[ger21]

Every now and then people ask about a Mach3 wizard for cutting dovetails.
There used to be one at Joe's forum, but I don't believe it's still available (I've never actually seen it). And I know of another one, but haven't seen that one either.

So I figured I'd pick up the torch and do something about it.
Rather than a Mach3 wizard, I'm going to do a standalone app. Eventually this may become a larger collection of woodworking utilities. But for now, it's going to start as a dovetail and box joint generator.

You'll be able to design the joints, get a preview of what they'll look like, and export the g-code to create them. I can probably add .dxf export at some point, if anyone needed it??

To use this, you'll need to be able to clamp stock vertically on your machine.

Here's a screenshot of what I have so far.
Feedback and suggestions are greatly appreciated.

[WoodSpinner]

Every now and then people ask about a Mach3 wizard for cutting dovetails.
There used to be one at Joe's forum, but I don't believe it's still available (I've never actually seen it). And I know of another one, but haven't seen that one either.

So I figured I'd pick up the torch and do something about it.
Rather than a Mach3 wizard, I'm going to do a standalone app. Eventually this may become a larger collection of woodworking utilities. But for now, it's going to start as a dovetail and box joint generator.

You'll be able to design the joints, get a preview of what they'll look like, and export the g-code to create them. I can probably add .dxf export at some point, if anyone needed it??

To use this, you'll need to be able to clamp stock vertically on your machine.

Here's a screenshot of what I have so far.
Feedback and suggestions are greatly appreciated.

Sweet!!!

John

[Trotline]

That would be very cool, Gerry. I've given some thought to putting a slot into my table so as to be able to cut them. Having a nice application to do the fiddly spacing just might motivate me to get on that.

Extra bonus points if you make it able to do blind joints! Lol, I don't mind cutting an extra slot to slant the board on a 45deg. angle.

Luke

[ger21]

Extra bonus points if you make it able to do blind joints!

Got a picture of what you mean?

[Trotline]

Something along the lines of this. These are parts for some boxes I did not long ago. I didn't try to undercut them, so I think this would properly be called a blind box joint.

Luke

[ger21]

Can't open an .stl right now, but from your other description, I think I know what you're talking about.
A blind box joint would be the same as a regular box joint. As you said, you'd just mount the board at a 45 deg. angle.

[Trotline]

Here's some photos of the parts. It's basically the joinery hidden inside a miter, with nothing exposed. I'm not really sure, to be honest, that a 3-axis machine can do the undercut that would be necessary for blind dovetails because of the half-round that goes past the straight line cut.
If you could figure out a way to do it, though, I'd buy the software just to say I had the capability, even if I never used it.

Luke

[louieatienza]

Here's some photos of the parts. It's basically the joinery hidden inside a miter, with nothing exposed. I'm not really sure, to be honest, that a 3-axis machine can do the undercut that would be necessary for blind dovetails because of the half-round that goes past the straight line cut.
If you could figure out a way to do it, though, I'd buy the software just to say I had the capability, even if I never used it.

Luke

The half-blind dovetail joint is the easier of the dovetail joints. Most all manual dovetail jigs do half-blind dovetails. It would be tough to do a full blind dovetail without some whittling afterwards.

I did start some work for through dovetails on the flat a while back, but have been too busy to perfect the technique. I think it would be cool to have an app for woodworking joints.

[WasteOfSpace]

I've given some thought to putting a slot into my table so as to be able to cut them. Having a nice application to do the fiddly spacing just might motivate me to get on that.
. Luke

Hi Luke

Have a look at this. You may not need to put a slot in your table.

[Trotline]

Mounting a spindle at 90 deg. would certainly work, and I've even considered it. A lot of work would go into designing, building and using it, though. Cutting a slot in the table, and installing the various support and clamping gear just seems like the more viable option, for my machine.

Some cool ideas in that thread, though, for sure!

