Assembling the X-axis...

In an earlier post (here ) you'll see my x-axis design and trial assembly. It's come time to assemble it more precisely and more permanently. To align the x-axis ends with the vertical rod clamp positions I simply left some length on the z-axis rods, extended them upwards, inverted the x-axis assembly and sat it on top (see pict). This kept everything in position until I secured the x-axis rods.

With the reprapped x-axis ends you have a captured nut and lock-down bolt to hold the x-rods in place. In my wooden rep-strap design I abandoned this as too complex to incorporate in wood. Instead, I've come up with the following simple approach to secure the rods.

A small brass screw, fitted to a pilot hole which glances the stainless rod holds it in place very firmly. The tapered nature of the screw means that it pushes more on the rod as it advances into the wood.

I drilled and fitted four brass screws in each end. Here you see the x-assembly in it's up-side-down position on top of the printer.

Here you see the x-assembly now in place on the printer. I slackened the bottom clamps on the z-axis rods, and raised and lowered the x-axis assembly by hand until it travelled without resistance up and down, then I locked the z-rod clamps. Next it's on to design my x-axis motor and idler mounts!

Thanks for viewing, feel free to add comments or ask questions. I'm also contactable via PM (personal message) on the RepRap Forum (forums.reprap.org) under username "NumberSix".

Z-axis motor mounts...

In the Prusa Mendel variant there are two Z-axis motors, on top of the printer. They are wired in parallel, turning threaded rods connected directly to their drive shafts. They lift and lower the X-axis assembly, which is held in the vertical plane by two vertical rods. This is a much simpler arrangement for the Z-axis, and seems to be working well for others.

The position of the motor drive shaft and the anchor point for the vertical slide rod must be exactly above the matching holes in the X-axis assembly. It helps to line the ends of the x-axis holes up with the z-axis blocks when marking/drilling the x-axis block.

I worked on these blocks at the weekend. Maintaining my wood based construction approach, I cut two 60mm x 80mm blocks with my chop-saw, from my trustee oak floorboard! Here’s my sketch that formed the basis of my plan, and some photos of the steps and finished Z-axis motor mount blocks.

In the RepRap printed version of this part, the large center hold is left much larger, to allow the motor to find it's own center (I gather). I'll see how it goes at 22mm but may have to widen it if my z-travel binds.

I drilled all holes first, then used a router to remove the 42mm square to a depth of 1/2 the block.

I test fitted the motor to ensure a comfortable fit.

I secured the block to the apex-rods. I've decided to use spring washers on all final external nuts - you can see them on the external nuts in this photo. (look like wider washers when squeesed down).

It is advised to secure the motor with some tape or strapping but no need to lock it down completely. I'll add something later.

This is what it looks like from the underside. (I made two, once block for each side.)

Feel free to leave a comment or ask a question. Thanks for viewing!

Y-Axis Stepper Motor mounting bracket...

Having received some Stepper Motors along with the electronics, I was able to tackle some barcket design. I've started with the Y-Axis Stepper Motor mounting bracket. Had some 3mm aluminium sheet which I figure will be strong enough, and relatively easy to work. I did a drawing (below), then cut and drilled out the plate to meet the requirement. Here you go!

I've been working with 60mm between centres on the vertex joints, so you see that measurement employed again here. I positioned one of the stepper-motor mounting holes to the third corner of a equilateral triangle, and this set the motor spindle in a good position. The rest was just eye-pleasing geometry, no major science behind it. (These dimensions may not match Mendel printed parts exactly! They are my own interpretation.)

Aluminium is a nice material to work. I cut this with a hacksaw, cut the larger hole with a piercing saw, and rounded the external corners with a hand file.

Here's the bracket in place, with the stepper-motor mounted. It is very rigid once the nuts are tightened.

This view shows the purchased drive-pulley (mendel-parts). People fit that pulley the other way round also. I'm happy with it this way for now.

