Building a CNC controlled router

[Barry Burgess]

I have seen many threads on the American and Australian sites but nothing on this site. My question is if any member has built a CNC router??
I am thinking of building one with a bed of about 2000 X1000mm. I want to see one in operation if possible? A number of the constructors have built a small CNC router then used it to build the parts for the larger model.
Many years ago I built an interface that allowed a mini computer to control a number of values and gates so some knowledge might still be there some place in the brain.
Hope members can help?
Barry

 

[George_N]

I seem to remember Ian Dalziel made a CNC Milling machine a year or so ago.

 

[AndyG]

Hi Barry,
I've toyed with this idea for a while too. We've got a small CNC machine at work for making PCBs. It's really just an extruded aluminium frame with some linear slides.
I'm after some aluminium extrusion for a router fence, the best online supplier I've found so far is http://www.kjnltd.co.uk but I've not ordered from them yet though.
Good luck with the project
Andy

 

[tombo]

wasnt there a member called kong that did one? i think he only joined our forum to show off cause he has not posted since, it was pretty cool tho

Tom

 

[Barry Burgess]

Kong has removed his pictures and does not appeared to have posted since.
Barry

 

[Ian Dalziel]

Barry,
Kong sold his machine not long after posting here....he went on to build a mill.
heres some links
http://www.cnczone.com/index.php?referrerid=150

youll get great advice on the above forum

http://www.geckodrive.com/

you’ll need some sort of drives for your motors...geckos are good

http://www.machsupport.com/

you need pc software to run them …mach is the standard


http://www.campbelldesigns.com/breakout_board_plus.htm

youll need a breakout board….this is one of many

http://www.dolphin.gb.com/

you’ll need a cam program…dolphin is UK based and supports mach 2/3 in post processers

http://www.arceurotrade.co.uk/

good UK source for stepper motors

on the cheap you'll do it for £1500 getting stuff through ebay and the likes
you will need good bearings and glides, ballscrews, ballnuts....access to some good steelwork/aluminium etc. building the electrical panel is straight forward......depends on how many functions you want the machine to actually do.

I

 

[tiler99]

Any use ???? ebay link

 

[Barry Burgess]

Tiler the Amazon version of the book is much cheaper
url here

 

[Barry Burgess]

Ian thanks for the details. Do you know of anybody with a home made CNC router verses a CNC millng machine?
Thanks
Barry

 

[Scrit]

Barry

I built a ShopBot (the original cable drive version and went to design a full 2.5 x 1.5metre flat bed machine before binning the idea and buying a Biesse Rover - a secondhand industrial machine was actually cheaper than building a machine the size I wanted but which wouldn't flex...... I - still have a spare ShopBot kit in the workshop, so maybe I'll build that up one day.

Scrit

 

[tiler99]

Tiler the Amazon version of the book is much cheaper
url here

Sorry i bothered

 

[Barry Burgess]

Sorry i bothered

No you gave me the book name - I was just letting you know it was cheaper.
Thanks again
Barry

 

[Barry Burgess]

Thanks Scrit I will have to reconsider over my Christmas turkey. I am running out of ideas for things to do for myself in the workshop and don't want to add to my 4PC 7Screen network in my office.
Barry

 

[Scrit]

Hi Barry

I found one of the biggest problems to overcome was rigidity. A CNC router needs a very stiff frame and an arm which will preferably not droop or bend when you are cutting (a typical industrial machine may well apply up to 25kg of side thrust to a cutter, enough to bend a small section arm). The rigidity thing becomes much more important when you are trying to make multiples of anything. Another thorny question rarely answered on forums is that of holding work in place - something which taxes even daily users of CNC routers at times. Then you have the question of programming the machine. A lot of small controllers such as the ShopBot don't use G and M codes - pretty much an industry norm in controllers and a way to port over your applications to a larger/alternative machine at a later date - and Windows is not an ideal environment to run a CNC either as it tends not to allow uninterupted processing of encoder/stepper feedback....... I have a set of plans for a smaller machine which is (unusually) well thought out - they guy reckoned it would cost about $6k (read £6k here) to build a 1.2 x 1.2metre bed machine a few years back, no hold-downs and with a DW laminate trimmer mounted on it. That machine is the Data-Cut and is a good example of what a CNC gantry router should look like IMHO

Scrit

 

[Ian Dalziel]

Barry,
Wot Scrit said....rigidity is required in abundance.....i built the mill rather than a router because of this.....I have since got rid of my mill and bought a bridgeport interact with heidenhain controller. Its a sore point at present because everything is now costing real money as opposed to playing hobby time at it. I was £1800 just for a few spare parts. Cnc is fantastic but its also not cheap.


http://www.k2cnc.com/

this co is american and offer it in stages of build.....

I

 

[Ian Dalziel]

meant to add in my last post, Scrit mentions uniterupted mention of encoder/stepper feedback...this is generally known as a closed loop system and home builds generally dont offer such....this guy here offers a supposedly closed loop board that allows a closed loop system for cnc but depending on how well you know cnc its not really a closed loop system....what it does is allow you you to use your DRO's when the machine is in off position and allow manual use. more appropriate for a mill than a router though
Proper closed loop monitors positions generally through tacho's and encoders and will adjust the system accordingly without you knowing youve even lost position.

http://www.rogersmachine.net/encoderinterface.html

There is a system being produced for proper closed loop for mach but for now its still in developement stage.

I

 

[jasonB]

I bought my mill (nonCNC) from this guy, he also does a lot of CNC stuff and I see he also has Router kits may be something of interest.

Jason

 

[Barry Burgess]

Thanks guys I have got lots more reading to do now
Barry

 

[Scrit]

To add to what Ian said, there are fundamentally two types of motor to provide liner motion - stepper and servo (I'll ignore so-called "hybrid" types as these are in effect souped-up steppers in many ways....). Servo motors are used with encoders to determine position, steppers require you to have software to count the steps or part steps and calculate position. Servos can be very finely controlled to an almost infinite degree which translates to smooth curves. Steppers on the other hand normally don't go down to much finer that about 1 degree increments/decrements (ol, you can chop to get microsteps....) and they can periodically loose/miss steps which makes "threepenny bitting" (or faceting) on curves a much greater problem, but steppers are a LOT cheaper than servos. The speeds you need to traverse at for routing becomes a problem as well - traverse too slowly and you'll suffer recutting of the material in the cutter which in turn leads to burning. That's why you'll struggle unless you have a controller capable of doing the calculations on the fly. When you get to doing interpolation in 2 axes (e.g. cutting an elipse) the processor will need to work a lot harder whilst 3-axis interpolation was beyond most industrial routers until the "new generation" of Intel I960 (and the like) PLCs became available in the very late 1990s. And we haven't even got into transmissions, effect of dust on linear guides, etc yet.....

Scrit

 

[jasonB]

A bit smaller than you want Barry but the videos are interesting

ebay link

Jason