X-Axis & Extruder Carriage

I decided to redesign this area of Huxley, as i felt that all those bearings and RP parts was a bit over the top.

X-axis (http://www.thingiverse.com/thing:4831)

I took inspiration for the Prusa Mendel, but tried to make the part simpler and slightly more attractive!

 

The axis is now made up of only 3 pieces: Idler side, motor side & the extruder carriage. I have not used any bushings or bearings for the idler or motor side; drilling the abs hole out slightly larger than 6mm allowed the silver steel z-axis rod to slide through easily without any play. As the axis is moved only a small amount by a lead screw the torque is high enough to overcome the increased friction, and there was no chance of an increase of heat. 

Extruder Carriage (http://www.thingiverse.com/thing:5421)

I wanted to make a very low profile carriage so I could allow for a concurrent second extruder in the future, which could be used to extrude support material. I used the same PTFE bushings as I did with the y-axis. These were turned on a lathe from 16mm bar stock (M6 hole and 10mm long) and push fitted into the printed carriage. 

From thingiverse:

‘Insert a M6 nut into the slot to allow a M6 bolt (or grub screw) to lock the thermal barrier in place (If you have a shallow M6 hole on the thermal barrier then the bolt can locate the extruder head in place... will hopefully save recalibrating when the extruder gets fiddled with!)

Finally use a short bolt (M6x15) to self tap into the side of the carriage to allow the timing belt to be attached.

Bushings:

Machine/acquire some 16mm round PTFE into 4x10mm lengths with a 6mm drill (or use US drill size C for a really nice fit). Then simply push them into the recesses with a small drop of glue (be sure to use a length of M6 silver steel to keep the bushings aligned)’

Y-axis

For the original Huxley design i felt that the y-axis was over complicated, and required the use of a froglet (complex flat shape to hold the bearings etc) which was recommended to be laser cut. I chose the simpler option of using a square of aluminium sheet (160x160mm) and bonding 4 PTFE bushings to the underside (using long setting epoxy resin was worse than super glue; which is still holding firm!).

To hold the timing belt i was feeling lazy so i drilled a couple of holes in a bottle cap and bolted it to the underside of the aluminium sheet to clamp down on the belt. Simple but effective!

Finally i wanted to make the build platform quick release using magnets, so i can get on with a new build while i clean up the old platform. To achieve this i used a nut and bolt with a spring inbetween (to adjust the level of the bed) I glued a neodymium magnet onto the bolt head (M6 bolt & 10mm diameter magnet) and to the underside of the build platform (making sure they were the correct orientation!) This worked surprisingly well, i could use the head of the extruder to align the build platform buy turning the nuts.

Also working to researching composites has its benifits.. a carbon fibre build platform!

A quick and ugly video of changing the platforms:

Building the Frame

To construct the frame i started with:

• 5m of M6 theaded steel rod
• x6 Silver steel M6 rod (comes in lengths of 335mm)
• M6/M3 washers and nuts (i bought 250 of each - overkill maybe but i may well make a couple more Huxleys!)
• Threadlocker

I used the following table from the Huxley Reprap.org page to know what lengths of M6 threaded rod to cut.

Dimension			Huxley SS All-Thread	Qty Needed	Comment
J1			314mm	6	Frame sides, the two equilateral triangles.
J2a			245mm	4	Frame bottom cross bars
J2b			335mm	2	Frame top cross bars
*			292mm	2	Z Axis Lead Screws
*			320mm	1	Z Axis Base Plate Rod A
*			295mm	1	Z Axis Base Plate Rod B

With the threaded rod cut i started to assemble the frame:

The silver steel rod is the perfect length in this case. Both the y-axis and x-axis was did not need changing. The z-axis bars were too long, but only by 50mm or so. I decided to keep them at that length as they act as legs when working on the underside of the printer.

The actual assembly of the frame is fairly simple as RepRap.org documents how to build Mendel, which has a very similar frame to Huxley. Once i was happy with the frame i threadlocked each nut.

Building an oversized Huxley

I am writing this blog to document my progress building the experimental Huxley RepRap. After looking at other people’s attempts i decided to make a oversized Huxley as it gave the best of both worlds – a decent sized build platform and a reduced cost compared to Mendel.

I am a postgrad at Nottingham University and am lucky enough to get limited access to a Stratysis Dimention 3D printer, which served as a source for the original parts i needed.

Below is a screen shot of my initial print bed. It contains the parts needed to make the frame, y-axis, z-axis, and x-axis. I chose not to print an extruder carriage as this is an area which is constantly evolving, and i chose to wait until the last minute to print it!

I chose to use MarcusWolschon’s hollow mini-mendel files as a base as i needed to reduce the build volume of the parts. Once the parts were printed i filled the shelled parts with casting resin which gave the parts excellent mechanical properties.

I replaced a few of the standard parts with some which simplified things:
Whosawhatsis designed some nice parts: y-bar clamps , Z-leadscrew clamp & Idler pulleys
Nophead's improved stepper motor pulleys

Below is a filled part (y-axis idler bracket)