Luke

[CarveOne]

My smaller steel frame CNC machine already has the potential for adding a clamping system to the 1-1/2 x 3" x 3/16" steel box tube frame on the motor end of the machine for vertical mounting of nearly 40" long boards. All I have to do is to rotate the machine 90 degrees on the work table so that end of the machine will hang over the edge of the 4'x8' work table. The router bit can go beyond the box tube by almost 2" if needed. This would be good enough for most drawer making projects. I looked at this option some time ago when reading the dovetail threads in the Woodworking forums here.

Many other DIY table top machines will likely work in this manner. Just needs a very rigid clamping arrangement to keep down the vibrations and chatter.

[Trotline]

I kind of side-tracked things with the blind dovetail issue. Sorry about that. I just want to say that I'm keen on this idea, and I encourage you, Gerry, to pursue it.

Luke

[PaulRowntree]

That would be very nice to have Gerry.

and export the g-code to create them

When you write gcode, do you make it as a snippet that the operator adds headers to or do you make them stand alone programs?

[ger21]

Complete standalone ready to run g-code.

[zool]

These are all on youtube

*joe's g-code compiler dovetails

[ame=http://www.youtube.com/watch?v=0Md-4_x0iX0]Dovetails - custom through dovetail G-Code compiler for Joes Hybrid 4x4 CNC - YouTube[/ame]

*Material clamped vertically

[ame=http://www.youtube.com/watch?v=zSbqnJOo6S0]Home built CNC router cutting dovetails - YouTube[/ame]


*Legacy CNC through dovetails.mp4
[I recall that their controller is based on Mach3]

[ame=http://www.youtube.com/watch?v=WKu6OC47Qv8]Legacy CNC through dovetails.mp4 - YouTube[/ame]

*Another vertical clamp device
[looks just like my porter cable router jig]

[ame=http://www.youtube.com/watch?v=ZGEYO1g6ZcU]cutting dovetails on cnc - YouTube[/ame]

*Don Ryan's CNC Dovetail Fixtures - RyansDoveTails.com

[ame=http://www.youtube.com/watch?v=ZimHcZGlyQw]Don Ryan's CNC Dovetail Fixtures - RyansDoveTails.com - YouTube[/ame]

*ShopBOT cuttign dovetails ..[this influenced the design of my ShopDroid]

[ame=http://www.youtube.com/watch?v=4Aw4lElTecg]ShopBot Cutting Dovetails - YouTube[/ame]


*Cutting dovetail joints on the pantorouter
Matthias Wandel

This is a power tool, though easily is a concept for a dedicated CNC machine, which may be the best route [and an excuse to build another machine!!!]

[ame=http://www.youtube.com/watch?v=VW8ldid7M-8]Cutting dovetail joints on the pantorouter - YouTube[/ame]


*A closing comment...

I own the JoinTech system for making dovetails, and have been, and hope to continue, using the techniques from that as the basis to start. My ShopDroid, which sits almost done ..still [reality sucks], was designed for vertical clamping.

There is a SketchUp plugin for dovetails, though cannot find the link in right now.

PS .. Gerry, I will buy yours at the drop of a hat....

[GaryCorlew]

Awesome Gerry! I am interested as well!!!

[ger21]

I'd appreciate a little input on an issue I've come across.

Looking at some of the YouTube videos, you'll see that most people cut the pins and tails in a single operation, with the two boards mounted like this. The quickest way to do this is in one pass, as you'd do with a manual dovetail jig.



To give the user as much flexibility as possible, I'm giving them 3 options on the starting location from the top of the drawer.

The problem is with the option to center the dovetails, when cutting them in a single pass. Certain combinations of stock width and tool size can result in a condition where gouging would occur. In the image below, the B dimension must always be smaller than the A dimension to prevent gouging when cutting in a single pass.


There are several ways around this.
1) Reduce the stock width.
2) Reduce the depth of cut, which changes the spacing of the dovetails.
3) Cut the parts separately, which takes much longer.

