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 Kit's New CNC Router 
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Location: Exmouth, Western Australia
Post Kit's New CNC Router
For those of our readers who have been waiting with baited breath, here are some details of my latest CNC router.
Previous machines have been based on a wooden/MDF frame and a mixture of belt and ACME thread drives. Although some useful work was done, I decided it was time to stop messing about and make a more solid machine. The prospect of some future paid work also inspired me to build something I could actually rely on not to smash up the customer's precious timber.

I'd already collected some lengths of aluminium V-wheel rails (and wheels) along with some 16x10 mm ballscrews and NEMA 23 motors. The piggy-bank needs fattening up a bit before I can upgrade to Hi-Win style rails so I decide to re-use the existing components but in a design that can be upgraded without too much extra work in the future and of a size that fully fits the available space even if the current rails are not long enough for the new frame.

Freight costs are a major component of the purchase price of anything that has to be delivered to my remote corner of Western Australia, especially heavy stuff like steel beams. So off I went to the local tip for a scavenging trip. Along with the results of previous visits I came up with this lot...
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After a lot of head-scratching and pencil lead ( I haven't yet bothered to master Fusion 360) I had a design.

Kit


Wed Jun 27, 2018 2:08 am
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Post Re: Kit's New CNC Router
The design was based around the materials I'd managed to scavenge, the size of the table it all had to fit on and the components I already had to hand.

The available space...
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Pieces cut to size (thanks to my employer for the loan of a disc cutter)...
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The pieces stacked up in their final positions...
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Kit


Wed Jun 27, 2018 3:08 am
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Post Re: Kit's New CNC Router
I only have hand tools and a drill press to build this machine so in spite of my best efforts at accurate marking out there will be inaccuracies in the construction as well as twists and bends in the steel pieces. The design is intended to allow adjustments and alignment to, with luck, make a silk purse from a collection of sow's ears (sorry if that confuses our non-British readers).

The X-axis consists of two 65mm square beams with the ballscrews and rails attached. In effect this creates a pair of linear accuators, the idea being that once I have the screws and tracks aligned on their beam, further adjustment consists of moving the whole beam. The aluminium tracks are simply bolted to the beams. If I upgrade to better quality rails in future I'll use self levelling epoxy resin to create a more reliably flat surface.

As you can see the existing rails are shorter (1000mm) than the maximum the machine can fit.
The wheel plates consist of a piece of 100 x 10mm aluminium plate, drilled and tapped for the M5 bolts holding the wheels. I've found from past experience that I can make these with sufficient accuracy that the wheels are a tight running fit on the rails, though one plate is a slightly tighter fit than the other :-)

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The rest of the base frame was bolted together and made square, a lick of paint applied to give a better impression to potential customers and a plywood baseboard installed.

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Wed Jun 27, 2018 4:03 pm
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Post Re: Kit's New CNC Router
After the shock of turning 60 yesterday, work continues on the router. I've taken a fortnight off work to 'celebrate', hence the amount of progress being made on the home front. The gantry is mounted (though not aligned) and the wiring is being installed.

I'm re-using the plywood backed Z-axis from the last machine. It seemed to work quite well so we'll see how the whole of the new design works before deciding where the next round of improvements are required, if any. This machine is only intended to cut wood so it does not need to be as accurate as some designs.

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Thu Jun 28, 2018 3:26 am
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Post Re: Kit's New CNC Router
Nice work for a budget machine, and no welds in sight.. What about filling the base tubes with concrete and make it even more solid?


Sat Jun 30, 2018 2:02 am
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Post Re: Kit's New CNC Router
wow kit you have been industrious. i have been working away from home for the week . our tip opens on a saterday morning if you dont get there early theres nothing left. besides the small fact the owners to the tip rights seem to think its all gold plated :roll: its been a bit like christmas in june over here i had several packages turn up in the mail this week so ill start a new thread about that shortly. obt happy birthday :D


Sat Jun 30, 2018 6:06 pm
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Post Re: Kit's New CNC Router
Gerald,
A while back I was seriously thinking of a lightweight (using pearlite as aggregate), cast concrete base for the whole machine. This design was easier! I have a friend who volunteered to weld up the frame for me but I may want to pack this machine away for a while if we move house and there are still some mods I want to make to fit longer rails (Hi-Win type or fixed round rails???) and allow a greater range of movement from the same overall width from the gantry. These changes may involve a change to the frame so a bolted construction makes sense at the moment. The frame is built to fully fit the available space but the current cutting area is seriously restricted by the other components I already had left over from the wooden-framed machine.

