BuildingAfloat

[Jonathan]

Opted for 12mm steel for strength ... I thought I'd keep the aluminium down to a minimum for stiffness.

20mm thick aluminium would be just as strong. You will save the difference in price between aluminium and steel from the relative machining difficulty.

I'll see what the 20mm gains me in reduced overhang, it might be worth a drop in stiffness over 25mm. What size do people tend to go for?

I think we're talking on cross purposes - I was referring solely to steel plate, not the rails. However since you've mentioned it - the 25mm rails are much better than 20mm since in addition to being a bit stronger due to the size they also have one more row of ball bearings in the blocks.

I had considered that, may look at the drawing again, I have to mount limit switches yet and thought the space could take the mountings for them, that was all.

Having the machine as strong as you can is far more important than having a convenient place for a limit switch. You'll find somewhere to put them.

1) A simple MDF bed with 2 layers, support and spoilboard
2) Aluminium (or maybe even steel) drilled and tapped
3) Open to allow a 4th axis to be mounted
4) A removable T Slotted Steel bed across the front cross member
5) Open to allow me to mount motorcycle engine casings on the bench beneath for engraving

Although clearly 1) is the weakest it's not a bad idea to use MDF to start with as it will be adequate for most things, makes clamping easier and doesn't kill the tool if you make a mistake.

take a look and see if you can spot the mistakes..lol

[...]

Thats better..

Your dimensioning still doesn't add up. Mine is definitely different to that drawing - size, aluminium piece on front is a different shape, smaller connector.

There's also now 4 bearing spindles readily available - these are 215mm long instead of 200mm.

[BikerAfloat]

Hi Jonathan,

Thanks for your post,

"I think we're talking on cross purposes..." - Yup my mistook!

I'm going to have to borrow a mates workshop for this build, so I'll be able to work the steel plate almost as easily as the Ally there, so from a rigidity and space point of view I'm plan to stick with Steel plate.

I wasn't aware of the extra row of bearings in the 25mm bearing blocks, that's a good reason to stick with them, the space saving is only 10mm if I went to 20mm rails on the Z Axis anyway.

Cheers,
Geoff.

[BikerAfloat]

Hi All,

Was wondering if anyone has seen my last post, been up for 4 days now. I'd like to know if I'm going in the right direction before spending any more time on the drawing?

Cheers,
Geoff.

[BikerAfloat]

Hi All,

Here are the latest drawings for the machine, it's nearly there, just need some advice on the X Axis belt drive, or more specifically the idler pulleys, I can work something out, but I'd rather go with a tried and tested system. They are currently set at 25mm OD, their construction and size are open to change.



I know steel rings like a very ringy thing and some form of filling is in order, I'm pretty sure I wont be able to use epoxy and agregate from a weight point of view, I have to consider the stability and balasting of the boat. I was wondering if expanded foam would act as a dampener, anyone got any experience/ideas?

Spindle shown is Chinese W/C - 2.2kW one, I also plan to have a dedicated low speed job for the harder materials. My supply is currently (Sorry for the pun) limited to 16Amps on the landline - going to have to do some sums to see just what a compromise this will cause. 2200W @ 240v = 9.2 Amps so 6.8Amps left. This means I would have not a lot left for everything else (Fridge, Lighting, 2nd PC!) , Me thinks either a 2nd landline or more likely a generator will be required!

I can pm the sketchup file if anyone would like to check it over, all I really need to know is that the design is buildable, I'm fairly sure it is, but sometimes you can miss little details when you are too close to something.

I'd like to learn the capabilities and limitations of this machine design, I've taken a lot on board for this design from previous posts to this log and from reading other peoples experiences, but there has to be a time when you stick a stake in the ground and this is where I find myself. If you see something is dangerous or impossible please tell me so and I will change it. Otherwise this is the machine I plan to build warts and all.

If the design is doable (Not perfect, but doable) I plan to start buying components sometime in the next week or two. The order I think I'm going to use is something like this:

1) Linear Rails and Bearings - Need this to be sure of the holes I need in the steel.
2) Steel.
3) Pulleys and belts - to make sure of the sizes so I am safe for the Ballscrew Machining.
4) Ballscrews and Bearings.
5) Steppers.
6) Electronics & controller software. 3 choices Planet CNC USB, EMC2 or Mach3(4?) Need to do a feature/cost comparison Gut says Planet CNC as I need a BOB and the software was written to work specifically with their BOB, Head says Mach3 as it seems to be the most used and the little perverted Demon on my shoulder says EMC2, as it's about time I learnt about Linux!
7) Spindle - probably use my hand router to start cutting and pay for W/C jobby and the dedicated low speed one.
8) Additional software for modelling - going to start with the free stuff to get the feel of the machine.

Does this seem logical, are there changes I should make?

Another long post, so I'll stop here and wait for a while before adding any more.

Cheers,
Geoff.

[wilfy]

sorry i can't add much again, but what i will say is consider emailing the dude your getting the rails and screws off first for a price and pay outside of ebay, this way you will get a better price and while your at it get him to quote you to include and also not include the spindle.. chances are due to combined postage and a big order you may find yourself getting the spindle alot cheaper than anywhere else.. this is certainly my play when the time comes.

also i only just realised your building this machine to work on a boat.. thats just awesome in its own right.

expanding foam is also something i was considering for my build.. it's very cheap and i think it would go some way to take the ring out of the steel as it wouldnt have any air to resonate through the center of the box section

[BikerAfloat]

sorry i can't add much again, but what i will say is consider emailing the dude your getting the rails and screws off first for a price and pay outside of ebay, this way you will get a better price and while your at it get him to quote you to include and also not include the spindle.. chances are due to combined postage and a big order you may find yourself getting the spindle alot cheaper than anywhere else.. this is certainly my play when the time comes.

