Here's one from a few years ago - at a Pneumatics Suppliers Counter in Nottingham.
Me: Can I have one of those XYZ-123/B, like the one that's on the shelf over there.
Jobsworth: I'll just look it up on the computer. Sorry mate we haven't got any, computer says zero stock.
Me: What about that one there!
Jobsworth: If the computer says we 'aven't got any, we aven't got any.
RobIt takes all sorts to make a world, I am just glad I am not one of them.
Machine tools and 3D printing supplies. Expanding constantly.
This thread has gone a bit weird!
Back to the OP post#1 If you set yourself a design brief to 'Develop and then market a very affordable CNC machine' then I do think it has some merits. High performance CNC machines (DIY and industrial) have 2 vital characteristics. They are very stiff, and they have precision mechanical and electrical components. Together this allows them to cut harder materials properly, and with good levels of accuracy.
However, to fulfill your brief you must wind back the budget and therefore these 2 vital characteristics must suffer. You are therefore left with no option but to build a machine which can only cut soft things, and with a modest level of accuracy. But this is not the end of the project as I would say there is a huge market for craft work, balsa cutting, maybe drag knife vinyl cutting.
The challenge is to come up with something cheap, robust, does not need constant maintenance, and delivers. I'm not sure this has been done for the price you are aiming for, but that should not stop you trying. Some aspects of your current design are interesting, but some need more work.
For info the FEA analysis looks like you clamped each end of the beam then loaded the rail normal to the surface with 30 N. You got 0.03mm deflection on the rail which is reasonable for that beam on it's own - but remember your beam end conditions are not infinitely rigid, the V-bearings and brackets and gantry will flex, as will the Z axis, and the tool (dremel type I assume?) will along with the cutting bit which will have to be small. Backlash in the threaded rod will allow the tool to vibrate as so on. Push the Z axis with a set of scales and measure the deflection with a DTI. This will give you the true machine stiffness and it will be quite low. This is where the challenge lies to come up with something simple and cheap that still works.
I agree with Dean, even if i did not want to at first, this video made me laugh.
People don't want to understand basic concepts:
-"A machine is a tool containing one or more parts that uses energy to perform an intended action" , what we see there is a toy, cause its and will be unable to perform that intended action. So lets call them "toys" if their purpose is for the people to play a bit with them.
-V bearings are not meant for that. The only way a V bearing to work properly for that purpose is an additional arm with say 608 bearing which eliminates the v bearing play.
V bearings simply are not made to take forces in that direction.
-I have seen machines made from roller bearings 608, capable of milling aluminum, i dont say that they are good, just that better than V bearing machine.
-How can sb build a machine not understanding the base concept that box section is stronger than plate?
So in short IMO that toy can do nothing, don't lie to yourself/and others/.The way is designed it can not even move reliably a laser diode. You are making nothing new. Instead watch, read, learn and try to make something real.
Hi everyone, it's been a while since I've been here, but I'm happy to say that my team and I have radically changed the design for our desktop CNC machine with many of the thoughts and comments that you gave us several months ago!
If you have any other feedback please let me know!
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