DIY CNC Build

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EV2Go
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DIY CNC Build

Post by EV2Go » Fri, 05 Sep 2014, 05:37

Making some progress with my DIY CNC
Last edited by EV2Go on Thu, 04 Sep 2014, 19:41, edited 1 time in total.

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Adverse Effects
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Post by Adverse Effects » Fri, 05 Sep 2014, 15:52

nicely done on the control box

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Richo
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Post by Richo » Fri, 05 Sep 2014, 20:36

Looks nice and neat. Image
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EV2Go
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Post by EV2Go » Sat, 06 Sep 2014, 01:40

Been helping my sister and brother in law over the last few days pull down some shelving in a massive factory he just bought. Since I didn't want any money for the job, he kindly gave me some dispatch area work bench I said I wouldn't mind having.

Unloaded it tonight into the garage... This is going to probably be enough steel to make a solid stand for the CNC.Image

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Post by Adverse Effects » Sat, 06 Sep 2014, 14:46

nice score that stuff is expensive (industrial version of it that is)

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EV2Go
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Post by EV2Go » Sat, 06 Sep 2014, 18:15

It's not the heavy heavy stuff, but more towards the light end of the industrial racking. I just measured where they cut a strip out underneath the bar (presumably to lighten it) and it is about 2mm thick, so it's not very heavy at all.

I could have gotten a rack the next size up, but it was about 3 meters long, and that would have required cutting and welding the ends back on square, and since I currently don't have a welder or a jig I opted for the lighter racking.

The 6 blue ~2 meter bars are much closer to the size I wanted, since the CNC will be about 1.5 meters long and will give me a small amount of work area on the end.

Clipping and bolting 3 blue bars on per side should make longest sides pretty rigid. Because I got 3 bays, I have 4 ends and I only need 2, so I can pinch extra bracing out of the other ends to strengthen it up the other way. The width is .9 meter which should be fine for my 1 meter axis of the CNC.

Edit:
There was like a 4th bay on the end that was made up of the creamy coloured angle iron you see near the blue, it can be used where required for any extra support it needs.
Last edited by EV2Go on Sat, 06 Sep 2014, 08:20, edited 1 time in total.

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EV2Go
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Post by EV2Go » Sat, 06 Sep 2014, 21:44

A bit of a reshuffle of some empty boxes and room magically appeared. I rearranged the garage weeks ago anticipating the need for CNC space.

I did a very quick mock up of the frame / CNC just to get a rough idea of size and height. Looks like I will need to get the trim the legs a bit to bring the CNC bed down.

I have plenty of end pieces left to add another 2 horizontal pieces in each end, plus plenty of diagonal bracing.

Under the CNC bed will be a 12mm piece of marine grade ply for rigidity. I am also looking at putting a piece of ~3mm alloy between the bed and the ply to stop any moisture reaching the ply.

The bike only just fits back in, but I already guessed that would be the case.
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Adverse Effects
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Post by Adverse Effects » Sun, 07 Sep 2014, 01:07

make sure you make at lest 2 legs adjustable in height and i would also look at some way of X bracing opist corners (top left back <> bottom right front and the other way as well ) i found its almost imposable to dress the bed flat if you have even the smallest amount of flex in it

me just walking through my house (cnc mill is in the lounge room) throws the mill out up to 4 mm on the Z corner to corner (yes my house moves and flexes a lot floor moves up and down 2 inches in 1 corner of the house)

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EV2Go
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Post by EV2Go » Sun, 07 Sep 2014, 01:52

Was thinking about remaking the end pieces from scratch... Where the long sides hook into the end legs there is a gap between the long sides and the leg.

This would make it very hard to put bolts in from the long side. If I get something like some 60mm square tube I could drill holes and bolt from long side.

This would mean I could make fully welded and braced end pieces. Been thinking about how to adjust height / putting wheels on to take outside to work.

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Post by Adverse Effects » Sun, 07 Sep 2014, 03:11

hmm movable makes it even more needed that the table carnt twist / warp at all

i'll pit $ on the fact that no 2 square feet in your shed / driveway will be flat / parallel to any other 2 square foot (unless you spent $1000's getting it all laser leveled

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Post by Adverse Effects » Sun, 07 Sep 2014, 03:13

thinking about it you could make the mill separate from the bench with 4 adjustments (one on each corner) between the mill and the bench

but you will have to do a level and twist removal on it in 4 directions each time you move it
Last edited by Adverse Effects on Sat, 06 Sep 2014, 17:15, edited 1 time in total.

