1220 × 2440 build

[HullMark]

Hi thanks for replying.

1. Hopefully the gantry won't be an issue as the design uses 50mm by 100mm mild steel side rails for the x axis, with 50mm support structures welded to the bottom. I'd seen somewhere that dropping the bed instead of raising the gantry makes the structure stronger, makes sense. 10mm aluminium plate for the gantry in an L shape. In theory, this is sound I think?

2. Backlash, which sounds similar to slop in a drivetrain, was one of my worries here too. In my design I was looking at using ballscrews, I guess I need to keep reading some more on that issue. Are you saying that backlash can be eliminated by using those methods? I'm sure I've read somewhere it can. The structure itself I think should be ok, I tried uploading a picture from my phone a few tims but it failed.

3) Most of the weight would be in the bed and support structure below made from mild steel, the only moving parts would be made from 10mm aluminium plate to keep the weight down.

4.Again this is an area I need to look into more, but I'm thinking I need to finalise my design and see how much it's going to weigh before I decide.

4. Hopefully this won't be an issue and is why I'm not even going to attempt to weld this myself. The lower supporting structure will be separate from the bed, bolting together so I can use shims to get the bed as level as possible. Not 100% decided on whether the resin route will be needed, probably, Hopefully someone else will come and clear this up.

You mean that rather than having 100mm travel they leave it at just having 2 axis and using different router bits? I could make that work for some things, but not others.

Many thanks

Ps sorry if I've posted this multiple times!

[HullMark]

Thanks for that link too, I have seen this and was thinking very similar, I was hoping though as you'll see from the dimensions I've given, mine doesn't need to be as robust for cutting just wood ... or am I wrong?

[JAZZCNC]

Thanks for that link too, I have seen this and was thinking very similar, I was hoping though as you'll see from the dimensions I've given, mine doesn't need to be as robust for cutting just wood ... or am I wrong?

Yes your wrong.!!
Don't under estimate wood because while it's softer than aluminium you have to cut it faster and often much deeper which requires strength/power.
Also don't just think strength but also think in terms of vibrations because resonance really does affect the machine in many ways, performance, quality of finish, tool wear and component wear.

Also just bare in mind CNC tends to open up other avenues and if machine is weak to start with then limits these avenues.!!

[HullMark]

It's not all doom and gloom at all, I appreciate the honest replies and is why I'm here. I don't want this machine building yesterday, sure it's going to take time, I'm not in a major rush but would like It to be complete in 6 - 12 months. It will take as long as it takes, any sooner the better, this is a side venture/ hobby and the time will give me the chance to research more and work on my CAD.

This is all sound advice, I won't be purchasing anything until until I have a fully itemised bill of materials, and like you say that will come once I have worked out a suitable design Clive. I've tried attaching photos to the posts I'm sending, but it says failed to upload.

It seems like The first and maybe most important things to consider are the strength and accuracy of all parts. The two companies I have in mind, I know someone who builds conveyors at one, and i know the owner of the other one. The other company manufactures all sorts of precision parts. There's no doubt in my mind that both of them will be able to achieve the accuracy, they both have decades of fabrication experience each. It's like jazz said though they are always busy so it'll be a case of finalising a design first, then fitting in the welding and fabrication around what they've got going on when I'm ready.

I thought first of all i'd draw a rough idea, get the structure looking solid for the bed, base and gantry before I go into any of the finer detail stuff. Then from there we can look at motors etc. I will look again at posting some pictures.

If it can't be done for that price, how much is more realistic Jazz? There's a few machines this kind of size on eBay for 7.5-11.5k with some offering training. I figure if they can sell them for that surely I can build one for less (hopefully, that's usually the case when you DIY as much you can) with the right kind of guidance and outside expertise. Maybe I don't know what I'm talking about? But that's why I'm here.

This thread as much as anything will serve as a reference for me so I can have everything I need in one place. Any links and information are much appreciated, I'm keen to learn as much as I can from the experts here and am not expecting things to happen over night.

Cheers guys for the comments, you've given me a lot to think about.

[JAZZCNC]

It seems like The first and maybe most important things to consider are the strength and accuracy of all parts. The two companies I have in mind, I know someone who builds conveyors at one, and i know the owner of the other one. The other company manufactures all sorts of precision parts. There's no doubt in my mind that both of them will be able to achieve the accuracy, they both have decades of fabrication experience each. It's like jazz said though they are always busy so it'll be a case of finalising a design first, then fitting in the welding and fabrication around what they've got going on when I'm ready.

