Stiffness of the spindle carriage plate

discussion of design changes / improvements / suggestions
northbear
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Re: Stiffness of the spindle carriage plate

Post by northbear » Tue Mar 08, 2016 4:47 pm

cvoinescu wrote:
northbear wrote:While I believe the SO3 is a *much* more capable system than the original Kickstarter, it is also $1000 (ok $999) machine rather than the $300 goal it started out as.
A valid point, but I have to say that the comparison is not entirely fair. The $300 in the Kickstarter was cost in materials for a hobbyist buying parts at retail, using parts they already have at hand, maybe pulling some favors to get plates laser-cut at "mates rates", and generally not afraid of spending time to save money. It's true that doing large batches saves money, because unit prices go down; but it's also true that doing it as a business adds a lot of costs. A business need to keep doing R&D so it doesn't become irrelevant, and earn some profit for the owners -- and, even more importantly, a business can't trade time for money the same as a hobbyist, because its employees' time is not free.

So the retail prices of the SO1, SO2 and SO3, on one hand, and the stated $300 project goal, on the other hand, are not the same kind of cost and can't be compared directly -- at least not fairly.
You are right, the comparison is not fair. The $300 price was never obtained (ended up around $332.58 or $365.90 according to --> https://www.kickstarter.com/projects/ed ... sts/148086) and even the full kit from the kickstarter was $500. When I built my CNC I believe my cost was more like $600-$650** USD even with "mate rates" and trading time to save money. It is important that a company makes money or it will no longer exist! (Edward's got a family to feed after all! :D ) For a business it makes great sense to make the best "bank for your buck" machine rather than a "race to the bottom" cheapest machine you can make with no profit margin.

I guess maybe I am just lamenting the fact that the $300 goal was never able to be obtained and is no longer a goal. Like WillAdams I think it would be interesting so see how good of a CNC could could be built for a $300 (or some other arbitrary "cheap" price). It may sound like I am trying to volunteer for the project, but don't hold your breath as I don't see it fitting into my time schedule any time soon! :mrgreen:

**edit** Doing a bit of searching, cheap cnc has already been tried by many people already most with limited success or are very one of a kind.


**Price is just an estimate off the top of my head. My CNC does have a larger work area than the Shapeoko which could be some of the higher cost -- Yes I had a bit of mission creep when building my machine also ;)
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cvoinescu
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Re: Stiffness of the spindle carriage plate

Post by cvoinescu » Tue Mar 08, 2016 6:32 pm

northbear wrote:I guess maybe I am just lamenting the fact that the $300 goal was never able to be obtained and is no longer a goal. Like WillAdams I think it would be interesting so see how good of a CNC could could be built for a $300 (or some other arbitrary "cheap" price).
I understand completely. Because I've had the various sizes and options of eShapeoko on sale for so long, I have some data. About a third of customers go for the largest machine with all the options, and they often order the electronics and motors from me too; a third buy smaller sizes (mostly 500 mm x 750 mm and 750 mm x 1000 mm), usually with NEMA 23 motors on X and Y and NEMA 17 on the Z axis; and the other third buy small machines, often with NEMA 17 motors, and they tend to source the electronics elsewhere. This tells me that there is room both for cheaper machines, and for larger, tougher but more expensive ones. As a business, I'm more tempted to pursue the top end, but I made the decision to keep offering the smaller kits for as long as practicable. That said, I'm still more likely to invest time in developing a larger, stiffer machine rather than a smaller, cheaper one -- unless it was radically cheaper, but I have no idea how to do that for now.
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WillAdams
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Re: Stiffness of the spindle carriage plate

Post by WillAdams » Tue Mar 08, 2016 6:39 pm

There's something of a list of the extant CNC kit / machine options here: https://www.reddit.com/r/hobbycnc/wiki/index
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AnonymousPerson
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Re: Stiffness of the spindle carriage plate

Post by AnonymousPerson » Tue Mar 08, 2016 7:05 pm

cvoinescu wrote:Because I've had the various sizes and options of eShapeoko on sale for so long, I have some data. ... This tells me that there is room both for cheaper machines, and for larger, tougher but more expensive ones.
Any idea how much demand there would be for cheap-ish 5-axis machine?

