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

[m_c]

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.

[JAZZCNC]

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.

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..