LISA Simpson with Extrusions?

LISA Simpson with Extrusions?

Postby Jason Fisher » Mon Jan 27, 2014 6:04 pm

Thinking over uncle_bob's scaling issues and it seems that beyond a certain sweet spot, the lead screw design is working against us.

The weight and power requirements are increasing at a rate much greater than the increase of the build area.

With a 6' MakerSlide extrusion only costing $40 (, maybe it makes sense to revisit a linear rail-based system?

- The carriage holds a short section of smooth rod a couple inches out from the rail. This smooth rod is basically just a joint piece for the LISA arm to rotate freely around.

- Probably belt based, looking at H-Bot/CoreXY setups for sourcing/arrangements/drive components

- Need to rethink support/structure. Maybe attach to the inside of an enclosure. The extended 'floating rod' should let you mount two of the rails against a flat backing surface for stability, or augment with additional crossed extrusions. The third rail would be flat against the opposite wall, or free standing.

- Electronics/motors on top as we do not need to balance large screws

- Use the same arm design
Jason Fisher
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Joined: Fri Dec 20, 2013 5:36 am

Re: LISA Simpson with Extrusions?

Postby Nicholas Seward » Mon Jan 27, 2014 7:27 pm

I don't know about the statement that LISA is bad at scaling. Well, I don't know if it is any worse. I think uncle_bob is doing a lot of good due diligence and trying to make sure that he is going to get a solid build.

Scaling in general is an x^3 function because we are dealing in 3 dimensions after all. As a general rule, to go from a 150x150x150 machine to a 300x300x300 you will need to spend 8 times the money. Maybe not that extreme but somewhere between x^2 and x^3.

I am not opposed to other kind of rails but it adds to the vitamin count if you want the shoulder to rotate the way LISA needs it to.

I priced out a 2X LISA the other day and I was under $1000. I am pretty sure I can get a 3X under $2000.

Additionally, I think uncle_bob wants to do more than just print so that adds a big layer of costs.
Nicholas Seward
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