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A word from a newbie

Posted by Ron Luttik 
A word from a newbie
July 28, 2007 09:44AM
Hello everybody,

A couple of months ago someone wrote an article on 3d printers on a website that I frequently visit and in the replies to that article a link was mentioned to a website called www.reprap.org. I visited it, and what can I say other than that it was love at first sight. Within seconds I knew I wanted one as well.

After reading more or less everything on the website for a couple of weeks I went to the reprap store where I bought the following: The circuit boards (comm, 5x UCB, 6x optostop), Heater barrel, 5 different nozzles, Nichrome wire, Teflon barrel and 5 PIC's. I then went to the hardware store and got myself all the rods, studding, fasteners and such and got the electronic components to fill the PCB's.

At that time there was still a little optimistic note from Zach on the store's website saying that the RP parts for the Cartesian robot would become available on the first of july. Unfortunately, the first on July came and the little note went away without the parts becoming available. After my tears had dried enough to see again, I started looking into the way that Joost van der Wiel was doing things with his printer called "Richard" and decided to follow him.

First task: the bed
Having the A4 templates thats not too hard.

Second task: Corner brackets.
Took the measurements from the PDF's that Joost uploaded and made it from 'vuren' wood (no idea what to tranlate that into), which I hapened to have. Thats not hardwood like Joost, but the rather cheap soft kind. Since I do not have a drill press, I had to visit someone to make these. They came out not too bad, but they splinter. If you cannot saw straight (like me) and/or do not have a drill press (as I do) these are quite hard to get right.

Third task: Diagonal tie brackets.
Went to the hardware store again to get myself some of that square aluminum rod that Joost is using for (among other things) the diagonal tie brackets. When I was there I noticed that they also had these square rods made from PVC, which drills and saws a lot easier (and was somewhat cheaper). So I bought some 1 meter lengths of it, measuring 19,5mm x 19,5mm and a thinner one of 11,5mm x 11,5mm.

So far I've made the following parts with it and they are all fairly easy to make. Even without a drillpress and without the ability to saw straight. I think the whole lot can be made is less than a day.

Corner Bracket (8) (can be made easier from PVC than wood. It won't splinter and its much easier to keep the angles right)
Bed Clamp (4)
Bed Corner (2)
Bed Corner / Constraint Bracket (2)
Diagonal Tie Bracket (20)
Optoswitch Bracket (3)
PCB Clamp (8)
X Belt Clamp (1)
Y Bearing Housing (3)
Y Belt Clamp (1)
Z Opto Flag Base (1)
Z Opto Flag (1)
Z Studding Tie (4)

That adds up to about 2500mm of the thick rod and 620mm of the thinner one. (I paid in euros 2,71 per meter for the 19,5mm one and 1,69 for the 11,5mm one. Total cost: slightly less then e10,-).

For the Y and X axis that would carry the sliding parts I cheated a little. I found that sliding the PVC over the hollow aluminum rod that I have was not as smooth as I had hoped. So I bought three printers from one of these recycling firms. 2 HP's and a Lexmark, total cost 18 euro. From these printers I took the rods (HP diameter=9mm, Lexmark 7mm), the cartridge holders with brass bearings some springs and the belts with accompanying pulleys. There are some nice steppers in there as well, but I have no idea how to get these working, so for now I'll stick to the 'official' ones. The rods are not long enough to pass through the corner blocks, but they are long enough to just screw to the side or on top of it. This glides so smoothly that if I'd put a little sail on it I would probably be able to blow it to the other side. It was in these printers that I also noticed that the belt(s) are kept under tension by a spring. Since my belts were a bit shorter than the required 950mm, I made a somewhat simple construction that does that as well. (using one spring and a shoelace :-) Dont know if it will work but I can always change it again.

At the time of writing the motors are in the mail (ordered from Farnell), so their mounting brackets and couplings are more or less the only remaining items on my RP glossary list.

If anyone is interested in the sizes that I've used for these parts I'll gladly write them up.

open | download - Photo-0005klein.jpg (26.6 KB)
Re: A word from a newbie
July 28, 2007 10:06AM
That is incredibly good and detailed feedback on going Joost's route with Richard. Thank you so much for sharing it with us.

