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Grrrrr! A chip of the old block.....

Discussion in 'General Talk' started by Colin Mccourt, May 23, 2019.

  1. Colin Mccourt

    Colin Mccourt Master
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    How many of you have experienced a chip out of a project you were machining after many many hours into the process. a great lump frustratingly sheared off either by use of wrong timber species, G-Code error, bit selection or parameters after a 9-10 hour process (or longer)
    A spoilt piece to which you are hesitant to re-mill in case it happens again. I would love to mill many an intricate project but worry about paying dearly for a nice slice of expensive hardwood for this scenario to play out, thus adding to the firewood pile.
    Tell me about your experiences (excluding the swear words of course :rolleyes:) What you were machining, if you re-milled after changes and the final outcome.
    Regards
    C
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
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    Well...... I havn't done any long projects but even short ones can end up surprising us. Just the other day I generated code to cut a Barbie bed from MDF and on the last piece it was suddenly cutting curves where there were supposed to be straight lines.
    Sketchup drawing looked good, Gcode bad. Removed Gcode, Phlattened the parts, reinsert Gcode, and got a good cut.
    Happily the erroneous curves lay mostly outside the intended cut.

    However, one must keep in mind that we are working with wood. This means we can flatten off that chipped area (pocket operation?) and glue a new piece on and recut (-: did this a lot way back when I was repairing antiques for pocket money. I would select a bit of new wood with similar grain to the damaged wood, route a pocket and insert a new bit, plane and sand flush, and pocket the proceeds.
     
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  3. GrayUK

    GrayUK Openbuilds Team Elder
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    I really do wish there were something as good as wood, that looked similar and cut as if it were wood. Likewise for laser etching. :rolleyes:
    I sometimes think our Colonial friends don't realise just how expensive and rare hardwoods are on this little island of England! :(
    I get the idea that at the end of every main street in the US there is a Hardwood seller like we have Charity shops or Estate Agents. :D
    Don't they have a material they use for 3D Printers that is mostly wood and can be sanded as if it were? Can't they make it, cheaply, in sheets for us to use?
    :rolleyes:
     
  4. David the swarfer

    David the swarfer OpenBuilds Team
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    yeah, I might use that stuff to make a relief carving my wife could paint (-:
    (some of your expensive wood comes from here in Africa (-: )
    we have some local woods that are eye watering expensive even locally. African Blackwood is one of them, very hard but beautiful.
    cheapest wood here is the common knotty pine, great big plantations of the stuff. remember to set feeds and speeds for the hard part of the grain! the soft part cuts like balsa.
     
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  5. David the swarfer

    David the swarfer OpenBuilds Team
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    an option is to test cut on insulation foam if you don't have a simulator to check for collisions
     
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  6. Giarc

    Giarc Master
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    You guys make me feel guilty. I have a garage full of oak, some cherry, walnut, birch, maple, and even some elm. Most of it from virgin forests so the grain is nice and dense. My dad bought most if it in the 1959s and 60s. He used to build cabinets for a living. I earned it though. Most of the oak came from oak pallets that, as a kid, I had to take apart and pull the nails from prior to planing it.
     
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  7. Alex Chambers

    Alex Chambers Openbuilds Team
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    I keep my eyes open for anyone throwing out old wardrobes - lovely mahogany or sapele, sometimes oak.
    Alex. :)
     
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  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    I used to love upcycling, but as free time grows less, I find myself giving in to plywood and mdf far too often now. Hating myself for it a little
     
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  9. Colin Mccourt

    Colin Mccourt Master
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    Oak for pallets....Unheard of in UK atleast...Wet and soggy Russian/Scandinavian 4th and 5ths (no furniture grade timber here, the lowest of the low) usually spruce and fir types. How lucky you are.
     
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  10. GrayUK

    GrayUK Openbuilds Team Elder
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    I remember, before the EU stipulated what pallets should be like, you could quite often get hold of pallets made of some unknown hardwoods. :)
    I've got quite a few door thresholds and the like made of some really good looking hardwoods. :thumbsup:
    But, that's because I'm old! :( Those were the days. :D
     
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  11. Giarc

    Giarc Master
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    These were late 1970s - early 1980s era pallets. My dad did not feel child labor laws applied to me. ;)
     
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  12. Tracy Ranson

    Tracy Ranson Veteran
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    I have ran into this issue myself. The project was a rush job for a client, took well over 14 hours of straight machine time and required 4 bit changes. Talk about being frustrated. Thinking that there had to of been a problem with the wood, I ran the project again, using all the same bits, A little more than half way through the job and using the last bit, the chip out problem happened again.

    I was running out of time and had to find the cause so I decided to take a closer look at possible causes. So I took a two hour break and made google my friend. In my research the most common cause of chip out was the tool. I figured that can't be, all of the end mills and ball nose end mills that I used were brand new. I knew the quality level of the first three end mills that I used, One of of them was an Amana and the other two were Onsrud, both of which are top notch suppliers. It was the last ball nose that I used that I did not know the quality, all I knew was it came from a supplier in the USA and it was a really cheap ball nose, so I contacted the supplier to get more info and it turns out that the bit was made from carbide and came from China. That was the answer, cheap Chinese carbide.

    Upon closer inspection of all the bits using a jewelers loupe, the edges of the Amana and Onshrud bits were still intact, very shiny and appeared to be sharp, but the Chinese carbide bit appeared to have lost it's edge, the edge was not shiny, it had a dull appearance and some areas it appeared as it the edge was rolled over.

    I ran the job again using ball nose bit of known high quality and the issue was resolved.

    So let me ask you, where did you get your bits, are the bits sharp and will they maintain that sharp edge that is needed to prevent chip out.
     

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