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Thread: Best Woods for CNC Monograms

  1. #1

    Best Woods for CNC Monograms

    I recently purchased an Axiom machine that has been performed well so far. I'm just getting into CNC but the focus right now is with cutting monogram initials and letters for bedrooms and front door hangers.

    1/2" MDF cuts like butter with 1/4" 2x Downflute Amana @ 15k RPMs and 130 in/min @ 1/8" cut depth per pass.

    The cut time for a 20" door hanger is about 25mins, which I'm satisfied with. However, I want to steer clear of MDF because I've read that the dust is very harmful compared to other materials. It is also not good for outdoor use as I understand due to its absorption of moisture.

    Other hangers like these on Etsy are being made from 1/2" Baltic birch -- so I tried this material and initially had a lot of tear-out on the bottom side of the material with the downflute. I fixed this with a 3/8" Amana compression bit but the chipload is much less so right now the feed is only 15-40 in/min @ ~15,000 RPMs and 0.1" depth per pass. These take around an hour a piece to cut.

    Just looking for some insight here to get the material requirements (safer dust, good outdoor material) and faster cut times.

    The key machine specs are

    Max RPM: 24,000
    Spindle motor: 2.2 kW liquid cooled
    Max rapid speed: 200 in/mi

    Based on this is there a better way to cut the baltic birch faster (100+ in/min)?

    Or..

    Is there another material that can be cut quickly using a tool with higher chipload? I've seen mentions of white pines, alderwood and some others but only worked with 1/2" BB and 1/2" MDF.

  2. #2
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    Casey, there are multiple factors at play here that include your machine's capability, the cutter choice and the material. MDF does "cut like butter" and is fine for painted interior decorative items. There is an exterior version available, too. Check a pro sheet goods supplier for that. One of the reasons that MDF cuts nicely is that it doesn't have any "grain" or layers. BB ply is beautiful stuff, but as you have found out, veneered sheet stock is prone to chipped edges depending on the cutter selection. Compression bits are the tool, but maximum benefit from a compression cutter comes when the machine can do the deed in one pass...most smaller, non-industrial machines cannot do that, so at a minimum, you need to be able to at least take enough of a bite on the first pass to clear the transition from upcut to downcut to avoid an issue on the top surface. While it will raise your material cost, you might consider cutting your monogram product from a non-wood material. I've been playing a lot with Corian, HDF and so forth as I figure out my own products and they cut wonderfully. The downside, again, is they are considerably more expensive than wood and composite wood materials.

    Also, if the detail level of your monograms allow it, going to a larger diameter cutter will allow you to push it a little more because they are stronger. The balance to this is if your machine is stiff enough. Compromises abound...

    As to the dust, if you have a proper dust shoe on your machine with a good DC attached, the risk should be minimized. Check out the Kent Dust Shoe sized appropriate for your particular spindle. (kentcnc.net) I have one on my Camaster machine as a replacement for the OEM shoe, and it's picking up a substantial amount of debris from any kind of material I've been cutting.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    To echo Jim's post I would be looking at toolpaths that hog off the bulk of your material fast and rough. The took change will pay for itself if you can then run your delicate toolpaths only at slower speeds.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  4. #4
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    The bit your using is meant to go much faster, If your only running at 40 ipm than your bits not gonna last long at all ($60 Ea ). To take advantage of the 3/8" compress your gonna want to take deep passes (.4" Deep) and move the bit as fast as possible.

    If your trying to sell your products and keep them affordable MDF and Baltic Birch are the two best options. The reason many people chose these materials is, they are easy to cut and if you have the right machine and the right speeds you barely have to sand the item to complete them. We cut several skids of 1/2" Baltic birch each week and we have nice clean smooth edges right off the machine, Not much sanding required.

    Hardwood is expensive when you compare it to plywood and MDF, its hard to find many customers willing to pay for the premium wood.

    MDF dust is harmful. You need to ensure you keep the dust under control, Your lungs are much more valuable than a $20 monogram. A good dust boot and dust collector are key when working with MDF. Another key factor is recirculating the air in your workshop - Bring in fresh air from the outside and pull the bad air out using fans. MDF is messy to work with, once you cut several items check your dust collector filter and you'll see all the dust caked on the sides.
    3X Camfive 1200 48" x 24" 100watt Tube
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  5. #5
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    One alternative that I use is PVC sheets. I use Versatex brand but there are many others. It is a building material that can be obtained from specialty building supply places. It comes in 4X8 sheets and thicknesses ranging from 1/4 to 1-1/2 inches. It is durable outside material and takes paint well. It will hold a finer edge than wood without splintering and pocket carves or v-carves equally well. I use it for outdoor signs as an alternative to HDU. Here is a link:

    https://versatex.com/pvc-sheet-material

    This isn't really an appropriate example photo for what you are trying to do but it is the only one I can find. I am not proud of the design as it was a reproduction from a business card rather than an original.

