EEVblog #274 - Makerbot Tweaking & First Print

[IanJ]

Dave,

Gotta say I love your blogs.......this one especially when the two pieces you made didn't fit.....had me laughing......but only because myself and probably most other folks here have been there and done that also.

Off the cuff.............indeed!

Fantastic!

Ian.

[robrenz]

Dave,  You need a lathe and mill in the lab.  Then I might be able to give you some professional advice

[SeanB]

I would like one as well, even a combination unit. But space is the problem, unless i can find an instrument lathe.

[robrenz]

Tooling ( chucks, vises, collets, toolholders, etc.) and cutters (end mills, drills, reamers, taps, lathe bits, boring bars, etc.) and accessories (digital readout, coolant, lighting storage, tool grinder, phase converter, etc.) are the killer. Plan on eventually spending at least 2 to 10 times or more the  cost of the machine itself to be reasonably well equipped.

[SeanB]

You are forgetting all the brass and aluminium you are going to turn into shavings whilst learning how to use the various bits, as well as getting to know the local metal recycler and suppliers well.

[bfritz]

It is a bit dissapointing that the prints don't seem to be turning out the correct diameter.

I would assume there has to be some scaling factor somewhere, that you need to tweak.  I've been thinking about buying a unit, and was interested to see your results.  You say in the video that you produced the parts with 0.5mm of clearance, which seems adequate to me.  Sounds like the tolerance on the unit is just pretty darn poor, or a scaling factor needs to be tweaked.

Please let us know if you figure this out, or if the machine just can't hold such tolerances.

[IanB]

The machine is extruding liquid plastic, which is going to spread out when it lands. However accurately you position the extrusion nozzle, the final part dimensions will be different. In all practical casting, extrusion and moulding processes you expect to produce a rough piece that is slightly over sized in the critical areas and then machine it down to the exact dimensions in a finishing step. It doesn't look like the Makerbot has eliminated this requirement.

[Spawn]

Great Dave, finally some nice processes there, I was watching your live show back then and making some suggestions with other guys but I think no one expected there are two different stepper motors they used.


OFFTOPIC:

I would like one as well, even a combination unit. But space is the problem, unless i can find an instrument lathe.

SeanB, I am really big fan of Proxxon and trying to get one of these combinations:
http://www.proxxon.com/eng/images/produkte/24004_24104.jpg

It is only 53cm wide. You can’t do big work pieces with this but it is nice lathe and mill on a small bench. I am also looking for a GoCNC A4 model, i think i have to make a decicion after summer vacation.
GoCNC: http://gocnc.de//images/A4Bas1.jpg

[ecat]

Flat spots on a circle, top/bottom and/or left/right, are more than likely due to backlash - the axis perpendicular to the flat is being asked to change direction but the change will not be reflected by actual movement until the slack in the mechanicals is accounted for.

So, a flat on the top/bottom = uncompensated backlash in the  forward/backward axis and a flat on the left/right = uncompensated  backlash in the left/right axis. Hope I have my ups and down the right way around!

Dave allowed for an extra 0.5mm in the internal diameters(?) of the microscope piece. If just one axis exhibits a not unrealistic 0.25mm of backlash, when applied to both a top flat and a bottom flat that's the 0.5mm eaten up. And that's ignoring however much the melted plastic spreads. Time for the digital callipers I think.

The spool holder is a different matter, external flats wouldn't stop the spool from turning.  A lot of unknowns in this one: internal diameter of the spool, external diameter of the holder vs the design dimensions, random plastic flash/seams - could be plastic spread, could also be bad design or just bad luck.

I do like these machines, but this plastic spread theory has me worried. Time to investigate... Maybe tomorrow 

[Mint.]

Has anyone seen this or tried it before? http://www.instructables.com/id/Soldering-Assistant/
I'd love to try printing something like that, except I don't have a 3D printer...

[amspire]

I think that Soldering-Assistant is just a bad solution when I think there are much more practical solutions.

A common solution is the PCB holder that include a top foam pad to hold the components in place, and the ability to flip the board over to the other side.  Something like this:

http://www.manixmfg.com/assembly.htm
http://www.dannell.net/site/pcss.pdf

Not sure if a soldering jig made from meltable plastic is the best idea.

Richard.