Monday, April 12, 2010

Assembly Begins!

It has taken a while but I have finally started construction of the Mendel. Definitely a very exciting day.

On Saturday, I went out to the garage and cut all the smooth and threaded bar stock for the machine. It took about an hour and a half. I bought stainless for the smooth bars and I went through two hacksaw blades cutting it. I smoothed out the ends of those on the grinder and I was ready to go. I actually still have to go out and cut the three jigs because I forgot about them at the time but, I will cut them as I need them.

My Molded Parts

The molded set of RP parts I bought from Ireland are extremely rough. The holes are all undersized, probably due to shrinkage in the mold material, and have to be drilled out. If the shrinkage in the rubber caused undersized holes it also probably caused the entire part to be slightly oversized. Many of the holes were filled with a rubbery substance and others were completely filled in with the casting material. I finally realized that parts of the rubber mold had broken off in the bolt holes when the parts were removed from the mold. The missing holes are where the bits broke off in the previous casting and were not present during the molding of my parts. This would indicate that the quality of these cast parts drops significantly from the first casting onwards. There is also some warping but not enough to cause problems

Anyone buying these cast parts should inquire whether they came from the first or second casting from a particular set of molds. Anything after that is suspect. Whoever bought the set that was cast after mine probably had most of the holes completely filled. I would not recommend these cast parts unless you can acquire them for considerably less than a set of printed ones. They require much more manual cleanup to be usable.


I started by cleaning up and drilling out the parts for the carriage assembly. The x-carriage upper and lower parts have a lot of trapped nuts and some of them needed to be enlarged or cleaned up with a Dremmel in order to get the nuts into them. The majority of them were OK, however, and a bit of pressure with a set of pliers allowed me to force fit the nuts into their cavities.

Strangely enough, my most serious problem was that I don't have any metric hex wrenches. None of my SAE ones would fit well enough for even rough work. I had to grip the cap of the screw with a set of pliers since they require more torque than I was able to apply with fingers alone. I will pick up a set of metric hexes this week.
My most serious problem was that one of the holes for the bearings on the lower carriage was missing and I drilled it at the wrong angle. You can see from the pictures that the bearing outlined in red will not sit correctly on the steel bar. I am going to have to remove this one and redrill the hole.

In the end, however, I was able to assemble the very first parts of my Mendel. I can see that the assembly will take quite a bit longer using these cast parts but they should all prove to be usable. I will certainly make printing a proper set of replacement parts a high priority as soon as the machine is operational though.

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