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Routy CNC Router (V-Slot Belt & Pinion)

Discussion in 'CNC Mills/Routers' started by Mark Carew, Nov 11, 2013.

  1. mightyevo

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

    The Dude Well-Known
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    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.
     
  3. mightyevo

    mightyevo New
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    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?
     
  4. The Dude

    The Dude Well-Known
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    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.
     
  5. Mark Carew

    Mark Carew OpenBuilds Team
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    Great info Dude :thumbsup: I also would like to throw out there a good one to use with the Ramps board is the control software repetier host (free)
    http://www.repetier.com/documentation/repetier-host/
    I use it exclusively for 3D printing and have not tried this feature, but from the drop down in machine types there is a cnc router option. My guess it this would be a good place to give routing with the Ramps board a go.
    Hope this helps.
     
  6. Ceiling Cat

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    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.
     
  7. Mark Carew

    Mark Carew OpenBuilds Team
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  8. Ceiling Cat

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    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.
     
  9. Robert Hummel

    Robert Hummel Custom Builder
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    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
     
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  10. Mark Carew

    Mark Carew OpenBuilds Team
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    Good to know Robert I have not tried this yet, thanks for the tip:thumbsup:
     
  11. Robert Hummel

    Robert Hummel Custom Builder
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    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.
     
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  12. David the swarfer

    David the swarfer OpenBuilds Team
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    How about making your own cable guides with your router?


    I've never had water causing cracking in acrylic, but alcohol will do it for sure.

    DO NOT plan to have the bit melting the plastic, the bit must cut it. If it is not cutting you are running something too fast/deep and not allowing the chips to clear. Remember the heat is supposed to depart with the chips.
    I got very good cuts in 6mm acrylic, 6mm 2 flute carbide bit (for wood), at 700mm/min feed at 15000 rpm (slowed the spindle down from 30000!), depth of each pass was 0.9mm.
    If you are planning to cut a lot of acrylic then please buy some real 'designed for plastic' bits, they really are very good. Low flute counts must be used in plastics to clear the chips. I also recommend using one of the many online feed rate calculators to accurately set your feed rates from rpm, tooth count, and chip load per tooth (which will be recommended by the cutter maker for different materials).

    Solid hook up wire? don't do that, it will fatigue crack. Anything that moves must use stranded wires, please.
     
  13. mightyevo

    mightyevo New
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    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
     
  14. Ceiling Cat

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    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.
     
  15. The Dude

    The Dude Well-Known
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    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 ;)
     
  16. David the swarfer

    David the swarfer OpenBuilds Team
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    Please do not guess at feed rates, this is science not art :)
    Feed rate calculators are all over the web, use them.
    an example, http://www.whitneytool.com/calculatorSpeedFeed.html that includes surface speeds for various materials as reference.
    from the material and bit size you get RPM, and from RPM and tooth count you get feed speed.

    Please do not use oil for cutting. Oil is too good at lubricating and causes high side forces, for cutting you need something to lubricate only a little and then allow cutting, while carrying away heat.
    On aluminum use kerosene or rub on candle wax, commerical high speed CNC uses ethanol spray (youtube Datron cnc) with suitable ventilation. If you really want nice cutting, buy a commerical 'made for aluminum' cutting compound, expensive but very good.

    and as with any routing, keep the chips clear, you do not want to recut the chips, it causes extra tool wear, and poor surface finish because the chips gets pushed into the surface making a dent before the cutter cuts it again.
     
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  17. Mark Carew

    Mark Carew OpenBuilds Team
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    Well said David :thumbsup: Thanks for these tips
     
  18. Ceiling Cat

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    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.
     
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  19. The Dude

    The Dude Well-Known
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    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.
     
  20. The Dude

    The Dude Well-Known
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    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.
     
    #350 The Dude, Mar 19, 2014
    Last edited: Mar 19, 2014
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  21. Ceiling Cat

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    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.
     
  22. David the swarfer

    David the swarfer OpenBuilds Team
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    chip load per tooth is 'how deep each tooth cuts' and is recommended by the tool maker. normally in the range of 0.002 to 0.008 inches for woodworking carbide bits, but again, look it up on the tool makers web site.
    inches, millimeters, just whatever is common wherever the manufacturer lives.
    SFM is the critical number, and comes primarily from the material being cut, and then the type of cutter being used. (and not primarily from the bit as the dude implies above) . This number tells you how fast each tooth can be moved through the material to get a good cut, too slow is as bad as too fast!

    The bit can be made from various metals, and coated with various other things.
    High Carbon steel is the cheapest, as in cheap twist drills. Get them too hot and they get soft, and this limits their cut rate. You can buy blank material from which to make custom cutters, and heat treat it at home with an LPG torch or stove. see http://www.warfer.co.za/lathe for examples.

    High Speed Steel or HSS has additives that make it heat resistant. This caused a major stir when it was revealed at a major tool show in about 1930, they ran it a half inch deep in steel with the tool glowing dull red and it stayed hard and sharp and still cut. Very tricky to heat treat, but so much easier to grind to shape at home (but don't get it red hot and dip it in water, it will crack).
    This is often coated with Titanium Nitride, the yellow one, which makes the surface more slippery to prevent galling.

