Scara based 3D printer V3 details

Scara based 3D printer V3

Details:

• 100mm arms, designed to cover almost all mk2b heated bed, 
• 1/4 reduction ratio (gt2-16 teeth to 64 teeth)
• 608 bearings used for center axis
• 624 bearings for other.

Scara 3D printer v2 - fail

Short review - fail.

Aluminum tubes (od-8, Id-6) too weak, on a 30 cm distance twists for a 0.5 degrees along 30cm. 5mm threaded rod have the same problem.

Because of issues above printing results does not match target quality.

But, v3 is started.

My v3 ideas:

1) classic arm scheme

2) platform is fixed, printing block movable

3) smaller footprint -50x150x20mm

4) ability to convert to robot arm manipulator

Off topic

V2 still In progress, but not fast enough.

There are a few funny reasons:

• I have 2 apps on Google play and AppStore - totally 4 apps.

• Apple new iOS 9.0 broke all 2 my application - 2-3 hours per day sleeping during last 7 days.

• One of my Android app suddenly reached tops in one big region - I did 6 updates during last 2 weeks.

• Because of previous - database for game push, options and etc grows on 10% in 2 days (10-15K installs per day) - some time required to fix it.

In a few days I hope come back to V2 development.

P.S. My idea with inverted belts seems to be successful - I installed 1 belt and after 3 days belt tension the same.

Scara based 3d printer - v2 in progress

GitHub repository

Scara 3d printer cost calculations for V1

Approximate cost calculation for V1:

• 51$ — 5 Nema17 (you need only 4, so you get 1 for spare parts)
• 32$ — Ramps 1.4+5 Dvr8825+LCD (you need 4 drv8825, so you get 1 for spare parts)
• 7$ — E3DV5 (china made) with 1m PTFE tube (0.5m for spare parts)
• 2$ — extruder gear
• 6$ — gt2 pulleys and gt2 belt
• 5$ — 6mm smooth rods (2x20cm)
• 4$ - 4 LM6UU linear bearings
• ~10$ — ball bearings+bolts+screws+other stuff
• 10$ - external power supply 8.5A 12V

Total: 127$ (with power supply, but without ABS filament — approx 200g)
NOTE: All prices from my aliexpress orders, free shipping to my country, no taxes (in my country taxes begins only from 200+$).

NOTE2: V2 seems to be in the same price level, but not cheaper.

Ways to save costs:

• ~8-10$ - get rid of of LCD module 
• ~5-7$ - Replace one Nema17(for gearbox) to small 2.5$(28BYJ-48 12V) stepper + printed high ratio spur gears.

Not a lot.

More global idea:
Replace 2x10$  Nema17 steppers to cheap DC MOTOR + Hall Sensor + L293N + gearbox. The main problem is a backlash free gearbox. I think gearbox should have approx 1:100 gear ratio.

Backlash free gearbox ideas.

1. Looks like it is possible to combine 2 stage of 1:10 belt driven gears. Belt driven gear theoretically backlash free. 1:10 belt driven gear is a 16 teeth gt2 pulley and 160 teeth pulley (~101mm diameter), or use more stages with less teeth pulleys (seems like better due to the less belts length).
2. Planetary gears - at least 2 stages required - i tried to print - seems like printed does not work well.
3. Hypocycloid Gear - looks better but seems like it does not work due to printing precision, plus vibration may affect print results.
4. Harmonic drive - not tested
5. Classic gears - seems like not backlash free, there are a few ways to decrease backlash, but i not sure.

NOTE: It is just an idea

Printrun is forked

https://github.com/pavlog/Printrun

My first ideas:

• Add mark to show center of ccordinated - DONE
• Fix or rewrite ugly 3d viewport rotation (is Repetier like viewport rotation) - DONE

Scara - idea to use big pulley without teeth

Seems like current version of Scara 3d printer is done.

12 hours of continuous printing time.

Summary is 3d approximately.

Quality is enough for current version.

In a few days I will finalize scad and read.me file and ... v2 development.

Ideas for v2:

• x8 or x9 gear ratio (current is 5, with x8 precision will increased in 1.6)

• Belt path will be shortened twice (no belt couplers at all)

• No teeth on big pulleys at all (more precision, easy to print).

• Smaller dimensions (but with the same print area).

• A lot of improvements - more modular and service friendly

• Z axis will be improved (at least 2 bearing for each rod and may be threaded rod, more modular way to attach - currently is hard to upgrade without disassembly)

Scara - new video (test wall printing)

OpenScad files and firmware - https://github.com/pavlog/sscara

Scara arms redesigned to match e3d v5

Note: This is not original e3d v5 (I did it on lathe), but sizes matched to e3d blueprint.