Looking for background info to cut plywood 8 x 4 sheets for small boat build

Hi Everyone.

I'm just finishing building a 6m trimaran in Hampshire made from 4,6,9 and 18mm ply - all very carefully drawn and cut by hand from 8 x 4 sheets. (and very slowly...)

It is sailing and working very well, so much so in fact that I am getting interest from people who want to build it for themselves.

I have my plans on paper and also in FreeShip (boat related CAD type software) which enables me to get my curved panels converted into dimensions on the flat plywood sheets, so when they are pulled together and glassed/epoxied they form the quite complex curved shapes.

I can export in various formats from this software.

I am hoping someone might be able to help with some outline advice on any potential machines that could deal with cutting the templates out from the gaboon ply so people could buy everything pre-cut to speed up the process - for people with less experience this would certainly be a desirable option. Various people would still prefer to loft it themselves and do everything by hand.

I am therefore looking for something that can deal with 8x4 gaboon ply sheets.

Sheet list is as follows currently but potentially better nesting might improve this:
4mm 8x4 - 5 sheets
6mm 8x4 - 12 sheets
9mm 8x4 - 6 sheets
18mm 8x4 - 2 sheets

A couple of initial questions if I could:

What are the file formats generally required?

Are there any machines that work with the working sheet in a vertical orientation which would be beneficial for space? I can work with a horizontal machine, I will just need to move stuff around, but a vertical frame seems vaguely sensible and leave everything attached with tabs and then break out afterwards.

It will be low use - if I sell half a dozen kits a year I will be beyond impressed. I could though with these kits also more easily build the basic hulls myself to sell to people to finish off the build which might also be quite attractive to less committed buyers.

Speed is not really an issues as once programmed it can be left quite happily - an order does not need fulfilling immediately. No panic boat building!

Better accuracy and repeatability is required more than speed.

What accuracy is required - if within half a mil is in reality perfectly fine.

Is there software that I can import my long 6+m panels that will split them up into 3 sheets and is adding puzzle joint possible within any of this for extra bonding area? I could potentially add a butt block behind it anyway.

Are decent scarf joints feasible at 12:1 with the 6mm sheet? I am guessing so.

The first one I came across was this
https://www.uk-diycnc.com/kit-pricing
and there appear to be a number around in kit form.

I am not at all experienced with CNC machines but am technically and practically competent so a kit solution is not a problem.

I will also check around to outsource this as well, but I'm guessing the cost involved could be pretty prohibitive and if I sell one or two kits even I'll probably get my cash back.

Any basic things to be looking out for eg software compatibility, reliability, getting functional on the software etc?

I will be most grateful for any advice you could offer to start me in the right direction. This is the first day I have started thinking about this and only for about half an hour so far, so if this is just not practical it is good to find out early.

Many thanks!

Lots of questions!

First off software.
For sheet work, DXF is the most common format you're likely to come across.
This will then either be loaded directly into the machine (some higher end machines will handle basic files like DXFs directly), but more commonly it'll be run through some form of CAM system to generate machine code. The most common machine code is G-Code.

I'm not that clued up on the more woodwork orientated packages, but I'm sure there is some software somewhere that will handle splitting sheets and/or creating puzzle joints.
I was going to suggest what software to do some research on, but I can't even remember the names of the more common woodworking packages :/
Fusion360 is probably worth a look at, although it has a far bigger learning curve, and the CAM side has been pretty restricted for hobby users.


Machine wise
I'm sure Jazz will be along shortly, as he has built, and I think runs his own personal vertical machine.
Any decent machine aimed at woodworking, should produce parts more accurate than you can measure.

Personally, at that size of machine, forget anything built from wood. Yes, they can work well, but unless built very well, they're not stable.
The big thing for me, is for the amount of time it would take to build a large wood machine, you could build one from aluminium/steel for a similar cost/time, and it'll be far more robust.

I suggest you begin by converting the pieces you have into .dxf files-with a scarph allowance where necessary.At which point you might ask owners of CNC machines to quote for producing them.In the short term you are unlikely to get close to their levels of efficiency.In the longer term you might calculate how many kits it would take to earn back the cost of a machine and if the numbers make sense you could look around for one.In the interim a few hours of dabbling with the demo versions of some of the popular software to see if they would allow you to create the programs to produce the parts might swing the argument in favour of laying out a fair chunk of money.The situation to avoid at all costs is ownership of a machine with no idea of how to produce the parts.By the time you get it figured out another designer with a tame CNC operator might have cornered the market for your type of boat.

Hi,
Thanks for the quick responses, really appreciated.

Yes it was this video of the Jazz CNC vertical table (and coveting the massive sheet cutters in B&Q that made me think of it
https://www.youtube.com/watch?v=4STVbn_EMoc

That looks amazing - I could see me spending a lot of time in the workshop if I had that!

So, any particular software that anyone can recommend for me to get starting on?

Also, I am based near Lymington (south Hampshire) - does anyone know of any good companies / individuals that I could approach to start bottoming out some pricing for sub-contracting it?