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EV2Go
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Post by EV2Go » Sun, 07 Sep 2014, 03:29

Provided the deck cant flex, I don't see it being a problem if it isn't perfectly level when operated. Each of the 30mm x 150mm lengths will be bolted through the two top rails in 2 or 3 places on each end, then with a stiff piece of ply and alloy under the deck which would also be bolted to the deck to increase stiffness I cant see it flexing at all.

Planning on putting about 150 T bolts on the bottom side of the deck and bolting through the ply and alloy plate. Couple that to a rigid frame and I really cant see it flexing.

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EV2Go
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Post by EV2Go » Sun, 07 Sep 2014, 03:36

I could potentially do something similar to what I did with my MDF work bench and put wheels at one end and adjustable legs at the other end with some retractable handles to move it in and out of the shed and onto the deck outside the garage.

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Adverse Effects
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Post by Adverse Effects » Sun, 07 Sep 2014, 04:06

trust me the "bed" of the mill has to be 100% flat in all directions any twist in it will cause problems not to mention will put stress on the bearings and rods that are on in both the X and Y directions

this is why mills are bolted down so thay can be trammed and trued before there used

i know i sound like "the sky is falling the sky is falling" but i am talking from experience and in the year i have had my mill i have had to replace both my X rails because the bed keeps twisting ever so slightly with the house moving and when it dose it puts a lot of stress in the bearings and throws the bed out of level / flat

i havent seen it talked about much but have seen it with mine and a few others
Last edited by Adverse Effects on Sat, 06 Sep 2014, 18:11, edited 1 time in total.

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EV2Go
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Post by EV2Go » Sun, 07 Sep 2014, 05:23

Understand where you are coming from and it is an issue that the guy who is helping me build this also keeps mentioning. One thing that is different from my design to many others is the amount of bracing the actual CNC itself will have compared to more traditional designs.

Many traditional designs have a flat bed, like a sheet of paper which can be very easily flexed over the length of it, especially diagonal twist, whereas mine will be more like a cube where there are six boxed sides to give it rigidity.

While I don't think it will eliminate it completely, I do think it wont be able to flex much.

Both ends will be capped of and bolted on three sides with just a slot in the end to slide full sized boards in, otherwise it will be boxed on all sides.

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Post by Adverse Effects » Sun, 07 Sep 2014, 06:23

my bed is a 1/4 inch Ali slab(upgraded from 4 times 20mm x 100mm of that form stuff you have there) with 3/4 inch fiber board screwed down to it so i can dress it down as needed (9 times i have dressed it in the last 2 months and its 3 mm thinner now lol) it still twists when i walk through the house


*this is an exajaion example*

now see the closest corner you have in your pic lift it up by say 1cm

see how it will

A:- bend the rail
B:- twist the gantry
C:- twist the gantry bearings that run on the X axis
D:- twist the gantry rails that have the Z axis on
E:- in doing so the Z axis will no longer be in the correct place in the Z and X axises and that inaccuracy will be different depending on where it is in the X and Y location on the table

so at one corner it could be all most +-0 but at the far travel on both X and Y could be out as much as +- several mm

and if you say its ok there will be enough clearance for that not to hurt the mill then you have to much play in everything for the mill to be accurate and if that is the case no real point in having a mill that is CNC

i have been fighting this problem for over a year with this house moving

its getting to the point i am thinking of making a insanely ridged 100mm box section table braced in all direction and sitting on sprung feet just to get around this problem as i can not bolt it down anywhere here
Last edited by Adverse Effects on Sat, 06 Sep 2014, 20:39, edited 1 time in total.

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EV2Go
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Post by EV2Go » Sun, 07 Sep 2014, 07:37

I see what your saying but imagine for a moment you stuck a 20c piece under one leg of a solid chair, the two legs either side of the lifted leg wont both touch the ground at the same time if the chair is rigid enough, even if you sit on the chair it will only touch the ground on the side toward where the weight is biased.

The seat of the chair wont flex if the chair is solid enough. I plan to make the CNC and the stand to which it is bolted so rigid that even if the floor isn't even, it still wont flex the table deck. it will just leave it with one leg in the air.

