so plan is strap dremel and RAMPS to bootstrap/routy, mill plates, build new spindle?
or am i missing a step?
cheers
mevo

 

No that should work. I don't have a dremel so I used the 890kv motor to make the 890kv spindle. Lots of people just use dremels but they have bad runout. Also, if you are just beginning, start with milling foam, then soft wood, then something hard but cheap... like acrylic. Then try the aluminum. One glitch in your code or one loose wire or one bad chip and you'll have a very expensive project on your hand with all the defective parts, broken bits, etc.

 

do i need any specific firmware for ramps in order to connect to a cnc controller, or do i just use printer software with gcode i gleem from hsmworks?

 

I don't know. I think everything is done in GCode. There's a program called Skeinforge that is used to do both CNC and 3D printing gcode generation. The difference is very subtle... in CAD we call it a pocket vs a pad. In CNC we start at the top, in 3D printing we start at the bottom. The firmware will not need a heater for CNC so that code may have to be reworked. I'd look around for a CNC firmware for RAMPS
https://capolight.wordpress.com/2010/12/05/cnc-milling-with-ramps/

My system uses LinuxCNC and all I have to do is throw in some new GCODE and it can run a 3D printhead. Some other code and it's a laser cutter. Some other code it's a drag-knife... Some other code and it's a pen-plotter.

 

I'll second that. I'm working with acrylic now and if you plan to cut it with a dremel then plan for it to melt a little around the bit. One tip when cutting acrylic. Do not try and cool it down like you would when cutting metal by using some sort of lubricant. Its a god aweful mess and your acrylic is going to start cracking and chipping like mad. Its better to just melt your way through it and clean up the burrs later. NEVER use water with acrylic! Lesson learned the hard way.

This is good advice. I just screwed up half a sheet of acrylic. Jog your machine about before cutting anything no mater how good you think your connections are. If your like me and don't have a workshop and have to move your machine around a lot you will probably want to get some cable drag chains. When the machine is in transit wires tend to come loose. Especially if your using solid hook up wire. Use stranded if you can, holds better in the terminal blocks. Pay particular attention to your Y axis with this machine. Since your driving 2 steppers from a single driver if just one of the 8 wires is not making a good connection your cut will be ruined.

 

I will give it a shot. The bit I was using was a general metric titanium bit. I can post a video of the fail later so you can see what happened, basically after water was put on the acrylic, chips started orbiting (yes orbiting is the right word) around the bit. These upcut O bits are a 'bit' expensive but if it keeps me from having to buy another 20 dollar sheet of acrylic then I guess its worth the investment. Just wondering if I should go with the 2mm bit 65-000M or the 1/8" bit 65-010. Any suggestions? I'm using a dremel.

 

I cut acrylic the same as I cut aluminum using my used aluminum cutting bits and a mixture of water and dish soap, 20 ipm 1/64 passes

 

Be sure to be careful if using MDF spoil boards as they will swell, the trick I find works best is a spray bottle misting the acrylic, if the mix is right it foams up contains the chips and keeps the bit clean.

 

ok. i have a really dumb question. how do i wire a dremel to this?
think i have some reading to do, anyone point me in the right direction?
yhnx
mevo

 

I used electrical conduit pipe straps to hold mine on the z axis. It is the most rigid I have found thus far. See page 17 of forum for the post.

 

Yeah I just cut aluminum with my settings I used on acrylic. 20ipm is a little fast for me because I haven't completed the spindle yet but I would think 400mm/min would work well if I had the spindle done. Anyway I just cut the acrylic with no lube. The aluminum I used 80weight oil and it was a mess but the bit is still sharp

 

Some of the information required by the calculator that you posted is confusing to me. For instance what is chip load per tooth? How do you find it out? What units is it measured in? I didn't see any surface feed rate for acrylic listed there on that site but maybe I missed it. Could you give an example of how to use this tool for us newbs? Say for acrylic for example or choose one of the more common materials that new people would be working with like wood and walk us through and example? I would be happy to use calculators if I knew what to put there or where I could find the information.

 

Who says we're guessing? The scientific method is what we're doing. We conduct experiments, publish our findings, and then reproduce the work of others to verify/debunk.

As for oil, yeah it's probably not environmentally friendly to use petroleum products. I'm switching to vegetable oil. Something which evaporates, like ethanol, would help with sucking the chips up without gumming up the dust boot. I'm wary of anybody selling special lubricants... repackaged vegetable oil at a premium price? This is pretty common nowadays. Just the other day someone tried to sell me fertilizer(poop) and they claimed that it was somehow magically better than other poop but they can't explain why or show me any evidence or ingredients.

