DIY CNC 8x4 mdf build

[njhussey]

Hi everyone
here's my 8x4 mdf CNC with vacuum table build
its a little agricultural but hopefully I'm getting there!!
I have some Vee bearings on order so once the vacuum table is finished I'll be on that next
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Hi Robert, firstly welcome to the forum , you might not believe it but there are some supremely helpful guys on here (the ones who have answered you are some of them!!) who will gladly help you out with any questions you have.

Where things have gone a bit pear shaped from the start here is that you didn't state that it was for a one off job so had to be done on the cheap using what scrap wood you had etc. etc.

feel free to comment and any heads up before I make any costly mistakes are more than welcome

Generally wood (and MDF specifically) is not a good medium for a CNC machine that looks as though it's needed for production (which is all we have to go on looking at your pictures of your workshop) and when you couple it to Vee bearings everyone on here immediately ducks for cover . Yes wood machines can be made to perform OK but at this size and for cutting wood you need speed and to get speed from ball screws you need large diameter ones with a large pitch and these need Nema 34 motors at a minimum with 230V AC drivers which starts to get expensive....even from China.

If it is truly for a one off job then have you considered belts and pulleys? You could use smaller Nema 23 motors and smaller drivers then and the cost will be minimal.

If it's not for a one off and you're thinking of using the mechanical and electrical components for CNC Router V2 then (normally designed when you're 1/2 way through the first build) what the lads are saying (and will continue to say) is do it once properly rather than as a compromise this time and then properly next, that's all

[Boyan Silyavski]

The way i see things, so its not a waste of money, is to make the gantry right and also the Z. So if you get into it, you will have good components for upgrade.

Go find 2-3 meters of steel profile 200x100 or sth similar and make gantry portal from 1 beam. You will need ~2m for the gantry and could use the rest for gantry legs. The other way to go is from aluminum profile but anyway you have to reinforce it with steel plate, so first option is cheaper.


As for movement, you will need ball 2510 ball screw to move the gantry and rotating ball nut, but as thats out of question here, better go with rack and pinion. 1610 ball screw for Z left right and 1605 for Z up down.


You could incorporate also 2 flat steel bars or simple frame so gantry moves on steel. Say if you buy 6m of gantry profile, you could use all that and have much more better machine, even if rest is MDF. We are talking ~50-100euro here. not 1000.

So hope still is not lost.

[JAZZCNC]

The other way to go is from aluminum profile but anyway you have to reinforce it with steel plate, so first option is cheaper.

Profile doesn't need reinforcing with steel at all Boyan. Provided it's sized correctly the it's perfectly strong enough for any wood router and it's much easier to work with than steel. It's also more accurate from the start and can be used without any other treatment which often isn't the case with steel.

Wood router doesn't need the Silly levels of strength your promoting with encouraging people to use steel. Infact it's wasteful and often negative to performance because the rest of the machine doesn't match.
Machine with heavy gantry needs more power than steppers can provide so everything goes to another level with servos etc and often people can't go to that level. Then the strength which isn't needed anyway just cripples performance.!

People need to start getting real and realise while it's Daft to build from weak inappropriate materials there becomes a point where over building is just has daft if the rest of the machine doesn't match.!

[Boyan Silyavski]

Profile doesn't need reinforcing with steel at all Boyan. Provided it's sized correctly the it's perfectly strong enough for any wood router and it's much easier to work with than steel. It's also more accurate from the start and can be used without any other treatment which often isn't the case with steel.

Wood router doesn't need the Silly levels of strength your promoting with encouraging people to use steel. Infact it's wasteful and often negative to performance because the rest of the machine doesn't match.
Machine with heavy gantry needs more power than steppers can provide so everything goes to another level with servos etc and often people can't go to that level. Then the strength which isn't needed anyway just cripples performance.!

People need to start getting real and realise while it's Daft to build from weak inappropriate materials there becomes a point where over building is just has daft if the rest of the machine doesn't match.!

We all have right of opinion. I dont promote anything. My opinion is that when you spend 3000 on a machine is false economy to save 100 more on material which will raise your machine to whole new level. You call that overbuild, i call that "ability to make more juice from one orange"


But we are here not to argue or police each other. Right? The man has a question, trying to make a cheap machine and i am giving suggestions as to how to make it without loosing money in future.

So what aluminum profile exactly you suggest for 1300mm travel that will not bend and what is the price of the beam? How much the gantry +sides will cost ?

[JAZZCNC]

We all have right of opinion. I dont promote anything. My opinion is that when you spend 3000 on a machine is false economy to save 100 more on material which will raise your machine to whole new level. You call that overbuild, i call that "ability to make more juice from one orange"

That's my whole point.!! . . . It's not just the material is it.? . . Lets look at You monster which is using servo's correct.?

Even the cheapest servos are 2 or 3 times the price of stepper motor and drive. Then you have the fact that Servos require high pulse rate to get there full speed and resolution. If not then your using electronic gearing which is wasting resolution of the encoder which you paid for and lessens the advantage of servos.
This then means a good external motion control card with at least 500Khz frequency for typical 2500ppr encoder is needed. Far more than the lower end ones like Pokeys, usbcnc or even Cslabs IP-M can offer. This also then means a quality BOB which can process high pluse rates, lots of the cheaper ones can't do this.
You also have the fact servos are very much more affected by electrical noise and require much higher attention to detail on the wiring side. Quality cables are needed and filtering for power etc and the list goes on and on.!! . . . . This is the TOTAL cost of over building.

Many won't do this and will suffer the price in some form or another. Often it's low speed/accuracy or unrelaibilty.!

Profile I DO USE for machine this size is 120 x 80 or 160 x 80 and arranged in "L" shape and can tell you now it doesn't bend even in Heavy use. Yes like anything it will bend if enough force is applied but still it's more than strong enough for any wood router or even one that's cutting aluminium.

It's also nearly 1/3 the weight of 200 x 100 x 5 RHS and not nearly has resonant. Initial Cost is more than steel but the time saving and less treatment required balances this out in the end.
Gantry sides etc are irrelavant even a steel machine will need these if designed that way.!

Also just to clear things up I'm not trying to stop you having an opinion. I'm putting my opion across and saying that what your promoting with your "Must use Steel to be strong" opinion isn't exactly true or even correct if not properly implemented and follwed up with correct components through out the machine. This you don't seem to mention often when preaching use steel.?

So I say what I do for the sake of those who see your posts and hopefully don't go blindly into something they haven't been made aware of by the preacher.!!