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Fivetide
03-03-2013, 06:02 PM
This isn't a proposal of any kind, more like what a forum is designed for that is a debate. I'd like to get the members thoughts on the viability of us as a group producing cost-effective CNC machines. The problem I have is that I don't have the tools or the know-how to create my own CNC machine. That gives me simply one choice, to buy a second-hand or new machine. I know that this forum's primary goal is to aid people who make DIY CNCís, and it does a pretty good job of that. However for people like me who are incapable of producing a single accurate thing the thought of starting completely from scratch is to daunting to consider. Plus the fact that it might take me over a year to make a single machine. And at the end of the day I will have teething problems no doubt just with the electronics which looks like brain surgery to me.

However I think I'm quite capable of making small parts for a DIY build or even construction manuals and videos and I do have some project management skills not great but they've had the ability to organise 10 people and complete the job on time. The thing is there is a massive amount of experience on the forum not just in the ability to create a machine but at the same time the experience of correcting problems that have occurred during the builds. It seems that progressively the forum and its members have whittled down the dos and don'ts what to buy and what not to buys but unfortunately the information is spread out amongst many threads.
I know people as they are reading this will think of many pros and many cons to why it's not viable. The idea that a forum could between them manufacture an excellent quality CNC at the best price. After watching some of the videos about shed based manufacturer, and people's ability to produce excellent quality things I suppose you have to ask yourself does China have the monopoly on prebuilt low-cost home-based machines. I'm always amazed at how people denigrate the Chinese machines pointing out their obvious weaknesses and flaws. But for some people that is their only choice a bit like when you're only choice of a car is a Skoda because you live in the Soviet union. I'm a member of DIY audio and I have participated in many group buys which have been excellent and a few that were not so good. But the ones that were good saved time and money and meant that the members really benefited from the group effort. I myself had 100 PCBs manufactured, for a group buy and although I was taking the risk of being stuck with all these boards I actually didn't have enough made in the end.

What are your thoughts on the possibility of a group build? I know the first and possibly the hardest part would be everyone agreeing on the builds design and parts. But of course once again that's why this is a forum to debate that particular type of problem. Then each member putting in their capabilities both as engineers and machinery. Certain things the buyers can buy them self with a bit of guidance from the forum for instance spindles, water pumps and things that can't be manufactured by the group. There's no way I'm saying we should do this for free the whole idea of cottage industries is to make money without placing themselves at financial risk. The logistics are simple these days I can ship 30 kg at about £6.35 using a parcel broker online.
Anyway your feedback on this subject would be most appreciated, please also let me know if you would want to participate in such a venture, and even if you weren't then at least let me know why you wouldn't because sometimes the negative side outweighs the positive and that's what I'm trying to gauge in the thread.

Swarfing
03-03-2013, 09:44 PM
Here we go again :-)

Have a quick search on the forum first to see where this has gone in the past? the idea is fantastic but just far too many cheifs in the mix

blackburn mark
03-03-2013, 10:35 PM
its been looked at before in some form or other
at first glance it seem like it couldn't possibly fail with all the mixed skills and experience but I think good engineers are artists and as such are like a herd cats, each one has its own way and be dammed everyone else
standing in a row is the last thing they want to do

I'm guessing another problem is there are easer ways to make a bob or two than building cnc machines ?

I reckon the only way to get anything like what your after is for one person to take charge of the design (like a build log) and carry all the financial and progress chasing weight and let users put bids in for the various machining jobs that need doing
its a big ask but the right person might be able to make something of it?

D.C.
03-03-2013, 11:00 PM
unfortunately the information is spread out amongst many threads.

I'm a member of DIY audio and I have participated in many group buys which have been excellent and a few that were not so good. But the ones that were good saved time and money and meant that the members really benefited from the group effort. I myself had 100 PCBs manufactured, for a group buy and although I was taking the risk of being stuck with all these boards I actually didn't have enough made in the end.

What are your thoughts on the possibility of a group build?

There are a million and one open source cnc routers out there, some very good. But if you go to their forums and ask a stupid question the stock response is "that is not in the plans feck off".

This site helps people to renovate old lathes, design oversized 3 axis wood machines, 4-axis, small alu machines etc etc There isn't a one size fits all but all machines have to operate inside of the laws of physics so that 3m gantry made of wishful thinking and puppy dogtails isn't going to shave atoms off titanium no matter what you do.

I think if people did a 'post build debrief' on the logs listing what they spent and where, what they screwed up etc it would help new people a lot.

It would be interesting to see if we could do some group projects for people that have finished their machines, make the site more interesting for people that finished. A group hexapod build would be awesome and servos are a bit cheaper if you buy them in lots of 100. :)

GEOFFREY
04-03-2013, 01:20 AM
I tried very hard with how about a mycncuk router project just before christmas, but the general concensus was that the members were not very interested and no experienced leader was prepared to take it on. I still think it was a good idea, and would be pleased to see your suggestion taken further. Good luck. G.