 

The acrylic is on another chart. It says to use 200mm/min @50% plunge rate and 0.0762mm cut depth. That was for a 1/4"(6.35mm) bit. My spindle runs at 10,680 rpm. I cut through 1/2"(12.7mm) acrylic and aluminium with those settings. The charts are good starting point.

The surface speed(surface feet per minute or SFM) is a property of the bit you are using. The manufacturer tells you this. It's like a max rating for the material and shape of the bit.

RPM = SFM x 3.82 / tool diameter
My bit manufacturer only gave me the max RPM of the bit as 18000 so:
SFM = .262 X RPM X Diameter of tool
So for me, my SFM = 98.23428

So according to the online calculator my RPM should be 18014RPM max. But my manufacturer already told me that, haha.

I'm just guessing but # teeth = # of flutes. Chip load is the thickness of the material being removed(e.g. plunge depth). So like if you're spinning a bit with 2 teeth, it removes material twice on each revolution. So it could go faster than a bit with one tooth. SO in my case, I have 2 teeth and plunge depth of 0.0764mm(e.g. chip load = 0.0382mm = 0.001504in) so the online calculator says my feed rate should be 54.19 in/min = 1376.4 mm/min. Note: These are all based on maximum values for the bit and bear no corrections for the material hardness, flexing gantry, flexing spindle mount, etc that happens on my machine. So yeah I'm running mine at about 20% of what it could potentially do. I may increase the speeds 100% one my spindle mount is completed.

I can see why this is confusing. There are many variables that go into deciding the settings for a CNC machine. My approach has been to use standardized bits that everyone is using and ask around when in doubt. The charts are a good launch-pad but ideally you should be performing the calculations based on the variables specific to your setup.

 

Thanks, I was way off in my assumptions about that calculator. That makes a lot more sense now. I had played around with calculators before but got some questionable values so I just stopped using them. I'll give them another shot now.

 

Wow lots of info there thanks for the example. So I guess my biggest problem currently... well besides for using the wrong bit is that I have no idea what my dremel tool spins at. There is a variable speed setting on it and I can adjust the speed but I have no idea how fast the thing actually goes. It could be 15000 rpm or it could be 5000 rpm. The is no indication on my tool so really I have no clue. Anyone know of any good tricks to find out / measure what your max RPM is on your tool?

 

I tried the vegetable oil and it works similar to 80w oil but is much thinner and doesn't stink as much. I'll give the beeswax a go next time and let you all know. One drawback to oils is that they bind the chips in place and you have to keep scraping out the lumps of oil+chips to keep the cutter from recutting them in deep cutouts.

What we're doing here is original work. It's different from DIY cnc. It's like reinventing the wheel to have spokes rather than solid wheels. Instead of paywalled journals and fancy academic titles, we have open builds and open forums. Sometimes that means putting your best guess out there and then humbly accepting feedback. Some of the key differences in what we're doing are as follows:

1. Low cost: $400 vs $4000
   
2. Newer materials: Extruded aluminum, garolite, 3D printed parts, etc
3. Libre and Gratis: free as in free beer and also free as in freedom
4. Boot-strappable: No kit required, no cnc machine required, etc
5. Community driven: We have the same thing as a company with 1000 employees because it's a large community of volunteers spanning all walks of life. Relying on one another makes progress possible that can't be done alone.

Also, thanks for correcting my info. As you may know, I'm not an expert on machining and have had no formal CNC training. I'm just a physicist who worked in sys admin until the H1B invasion and then became a farmer and beekeeper(way cooler BTW). Anyway, from what I've seen, degrees/training/etc don't mean jack these days. The heavy hitters in machining are probably something similar to what we call script kiddies in hacking. They can follow a script but ask them to build a cnc machine from the ground up and they can't do it. That's probably why all those things in the videos looks like something from 1960, because that was when they were designed. The companies have survived because they were the only game in town for 50 years. I'm surprised they're not still using vacuum tube transistors, haha.

So now it's a new time. We have lots of advancements that make CNC a whole new ball of wax. New materials, new knowledge, new computers, etc. But where are the ivory tower scientists to lead the way? Where are the almighty job creators? Anyone? Bueller? As far as I know, some kid in his mom's basement lead the development of 3D printing. Some dude in an apartment who works at McDonalds is leading the development of CNC.

Anyway, that's just like my opinion man.

 

Some places sell handheld rpm meters too. You could attach a plastic disc with slots cut out of it and then pass the slots through an optical switch to count the rpms digitally.

 

I found one of these online. I'm kinda howto-ed out so I just bought it. Was only 15 bucks. http://www.rakuten.com/prod/new-non...e&adid=18172&gclid=CO3TnOSGpb0CFYyhOgodwQYAiA