Chardie,
Looking forward to hearing about the contents of your 'Christmas' parcels. Thanks for the birthday wishes, two weeks off work playing with my own toys has helped with the shock.

I've got the machine finished and have started making things with it today. So far it seems pretty solid and significantly more accurate than the old version.

Kit


Mon Jul 02, 2018 4:21 am
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Post Re: Kit's New CNC Router
Hey Kit looking good only just noticed your post . I have been in advert hell for last few weeks ! I may post something on it when its been aired as quite a bit of motion control in it .
Think you wise going the steel route its amazing even with steel how much deflection you get . Put a gauge on it, that said its going to be a lot better than timber.
When ya all set and done your changes i do recommend filling as many spaces as possible with concrete. I did my gantry and i wish i had filled the base to . It not only increases strength it deadens the sound to . Empty steel box acts as a sound amplifier .
I still have changes to do to mine but to busy using it to do them . But thats good best to be using than fiddling all the time :D
Wonder how Edward his getting on with his . Keen to see as he as a completely different approach to a build and both methods are equally good .
D1


Mon Jul 02, 2018 11:45 pm
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Post Re: Kit's New CNC Router
D1,
Good to hear from you! I'm glad both you and your machine are being kept busy.

The received wisdom from the very brainy chaps on MYCNCUK is that steel is more rigid but aluminium is more dimensional accurate due to being extruded rather than rolled and welded, hence the use of self-levelling epoxy on steel rails. I used steel because I could scrounge it for free. Aluminium costs an arm and a leg out here, especially since the local light engineering firm changed hands. The new guy sells every tiny piece of scrap at full per-metre price.
Concrete filling sound like a good plan once I have a decidedly final design in a final location. I'd want to use light-weight concrete though with either polystyrene beads or pearlite as aggregate.
The current gantry design is a major compromise which actually has slightly less range than the old wooden machine. I can see that being the first part to change even if the long axis stays as it is for a while.

One of the key things I want to do is have separate homing for the two X-axis motors for squaring the gantry. LinuxCNC doesn't easily provide this. I currently have an Arduino which uses the pendant input connection on my break-out board to provide a Z-axis touch-off control. I might be able to extend it's function, with the aid of some logic ICs, to do the separate homing externally to the LinuxCNC control. Watch this space!

Kit


Tue Jul 03, 2018 3:03 am
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Post Re: Kit's New CNC Router
Just thought would post how my 4th axis is doing.

Not had a chance to really machine anything yet other than a bit of foam . Still getting my head round software tool change is a bit of a issue.
This 4th axis is the only reason i went for two ballscrews on the X axis as it sits bellow bed height. One ballscrew would have been my preferred option ;) .
D1


Tue Jul 03, 2018 1:32 pm
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Post Re: Kit's New CNC Router
I've always been wary of the one ballscrew option as it relies on the gantry's rails and sliders to hold everything perpendicular under off-centre cutting loads. Two ballscrews turns this rotational force into straight forces along the ballscrews themselves, which is the only reason why my own past and present designs, made with plastic v-wheels and aluminium rails, have not been torn apart by their own motors.

Whether to have two screws with separate motors (racking removed at every switch-on by separate limit switches) or just one motor and some belts (racking adjusted once and left permanently set) is an on-going debate with advocates on both sides.

Kit


Wed Jul 04, 2018 12:40 am
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Post Re: Kit's New CNC Router
If it is so debated surely there is a conclusion by now? :)

But logically if the bearing trucks are arranged in a near square pattern, then a single drive will suffice. As the arrangement gets more rectangular with the rails further apart, then there will be a point where two drives are better. It will also depend on the rigidity of the rails/framework and the precision of the bearings. A good compromise surely, would be to use two drives from a common belt drive. Then both will always remain in sync...


