Saturday, December 19, 2009

Mendel build Day Two

I spent about 2 hours last night working out the X axis parts on the computer printing stl files out on paper. And using this little application for gaining the external dimensions.

It was good in a way to have break from Mendel last weekend particularly as the ground outside is frozen solid this weekend.

As I have re thought the design. First I will remove the two extra Nylon corner blocks on the bottom bar of the two A frames they are used in a real Mendel.. my lazy / simplified design they are now not required.

I have cut 2 MDF plates 2 off of 150mm x 60mm X 12mm and 2 off of 90mm X 60mm X 12mm for Z axis.

Finding that I did not have along enough belt I found a little draw with some of these Geeenweld gears for the Extruder V1 its a pack of 5 for £1:30.

Screwing one gear through the threded rod hole then positioning other meshing with it. I got the center mark to stick my photo copy of a stepper motor on. Drilling out the tiny hole in one gear to 5mm so I could screw it to the brass hub from Conrad means ~I can fitt it to a stepper.

First I thought I would keep this true to Mendel so I drilled the other two gears out to 8mm big mistake the colar causes the drill to run off center here is the first experimental result.

Making a few diffrent machines ~I also did not have enough 8mm bar but I did have 8mm tube that a 6mm bar fits I used tube on Bertha CNC so I know this works.

So to regain a concentic hole I found 6mm penny washes fited the gear center perfectly one each side of gear removes wobbly gear effect the skate bearings then needed to have a skate bearing insert to reduce the 8mm hole to 6mm great problem solved no need to use belt for Z axis just two cheap steppers.

Final assembly picture

My X axis is about 10mm wider than the printed parts. The Z cartridge is made from 1off 97mm X 84mm x 6mm the 2off X end plates are 62mm x 84mm 6mm.

I have not made proper drawings yet as it was a simple process of positioning the bits and holes to suit I have set the Slider 30mm from the Screw drive on both sides of the Z axis. To maintain the alignment I drilled these holes out using a 2.8mm drill then drilled the bigger holes.

Just a few parts left to make now.. the build base carridge to mount the build base madelast week and the Z axis drive and slider/bearing mounting board.

From Blogger Pictures
Sofar its been about 8 hours today spent building Mendel Im not far short of finishing the whole of the Mendel frame work. next it will be building the electronics fixing belts and testing.

This an ongoing post through out Saturday 19 December pictures to be added.


Unknown said...

of all the repstraps I think this is my favorite. excellent job, and i look forward to future posts.

are those corner brackets you are using custom or something from a hardware store? something mcmaster-carr stocks by any chance? I saw your prior post about drilling out the centers, but didn't know what the original part was.

Unknown said...

Fixing Blocks in pks from DIY stores in my blog notes I re Drill some holes out from the original 4mm hole to 8mm or 8.5 mm

In the Uk every single DIY shop sells these blocks all use a diffrent name to describe them.

I used the same blocks in this Blog

Also to build Bertha my original CNC machine

here are some UK on line Diy store links to thes parts.:-{9372218}&fh_search=fixings+&fh_refview=search&ts=1261270332595&isSearch=false

Unknown said...

A nice little web site I found detailing the usual use of thes blocks.

Unknown said...

Your doing really well, Im looking forward to seeing your results.
Can I just ask a couple of questions?

* If you have a couple of repstraps already, why didnt you print the parts to make a full blown Mendal RepRap?

Im at the point where I either pack in with CopperRap 2 and go for a Mendel, or finish it and print the parts for a Mendel.

* You have added a pair of gears to the drive chain at the end of the sliders - arent you concerned about the backlash of the gears? Will you add some anti-backlash device or are you going to risk it?

Unknown said...

Untill I build the Modular Flat Pack Solar Shed I dont have the table space for the Two Darwins I have I have spent almost all day moving stuff out of the Kitchen ready for Christmas. I have literaly just started playing with Mendel again.

Mendel fitts on thw small £6 Ikea folding tables as it is not so high and looks narower (its not) I can get away with having it in the Dining room it covers over and dosent look so ugly as Darwins do.

The gears are plastic and seem to be a tight fit. The Z axis usualy is only moving upwards as it builds so I am not to concerned with backlash as each layer is about a third of a turn of these gears. So I dont think I will be affected by backlash as tis is only moving in one direction. Maybe Nophead will corect me if Im wrong on with this idea.