A friend asked me to copy a tray

Projects
1

I had a friend ask if I could make a “tray” for someone with my Xcarve. The tray was a strange shape, with a ledge and pocket, and the same mirror image on the second side. It would be very difficult for normal woodworking tools to create but the Xcarve should be able to do without trouble.

Being a novice I said sure. So I started to draw it up on Easel and finally had a fair representation. With some help from the forum I figured out the toolpaths and tried the cut. Turned out my drawing wasn’t that good and I wasn’t able to get it much better using Easel or Inkscape. Turned out my dimensions came out a bit long in the “X” direction. Being 2-sided I did a fair job on the mirroring of the tray (with help of alignment/locator dowel pins), but all in all it was a unsuccessful project. It was a good learning experience. It lead me to recheck my machine for alignment and calibration, all OK, Next was reading on a number of CNC topics to determine where to go next. I found I had used nominal bit OD rather than actual which accounted for a longer than expected part.

Having a new copy of ArtCam express I decided to try it and found the drawing process was actually pretty straight forward and after some practice I can draw a project such as this fairly quickly. The toolpath process in ArtCam is more complex than Easel and required a number of Project files (side 1 and side 2) and required a number of toolpaths: locator pin pocket cut, ledge clearance cut (side 1 and side 2), pocket clearance cut (side 1 and side 2), outline relief cut with careful use of the single bridge in ArtCam.

I ran the 1st tray using a 1/8" 2 flute 22mm DOC bit and the total time was in excess of 6 hours (my Xcarve has the standard spindle). My side 1 looked good, but when flipped the outline was not correct, my mirroring was off. Back to the reading, more tutorials. Turns out I had not been centering my drawings within the workspace correctly as needed in ArtCam. I have this correct in my process now.

To address the job duration I revisited the bits I chose and tried using a 1/4" upcut 2 flute 3/4" DOC. Problems again, chatter, rough top edge. I was unable to find a shorter 1/4 bit than 2" which lead to deflection. Some of the chatter was cleared up with adjustment of spindle speed and depth of cut.

My last problem is that of start point. I have the end stops installed, but when I home my machine it races to the “X” “Y” spots stopping with a thump, enough to suggest this is not a good thing. The way I have been getting repetitive start point (home) is by using a small laser pointer with a smaller beam than as supplied and cross hairs marked on my waste board. This works pretty well and is fairly repeatable but not always, but then sometimes I miss something in Chilipeppr too which ruins my toolpaths.

So, at the end of my tale of “discovery” I decided I could not do the project as well as I felt it could be done. My question to you the reader is what can I do to improve my results, and would a edgefinder/touch plate benefit me by providing reproducible start points.

Photo of original part

Photo of reproduction

Photo using 1/4" bit

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Like you I am new to the whole cnc thing. In combing through the forum, it seems that using an upcut bit is not necessarily the best way to go, as it tends to lift the work piece if it isn’t secure properly. A downcut bit works better. that being said, another tip I have gleaned from here is that the potentiometers need to be set properly (you have probably already done this), along with checking belt tension, and overall machine calibration. Of course i could be over stepping my bounds being just as new to this as your are.

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Make 0,0 the lower left corner of your work piece, outside of where your piece is cut out. Zero your machine the first time with bit chucked in. Once zeroed, lower your bit until you drill a hole at that spot. Good and deep. Next time you need to re-zero x and y, jog your machine over, get it close, lower your bit till just above the work surface. Shut off machine. Manually position your bit over the hole and using your fingers, lower the same bit into the hole. Turn on machine, set it to x and y zero. Perfect every time.

As for z, I now use a touch plate. Without one, draw a circle next to your x,y hole with a pencil. Jog your bit over inside the circle. Lower your bit until it is just hair above making contact. Loosen your collet, let the bit drop onto the surface and carefully retighten. Perfect zero every time.

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I was guessing he meant total depth of cut after multiple passes given how long it took to pocket that piece.

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That’s just classic up-cut frillies as far as I can tell. He’ll be good to go in no time, especially with a downcut bit, good tight machine and repeatable zeroing. You just get better, and better the more you experiment… the more you absorb. It’s weirdly unquantifiable… but it happens nonetheless.

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I’m pretty sure that is a down spiral but. The bits are being ejected down and ricocheting out of the cut. Can’t tell for sure though because it never stopped.