    1-Drlynsey.jpg

  6. #6
    Art,

    Thanks for the suggestion this example looks really nice. Is the PVC dust supposed to be safer than MDF?

    It looks like we have one local store who is a supplier. What's the price per sheet and the sheet size that you get? I'm just looking for comparison to what I'm paying for MDF and BB. Thanks!

  7. #7
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    I usually use 3/4 material and it is expensive - about $120. Thinner material would be cheaper. PVC makes a mess because of static electricity. It sticks to everything. It doesn't make super fine dust like MDF so I don't think it is as much of a threat but I still use a dust mask when I cut it.

  8. #8
    Hi Robert thanks for the response. As mentioned I'm new to the hobby but was thinking the 18,000 RPM on the feeds and speeds sheet for the tool was the maximum, but have seen discussions on forums of 350+ ft/min feed so this is a key part of the clarification that I need.

    The max traverse in x, y, and z is 200 in/min with a max spindle speed of 24k RPM so it's not as capable as the $12k-$15k machines out there but obviously I would like to cut as quickly as possible while maintain long life for the machine/components.

    I'm using GWizard to help get a start on the feeds and speeds, also paying attention to tool deflection. For the 3/8 compression, based on mfg 0.0036" chipload per tooth its giving me 130 ipm @ 18k RPM (tool deflection is 9.3E-5 [I assume inches] or 46% for 0.4" cut depth). Do these numbers sound valid to you? I also have a 1/4" compression but the chipload is much smaller so I don't see using this a lot for 1/2" BB.

    As far as dust shoe I have the one that axiom makes for this machine (https://www.axiomprecision.com/acces...-dustshoe.html). From the little experience I have so far I'm pleased with it.

    The DC is a harbor freight 2hp with a Wynn Environmental MERV 15 filter (https://wynnenv.com/products-page/wo...cartridge-kit/) however there are some leaks in the system that I need to fix.

  9. #9
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    I cut lots of PVC and there is little dust most are nice small chips. I normally cut at 300 IPM with a 1/8 bit faster with a 1/4

  10. #10
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    I do better with PVC (azek, versatex, etc) with a light dusting of spray static guard like you use on clothes. No sticky chips.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  11. #11
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    Quote Originally Posted by Casey Thomas View Post
    As far as dust shoe I have the one that axiom makes for this machine (https://www.axiomprecision.com/acces...-dustshoe.html). From the little experience I have so far I'm pleased with it..
    That appears to be an OEM version of the Kent Dust Shoe I mentioned. You're good to go.

    The PVC that Art mentions is another material I intend to work with, too.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #12
    I cut these Longworth chucks out of 1/2" Baltic Birch at 175 ipm, 18k rpm, 0.2 depth of cut, with a Whiteside 1/4" 2 flute downcut spiral. It feels like I could go faster but the cutting time is only about 6 minutes like it is so I don't see the need to go faster (slots only, the finger holes add about 2 1/2 minutes). My CNC is a Saturn from Fine Line Automation and is very rigid and I have a 3 kW water cooled spindle, just for reference.

    I don't know why you couldn't get a bit more aggressive with the Baltic Birch and MDF both. Your machine will go 200 ipm and I'm not suggesting cutting at that speed but you should be able to cut at 100 ipm with no problem.

    018 - 16 inch Longworth chuck, long slots, on CNC.jpg

    David
    David
    CurlyWoodShop on Etsy, David Falkner on YouTube, difalkner on Instagram

  13. #13
    David, thanks for the response! Do you not get a ton of tearout when you break through the other side of the baltic birch material with the downspiral? This is what drove me to compression bits and to some extent lower feeds.

    Based on some feedback from the forum I am going to try 100-130 ipm at 0.3 to 0.4" cut depth. I am using a speeds and feeds calculator to try to pair the two and also reduce tool deflection; However also don't know to what extent the x y and z traverse motors as well as ball screw and bearing loads play a part in being up to the task.

  14. #14
    Thanks to everyone who has responded! Each post has been helpful and, as mentioned, I am new to this with a lot of questions and your feedback is very much appreciated!

  15. #15
    Quote Originally Posted by Casey Thomas View Post
    David, thanks for the response! Do you not get a ton of tearout when you break through the other side of the baltic birch material with the downspiral?
    No, not really, Casey. About two light passes with 220 on the drum sander and it was gone. Some holes/slots didn't have any tear out.

    David
    David
    CurlyWoodShop on Etsy, David Falkner on YouTube, difalkner on Instagram

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