Sunday, August 10, 2008


RepStrap Build Using Laser Cut Parts Kit

I started my mechanical build of a RepStrap this weekend using the laser cut parts kit that I purchased from Bits From Bytes. Here are some of my sub assemblies.

What went right:

1. Parts are very well made. Well done Ian!
2. Drawings were easy to follow and no major assembly problems so far.
3. I have all of the sub assemblies built as far as I can go with the parts that I have.

What went wrong:

1. Some of the M3 and M8 clearance holes in the laser cut parts were very tight. I opened the holes up a tad using a small fine round file.
2. The areas meant to captivate M3 nuts are very tight for nuts measuring 5.4mm in width. I didn't want to force them and possible crack the part so I ended up taking a fine flat file and opening up the cavities ever so slightly.
3. I ordered some of the wrong hardware, M8 bolts not threaded the full length for example.
4. Having trouble locating a few parts such as the sleeve bearings.
5. I had already cut the plain rod lengths from the old Darwin specification and the new lengths are different. Need to order more stock and and re-cut the rods to the new lengths.


1. Don't throw away anything from the sheet of laser cut parts. I lost one of the smaller parts.
2. Print out the PDF of the parts sheet available on the Bits From Bytes web site and check all of your parts.

2. Take a fine flat file and remove any small bumps on the edges of the laser cut parts.
3. Before assembling any laser cut parts, run the proper bolt through any clearance holes to make sure they fit before trying to assemble them.
4. When you get to the extruder construction don't forget that there are 2 videos that are absolutely essential. One of them locks up and I seem to remember a post on one of the forums about the lock up but I can't seem to find it.


I already have the electronics built and tested as well as the Java host application up and running using source code in Eclipse. I have built the firmware from source and that's what I'm running in the PICs. I don't have an Arduino yet.

I will have my rods cut this week and order more parts so I should be able to get a lot done next weekend. This is the most fun I've had in a long time.


Wow! Shiny! Thanks for the beautiful pics. I hadn't realised that Ian had done such a lovely job documenting how to put the laser-cut Darwin together.
I'm also part way through building a laser cut reprap/strap, but I was a bit more of a wimp and went for the full kit ;-}>.

The tight holes can be expanded by running a drill through, but watch out for the drill grabbing the part and spinning / breaking it. Before getting carried away a couple of the parts are intended to be tight though, such as the belt gears and parts on the motor shafts. Although it’s not a problem if they are opened out as they are secured in other ways as well.

For the nut slots make sure you are inserting the nut from the correct side. The slight slope the laser cutter leaves can make enough of a difference for it to go in easily on one side and not at all from the other. I found it easier if a bolt was put temporarily through the nut to get a better grip, especially when it just starts to go in.

Being more used to working on cars than repraps, e.g. gently tighten means about 20Nm, I have cracked and or broken a few of the parts. Fortunately superglue is very effective on acrylic. It bonds well enough that I’ve not had any parts re-break, of cause I’m sure it’s possible to have no parts break in the first place but it’s good to know it’s not the end of the world if you do.
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