Lessons Learned

Sometimes it helps to have a list of lessons for the next person.  Here are a few categories related to lessons learned with Milling and hopefully 3D Printing.  Warning, the lessons so far are meant for very newbie individuals and are only based on personal experience.  

For background, one day recently, I decided to buy a CNC Mill / Lathe combo and start making chips without ever having taken an engineering course or a shop class.  It is painful not knowing what a "good chip" actually looks like, but guessing instead.  This is a list of lessons learned for those types of individuals.  I am not 100% sure all these lessons are good lessons or possibly the start of bad habits.

General Lessons Learned

• Take Notes when fabricating something.  It is handy to write down what you did to get the results.  I record the process I went through to generate the gcode as well as my "quality observations" with regards to the final product.  It helps others in troubleshooting your problems as well.

3D Printing Lessons Learned

ToDo

Milling Lessons Learned

• Turn off all the damn power save options on your EMC / Mach3 PC.  Especially don't be dumb like me and set them for 4 hours ahead.  That will REALLY piss you off. 


• On a hobby CNC mill, a small Target shop vac for $28 can vacuum up the metal chips during milling much cleaner than an air-hose can blow the chips away.


• When buying a hobby mill + CNC kit + software, you do not need to buy everything as a complete package from a single vendor.  Even if you do, it is likely to arrive in pieces from different locations (such as the PC shipped direct from Dell) and will require that you install all software and troubleshoot all problems yourself anyway.  Buying a complete package allows the seller to mark up the price by $500 - $1000 and give you the cheapest parts.  Go to Sherline, or wherever, and buy a mill (with CNC if you want.)  Go to Dell and get a cheap pc.  Connect it all together over a day and install the software.  You would do that anyway, so what is the benefit of a package???  I will even relay the story that the vendor which shipped me a package had not tested all the parts together, such as a usb to parallel adapter with Mach 3.  The whole package didn't even work and I was off to Comp USA.  There were other integration issues as well and for a newbie, it was not fun, especially since I only wanted to start machining.


• When calculating true origin of your work relative to the end mill, don’t make the mistake of pushing the end mill up against the X or Y axis and not accounting for the radius of the tool / cutter.  If you have a 1/4" diameter cutter up against the left edge of the work, then you are not at X=0", but rather X=-.125"  Honestly, I don't know why I didn't figure that one out a week sooner.


• Not all dial indicators will work with a mill (in other words, attach and tell if everything is square.)  The dial indicators at Sears or the local hardware store is probably the type that will not work.


• There is an initial period of time that every newbie needs to manually work with their machine.  The CNC software has come easy to me, but stopping "vibrations" and getting good chips required manual work on the machine.  CNC does not stop vibrations on a cheap mill since it does not have full control of the mill, so you must manually learn the traits of your machine.


• If you do not have automatic stops, check for collisions prior to a milling job.  I have found it easiest to slowly send the mill to the extreme positions in the gcode file in order to see what will be.  I watch so that I can shut off the movement if there is going to be a collision.  It only takes 2-3 minutes, and it saves a lot of trouble.  More than once, I have saved a work by testing the Min/Max positions prior to starting cutting.


• The Sherline Mill appears to have the X/Y measurement markings in the wrong quadrant.  The Y axis appears to have the 0" mark where the 7" mark should be.  It gets confusing trying to match the Sherline Y axis scale up with the Y axis DRO in my CNC software.


• When "jogging" the position of an end mill, it is the end mill that should move away from you as the Y axis reading gets larger, not the table.  It is the end mill that should move to the right as the X axis reading gets larger, not the table.  After a while, that becomes a more natural concept.  The conceptual problem never existed for me on the Z axis, since the table doesn't actually move.

Mach3 Lessons Learned

• Don’t believe the Mach 3 manuals that you can ignore areas of Mach 3 that you do not understand until you get more experience. If something is in the Mach 3 screens and you ignore it (like the “Edge Finder Dia” on the Offsets tab) you will pay a price…   After the first cut or two, take the time to examine everything on all but the last screen in Mach 3.


• Mach3 does NOT like other programs to be present when it is running.  Turn off everything not Mach3, remove all unnecessary interfaces, and reboot prior to running a job if you cannot dedicate a PC to Mach3.  Then, manually record the X, Y, and Z locations where the job started if the cutting is very important to you, so that you can precisely move the mill back to that location in the event that Mach3 does crash.  I have a special boot sequence for Mach3 and have not had any crashes since using that boot sequence prior to any Mach3 start.