Hi All My son and I are building our first OX CNC machine. For the most part it has gone fairly smooth. This morning we tried to do a test run with a sharpie and the Logo code in Chilipeppr. After setting 0 for Z away we went. Well not completely. The machine went through the motions but not all of the logo printed. What should I look at that could cause this issue? The whole frame is true and square from what we can see. Video of the drawing.. https://goo.gl/photos/hHTcmyHz665KFmJr5 TIA Michael
Could be just my eyes but it looks like your spoilboard might not be completely flat. The logo looks darker and thicker on one side. Is the sharpie touching where the logo is missing? Might want to try -.015 for the Z depth, just to "preload" the marker a bit.
I thought about that.. But I checked it and its flat. I gave the sharpie a bit more preload and that helped. Except I could hear it drag more on one side of the bed than the other. I assume there must be some play in the joint of the gantry and the X axis track?
Even though you may be able to put a straight edge on the spoilboard and it's flat that way it may not be to the X, the easiest way to ensure that it is, is to use the router and surface the spoilboard. That will make it completely parallel to the gantry. Try putting the marker just above the spoilboard until there is just a slight gap then move it around to different parts of the spoilboard and see if the gap increases or decreases..
If I could figure out a way to attach my dial indicator to the gantry that might yield better info. I don't suppose there is a documented method to level the spoilerboard with the gantry along with gcode to run it all around the board?
What folks usually do is just run a pocket toolpath the size of the cutting area with a large flat end mill (3/4-1" for the smaller routers and up to around 2 1/2" for the 3hp+ you could always use a 1/4" but it takes along time for a good size machine) and make a shallow cut like .01-.02 to surface the MDF. The spoilboard will always need to be brought back to a "true" state after heavy use and/or in my case alot of humidity changes. MDF tends to swell over a rather short period of time, throwing everything off.
You'll have to run several straight toolpaths. You can program it yourself or figure it out with a cam program.
In sketchup, draw a rectangle the size of your spoil board, actually just the size of the area your router can reach otherwise you might run into limit switches. Using SketchUcam, pocket the rectangle, set the pocket to 100% deep. set stepover to 70%. set the material thickness to 1mm and generate Gcode. Now you have a gcode file that will cut 1mm deep, but if you only want to take off 0.5mm you can just set Z-zero 0.5mm above the surface (or other values). or if you want the dubious fun of installing python, or are already using LinuxCNC, you can use this http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Simple_LinuxCNC_G-Code_Generators#Facing_Software
Would this bit make a sensible bit for surfacing? http://www.amazon.com/CMT-811-191-1...1&sr=8-15&keywords=mortise+bit+1/4-inch+shank
Consider http://www.amazon.com/gp/product/B0006B0PVW/ref=s9_dcbhz_bw_g469_i2_sh or http://www.amazon.com/Magnate-Surface-Planing-Bottom-Cleaning/dp/B0093C1YNI/ref=pd_bxgy_469_text_y
The hardest part now is having it sit there while I wait for the orders to come in with the new parts. Is chilipeppr the only app that can control the tinyg? I like having options although chilipeppr looks to be well outfitted.
As for bits, you can always go down to the local Lowes or HD and pick up a bit like this: Shop Skil Carbide-Tipped Bit at Lowes.com or even the Bosch counterpart. In my experience they work just fine for surfacing a spoilboard, set the step over closer to 40% and they surface just fine. In fact I use a 1 inch Freud 1/4" shank version for my smaller machine I picked up at the local HD. As for the TinyG, I can't help you with that one, I haven't tried that board yet...
I use and enjoy micromark fly cutters. They're nice and cheap at $10 + s&h. It takes a standard 1/8" HSS blank so it's economical in the long run and you can have different edges to use for different materials or situations. The bit has to be shaped some when you get it though. Just a little radius at tip is really all that's needed in most high rpm cases. It's nice because it's single point so I get less dust. Micro Fly Cutter
I am becoming a believer in 'always' using ramping. The few jobs I have done with it since adding it to SketchUcam have benefited, even in plywood even though the feature was added to cater for aluminum cutting with the C-beam machines. just read the SketchUcam help section on ramping, and watch this for tips on using it. you can see it in action here (yes, I know the sound sucks)
Yes ramping is very handy. Only time ramping shouldn't be used, well at aleast one time, is when your using compression spirals where you need the up cut part below the surface of the part to reduce burring.