Hardware wise, there's enough "stuff" around these days to get it happening. The TinyG guys have a working solution, even though they don't seem to be interested in building any Community around that side of things.

Software wise for controlling it seems like it could be a challenge. Fusion 360 has 5-axis support now apparently, not that I've been able to try that. :D Chilipeppr has some TinyG support now too, though I've not used that software yet either.

Thoughts? :)
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bharbour
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Re: Stiffness of the spindle carriage plate

Post by bharbour » Tue Mar 08, 2016 8:44 pm

i'm a relative CNC newbie compared to a lot of you guys, but I don't see why you can't have a good machine at a low price point. It's a matter of design in my opinion.

WillAdams wrote:Yeah, the price point is the crux of the matter.

The question becomes, how good of a CNC can one have at what low price point(s).

I'd really like to see a machine at the original $300 (slightly higher adjusted for inflation?) --- esp. if matched up w/ the original goal of fitting w/in a USPS flat-rate box.
No longer have a Shapeoko, but use a machine of my own design...
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cvoinescu
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Re: Stiffness of the spindle carriage plate

Post by cvoinescu » Tue Mar 08, 2016 8:51 pm

AnonymousPerson wrote:Any idea how much demand there would be for cheap-ish 5-axis machine?
I have received maybe two queries about a 4-axis machine, compared to dozens for a machine larger than 1.5 m. That doesn't mean the demand for 4 and 5 axes isn't there, just that it's not pointed in my direction. :)

TinyG supports four axes (actually, it supports six axes, but only four motors, and I don't think their idea of using two TinyGs in a master-slave configuration to run up to eight motors was ever implemented). G2 (TinyG2) supports six axes. LinuxCNC and Mach also support rotational axes. Marlin can drive at least four axes at once (X, Y, Z and E), so it shouldn't be too difficult to add rotational axis support. Once GRBL is ported to ARM, more axes should be a natural extension.

As you say, CAM software is an entirely different beast, and I'm not aware of anything other than Fusion 360 that doesn't cost an arm and a leg.
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TomDChi
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Re: Stiffness of the spindle carriage plate

Post by TomDChi » Fri Mar 11, 2016 5:10 am

Personally "three plus one" axis would be nice for me - standard 3 axis operation with the workpiece mounted on a 4th axis, which only rotates between complete "3 axis" operations. This could be implemented with GRBL or similar continuing to operate the normal 3 axis, and the control software on the PC (or equivalent) parsing the G code to find the commands for the 4th axis and sending those to a separate controller/motor. (Of course, if such a system weren't terribly difficult to implement for true simultaneous 4 axis operations, that would be great, but I doubt you could synchronize the 4th axis with a GRBL style controller, which gets you back to more involved hardware/controller.)

cvoinescu
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Re: Stiffness of the spindle carriage plate

Post by cvoinescu » Fri Mar 11, 2016 12:23 pm

The separate controller thing is a non-starter. It's much easier to synchronize axes by moving all of them with a single controller. GRBL's algorithms will work (witness Marlin, which is based on early GRBL, and can move four axes at the same time). GRBL is currently limited by program memory size, RAM size, and pin count, more than anything else (the Mega 2560 is not any faster, just bigger). It's amazing what can be done with very little computing power, if you're willing to spend the time to program it carefully.
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WillAdams
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Re: Stiffness of the spindle carriage plate

Post by WillAdams » Fri Mar 11, 2016 1:25 pm

Hang on, let's start a new topic....

Microcontroller options for 4th axis: http://www.shapeoko.com/forum/viewtopic ... 830#p61830
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cvoinescu
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Re: Stiffness of the spindle carriage plate

Post by cvoinescu » Fri Mar 11, 2016 2:19 pm

Yes, we derailed this topic quite badly. Sorry.
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