    Tungsten carbides are even harder, and hence more brittle so are unsuitable for interrupted cuts in hard materials as the shock loads cause cracking. This is most commonly seen as solid endmills, brazed inserts, or replaceable inserts. You need special grinding wheels to sharpen this stuff. Recommended for cutting glass filled nylon and other abrasive materials.

    surface feed rate for acrylic should really be had from the acrylic manufacturer.

    Tool bits are made with different angles to suite cutting different materials even though the bit itself is made from essentially the same metal. This is where the big differences come in. A bit for metal has completely wrong angles for plastics (and a steel cutting bit has the wrong angels for brass, etc), hence my previous advice to find aluminum and plastic specific tools, they really do make a big difference, especially on our lighter 'flexible' CNC machines.

    So, an example calculation
    I have a 2 flute carbide router bit, 6.35mm (1/4") diameter and I want to cut some aluminum.
    so I put in 1/4" for tool diameter and check the chart for SFM which says
    ALUMINUM ALLOYS 1200+ FT./MIN.

    for uncoated carbide, so I put in 1200 and press the calculate button,
    This gives me 18335 RPM as a minimum speed for the router. At this speed, each tooth will be going past the material at 1200 feet per minute at this tools diameter. A smaller tool would have to run faster, a larger one slower.

    Now, I put in 2 for 'no of teeth' and 0.002" for chip load per tooth, starting at the low end because I have a wobbly machine.
    This gives 73.34 inches per minute feed rate at this RPM. You can use 73 or 74 depending on your machine stiffness.

    So to sum up, the material and tool bit material give the surface speed that gives efficient cutting for that material, the SFM.
    The bit diameter and SFM give the RPM
    The RPM and 'chip load per tooth' = 'depth of cut per flute' give feed rate.

    Note that I used 2 low end values above, 1200 is a starting point for SFM in ali, depending on the specific alloy, and the type of coolant, and the shape of the toolbit, and the strength of the machine, you can go a lot faster if your spindle can get the rpm.
    0.002 is a low chip load, 2 thousands is not a lot to cut off and in production (where speed is king) you'd be looking more at 0.005 to 0.015 at higher SFM. They make 100000rpm spindles or a reason (-:

    An example of high speed aluminum cutting with good solid carbide cutters, ethanol coolant (not lubricant).

    I'm not saying our home shop machine can do this, that Datron machine is big and heavy and very stiff compared to a Routy. I'm saying that this is the result of doing the science properly. We don't need to experiment because it has all been done before.

    Note: if your spindle cannot get to 18000rpm you need to insert the speed it CAN do and then do the feed rate calculation because chip load is critical to surface finish, though too low a SFM will give poor results too.
     
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  23. David the swarfer

    David the swarfer OpenBuilds Team
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    yes
    no.
    chip load is how much each tooth cuts off as it passes, and is governed by the rpm and feed rate.
    'plunge depth' is not the same thing, this is how deep you are cutting, usually expressed in multiples of the bit diameter, as in 1/4D or 1D for once piece bits, and given by the maker for inserts since their edges are highly specialized.
    (plunge depth is not the right term but I just cannot think of it now)
     
  24. David the swarfer

    David the swarfer OpenBuilds Team
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    I do :)
    environmentally friendly or not, it has nothing to do with whether or not it is the correct cutting coolant for the material being cut. We want to be careful to spread correct information here don't we?

    kerosene and ethanol are the correct coolants for aluminum unless you want to purchase one of the specialized products.
    any kind of lubricating oil is the WRONG THING for cutting.

    vegetable oil might work, but I've never seen it mentioned as a cutting fluid, despite years of actually cutting metal with a screw cutting lathe, and participating in forums and email lists, and reading magazines like 'Model Engineers Workshop'.
    for cutting steels, chicken fat, lard etc work very well if you want to avoid pumped coolants which are 95% water anyway, being an emulsion of a little of the right kind of oil, and water. why avoid pumped coolants? makes a mess, and it goes rotten in your machine.

    I have found bees wax to be very effective on all hard materials, just rub it on before each cut in the case of rotary tools, and just rub it on the saw blade now and then in the case of hacksaws. Using this I can cut through a 60x60mm block of steel in under 20 minutes, by hand. candle wax works well too, I use it when I cannot find my lump of beeswax. (and thinking about it, candle wax is really 'paraffin wax', and kerosene is part of the paraffin family)
     
  25. Mark Carew

    Mark Carew OpenBuilds Team
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    Great info David thanks and I really like the idea of the bees wax. :thumbsup: Thank you
     
  26. Ceiling Cat

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    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?
     
  27. The Dude

    The Dude Well-Known
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    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.
     
  28. The Dude

    The Dude Well-Known
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    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.
     
    #358 The Dude, Mar 21, 2014
    Last edited by a moderator: Mar 29, 2014
  29. Ceiling Cat

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    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
     
  30. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    I have that model and it works fairly well. What the photo doesn't show is the adhesive backed reflective strips provided that you cut to length and apply to whatever you need to measure. Not sure how well they will stick to high speed bits. Measured my dremel speeds all the way up by grasping the reflector in the chuck slots.
     

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