I've been trying to build a cnc machine for almost a year now, but my lack of knowledge seems to be holding me back. I've invested thousands sofa on parts but am literally no closer to cutting than the day i started research. i have tried many programs..sketchup, rhino, fusion, and mostly onshape. it seems like onshape is the most powerful program but despite their "easy to use" tutorial videos, doing what you want in the program seems considerably more difficult. it seems like i try to do the simplest thing, but get hung up on some little detail, get confused, waste an hour and end up so frustrated that i put the thing away and come back next week to more of the same. getting these complex assemblies together baffles me. i bought a bunch of 5010 extrusion, but am not able to get even close to designing the side plates necessary to assemble to the machine. it seems like a watch guys come on here all the time and they are immediately designing models and building machines. what am i missing?
First you need to determine if you actually need 3d CAD to design this. Most of my designs never go past 2d plan and elevation sketches and I work out all the dimensions I need from there. Taking things into 3d is often far more work than necessary.
^ Agreed, One program I don't see referenced here enough is Draftsight it is a free 2d cad package by the guys that give us Solidworks. It also runs on Linux ( a huge plus ) / Mac / Windows. A lot easier to pickup then a full 3d cad suit. Also, When building your cnc. Don't over look good old C.A.D "Cardboard Aided Design" It has gotten me out of a bind faster then digital many times. When you have parts on hand and a good idea of what you want to end up with. Nothing wrong with just building. A straight edge ruler / compass / slipstick Can get you a long way on laying out patterns / bolt holes / checking numbers / Ect. I also found learning cad was a bit of a struggle. When I stepped back and started to tackle a single part at a time it made it easier. I tried jumping right in and making complex fully detailed assembles with every part in place. But this approach just made more work for myself. Youtube tuts and library books are also a great source for learning cad.
That's what I have found. Single parts are totally doable. Complex assemblies with mates and constraints make my head hurt and sometimes when I can't figure out what to do I get stuck until I give up. I guess I have trouble sometimes even pulling dimensions off existing parts and assemblies. I'm happy to draw by hand to figure out distances, but it's hard to get those sometimes. trying to design side plates and have the holes all align centered to mate with other parts in other directions, racks, gear reductions and motors seems like it needs the complex assembly a parametric modeling program provides, but actually assembling the parts is bit over my head at the moment. So I can't pull the distances or relationships to design the plates. I decided tonight to ditch the x axis lead screw I wanted and spend a little bit extra to go r&p throughout the machine. Then I can use the f117 plates which are already designed. I have a guy locally that can help me cut out the plates from g10 or phenolic and I may be able to find some local to cut them out of aluminum. I'd like to a belt reduction drive, but I think with the spring tensioning gear to rack I should be able to design and retro fit that into the existing stock plates by hand later on, or ideally with a little cad work so I can start off doing it right. I may just try and get the plates cut and deal with the belt reduction later. I've noticed with big projects that small setbacks can stop progress and make you fall off the wagon. Sometimes it's best to do what you can do with what you have and hope you can come back to the problem later with more experience and solve it.
I guess another part of my frustration is that it feels overwhelming to learn all this assembly and mating stuff..just to design one set of plates for one machine and then likely not use it much again afterwards. Most of my cuts will be 2d. What 3D stuff I do will be simple and easily designed as single parts in a solids modeling program. Feels like to design a machine you have to try and figure out the hardest stuff first if you are starting from scratch. Frustrating...
I started out in 2D CAD using Torchmate CAD for my CNC plasma table (Torchmate CAD is a private label version of signlab) I then started using sketchup but found it too limiting in some geometry I wanted to use, and orienting/manipulating parts is not very straightforward. I then tried Solidworks, went thru the tutorials but at the same time I started using DesignSpark Mechanical (free) I found that DesignSpark was the easiest of all to learn to use. Basically took me a few days to do basic stuff and it was a couple months before I was able to do advanced designs. Version 2.0 of DesignSpark will export to 2D DXF and STL so I can send the dxf to ESTL CAM ($50) drill holes, and make the gcode that will work with GRBL (GRBL code will also work on 3D printer electronic based mills) When I want to machine a 3D part I can also use ESTL CAM to machine a .stl file like something from Thingiverse. My biggest motivation was I had to earn a living so lots of late nights and lots of practice.