Before I started typing this, I had no idea which direction I should take, but now I think just throwing up a warning message is the best option. I'll give the warning when the preview is calculated, so the user can make changes and recalculate. I can also not allow g-code (for both parts together) to be created if gouging will occur. But you can still output separate code for each part.

As I look at the first picture, I'm seeing another issue that I'm not sure how to deal with. The way I'm designing this, is that the vertically held piece (drawer side) will go against a fence, which is the zero position.
The horizontally mounted part (front or back) will need a spacer to locate it. The software will calculate the spacer thickness.
The issue is that the joint shown in the first image, would be the front left corner of a drawer. But it gets machined at the right side of the machine.
This will undoubtedly confuse users, but I feel that it has to be this way.

You could say that the bottom of the drawer is against the fence. But, the top edges of the drawers should always be mounted against the fence, to eliminate errors caused by width variations in the stock
I need to come up with a way to make this clear to the user, probably with some images on the screen when selecting options.

[PaulRowntree]

I haven't cut a dovetail in my life, so this may be a silly comment ...

I see why the single pass is good for jig based cutting, but the advantage for CNC based is not so clear to me. In my ignorance, I would have thought that making the initial alignment simple and bulletproof and letting the CNC figure out the precision cuts would be an advantage. For me, that would mean using a straight reference to line up the top or bottom edges of the pieces exactly, but leave a gap between the two pieces by at least a tool width. Then cut the two pieces as required, with a somewhat more complicated toolpath.

It would take a few seconds more to cut, and edge tear out may be more of an issue.

[ger21]

By single pass, I mean that the sockets are the width of the tool. Making them any wider makes it a multi pass. I was going to say that going to multi pass automatically doubles the time, but I just realized that it doesn't, until the socket is more than 2x the tool diameter.

As you alluded to, tearout is the bigger issue here. The visible side of the vertical piece is mounted against the horizontal piece, which should nearly eliminate all tearout.

I would have thought that making the initial alignment simple and bulletproof and letting the CNC figure out the precision cuts would be an advantage. For me, that would mean using a straight reference to line up the top or bottom edges of the pieces exactly,

You'll be able to do this if you cut them separately. A spacer will only be required when cutting them as a set.
While using a CNC can greatly speed up the dovetail process, it's still time consuming, and for those cutting a lot of them, the faster it cuts, the better.

[zool]

Ger21 stated: Certain combinations of stock width and tool size can result in a condition where gouging would occur. In the image below, the B dimension must always be smaller than the A dimension to prevent gouging when cutting in a single pass.

RESPONSE: Using the Jointech dovetail system, a user is limited to certain width of lumber if they want to have the dovetails cut symmetrically in the piece of stock, though there are formulas/methods to adjust the cuts for stock that are not these "symmetrical cut" sizes.

Could you do that, that is, limit the size of the stock so the stock would not be gouged.

I will scan in some of the pages from the Jointech instructions and send them to you so you can see what I am talking about.

Another idea: Is there some way you can make it so that the dovetails woudl not necessarily be evenly spaced? This woudl make it so the gouging woudl not be a worry, and it woudl make it so the dovetails did not look so mechanical.

As for the set up time and using spacers being too time consuming: I have used a dedicated dovetailing machine with pneumatic clamps for holding the stock ... faster than the Jointech system and faster than a Leigh dovetailing jig ... and definitely faster than cutting them by hand.

All that being said, it is not alway speed with the CNC that matters, there is also the repeatability and accuracy. There seems to be a bit of a trade off here between the three.. and I for one will take accuracy over speed, especially when you start taking about gluing and clamping the drawers up. The glue forces speed on you as it sets up relatively quickly, and if the fit is difficult or comes out not square or leave a drawer that need a lot of filling and sanding, speed means little then.

I suggest thinking about the whole process and the CNC cutting the dovetails as part of that process, and not just thinking about the CNC cutting isolated from the making the final product.