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IndustryArena Forum > General Manufacturing Processes > Milling > Help with CNC Router milling strategies for a piece i want to make
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  1. #1
    Join Date
    Nov 2018

    Help with CNC Router milling strategies for a piece i want to make

    Hello all!
    It's my first post here and i'm glad to join this great community.

    I recently bought a CNC Router for milling wood and since i am new to this area, i have many problems and questions and i couldn't find any serious guide that would help me.

    Can you suggest me a place to learn and get better with milling strategies, do's and don't's, feeds and speeds rules, etc? I had end mills slip out of the collet and cuting the machine bed, bits breaking, etc. and i'm not sure what i'm doing wrong. I searched the forums for answers but it would be much better if i could just find a guide/book/tutorial to learn from.

    - I have a 1300mm x 2100 x 450mm piece that i need to mill(image attached) and an End Mill 100mm overal long, with 72mm cutter length and 6mm diameter. Let's say i slice it in 5 pieces. Can i dive deeper than the cutter length using several passes? Would the shank rub against the wood and burn or break? (shank is the same diameter as the cutter).

    - Also, would it bend and break because the end mill is so long? Should i avoid using long endmills because they are prone to break?

    -Machine manufacturer suggested i should use a lubricant (like wd40) on my collet and cone to avoid rust long term. Could that be the reason my bit slipped in and out of the collet? I cleaned and degreased the tools now and tried a few more cuts and it slipped again. Could it be that i'm not tightening it enough? Should i use another key to counter the torque so i can tighten it better? Would i damage the collet if i tighten it too much?

    I've uploaded some images with my machine, tools and the piece i want to mill, just in case it helps. The bookshelf is 2600x2100x450 mm approximately. My machine XYZ is 2500x1300x300. I want to use Oak wood. I was thinking about slicing it in half to fit my X limitations, then slicing it several times on Z. I use vcarve pro software and i was thinking about doing a profile cut first to remove the material i don't need (round shapes), then use a roughing and finishing strategies to mill the 3D areas. I would also need to turn the material on the other side because i have concave areas. The spindle can rotate on the x axis, but vcarve doesnt support 4 axis milling and i am not advanced enough in fusion 360.

    I would really appreciate your advice on this.
    Attached Thumbnails Attached Thumbnails 20181115_154115.jpg   IMG_20181017_060912_873.jpg   Photo from Alex Pavel.jpg  

  2. #2
    Junior Member
    Join Date
    Nov 2016
    That looks to be a nice large machine.

    I learned by a lot of reading, strategizing and planing and trial and error of course. It was a big price to pay but well worth it. There is a lot of 3D design and modeling in your project. If I were to start over. I would start by creating several simple models. One for a Cylinder, one for a Cube and one for a flat 2D (perhaps a sign). I would design them and cut them. Master these and you will prove that 1) the machine is working correctly and 2) you know how to design simple models and can produce the desired results. You might want to check out for free the Titans of CNC Academy at https://academy.titansofcnc.com/ or cncCookbook at www.cncCookbook.com also free. Lots of free education out there. cncCookbook has a Feeds and Speeds calculator for a fee of course or you could start with the spec sheets from the end mill manufacturer and determine the Feeds and Speeds from there.

    You can dive deeper than the end mills flute length however as you suggest you will most likely burn the wood with either the end mill or hit it with the collet. Not good in either case. I think in these cases I would look for a longer flute (cutting depth), so that as you are diving deeper you are also cutting the sides of the stock instead of burning the stock with the sides of the end mills.

    Verify that you are using the correct collet for the shank size of end mill that you have chosen to use. If you are using a collet that is to big for the end mill then the end mills could fall out of the collet. You probably could tighten the collet more but it usually is not necessary or advisable to over tighten, so check your sizes first. I doubt that it is the WD40 that you are using that is causing the issue. Other than that I can't help you with the end mills slipping out of the collet.

    As for the end mills hitting the table bed, I can't tell you how many times I have done that. Initially I did it when I first set up my cnc due to the movement being backwards for the z axis.I use Mach 4, so I reversed the settings within its configuration settings. The other times it was a learning experience and a operator error each time.

    I use both Fusion 360 and vCarve Desktop latest version depending on my needs. With the photo that you posted that you want to design/model I would be looking to use Fusion 360 as it is very powerful. It will take a while to learn Fusion360 but I did it over the last year, so it can be done. As for the length of the end mill, it is true that the shorter the end mill sticks out of the collet the less deflection you will achieve. The less deflection the lesser chance you will break an end mill. That being said I sometimes use a 4 inch straight ball or flat end mill to accomplish deeper depths of cut. You will want to look at reducing the feed rate in order to reduce deflection of the end mills (and hopefully save them). The rule is to always use the shortest end mill that you can to accomplish the task at hand. In other words don't use a 3 inch end mill where a 2 inch end mill will do the job.

    You mentioned slicing the model up and cutting it as separate jobs. Too much of this and you will rethink your strategy very quickly. Sometimes less is more and this is probably on of them. Fusion 360 has no job size limitations like VCarve Desktop has. So something to consider if that is why you are planning on slicing because of the design/modeling software.

    One more thing, VCarve does now support 4th Axis in its latest release, however I'm not sure where you need a 4th axis with your planned project.

    Good luck and I hope I helped you at least a little bit.


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