Sat Jul 07, 2018 9:47 pm
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Post Re: Kit's New CNC Router
I haven't been on the MYCNCUK forum so not sure how big a debate it is but i do find some forums do like to go round in circles.
My own personnel experience is one ballscrew is def enough . I have had lots of problems with twin ballscrews and as part of my experimentation i disconnected one of the ballscrews so the gantry was driven only by one side only . You would think you would get a instant lock up . I didn't so i applied quit a force to the end of the gantry without the ballscrew still no lock up. Draw your own conclusions to how well a single ballscrew in the middle of the gantry would work on a smallish bed .
I am a strong believer in testing rather than surmising :D
D1


Sun Jul 08, 2018 12:52 am
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Post Re: Kit's New CNC Router
You can talk/think yourself round in circles without much effort if you're not careful. I do it all the time!

One of my friends at work visited a factory in Brazil owned buy a man who had started building a machine for himself in his garage, sold it to a friend, built another one and is now a major supplier of CNC machines in Brazil. He has learned by experience and emphasised the need for a very rigid gantry and I think you've proved the point from what you've said about being able to drive your gantry from one side. Very solid rails is also key for that.

For designs using bolted aluminium profile and 'fully supported' round rails intended only to cut wood (which is an easy DIY option for those with limited tools), I suspect the dual ballscrew option is necessary to compensate for the lack of rigidity. This is certainly what I found when fitting the ballscrews to my wood/MDF based machine. When one screw locked up, the sides of the gantry bent like butter while the other screw merrily kept going! I didn't realise MDF could bend that far without breaking. The plastic 'V' wheels wouldn't have put up much of a fight either, I suspect. It all comes down to the compromises you choose to make.

My current version avoids having the vertical side plates but doing that has seriously compromised the cutting width I can achieve within the size of the frame so once I've got a few other projects out of the way and find I want the extra width I'm going to change it again.

Making sure the two long 'actuators' were aligned and working seperately has helped avoid any jamming of the ballscrews which was a big problem when I tried to shoehorn them into the wooden frame and align everything at once so I'll be sticking with those for a while yet, just changing the rails to either fully suported rails or (if the piggy bank gets fat enough) some Hi-Win clones from Fred in China. Does anyone know a supplier of self-levelling epoxy in Western Australia?

Kit


Sun Jul 08, 2018 5:19 pm
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Post Re: Kit's New CNC Router
Hi Kit yep think my extremely rigid gantry helps a lot but i think its the Hi win rails that are the key . They can be loaded from all directions without any binding so money well spent .
So i think best approach to all this is 10mm pitch balscrews , Hi win rails all round and big ones on the X axis , and single ballscrew on the X axis . The money you save buy a single ballscrew on the Xs will help towards the cost of the Hi Wins . Not to mention all the time and hair pulling you get with twin ballscrews on the X :(
Also we are all quit happy with a single ballscew on the Y axis . When you think about it the actual router bit is quite far away from the rials and under considerable load with ya pushing it threw material; you cutting . Almost similar to my x axis experiment with gantry driven from just one side .
Anyways no matter how its done as long as you get something that is actually cutting stuff out then be happy with it .
These are tools not a life long project .
D1


Mon Jul 09, 2018 12:02 am
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Post Re: Kit's New CNC Router
D1, you're a bad influence on me! Now I'm thinking I could use the two 1100mm ballscrews I currently have on the X axis for a much more square machine with one screw on each axis. I may only need to buy one 8 metre length of 75mm square steel plus all the new rails to make it. It would even free up a larger motor and a 16 x 10mm ballscrew for a stronger Z axis unit.

I don't actually have space for a machine that wide at the moment, but it's a though for a post-retirement upgrade if I ever get a bigger workshop. I might be able to use it to earn some pocket money in my old age.

