Hardware store fix for prusa belt tensioner

On my self sourced prusa I have been going back and forth on how best to tension the belts lately. I had a zip tie hack that actually worked out fairly well, but it had a fair bit of slop in it, and I think that helped set up some vibrations and Generally keep it from being the best it can be.
I love my local hardware store. I went there (twice) today and on the first walk there I remembered this piece of hardware that is generally used to tension screen doors to keep them square. I checked one out and I think it will be perfect for my y belt. I may even throw one on my x axis, but I’m not sure if I need it.
Here’s a pic

As you can see in the pic I have been experimenting with a very light y stage. It is perforated hardboard that they sell for hanging tools. The actual bed will go on top of there with 4, 5mm bolts and have the glass and hbp clipped to it.

I have also gone with a double wide skate bearing for the idler end of the x and y axis. If the two ends are aligned, then you don’t need anything else keeping the belt “on” the pulleys. Simple tension holds them there. This has made things much smoother and simpler compared to using fender washers.

Advice needed for Makerbot rebuild

To be honest: I posted this to the makerbot forums. I have had limited luck on those forums before so I am also posting here. I’d like to be able to get input from reprappers as well as makerbotters.

I’m rebuilding a late-model cupcake for fablab Boston. It has had some parts stolen, and I’m looking for advice on what route to go.

The two issues are that the motherboard has been stolen and it has a mk4 extruder. I know that the simplest thing to do would be to buy a new motherboard but the direct replacement (1.2) seems to be perennially out of stock.

Then we get to the fact that it still has a mk4 extruder. Since this will be used to teach kids how to print and do 3d design, I would really prefer if it had a bulletproof hot end. I think that generally means stepper-based, either mk6, mk7, or a wades style printed one.

Option 1_ I can get a motherboard v2.4, stepstruder mk7 complete kit, and an arduino mega 2560 from Makerbot for $85+$229+$65=$379

Option 2_ I can get a motherboard v2.4, another stepper driver, a stepper motor, arduino mega 2560 from Makerbot and some printed wades extruder parts for $85+$92+$65+free=$242

Option 3_ I can just get the motherboard v2.4 and an arduino from Makerbot and fight with the old dc extruder for $85+$65=$150

Option 4_ I can get a full reprap-style ramps board from reprapworld.com with stepper drivers, an arduino mega, a stepper motor and printed parts for a wade extruder for $130+$16+free=$146

Am I missing any better options? I’m leaning towards option 4 currently, but I could be persuaded. Am I correct in assuming that I can’t use repg on a RAMPS setup? That would basically be a full reprap toolchain conversion.

I’m honestly fairly excited about moving to a slic3r / pronterface toolchain because repG has always been fairly buggy and I feel like the cupcake is not that well supported in recent versions.

Direct drive Extruder gear

I’ve been on the lookout for the same kind of gear that makergear uses on their extruder for quite a while. Not the gearhead for the motor, but the actual part that bites into the filament.

I found cornwall model boats this morning, and I ordered a few from England. It appears to be a fitted end for a model boat u-joint, but it looks like it could easily work and they are available in both 5mm and 1/4″. I have a vague idea of using two of those on the shaft of this motor to make a dual filament bowden extruder.

The point of that would be to print the same part on the same machine twice at the same time. RAMPS has support for three thermistors and three outputs, so I could effectively double my print speed for parts that occupy less than half of the bed! An alternate idea is to use one RAMPS to control two machines, by either getting more powerful motor drivers or by getting twice as many. The only issue with that would be the 4 thermistor issue. Either printing PLA or some external circuitry could be fix that. I’ve been meaning to build up a bang-bang heated bed for some time now…

Boston Reprap User group meeting

I’m trying to put together a meeting of people interested in 3d printing. It’s called reprap because I think most of the people will come from there, but makerbotters and professional printers alike are more than welcome!

I’ve got a post over on the reprap forums trying to get an idea of how many people are interested and when we should do it. If you want to come out, then post a little bit about yourself over there and hopefully we can meet up!

makergear prusa z-axis fine adjustment screw detail

The makergear google doc only has a mention of this adjuster screw. I was really confused regarding what they were talking about. I finally saw it in one of renosis’s flickr pics and I decided I would take a closeup to show it in all of its glory.

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