If it can't be done for that price, how much is more realistic Jazz? There's a few machines this kind of size on eBay for 7.5-11.5k with some offering training. I figure if they can sell them for that surely I can build one for less (hopefully, that's usually the case when you DIY as much you can) with the right kind of guidance and outside expertise.

Ok well obvioulsy depends on lots of factors and how good job you want to do but £4k will be more realistic figure and that is doing everything your self, welding machine work for aluminium parts the job lot.
So straight off the bat your backs against the wall if paying these companys or even if working on mates rates you haven't got much room to play with.

Also you'll all most certainly have to buy all the major components ie: linear rails, ballscrews etc from china to do this for £4k- £4.5K.
Here's Little break done for you.

The Linear rails & bearings, ballscrews & end bearings will cost about £2k and that's working on 20mm rails. Really 25mm would be better for long axis. Then throw another £300-400 into things like Timing belts, pulleys, Cable chains, nut's bolts etc.

Frame materials will depend on design but You'll not have any change from £500 and that's working on steel prices at wholesale not retail. By the time throw aluminium into mix for Z axis and brackets etc and you'll be at £750+.
If you use Profile type gantry like I do then will be easily over £1000.

The electronics will cost best part of £1000 to be done properly. That's working on using Closed loop steepers and using Motion control card all done correctly in Steel cabinet. Including all cables relays, e-stops, limit switches etc.
Wouldn't use open loop steppers for machine this size because using slaved motors as there is lot of inertia and easy to loose position. Plus the difference is cost isn't massive so well worth little extra.

So
Rails/screws etc £2000
Rail/screw sundries £400
Steel/Ali £750
Electrics/Motors etc £1000

These prices are not OTT and based off prices I've paid from China so you don't have massive wiggle room. Plus there will be extra hidden costs like paint,Drills etc which could easily account for another £200-300.

So you see £4K soon gets eaten up and that's allowing for someone who knows what there doing and doesn't screw up. Which is very easy to do for resonably experienced builder and almost guaranted for new builder.!!

Regards the Ebay machines then I've yet to see one that is any good for under £10K and most are Chinese machines which have there problems like coming with DSP controllers which expire quickly and limiting to use or cheap nasty electronics which will need some fetteling costing more money still. Most 8x 4 that are any good are between £15K-£20k.

If you expect to spend £5K you'll end up with machine that will last for years cut everything you want and be very reliable. The same would cost you £20K+ to buy.

[HullMark]

5k sounds reasonable to me, thanks for the break down Jazz, that's helpful and exactly what I needed, a ballpark figure ... have you seen CKJCNC on eBay? They seem to be doing a lot of business selling CNC machines, sub 10k plus VAT for the 1325 model (1300 x 2500 x 200 working area). Certainly looks the part, at least to my untrained eye! About 11.5k inc VAT.

[JAZZCNC]

5k sounds reasonable to me, thanks for the break down Jazz, that's helpful and exactly what I needed, a ballpark figure ... have you seen CKJCNC on eBay? They seem to be doing a lot of business selling CNC machines, sub 10k plus VAT for the 1325 model (1300 x 2500 x 200 working area). Certainly looks the part, at least to my untrained eye! About 11.5k inc VAT.

They are just Chinese imports. If you notice they say Orders being Taken. You could import one of these your self for lot less money. Shit loads on Ali express.
https://www.aliexpress.com/af/1325-c...ewCP=y&catId=0

[malcolm01]

5k sounds reasonable to me, thanks for the break down Jazz, that's helpful and exactly what I needed, a ballpark figure ... have you seen CKJCNC on eBay? They seem to be doing a lot of business selling CNC machines, sub 10k plus VAT for the 1325 model (1300 x 2500 x 200 working area). Certainly looks the part, at least to my untrained eye! About 11.5k inc VAT.

Hi Mark
I’ve just finished building an 8x4 CNC. It works ok,
I fitted it with 25mm ball screws on x and y axis and fitted a ready made z axis. The guys above were correct about ball screws whipping or wobbling while running, the y axis is fine, but the x axis has vibration issues. I’m planning on changing the x axis drive to rack and pinion which I’ll be buying from America ready made, I would recommend if your building a machine to avoid ball screws over 1500mm like one of the other guys said.
It will cost around £5k, it did for me, but when you see that thing cutting out your parts you’ll be glad you did it. I love my machine, I hardly cut anything buy hand if I can help it.
Best of luck.
Malcolm, from Ayrshire, Scotland


Sent from my iPhone using Tapatalk