Acrylic I3 Conversion

Hey all, I converted my Acrylic I3 from dual Z steppers to a single stepper. It was actually very simple to do. I purchased some 8mm pillow block swivel bearings to fix the tops of the Z threaded rods and some 8mm x 20 tooth GT-2 pulleys with dual set screws and a 6mm x 690mm (345 groove) single sided belt. I used a spare 8mm rod to align the bearings with the feed rod through hole, marked, drilled and tap for 8-32 button heads. I removed the right Z motor wire connection and assembled all of the parts leaving the right pulley loose. Adjusted the X carriage to within .003 inches of level with my lower build plate and then tightened the set screws on the right pulley. Before the conversion my right side motor was varying at Z position by as much as .060 inches making repeatable bed leveling impossible. After I leveled the new assembly I ran the Z axis up to the top and back down 3 times and my nozzle to build plate gap remained the same. What a difference. The total cost was as follows: (5) bearings $5.79 (shipped), (5) 20 tooth GT-2 Pulleys $5.50 (shipped) and the belt was $7.02 plus shipping. The bearings were a little stiff so I took them apart and sanded the sharp edges off and lubed them so that they swiveled smoothly. Maybe 2 hours to convert everything. Below are the links to the parts. Enjoy.

Pulleys:
[www.aliexpress.com]
Bearings:
[www.aliexpress.com]
Belt:
Stock Drive Products part# A 6R51M345060. Notice the space between the A and the 6.

I forgot to mention that I lost about 30mm of build height. This could be avoided if steppers with longer rods were used so bearings and pulleys could be mounted above acrylic caps. P.s. the belt fit perfectly without a tensioner. What are the odds of that?

Edited 1 time(s). Last edit at 09/19/2015 04:08PM by elwood127.

Congratulations on your first successful step toward quality and reliability!

What's next?

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Next is remotely mounting the extruder motor with a Bowden setup. Just waiting on the Bowden fitting. Then I need to get my 5/16" jig and tooling plate flycut and cut to size and mounted with a three point leveling system.Thank you D.D. for setting the bar.

Hi elwood127!

Thank you for this post! I have bought an Aliexpress Acrylic Prusa I3 more than a year ago, and I always had problem with it, especially with Z motors. I always faced with misaligned X "bridge" during the print job. I had to continuosly check the two heights with caliper and fine tune it during print! I also used a belt to connect the two threaded rods, but I kept the two Z motors, but the result was even worse: The Z lift was weak, less than expected. After some time, the printing head started to bump on printed object, in worse cases, it kicked the half-finished print from the bed. Maybe the output power is too weak for two motors, maybe they work against each other, maybe the not existing holding torque caused the carriage to slightly descend from X shakes. Anyway I also found that if I connect only one Z motor on output, then it is strong, and if it is stopped, than the motor is stiff. (Can't rotate it by hand.) I plan to buy this printer next time.
It has no printed parts which are inaccurate on mine, it has bowden extruder, and all the belts can be fine-tuned. I am sure it also has the dual Z motor problem, but thanks to you, I have a solution for this problem.

One question: Is the one motor strong enough to replace the two motors?

Edited 1 time(s). Last edit at 12/28/2015 05:46PM by DeXTeR323i.

I disconnected the wires for the right Z motor. I up the voltages of all motors to .7 volts. Works very well. If you go to my Thingiverse page there are all kinds of replacement parts to replace the originals. The acrylic frame is all that is left on mine and I get very nice prints. Good luck.

I've often wondered why some one doesn't make a Prusa kit with both z screws being driven by pulleys and a single stepper like you did.

Quote
WZ9V
I've often wondered why some one doesn't make a Prusa kit with both z screws being driven by pulleys and a single stepper like you did.

My suspicion is that the z axis can carry a far amount of weight depending on the configuration. And the two motor axis enables fine tuning of leveling.

Actually quite the opposite. Getting 2 motors to move exactly the same was problematic. My X carriage was constantly varying from left to right as much as .060 inches. Switching to 1 has dramatically simplified the leveling process.

Hey elwood127

You have cleared up a problem I have always had. I have seen so many youtube videos of people aligning the 2 pulleys by hand and then making another adjustment that throws the inaccurate hand adjustment out.

I read an article "Son of MegaMax 3D printer" on Instructables and what that guy says makes sense, especially about having a single stepper for Z.

Since I use the Global version of Ali, your links are just a reminder of what is needed.

I found these links on Global Ali:

1. Pulleys
Pulley

I was wondering why you require 5 pulleys. Won't just 2 pulleys for the top belt do?

2. Bearing
KFL08 Bearing

3. I found this link for the belt you mention.
[www.sdp-si.com] and entering the part number, brought up the belt.

If these parts are not correct, please post here.

Thanks for your post.

Addendum

The closest dimensions to your belt is this one on eBay:

Timing Belt

Unfortunately it is 6mm too long.

Do you have any suggestions how this belt which is 696mm long, can be used with your design?

I have some ideas how it can be used with a belt tensioner but any ideas you or anyone else have would be really helpful.

5 pulleys were the amount in that lot. Only used 2. The parts you show are perfect. If you go with the longer belt you will have to add a tensioner on the acrylic frame. The 690mm belt fits perfectly. If you can draw, the tensioner should be a breeze. If not I would be willing to draw something up for you to print. PM me. Good luck.

Hey, you could get slightly bigger pulleys to take up the slack of the 696 mm belt. Maybe one of the local genius's could calculate the size for you.Center to center of the threaded rods is 324 mm. 20 Tooth pulley diameter is 12 mm. Stock Drive Products does have a center to center calculator.