New CNC user mistakes and info

[JAZZCNC]

So one thing I've been reading is about mistakes, some minor, some more costly. Snapped bits seem a common issue. I'm assuming this is down to incorrect feed rates or more likely errors in the programming and plunging too deep. Hopefully this is short lived and checking your toolpaths thoroughly is a must early on. Anyone experienced this when a novice? Or still experiencing this? How much is down to user error or can it sometimes be hardware error?

Broken bits are just part of the learning process and they can and probably will happen from a mixture of all of the above, however the one error I see most often from new users is forgetting to reset the Z axis offset (Zero) after changing tools.
Checking toolpaths carefully with a simulator is a good pratice to get into however then it won't always stop crashes.? Common things that can and will bite you at some point are Clamps and screws which hold the material.
Many jobs require the tool to move around between cuts and the code doesn't always move in ways you'd expect so it's very easy to hit a clamp when it moves locations or hit the head of a screw you are using to hold waste material etc which doesn't show in the simulation.

This can and does happen even for experienced users, but obviously I've never done this.. . . . It's 99.999% user error most of the time.

I have a few carving/inlay projects planned. Hopefully in some nice hardwood. I'm thinking of during the early days running the project on some cheap pine or ply first as a test before buggering up an expensive piece of oak. Is this a reasonable idea or am I thinking over cautious?

I'd advise at first to cut Air by setting the Z zero in Midair. This will prove your code is working as expected.
Then I'd practice on soft materials like Dense foam(kings span) or MDF. However, you will have to tweak the speeds n feeds, DOC, etc, to suit the material your using and MDF is a better practice material than foam because it's harder and closer to Real wood.

Dust shoes seem a good idea as carving produces a lot of chips/dust. But again as a novice user, I'm thinking I want to be watching the cut, firstly out of interest, but secondly out of safety. Are you all confident enough in your cutting to be blind to the cutting bit? Are you confident enough to leave your workshop while cutting is in progress or would you at least want to be in the workshop doing other things so you can hear an issue and stop it swiftly? Do you expect issues or is it now rare when experienced?

At first, it's ok to watch the cutter for the reasons you stated but I'd advise putting one on ASAP because while it does obviously lower dust it does a more important job in that it stops chips from getting recut giving a poor finish and excessive tool wear.

Maintenance. Apart from keeping clean and dust free, what general maintenance is required? greasing ball screws? I'd guess that attracts dust sticking? WD40? silicone spray?

Keeping it clean and greasing the screws and bearings is often enough, bit of light oil on the rails won't hurt either just don't go crazy.

What were your first projects? Why? Anything nice and simple that teaches a new user a thing or two or just blast straight into what you are after doing and make mistakes to learn?

My first CNC job was making new gantry sides to replace the MDF ones.!

KISS is the best advice and in MDF to start off with. Start with simple 2D shapes with a few pockets and holes. If your feeling confident maybe try a bit of V carving.

A good practice exercise that will have all of the above plus more and will be useful is a Collet holder.
If your feeling really confident instead of collet pockets with straight sides make the pockets tapered and use a 2.5D toolpath with a ball-nose cutter. Also, try putting chamfers on the edges.
This will give you all the major tool-path types in one Job and will teach you how to do tool changes in the same job. Just about every job you do from then one will have one or a combination the tool-paths used in this practice piece.