If the deck is rigid enough I should be able to operate the CNC on a 45 degree angle. Granted it would never be optimal to operate the CNC with one leg in the air even a little bit, but as long as the rocking can be adjusted out, the deck should never go out of square to the other axis.

Of course this is purely hypothetical, and I wont know if I have built it rigid enough until after it is done. And if I find it does twist when moved, I will just have to square it off and leave it in place and not move it.

But think about this for a moment, if the whole deck is bolted to the top rails and the frame underneath is super solid it is going to be awful hard to twist a fully welded and braced frame that has been cross braced in multiple directions.

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EV2Go
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Post by EV2Go » Sun, 07 Sep 2014, 08:19

This is the kind of overkill I have in mind...

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Post by EV2Go » Sun, 07 Sep 2014, 19:04

All along this build I have been trying to work out where to float the CNC table to the frame underneath.

In order maintain the rigidity I want (irrespective if I move it or not) one of my prime aims has been to try eliminate the flex out of the CNC bed.

In order to make the CNC bad as rigid as possible it may be necessary to go as far as doing this...

I could build a less solid frame underneath to provide the height I require.

Image

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Post by EV2Go » Mon, 15 Sep 2014, 21:02

Adverse Effects wrote: my bed is a 1/4 inch Ali slab(upgraded from 4 times 20mm x 100mm of that form stuff you have there) with 3/4 inch fiber board screwed down to it so i can dress it down as needed (9 times i have dressed it in the last 2 months and its 3 mm thinner now lol) it still twists when i walk through the house


*this is an exajaion example*

now see the closest corner you have in your pic lift it up by say 1cm

see how it will

A:- bend the rail
B:- twist the gantry
C:- twist the gantry bearings that run on the X axis
D:- twist the gantry rails that have the Z axis on
E:- in doing so the Z axis will no longer be in the correct place in the Z and X axises and that inaccuracy will be different depending on where it is in the X and Y location on the table

so at one corner it could be all most +-0 but at the far travel on both X and Y could be out as much as +- several mm

and if you say its ok there will be enough clearance for that not to hurt the mill then you have to much play in everything for the mill to be accurate and if that is the case no real point in having a mill that is CNC

i have been fighting this problem for over a year with this house moving

its getting to the point i am thinking of making a insanely ridged 100mm box section table braced in all direction and sitting on sprung feet just to get around this problem as i can not bolt it down anywhere here


Not as confident as I once was about getting it absolutely flex free...

Have just picked up my 1500 x 1000 sheet of 4mm 5083 alloy. It is setting next to the 1500 x 1000 sheet of 12mm AA marine grade ply.

With the deck, the alloy and the ply bolted down to a boxed and welded steel frame I am not so sure it will be completely without movement.

Image

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Post by Adverse Effects » Mon, 15 Sep 2014, 23:22

yep something that big will have lots of twist in it very easly so ridgity will be hard to achive

do you have access to a welder?

if not i have a gasless one here you can use to make a isolated frame

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Post by EV2Go » Tue, 16 Sep 2014, 00:06

Not at the moment I was looking at buying a TIG for when I get around to doing the frame on my trike, but was trying to hold off until I actually get that far.

If you have a gassless MIG I can use to make the frame that would be a huge help when the time comes.

Little disappointed it wont be a little more rigid, and by the time I bolt everything together I expect the individual pieces to increase greatly, but only time will tell.

I am more a visual person so I kind of need to see the finished part before I know if it is right or not. I might bolster up the side pieces of alloy with ply as well like the bottom.

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EV2Go
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Post by EV2Go » Tue, 16 Sep 2014, 00:27

Thought it was kind of pointless going too thick on the end pieces as the 40mm x 160mm surface isn't that thick (about 4mm), so I think I will achieve the best strength by bolting the X axis on both sides.

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Adverse Effects
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Post by Adverse Effects » Tue, 16 Sep 2014, 01:02

what are you going to do about the rest of the bed if the sides bow even 1 or 2 mm the center will sag 10's of mm just under its own mass then you will have the trouble of any thing you put on there will push it down as well

the bigger you go on the X and Y axis the harder it will be to level and keep level the bed

honestly i would love a mill 1.5 x 1 Mt but it would be a night mare to level and keep level with out going with a slab of 1 inch Ali and adjustable cross bracing in all directions

plus its better for me to play devils advocate now in the planing stages then you finding something bad out once its all built

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Post by Adverse Effects » Tue, 16 Sep 2014, 01:11


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