My washers are slightly oversized (40mm as against 30mm). Was all I could find. The old scrap piece of aluminium is a bit pitted also, but is going to serve me well I think!

GEN6, batch2...hmmmm...nice!

Mendel-Parts delivered this week! Thanks guys! I ordered motors, electronics and some other bits 'n' pieces. The Generation 6, (Batch 2) electronics is a neat looking board, even to me, and I'm not really that geeky. It's tiny (use the network connector for scale). It's amazing, and open-source... I'm so impressed and that's before I even power it up! :)

The batch 2 version's characterised by the little black heatsinks on the stepper driver chips, and I'm sure there's a few other goodies. I took a pict or two (below). I hope the guys at Mendel-Parts won't mind me sharing. Now I better crack on with mounting motors and fitting drive belts and all that good stuff. Hmmmm.... more RepRap fun! :)

Reverse angle...

Hex Coupling Nuts as bushings?

A friend of mine, who's recently also caught the RepRap bug, was looking for bushings to use with the 8mm rod. With access to a lathe, he reamed out some Hex Coupling Nuts, using an 8mm reamer, and gave me some to try. The process was quick and the result was excellent!

With 8mm centre removed what's interesting is that a sliver of thread groove remains inside. We figure this would serve well to retain some light lubricant.

It's a lovely fit and a very smooth movement.

I've fitted a pair to my X-Axis just 'cause! I'm begining to think the extruder platform might actually be stable enough with only two of these... they are such a good fit!

Motors and electronics ordered...

Quick update: I've ordered Gen6 electronics and motors today. I'll continue to investigate extruder designs and only move on parts for that once I've chosen a design I like. I plan to experiment with extruder variations once I have a functioning chassis.

Thank you for visiting! Feel free to leave a comment.

The Print Platform...

This week I gave time to the print platform construction, reviewing images, approaches and discussions on the topic. The basic Prusa Mendel style print platform is a two tier structure. The lower smaller board has bushings attached and rides on the parallel rods of the Y-axis. The upper board is typically square (225mm) and held aloft by springs on four bolts, and usually carries some kind of heated bed.

The debate continues on-line about the purpose and merits of the spring platform arrangment, and even about the number of supporting bolts to use. The springs are to allow easy levelling, and possibly absorbe accidental impact of the extruder head. The argument in favour of three bolts instead of four is that you can more easily level the platfurm with three spring loaded bolts vs four. I'd agree with this but would thing the down-side is a larger section of the square platform is now unsupported and may flex depending on the rigidity of your platform material.

I'm not sure of the need to have any leveling capability at all though. If your rods are alligned on the horizontal plane, and parallel to each other, your Z axis accurately perpendicular to the horizontal, and your X axis perpendicular to Y, then why are you levelling the platform? Surely you should get the Y axis right and step the 'print platform' up to the desired height with fixed height rigid risers from the Y-axis bushings.

For me, the four bolts with springs design will do to get started, but I've beefed up the bolts and springs. I'm choosing a 'mushroom head square neck' bolt which secure nicely and have a low-profile. I could have gotten away with 5mm bolts but had some 6mm to hand.

Here's my construction method including the attachment of the bushings... Time will tell how well it works!

The upper and lower boards were clamped together and four holes drilled. The positioning of these holes isn't actually critical. Just mark the boards so you can assemble in the same orientation as you drilled. The round holes were then squared out with a needle file to receive the bolt neck.

To position the bushings accurately I put two scrap lengths of wood together and drilled two 8mm holes in them at the desired distance apart for the Y rods. This is an easy way to get the holes perfectly alligned. I then temporarily fit the bushings and rods as per the photo.

 I used Araldite 2 part epoxy to secure the bushings to the under-side of the base platform, allowing it to set over night.

I then fitted the bolts to the top platform, first squeezing them home with a wing-nut for convenience, then fitting a washer and nut and a dab of thread lock.

Finally, I fitted the springs, attached the top plate to the base plate and secured it with some nylock-nuts.

That's it for now!