[Blabber] CNCing the mini-mill / shop classes

Chris Stratton cs07024 at gmail.com
Fri May 31 13:23:00 UTC 2013


4-5 square feet capacity for plywood.

A metalworking machine of that size would have to be mounted on a concrete
slab.

I'm going to have to disagree with the "easy" of using a cnc conversion of
a manual machine.  Machines of our size, using hand mounted tooling just
aren't consistent enough to cut what the program says (too much flex under
load, too much variation in cutting tool), without extensive tuning each
time they are run - what is really significant about actual cnc machines is
not the control system, but the mechanics engineered to mitigate these
issues.

Aside from non-critical art/engraving, the one thing conversions can really
let you do compared to a digital readout is calculated curves and tapers.
But most of the time, the motors just get in the way of ordinary usage.
On May 31, 2013 1:03 AM, "Matthew Duepner" <matthewduepner14 at gmail.com>
wrote:

> I meant for the 2 grand you mentioned spending.  For that kind of money,
> you can get machines with 4 or 5 square feet of work area.
> On May 31, 2013 12:45 AM, "Nickolai Belakovski" <nbelakovski at gmail.com>
> wrote:
>
>> Chris, digital readouts won't improve the mill's capabilities. They just
>> make it easier to use for the things it already is capable of doing. Doing
>> a full on CNC conversion allows people to make some really complex shapes,
>> and relatively easily, once you've had the proper training. Arguably, no
>> one has any projects which require CNC right now, but it's a sort of
>> chicken-and-egg problem. I'm sure that if we build the capability people
>> will find uses for it. Force feedback is not necessary in a CNC setup.
>>
>> Matt, I did some more looking around, and I don't know where you're
>> looking but the cheapest desktop CNC mill I could find was this one<http://www.kickstarter.com/projects/otherfab/the-othermill-custom-circuits-at-your-fingertips>,
>> which is quite a bit smaller that ours. It's actually a pretty interesting
>> mill but for the price point they're asking we can build CNC capabilities
>> into the one we have. Also, I'm not sure how we'll divide up the cost. I'd
>> be willing to carry some of it, but probably not all. It might work to
>> split the cost evenly between everybody working on the project + HM (i.e.
>> if there's two people working on it, each pays 33% and HM pays 33%, we can
>> talk about this in more detail with the officers).
>>
>> Plus, I think this will be a fun project. There's lot of interesting
>> technical aspects and opportunities to get one's hands dirty. Plus, after
>> this is done, I want to look into adding flood cooling, which would be
>> especially useful since cutting fluids generate fumes and the machine shop
>> is not exactly well ventilated.
>>
>>
>> On Thu, May 30, 2013 at 8:57 PM, Chris Stratton <cs07024 at gmail.com>wrote:
>>
>>> The problem with a "large" surplus machine is that you would pay a small
>>> fortune to get it into the space, possibly even having to modify the
>>> building to install it...
>>>  On May 30, 2013 7:21 PM, "Matthew Duepner" <matthewduepner14 at gmail.com>
>>> wrote:
>>>
>>>> Sounds like a lot of money when you could but a rather large CNC mill
>>>> for the same cost.
>>>>
>>>>
>>>> On Thu, May 30, 2013 at 7:12 PM, Chris Stratton <cs07024 at gmail.com>wrote:
>>>>
>>>>> Generally I think digital readouts would be a better compromise of
>>>>> capability, usability, and price than actual automation - especially for
>>>>> machines of this hobbyist nature where feeling force feedback can be
>>>>> important.
>>>>>
>>>>> I did temporary conversions once years ago, but only bolted them on to
>>>>> do a few complex shapes.
>>>>> On May 30, 2013 7:06 PM, "Nickolai Belakovski" <nbelakovski at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> So we've been talking about a shop class on and off for a long time
>>>>>> now and nothing ever seems to come out of it. A main concern I've had is
>>>>>> that even though I've had some experience with mills, and could probably
>>>>>> figure out how to work the lathe well enough to teach people how to make a
>>>>>> turner's cube, if anybody wanted to make something a little bit more
>>>>>> complicated, I wouldn't be of much help.
>>>>>>
>>>>>> So as I think about ways to make the shop more accessible I've been
>>>>>> doing research into what it would take to do a CNC conversion on the
>>>>>> mini-mill. CNC capability would enable the mill to do a much larger range
>>>>>> of projects, all for (roughly) the same 'training cost.' This is a popular
>>>>>> mill, so a number of tutorials and kits exist for doing the conversion.
>>>>>> From my research I estimate the cost to do so would be between 1000-2000
>>>>>> dollars.
>>>>>>
>>>>>> I think it's a fairly involved project with lots of parts and so we
>>>>>> should have at least 2 people working on it. Ideally 3 or 4 so that more
>>>>>> people have the knowledge of how it all works. Here's essentially what we
>>>>>> need to do:
>>>>>>
>>>>>> Mechanics - Replace the lead screws with higher precision components
>>>>>> and install mounts for the stepper motors. Kits exist to do this, I've seen
>>>>>> one for around $500 that replaces them with ball screws, which are pretty
>>>>>> nice.
>>>>>>
>>>>>> Electronics - Hook up stepper motors and controllers and things with
>>>>>> circuitboards and wires and such. This is the part I'm weakest on so if
>>>>>> someone would step up here that would be great.
>>>>>>
>>>>>> Software - Get a computer hooked up to the machine running LinuxCNC,
>>>>>> which is free, open-source control software. Think of it as your
>>>>>> "Pronterface" or "Repetierhost" for all the 3D printer folks. We should
>>>>>> also load it with and learn/teach how to use PyCAM, which is kind of like
>>>>>> Slic3r in that it generates the G-code file for the machine.
>>>>>>
>>>>>> I think this would be a great addition to our space and I hope that
>>>>>> there are some people out there who are willing to put in the time and
>>>>>> effort to help make it a reality. It's really not a whole lot of work given
>>>>>> the amount of information already available, but it will be a serious
>>>>>> commitment.
>>>>>>
>>>>>> What does the group think? Do people like the idea? Are people
>>>>>> interested in being involved?
>>>>>>
>>>>>> --
>>>>>> Nickolai Belakovski
>>>>>> Purdue University : Class of Dec. 2011
>>>>>> School of Aeronautics & Astronautics
>>>>>> Department of Mathematics
>>>>>>
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>>>>>
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>>
>>
>> --
>> Nickolai Belakovski
>> Purdue University : Class of Dec. 2011
>> School of Aeronautics & Astronautics
>> Department of Mathematics
>>
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