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Don’t know what to tell you. That is exceptional for an upcut bit. Either very sharp, very good wood, or a mislabeled product. Can you take a picture of it?

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Perhaps I used wrong term, my 1/4" upcut has a DOC of 3/4", or ccutter portion is 3/4" long. The depth of cut I use on my project was 0.040". What should I call it?

My spindle speed was 12,000

My cutting speed was 40 ipm

I like the “X Y” zeroing idea from Earwigger, altough my laser pointer is doing essentially the same but is not a posative as the “hole” technique. I plan to make a 3 axis touch plate for the zeroing all three axis. His “Z” method is pretty neat too!

I have 1/4 and 1/8 downcut bits too, but they are both long and subject to deflection so I didn’t want to use it and jam in my profile cut particularly using ArtCam which provides only a single bridge. I have used it successfully on Pine and Poplar.

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Charley Thomas makes a really great touch plate. He has a video on this forum and provides a spreadsheet on how to use it to get repeatable X, Y and Z axis results. He was kind enough to make one for me and it came out really well. You should contact him to see if you can get one from him.

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That’s definitely a down spiral. It’s a keeper!

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I meant up spiral - sorry. For an UP spiral - that bit is a keeper.

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That is called “Flute Length”

The vocab that I have learned so far:
Tool Diameter - the diameter of the cutting bit
Shank Diameter - the diameter of the part that goes in the collet
Flute Length - the cutting length of the bit
Sickout - the total length of the bit that sticks out from the router (this has a major impact on bit deflection)
Depth of Cut, AKA Pass Depth - the depth the bit is cutting on each pass (this can have a major impact on tool deflection)
Width of Cut, AKA Step over - the width of each cut, often expressed in % of bit diameter. (this can have a major impact on surface finish and impact on bit deflection.)
Feed - the feed rate the cut is running at usual in inch per min or mm per min.
Speed - the RPM of the spindle

23

Does your machine have homing switches installed? If not, or if they’re miswired, the machine won’t know where to stop when it tries to home itself and will crash into the ends of the rails.

Regarding the mirroring, it sounds like you’re trying to get 2 profile cuts to line up, like you’re cutting halfway through the wood, then flipping it over and trying to cut halfway again trying to line the two up perfectly. Personally I would have a really hard time getting that to work. What I’d likely do, is this: bearing in mind that I mostly use Easel for my CAM setup

  • Center the artwork in the work area. In my case I have the 500mm machine, with an active workspace of about 300mm per axis. So, first I’d center the artwork on the 150mm mark in Easel, then I’d find and mark the center of the wood along its edge, and position it at the 150mm mark on the wasteboard. If the machine is calibrated well, you should just be able to flip the wood over, once it’s been cut, line it up on that same 150mm mark and cut the mirrored image out.

  • Cut the pockets out on both sides first. Once you get the back pocket done, then cut the outline. Go as far as you can with the bit you have (I generally use a 1/8" diameter 2-flute straight bit for profile operations like this because it has almost a 1" cutting depth available.)
    This means you’ll need to use 3 machining operations: The front and back pockets, and the profile.

I’m assuming the gridlines on your cutting mat in the photo are .5" each, making your tray about 9" by 7" or so, and I’m guessing that you’re using 3/4" pine as a material? That 1/8" bit I mentioned above should be able to clear the profile from one side so you don’t have to line them up. The pockets might be a little off from front to back, but it shouldn’t be that noticeable. At any rate it’ll be easier than trying to perfectly line up 2 profile cuts. :slight_smile:

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Part was 8.5" x 6", cut from 3/4" hard maple.

I had my technique for Easel just off a bit for centering and flipping. When I did it in ArtCam I was able to center work OK.

My process was cut alignment holes, then cut ledge (the 1st clearance cut), cut the deeper pocket, this competed side 1. Flip the piece (mirror horizontally), cut ledge, cut pocket, this gave a duplicated side 2. Then do profile cut to complete the tray.

1/8" bits did best job but also took longest time compared to 1/4" (I use the standard 300w spindle, not the DeWalt or Makita powerhouses). The final profile cut worked well with 1/8" 2 flute, down cut, which would cut up to1" deep. Speed was 40ipm, depth of cut 0.040".

I learned a lot from this project and received soome good tips in this topic, so THANKS to all!

Bob