Fivetide
04-03-2013, 01:39 AM
Thanks you all make very good points and I had read a thread earlier about a similar idea. The consensus seems to be someone needs to take charge, in no way am I a leader but I do want to see if I can beat the Chinese with a better and possibly cheaper build but cheaper is not exactly the issue the issue is built quality and the quality it produces. The problem I have is I need to team up with someone who is an engineer and willing to break down the parts that can be fabricated and the parts that need to be bought. Then as you suggested Geoffrey I will attempt to outsource the part building to members and see if they are willing to bid a price for the job. This way if the only thing I achieve is a bigger and better second CNC then at least I have achieved something. Then I can post my experiences and costs etc to see if building them for sale either to members or outside the forum is viable.

D.C.
04-03-2013, 02:11 AM
If you are willing to spend a little bit of cash experimenting on this I have an idea.

Most builds tend to be out of aluminium (weak) or steel (need welding skills) even though it has been known for a rather long time that big lumps of cast iron or granite do the job better and modern epoxy granite is much better still.

If you want to carve out a niche instead of offering a full cnc machine offer a standard gantry design that makes a brick shithouse look like it's a straw bale, but comes in user defined lengths.

You will probably be able to put food on the table doing this because buying small quantities of epoxy costs an insane amount, if you can invest a few grand up front to buy the epoxy can get a lot more for your money. By contrast the bulk cost of steel/alu vs the retail is not that great.

Make sure that you can mount either supported round rail or hiwins, have a seperate foot plate so that people can choose their own block spacing and you have pushed the hobby market up a notch.

PS: If you are after some cheap but rusty steel up your way I found these guys the other day:

Steel Beams and Columns, Gates Fencing and Railings items in AinscoughMetals store on eBay! (http://stores.ebay.co.uk/ainscoughmetals)

GEOFFREY
04-03-2013, 10:49 AM
D.C. An interesting idea ( from previous posts I realize that you may be "biased" towards epoxy granite) would a granite gantry be very heavy?

I suspect a granite gantry would be far better suited to a fixed rather than moving design (fixed being my "bias"), but the preference on this forum seems to be for moving gantry, mainly I suspect due to space limitations.

I have a good friend who has a fibreglass factory who has an injection/vacuum unit and whilst I have not asked about granite I feel sure that it would be no problem for him to make it the various gantry components complete with any correctly positioned captive fixings that may be required. Just a thought.

Fivetide, if you really want to get this off the ground and none of the real experts want to get involved, I would be prepared to act as leader/coordinator although I would still be looking for help/constructive comments from those experts. G.

blackburn mark
04-03-2013, 10:55 AM
modern epoxy granite is much better still.

that's right up your street that fivetide!
you probably know as much as anybody here about epoxy
the advantages of a solid machine may make it stand out against the competition

if you can crack the epoxy granite conundrum you may be onto something interesting

GEOFFREY
04-03-2013, 11:05 AM
that's right up your street that fivetide!
you probably know as much as anybody here about epoxy
the advantages of a solid machine may make it stand out against the competition

if you can crack the epoxy granite conundrum you may be onto something interesting

What exactly is the conumdrum? It doesn't look like rocket science to me. -Waiting for lots of comments to the contrary. G

blackburn mark
04-03-2013, 11:24 AM
to be honest I don't think there is a "conundrum" but as it is, nobody seems to go for it and actually make one

there is a thread on the cnczone that goes on and on about mix ratios and filler type and it seems to just drift past logic into an endless pissing contest

I'm sure some care and though is needed for a choice mix but like you say "It doesn't look like rocket science" and the real nack to the job in my opinion is managing to commit and deciding to crack on with making it happen (like anything else)

D.C.
04-03-2013, 11:42 AM
D.C. An interesting idea ( from previous posts I realize that you may be "biased" towards epoxy granite) would a granite gantry be very heavy?

I suspect a granite gantry would be far better suited to a fixed rather than moving design (fixed being my "bias")

I'm not really biased I don't think, the reason I keep banging on about trying this approach is that if you look at what the "I have more than god to spend and a team of PhD's working for me sort of places" Things like epoxy granite and carbon fibre are the materials of choice (and trusses are the arrangement of choice).

Cast iron is 250 year old tech for machines and we are using alu and steel because we can't afford to get custom lumps of cast iron done for us and it isn't really feasible to start a smelting foundry in your garden just to make a cnc machine.

But homebrew epoxy granite is feasible. If you use some thin walled steel box section, source a carboard tube for the centre, devise a reasonable mix and do a few experiments to find a good setup that is superior to the empty steel box or alu extrusion/alu plate designs people are using now there is no reason why you can't make a moving gantry with the stuff. Don't forget if you are relying on the epoxy granite for stiffness you can cut down a lot of weight in metal.

A few things to read:

http://www.mycncuk.com/forums/diy-cnc-machine-building/4970-epoxy-granite-mineral-casting.html
CNCCookbook: Epoxy Granite Fill (http://www.cnccookbook.com/CCMillEpoxyFill.htm)

You can actually save weight and get better performance using EG:
http://annals.fih.upt.ro/pdf-full/2012/ANNALS-2012-2-13.pdf
If you design a beam from EG to have the same deflection for a given force it will actually weigh half what the steel does and have superior dampening charcteristics to boot.

PS If you are wondering about the cardboard tube, it is there to turn the energy in the vibration passing through your beam into heat (the energy has to go somewhere and if you want to dampen a vibation you need to suck the energy out of it and turn it into a different form energy or it will just keep on vibrating your beam or be passed into the rest of your machine) The cardboard tube is proven to work in cnc machine beams and also in things like automotive shafts.