Friday, 26 August 2011

LM8UU Linear bearings and T2.5 pulleys and belts

Ive also upgraded my system to use real LM8UU Linear bearings on all 3 Axis.

For this you need to print new x-carriage, x-end-idler and x-end-motor parts, and some LM8UU Holders to replace the bushings on the Y axis.

Currently all these things are in different places on the net.
LM8UU x-carriage is here in scad format
LM8UU x-end-idler and x-end-motor is here
LM8UU holders here

This is the underside of the new x-carrage.


This is the underside of my Y axis
This is the new x-end-idler
This is the new x-end-motor

In all of these I found the LM8UU holder to be very very tight, and inserting the LM8UU was difficult.

With the Y holders I broke several before I got a good set. I found that PLA is a little to brittle for these to be pressed into position and they just snapped. The best way I found to get these in was to reheat the holders in an oven to about 50c and then put the bearings in, while it was warm.

With the x-ends I put them in a vice and slowly squeezed it shut, forcing the bearings in.

One unexpected result of this upgrade is my commercial 11 tooth t5 pulleys was to large a diameter for the new x-end-motor. It physically fitted, but belt would rub on the lower stepper mount. The quick fix was to upgrade the belt and pulley to T2.5. These fitted without issue.

I then updated the Y pulley and belts to match

This image makes things look twisted, but they arent.

I got the t2.5 belts and pulleys from http://www.redwizard3d.com/products/prusa-2-5t-belt-set-2-x-900mm/ and http://www.redwizard3d.com/products/set-of-2-aluminium-pulleys-16-tooth-t2-5t/



Sunday, 21 August 2011

Z axis stabilizers

A while back I also added some Z stabilizers. When I upgraded my Z threads from BZP to stainless steal I lengthened them with the intention of adding Z stabilizers, many months later I finnlay added them


I first saw these on pictures of makergear Prusa's and thought they where a good idea. I hunted around the Internet till I found them Left here and Right here

These added a lot of stability to to the entire X axis, and made a much nicer print.



Monday, 15 August 2011

HBP (Heated build platform)

I have had a heated build platform for some time, but I havent written about it.

This is a PCB headbead, its just a Standard PCB with tracks that have been made so that when its pluged in its about 1ohm of resistance.

I got mine from http://ultimachine.com/content/prusa-pcb-heated-bed

There are a bunch of options for printing onto this, some people print directly onto it with Kapton tape.

I decided I wanted to print on glass. With glass you have to be careful not to create any hot spots or the glass may shatter, especially since its normal glass, in this case recycled from an old flatbed scanner. So I put a 3mm piece of aluminum on top of it as a heat spreader.





This is the underside of my HBP, the thermistor is stuck to the board with Kapton tape. The wires are in a loop so that board can move in and out and not pull the wires off. The wires are only rated to 80c, so ABS is off the menu for now.


The PCB holes are countersunk into the 3mm aluminum plate, so they are flush.
These are bolted onto the L pieces, with the PCB sandwiched in between them.
The Standard mounting screws are countersunk into the L peices and are flush with the PCB



The glass is simply held on top by Bulldog clips, which makes for easy removal for cleaning

The glass must be clean and free of finger prints, I washed the glass in standard dish washing liquid as you would a plate. I then degreased it with acetone, making sure to only hold it on it edges.

This just plugs into the Sanguiololu, as does the Thermistor.

NB this takes 10AMP at 12volts on startup,make sure your electronics and power supply can handle it.

I found that 60c is a good temperature for PLA to stick to the HBP, and they come free after the glass cools to below 50c.

This does take a we while to get to temperature. Some people put their HBP on a wooden backing board. This probably keeps the heat in better, and it should get to temperature sooner.

The final prints are now very flat, and the finished surface is really glossy.