Kit


Fri Jul 13, 2018 2:53 pm
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Post Re: Kit's New CNC Router
Hi KIt soz for confusing you . I am going to make it even worse now :D
You have never mentioned making a fourth axis but you might be best to consider it . I do believe a bit of pocket can be made if you have a cnc . Thats my plan anyways .
This fella seems to think ya can .


I always wanted to build in the forth in my machine mainly for the day job but as i do less of that i hope to just turn out little things every now and then that keep a bit of spare cash coming in.
If i every get the aluminium casting up and running that will be part of the fourth axis set up . I can machine stuff in poly and lost cast then in ali and hopefully sell a few things in my retirement.
So maybe back to the two ballscrews on the x axis :D
D1


Sun Jul 15, 2018 2:52 am
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Post Re: Kit's New CNC Router
Some interesting videos from Roger Webb there. And he's in Tasmania which is where we plan to retire to at some point in the future.
One of his videos shows a 4th axis which is on a base that simply clamps onto the normal bed of his chinese router. A simple way of doing it but you'd need a very high gantry to make that work well, which would compromise the rigidity for all the normal work you'd want to do with the z axis on a long reach down. Still a useful retro-fit for some smaller diameter jobs though.

I quite like the idea of combining the use of hand turning of a bowl (I used to do that but there's not enough timber round here) with the addition of engraved decoration round the rim for example. That would best be done with the spindle mounted horizontally on a cross-slide and the lathe motor replaced with a stepper. You could work on quite large diameters that way. Another completely new machine I will have to build someday!

Kit


Tue Jul 17, 2018 5:20 pm
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Post Re: Kit's New CNC Router
Hi Kit yes i considered the high gantry to allow space for the 4th axis but like you i came to the conclusion it would compromise rigidity. So went for what i thought was the lesser of two evils and put the 4th bellow the bed height and this is when the twin ballscrew became a inescapable necessity .
Did come across this interesting solution to the 4th https://www.aliexpress.com/item/AKM1330 ... 45700.html
I still havent done any changes to mine as i say busy using it . But if i do get a chance i will tackle my top speed issues .
I also came across these cutters more suitable for spindle speeds. Dont know how much they cost but Cutwel will stock them .

D1


Thu Jul 19, 2018 12:08 am
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Post Re: Kit's New CNC Router
That's a very neat variation on the 4th aixs if you have the floor space for it. I'd want that table carrying the 4th axis to be variable height and have the option to swing the head round so that quite a large turned bowl could be spun under the tool. That would allow the kind of rim decoration I was thinking of. Potentially a very flexible way of doing the 4th axis. Something to file away in the memory banks for who knows when.

Is that aluminium or butter in the tool video? I noticed that the machine is a fixed gantry design as the work piece was moving for one of the axes. A very rigid design for cutting smaller pieces. Tormach have some videos showing their machines throwing off huge shavings of stainless steel but I doubt we'll ever be making that kind of machine in our backyard sheds.

Kit


Sat Jul 21, 2018 4:59 am
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Post Re: Kit's New CNC Router
Yes Kit. That is a very rigid professional CNC mill, hard to do that on a home made router or modified hand mill like mine. The cutters are a very good brand and Edward swears by them, but they also cost a bit more than the average Chinese tools... :(


Sun Jul 22, 2018 7:23 pm
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Post Re: Kit's New CNC Router
Gerald,
There are some things even the most ambitious of us DIY machine builders should leave to the professionals.

One of the differences between my new steel framed machine and the old version is the very satisfying way it can snap tools as easily as I snap carrots. I junked several 2mm end mills over the weekend doing tests on maximum cutting speed. Fortunately they were from a cheap Chinese box of 10. 2mm is a reasonable compromise between fragility and size for cutting clock gears and I can run at 2000mm/min and 3mm cut depth. This machine is only intended for cutting wood.

