First Build - Yet Another Alu Profile Router - 900 x 800

[Kitwn]

You may like to mock up some parts of the construction in ply or MDF before committing to expensive aly plate. This works especially well for complex structures like the Z axis and is easy to do with hand tools only. In fact I spent yesterday finally building my Z axis in aluminium plate after running it as a plywood 'mockup' for the last 18 months.

I'm also changing from microswitches to inductive sensors for limit switches and they're going to resemble sore thumbs, whether I like it or not. Andy's right about working out these details in advance if you can.

[JAZZCNC]

Cheers for that Jazz

It's stuff like this where years of experience really show. It all looked good (to me) on my plan but the practicalities such as being able to access screws or adjust alignment etc just don't become apparent (again, to me) on a model. I would have been stuck into the build before having one of those "d'oh!" moments.

It's common for the little details to get overlooked and it's the little details that can make a big difference to how the machine performs and ease of maintenance etc.

I model all the major mechanical components individually in CAD right down to the exact mm and with every hole for bolts etc in their correct locations. Then I build sub-assemblies with the components ie: Z-axis, Gantry, Ballscrews with end bearings and ball-nut mount, this lets me check for clashes with bolts, etc.
Then finally I build a full working assembly with the sub-assemblies all mated together accurately. This way I can check every detail and catch if any interference or if access is restricted etc. You'll be surprised just how easy it is to miss quite obvious details that would be major problem after parts are made.

My personal opinion is that making mock-up parts from MDF etc is a waste of time and provided you are accurate with the cad models then it's not required and defeats the purpose of CAD. Every machine I build is done solely in CAD with each part machined straight from the model and they fit together perfectly every time. (Unless I screw up the machining which never happens.!. .Honest.!!)

However for those who don't have good CAD skills or use lower-level packages that don't allow mating and assemblies etc then I agree it's a good and safe way to work.

The best advice I can give is to build in as much adjustment as possible and pay close attention to bolt hole locations/access to prevent clashes. Think about the little details right at the start like Limit switch locations, Energy chain mounting and paths, Cable routing and access to grease nipples, etc.

Break the machine down into segments and think about how each segment interacts with the next. ie: Z-axis and how it mounts to moving axis on the gantry and how the Energy chain runs along gantry and mounts to moving access does it clash with ball-screws or motors or limit SW etc when moving.?
These little details can be a right ball-ache if left until the machine is built only to find out there is no way to avoid clashing. Often the difference between something fitting or not is only mm's and can completely screw the job up or cause major part remake or big compromises on design.

The extra time in CAD is well worth the time and frustration it can save, not to mention expense if screw up big.!

[Kitwn]

However for those who don't have good CAD skills or use lower-level packages that don't allow mating and assemblies etc then I agree it's a good and safe way to work.

This probably applies to most of your readers.

MDF can be the old man's CAD. Perhaps we need a new acronym? MAD..... Model Aided Design

Either method will help you avoid creating a TURD... Totally Unbuildable Router Design

[CaptainBarnacles]

Some really amazing advice and words of wisdom, thank you so much guys.

I had a go at mocking up a couple of components in ply and it was useful to help visualise assemblies before commiting to cutting aluminium. That was a while back and since then my CAD skills have moved on a bit so I am more inclined to model it in CAD now than in MDF or ply (although sometimes it would definately be quicker to just go and knock out the part in ply!).

I will certainly be using CAD with a different midset going forward. Back when my CAD skills were very limited I was using it as a way to visualise the overall machine and give me an idea of what the finished thing would look like. From the advice here I can see now how it's real power is the ability to precisely model the real world and to resolve issues and conflicts before I go anywhere near a power tool.

Looks like I'll be spending this rainy weekend in front of the computer and trying to lock down the design as much I can. I'm really itching to get started with the build but I now appreciate how much time and heartache can be saved by spending the time on the design (although it is starting to annoy Mrs Barnacles - every time she walks past I'm staring intensely at a virtual CNC router. I told her it would only take a few weeks to build, that was over two years ago!).