The main reason I am looking into a machine for me is that my experience with sub-contracting out anything pretty much (both work and personal) always leaves me frustrated, disappointed and mostly re-doing what ever it was I was trying to save time on... I tend to prefer to do and control everything so at least if something is not right I know it was down to me and I can resolve it.

Thanks again for your time on this.

Hi Adventuretrimarans

Have you considered cutting the plywood with A CNC water-jet, I am sure you will be able to find one not to far away, you could also use A laser cutting service however you may not like the brown edge. Water-jet cutting will leave the material clean with no burn.

I assume you are using marine ply so the water should not be a problem. The machines are so fast the cutting time for a whole sheet will probably be under 5 minutes.

A water jet will slice through 20mm material like a hot knife through butter. You can even stack the sheets in some cases.

The kerf is minimal less than a millimetre, this allows square holes to be produced something a CNC router will not be able to produce easily, you have to allow for the tool radius.

If your files are accurate you should expect better than 0.25mm accuracy.

Farming out the cutting will allow you more time to get new orders.

Regards
John

John thanks for that.

I'm going to spend a little bit of time looking at Fusion360 and FreeCAD software and get some understanding of the process then come back and ask some more possibly embarrassingly simple questions!

Again, I appreciate you taking the time to reply.

Quote:

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Originally Posted by m_c

Machine wise
I'm sure Jazz will be along shortly, as he has built, and I think runs his own personal vertical machine.
Any decent machine aimed at woodworking, should produce parts more accurate than you can measure.

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Someone mention my name.!!

Ok yes, lots of questions but I'll get the vertical machine out the way first.
For this type of work and to be honest most other work, a vertical machine is perfect, lots of advantages other than the main one that is space-saving which is massive.

#1 Tool life is greatly increased because gravity is helping clear chips which then don't get recut causing excess heat and wear.
#2 Edge finish is improved because again chips are not being re-cut and pushed into the surface.
#3 Mess is contained at the base of the machine rather than chips being slung around the workshop, because it's vertical most chips just go up or down and gravity brings them down at the base of the machine. Obviously, this relates to when NOT using dust extraction, with dust extraction it's super clean and the advantages are still much the same with less power required for the vac system.
#4 Small Part loading/unloading and fastening is much easier as your not reaching over a wide machine. Important for someone like me who suffers from back problems.
#5 Less space is required around the machine for sheet materials as you don't need them flat because now you load them on their edge rather than face.

Here's a video showing an 8 x 4 I built for a signmaker. I also have a 10 x 5 version with vacuum bed and automatic tool changer but don't have a decent video of this one yet.

Software-wise and formats than others have covered but the higher-end vectric software like V-carvePro or Aspire will break a drawing down into multiple sheets, it will even nest and rotate the parts to get maximum material usage.

Don't waste your money on machines built from wood as they are a false economy, as are most of the cheap kits, because you'll constantly be chasing issues with the machine. You'll spend more time repairing or trying to upgrade than you will be cutting parts, often with the end result being you just get frustrated and give up or at best call it a loss and buy a proper machine.
I've built dozens of machines for people who have done exactly this and while great for me it's bad for the user and something I'd rather steer people around than profit from.

You mention speed not being important.! . . Well, it is actually and it's common for new users who don't understand the importance of speed and feeds to think they can cut at any speed they like, which you can't. There are many parameters that determine the speed you cut at and if not correct you'll get very different results ranging from poor finish quality to excessive tool wear.

The variables are many and the mechanical strength and spec play a large part.
There are many machines sold that are not fit for purpose because they can't reach the feeds required. For instance, one common eBay machine bought from up Peter Lee way which I recently visited which was 8 x 4 size sold for cutting sheet materials and was so poorly built and designed that it couldn't reliably cut above 3500mm without stalling. This is roughly half the feed rate that would be required to correctly cut MDF or plywood.
Then the gantry of the machine was so weak that it couldn't take any decent depth of cut without vibrating and introducing chatter which would lead to broken tools and at the best poor finish.

The machine strength directly affects the depth of cut you can take along with spindle power, this lowers the number of passes required to cut thru. But the speed is mostly determined by the material and tool, different materials require different spindle speeds and feed rates.

Feeds n speeds are very difficult for people to advise on because the variables involved are many and the cocktail for each machine, material, and cutter can and does differ greatly. Trial and error are mostly how you determine what works best for you and your machine but there is a common theme which 100% affects the feeds you can achieve and that is mechanical strength.
If the machine is weak and performance slow then quality will be negatively affected at best, too weak and it will be virtually unfit for purpose.

Accuracy for any decent CNC router will be 0.1mm at worst with 0.01 being more common. Repeatability is something that is more important and again something poorly built and specified machines struggle with. For instance, the above eBay machines don't even come with home or limit switches so ensuring repositioning or repeatability after an e-stop or crash is not possible.

My advice is that if you don't plan on building many kits then look at outsourcing because buying a cheap machine or kit will cause you more trouble than it's worth.
However, my experience with building machines for people like yourself who have no experience but do have good ideas and a creative imagination then a CNC machine opens ups other very successful and profitable paths they never even dreamed they would be taken down. When they start to realise exactly what can be done with them and the creative side kicks in it's amazing to see them flourish.
But this requires a decent machine and that sadly can't be done cheaply unless you build your own and that's not everyone's cup of tea. Also, often if it's for business use then just buying a ready-to-go machine can pay for its self in the time it takes you to build one.