I've been looking at welders recently. Cheap stick welders are getting some good reviews online and I'm interested in the 140A unit linked below as it's one of very few rated for use on an Australian 10A mains outlet. Problem is the handbook says it pulls 27 Amps. I'm assuming this is absolute maximum peak instantaneous current and running current will be a lot lower. Do any of our readers have experience with one of these cheap inverter welders and can comment on the size of mains breakers you need to avoid repeated tripping? my shed has a measly 16A breaker feeding it so even this little box is probably going to go very quiet the first time I try to strike an arc.
https://www.ewelders.com.au/uni-mig-arc ... er-welder/

Kit


Wed Jul 25, 2018 4:26 am
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Post Re: Kit's New CNC Router
Hi Kit i always cut quite slowly to avoid breaking bits . As long as the bit isn't getting hot i am quite happy going slow. I think their is a rule the depth of cut shouldn't be more than half diameter of bit .But could be wrong. If ya cutting ply its not a constant toughness could be pockets of glue etc that cause problems . MDF as a more consistent constitution so machines very well .
Not had any experience of stick welding migs are so cheap and tigs are getting very affordable . Think i have mentioned before i went for a cheapish tig and its been great as it can weld ali and stainless .
Its 160 amp model https://www.r-techwelding.co.uk/tig-wel ... dc-160amp/ and its never tripped my supply even at high settings .
Their was a debate on one of the CNC forums whether a 2.2k spindle motor would trip a supply . They do tend to worry about things rather than just taking the plunge and giving it a go . Mine as tripped occasionally but thats usually when i turn my large disc sander on. Its got quite a big pull when the motor starts up or if i put a load on it .
My bigger worry on the power front is i never got a electrician in on the shed. I just split the supply for my electric oven in the kitchen and put a separate consumer unit in the shed on that split supply . I am sure if i got a professional electrician in much tutting would be done :D .
D1


Sat Jul 28, 2018 2:09 am
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Post Re: Kit's New CNC Router
Hi Kit. I think "fitted with 10amp plug" is a clue. Ideally it may need to run from a 15amp circuit to allow full capacity. But if you don't use it flat out it will work with a 10amp circuit. At worst you may blow the breaker, so suck it and see like D1 says. The actual mains current it draws will be a lot less than the rated 140amp, as that refers to the current across the low voltage arc output. The knob adjuster thingy probably changes the voltage which also adjusts the total power being sucked from your mains...


Sun Jul 29, 2018 10:49 pm
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Post Re: Kit's New CNC Router
Gerald,
The handbook for this welder claims the mains input current is 27A. Apparently that's OK for a welder on a 10A socket (according to other forums I've checked) because of the duty cycle of the welder. If you have to let the welder cool down after every few minutes use, you have to let your house wiring cool down as well, which is the main concern with overloading a mains socket.
27A will be the peak current, it works out to an arc voltage of around 40V for 140 Amps, which is higher than you'd need (according to yet more forums).

My shed is fed via a 16A breakers but 'C' class breakers (medium slow-blow) like mine have an instantaneous trip current of 5-10 times the rated current and the time/current curve shows that it should carry 27A for several minutes before tripping and 20A for an hour! So I've ordered one.

I've never touched a welder in my life, but for $189, including an auto helmet and delivery (that's just over a hundred quid for our pommie readers) it's too tempting a toy not to play with.

Kit


Mon Jul 30, 2018 3:17 am
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Post Re: Kit's New CNC Router
For the price you can't go too far wrong... Just keep an eye on your mains wiring. I mean feel it and see if it is getting warm. :)

But also you should have an RCD - which is actually more ultimate protection if something goes awry...


Thu Aug 02, 2018 1:49 am
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Post Re: Kit's New CNC Router
Gerald,
When we bought this house I had the old fuses replaced with RCDs and modern breakers, though an RCD will not protect you from the isolated output voltage from a welder: no earth leakage current back to the mains supply.
My biggest worry about buying this welder has been the risk of tripping the whole house and therefore my wife's PC while she's in the middle of some important work. That is a greater risk to my health and wellbeing than the welder itself :D

Kit


Sat Aug 04, 2018 1:39 am
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Post Re: Kit's New CNC Router
the welder itself may sustain damage if she who must be obeyed uses it as a weapon :roll:


Sun Aug 05, 2018 7:03 am
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