a complete extruder assembly (carriage w/ bearings, hot-end, motor, fans, etc) ready to drop in place, but you know the old adage:  If it ain't broke...

Have you ever tried to create an x carriage(Left & Right) out of lawsy's setup along with the sd4 setup and your's combined? I like the design, I'm kinda leary about stuffing an lmuu bearing into a print and making it stay there. I like your design, just afraid of the bearings popping out of printed carriage.