Good idea Wilfy, my strategey for ordering bits is based on me funding the job myself, so the spindle is my last purchase, however I am pursuing a couple of other avenues for funding - I am Bi-polar (Manic-Depressive) and it is difficult for me to be employed, hence building the machine to enable me to be self employed. The upside of my illness is the support from the Mental Health team. They beleive there may be some funds to help people like me back to work. If the funds come from there in a lump sum, then I will be looking at making them go as far as I can and that is a good strategy, Thank you for the idea.

also i only just realised your building this machine to work on a boat.. thats just awesome in its own right.

Hee Hee, Home is a 53' Narrowboat, I'll be lossing quite a bit of living area to accomdate this, but if I can keep my costs down by not having to rent a workshop, the the plan for self-employment is that bit more viable.

expanding foam is also something i was considering for my build.. it's very cheap and i think it would go some way to take the ring out of the steel as it wouldnt have any air to resonate through the center of the box section

Glad to hear I'm thinking along the same lines as someone else, makes it seem a more viable idea. Thanks again!

Cheers,
Geoff.

[Jonathan]

I notice on your design the X rails are the same length of the box seciton. I would leave about 5-10mm clearance at both ends to ensure they lie flat in case the box section is distorted at the ends.

Going by your order;

1) Bear in mind the holes in the SBR rails look like they've been drilled by an ape swinging on a pillar drill - you can sometimes even see the pencil lines which mark where the holes go, so don't expect them to be accurate. Make the frame and gantry then mount the rails to the frame by drilling and tapping one hole at a time until you have them aligned and running smoothly, then drill and tap the rest.
3) I found recently that a local shop is cheaper than getting the pulleys and belts online, plus no long delivery time and additional delivery time to send back the items they got wrong!
6) I reckon try LinuxCNC then mach3 then Planet CNC because clearly if you get on well with LinuxCNC then you've saved a lot of money compared to the other options. If not by all meant buy mach 3. Either way don't expect to learn much if anything about Linux though, since one it's installed it's just like using a program on windows.

Foam is an interesting idea, by all means try it but I don't think it would help that much with resonance. As far as I know the issue is not the 'air resonating through the centre', it's the walls of the steel box section that vibrate. To prevent resonance on the not moving parts you should add mass, or some material with good damping properties which tends to be materials made up of particles which rub against each other to dissipate the energy as heat. Sand covers both criteria, but it sounds like that's not an option.

[BikerAfloat]

I notice on your design the X rails are the same length of the box seciton. I would leave about 5-10mm clearance at both ends to ensure they lie flat in case the box section is distorted at the ends.

Was looking at that, I think I will do that as it gains me some extra working area too, for not a lot more cost.

1) Bear in mind the holes in the SBR rails look like they've been drilled by an ape swinging on a pillar drill - you can sometimes even see the pencil lines which mark where the holes go, so don't expect them to be accurate. Make the frame and gantry then mount the rails to the frame by drilling and tapping one hole at a time until you have them aligned and running smoothly, then drill and tap the rest.

Yes I thought they'd be added manulally after cutting, that is why I plan to drill to suit as you suggest!

3) I found recently that a local shop is cheaper than getting the pulleys and belts online, plus no long delivery time and additional delivery time to send back the items they got wrong!

Not sure in the wilds of Cambridgeshire will be that advanced, but I'll have a look!

6) I reckon try LinuxCNC then mach3 then Planet CNC because clearly if you get on well with LinuxCNC then you've saved a lot of money compared to the other options. If not by all meant buy mach 3. Either way don't expect to learn much if anything about Linux though, since one it's installed it's just like using a program on windows.

I like the Linux price, but it's uncharted waters! And yes I guess I'll be too busy making stuff to learn much! I'm stll very much in favour of the Planet CNC stuff as the BOB and software are less than Mach3 and I believe the USB BOB has some buffering to help with the non-realtime windows performance. Would be best to be able to try all three hands on, or at minimum get a copy of the manuals to compare features & interfaces.

Foam is an interesting idea, by all means try it but I don't think it would help that much with resonance. As far as I know the issue is not the 'air resonating through the centre', it's the walls of the steel box section that vibrate. To prevent resonance on the not moving parts you should add mass, or some material with good damping properties which tends to be materials made up of particles which rub against each other to dissipate the energy as heat. Sand covers both criteria, but it sounds like that's not an option.

[/QUOTE]

Mmmm, as Jazz has tried it without success (Thanks for that Jazz) the foam seems to be a no-no. I will have to see how the boat is when the machine is done. Sand can always be added later if I make the boxes "water tight" from the start. I guess if it is too noisy and the sand becomes a must, I can always use the router to make book cases along much of the other side of the boat. That'll give me an excuse to by more books as they are needed for ballast!

Cheers Geoff.

[TrickyCNC]

I like the Linux price, but it's uncharted waters! And yes I guess I'll be too busy making stuff to learn much!

I use linuxCNC and as Jonathon says, there is no learning involved on the linux side of things.

You can try it for free. It's very easy to install (just a wizard mouse click install ! ), and once it's installed, it's very intuitive. Linux, is basically the windows desktop, and EMC is an Icon to click on to use it ! no need to learn linux in the slightest :)

Rich

[JAZZCNC]

expanding foam is also something i was considering for my build.. it's very cheap and i think it would go some way to take the ring out of the steel as it wouldnt have any air to resonate through the center of the box section

Doesn't work I've tried, it's not dense enough complete waste of money if you do.

By far the best thing is kiln dried sand nothing really comes near for ease of use or cost.