The pic looks great!

> Took the measurements from the PDF's that Joost
> uploaded and made it from 'vuren' wood (no idea
> what to tranlate that into), which I hapened to have.

Vurenhout translates over into English as "fir" wood, from the fir tree. Although there are dozens of species since you're in Europe I'm guessing that you're using Picea abies, varieties of which are cut commercially all over Europe.

While English speakers will refer to fir trees, they generally refer to the tree or wood when talking about lumber as spruce (dinnehout). While I'm sure that someone with a lot of expertise in the field could point to the difference between fir and spruce they're pretty much the same thing in practice.

Cutting to the chase, vurenhout, especially that grown in warmer climates, does tend to be very splintery. Better choices would be either poplar (populierhout) or oak (eikhout). You want a wood with more radial fibres. Those tend to hold together better when you're making small pieces with lots of holes.

You need a thick piece of wood to make those corner brackets, which is, I expect, why you used spruce. While poplar would be good at least here in the States you don't see it sold in the thicknesses you need except in very large pieces which are a bit expensive when you only need a few cubic decimeters. Oak, on the other hand, can be bought in thick, small pieces, so it might be a more cost-effective choice.

Edited 4 time(s). Last edit at 07/28/2007 10:51AM by Forrest Higgs.
Re: A word from a newbie
July 31, 2007 12:25PM
Hello Forrest,

Thanks for the kind words and the detailed explanation of the different kinds of wood. The only reason I chose the fir wood is because I just happened to bump into it and it had the right size. Someone elses was throwing it away. As you can see in the picture I made the next version from PVC as well. Glued some washers on it where the studdig will go to prevent wear and stuck some trapped nuts in it where needed.

Ron Luttik

Edited 1 time(s). Last edit at 07/31/2007 12:27PM by Ron Luttik.
Re: A word from a newbie
August 01, 2007 01:10AM
Hey Ron,

Interesting approach! Have you also tried to assemble the frame, and check if things are aligned? It is a problem I now seem to bump into with my wood corner brackets. When the vertical holes are not parallel, you risk that the studs for the Z bed are not parallel, which causes problems with the Z belt tension. I found that tolerances actually do play a bit of a role ... :-)

Re: A word from a newbie
August 01, 2007 12:12PM
Hi Joost, nice to hear from you.

To keep it somewhat aligned, all the holes were drilled before the glue was put on. I also measure and drill the holes from 2 opposite sides. Checked for straight angles after every step. Your wooden brackets already tought me that proper alignment for them is quite important. (too much tension on them already bends the hollow aluminum tube that I thought of using for the top frame somewhat)
I assemble everything on a piece of paper which has a raster on it so I can see whether or not its all still square.
The PVC is very easy to work with. I just drill the holes 8mm only (except Z studding hole, which is 8,5mm). If you stick a piece of studding through them and check if the angle is right, it's easy to correct small deviations using the studding as a file.

Getting the Z pulleys and belt somewhere is next on my shopping list. So I've got no experience with the tension on them yet. If I remember correctly you wrote somewhere you found something suitable in a 'modelbouw' shop? Can you please tell me which one? Here in Zaanstad there are none of them left :-(

BTW. My wooden corner blocks are not exactly the same size as yours, I made them 44x44x44 instead and drilled the vertical holes in one of the sides. Someone with more woodworking skills than me said that would be somewhat stronger and easier to drill. It also meant I had to drill only 1 hole on a side that I had sawed myself (not really 'haaks').

Re: A word from a newbie
August 01, 2007 02:45PM
Hey Ron,

Sounds like you thought it through :-)
The size of the brackets shouldn't matter; as long as it is around 14 mm between the holes for the horizontal rods you're fine. About the gears: got 2 from a shop in Leiden, but they were very expensive (specially the belt) and not very good.

My advice: get the belts from either an old printer or from RS components (get 6), splice them for the Z belt (2), use some for the Y (2) and X (1) belt and use the 6th for making gears yourself using CAPA (can be ordered from Teacher's supply). I made some small moulds for the X/Y pulleys (with a 14 mm hole) and a larger for the Z pulleys (50mm hole) using 19mm multiplex. I can post some pictures and process description if you want.

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