Hope this helped and hasn't put you off CNC, but please don't try to take the cheap route if your thinking to make money from CNC, and if you were thinking to buy cheap and it has put you off then I've done my job so I'm happy..:thumsup:

https://www.youtube.com/watch?v=wJB_75bLEIM

I know nothing of Fusion but do use Freecad and I like it a lot-in spite of it's quirks.It takes a slightly different approach to get to grips with parametric modelling and you get a lot more versatility once you make the leap.The Draft workbench might be the best place to start drawing things but for machining I stay with the Part Design workbench as the solid models you can easily create make it easy to create the toolpaths and you can run a simulation to see the part appear in the manner that the machine will cut it.I recommend an hour or two watching the videos on youtube-sliptonic and Joko engineering are very good.

I'd have reservations about either laser cutting or waterjets because of the edge conditions they leave and it also wouldn't be possible to cut the scarphs.The scorched edge of a laser cut might not be the ideal surface for bonding and the pressure of a waterjet-they can operate at 60,000 psi-might drive water into the plywood and need a good deal of drying.If using either it would be worth doing some experiments to verify that the bonds would be sound.

Once you have the level of proficiency with a chosen CAD system you might like to try nesting the parts so that you can try presenting a cutting business with a project that has a good deal of the legwork done.They will thank you for making sure the outline entities are joined together and then they can just select the tools and the cutting depths and I would expect their software to give a good idea of the time needed and hence the cost you would bear.I would expect a quick google for CNC router services in Hampshire or Dorset would turn up a few.

It has to be said that conventional flat bed machines will outnumber tilted machines by a huge factor.If you are looking to acquire one you will need a healthy amount of electricity to run it because it will need extraction and quite possibly a vacuum pump.All of which will eat up workshop space

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Originally Posted by routerdriver

It has to be said that conventional flat bed machines will outnumber tilted machines by a huge factor.If you are looking to acquire one you will need a healthy amount of electricity to run it because it will need extraction and quite possibly a vacuum pump.All of which will eat up workshop space

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If you are talking about the vertical machine requiring vacuum then that's not the case. Yes, it makes it more convenient as you don't need to fasten material but other than that being vertical is no different from a horizontal machine.

You still need to fasten material and waste material when horizontal if you don't want the part or endmill getting damaged and this can be done just the same on a vertical machine either by tabs or screws. And actually, if you program the finish/start point at the top of the part so when the part is cut through gravity helps and the part drops away from the tool which reduces the chances of the tool pulling it back in and snapping the endmill or marking the part.

Like I said, lots of advantages often not realized unless you have used one vertical.

Jazz,

That is a fantastic amount of useful info there, so many thanks.

Ref the speed, I meant that if a machine requires multiple passes as it can't cut too deeply per pass and takes even a week per kit instead of a say a day, would present no issue as the numbers involved would not require one a week even for sure.

So, how much would it be approximately for a machine like yours?

What sort of lead time would there be in building and installing?

Where are you based for outsourcing my kit production?!?!

I have a handful of people already interested currently and the project is not even officially live yet, but I really need to get out on the boat once this lockdown eases, thrash it around and get a load of videos out there showing what it is capable of - then I can gauge the level of interest.

It is the initial drawing and cutting that is quite tedious and hard in a home workshop - also would speed things up for me if people want a part built kit to get on with the finishing etc.

So this is all about me planning ahead at the moment so any ideas will be super helpful for my roadmap - I don't want to suddenly get the first half dozen orders (I wish!) land and not be able to fulfil them!

I'll get on with importing some example sheets into FreeCAD and see how things progress on that front so I can see how feasible that end is for me.

Quote:

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Yes it was this video of the Jazz CNC vertical table (and coveting the massive sheet cutters in B&Q that made me think of it
https://www.youtube.com/watch?v=4STVbn_EMoc

That looks amazing - I could see me spending a lot of time in the workshop if I had that!

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If you like it, contact Dean with a PM. I am not sure if that is a 10x5 or an 8x4 cutting area

I will send you my details in a PM but first, let me explain or clear this up a little.

Quote:

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Originally Posted by adventuretrimarans

Ref the speed, I meant that if a machine requires multiple passes as it can't cut too deeply per pass and takes even a week per kit instead of a say a day, would present no issue as the numbers involved would not require one a week even for sure.

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I understand your thinking but you still need to be aware that no matter the depth the machine still needs to be able to move at a certain speed to cut correctly and if it can't then the depth doesn't matter. In fact, it's worse because the shallower the depth of cut the faster you need to travel to maintain the chip load the cutter requires to perform correctly and not start rubbing the material which causes heat and tool wear.
Cutting deeper and slower is often better if the machine and spindle are strong enough to handle the forces but the machine is lacking velocity.

To see this play with a feeds & speeds calculator to get some idea of how changing one parameter affects another.
https://app.fswizard.com/

Thanks Dean.