Progress on Chairs

There's been some movement on the chair project. I have used the CNC3020 to make joints, which makes a very neat joint and parts that are more or less interchangeable. 

Both mortices and tenons are done with custom gcode programs. I have finished all the parts for the first (trial) chair and have glued it up.

The chair is pretty solid so far, the seat needs fixing now and some covering with fabric. Some foam is also needed as these won't be wooden seats, the thickness of the foam needs to be determined.

The seat blocks were originally going to be wooden, but with the 4 degree sides and three screw holes, I have decided to 3d print them.

They really are much neater and are very strong. Also, I get to do something else while they are being printed (I can probably print a chair set at a time if it'll fit on the print bed) and I can have almost any colour I want.

More Tenons on the CNC3020

I've done some more joints on the CNC machine. Here's one at a fairly accurate 4 degrees:

This is for the seat of the chair. It's a pretty accurate 4 degrees, set up using wedges that I 3D printed at various angles. This is the joint being machined. It's a fairly simple tool path but fairly efficient. It takes about 25 minutes for a tenon (mortices are quicker), but that time isn't dead time, I can do something else while the machine is working.

And the final result (these are test pieces):

Mortice and Tenon Test Pieces

These are some more mortices and tenon test pieces. They fit nicely but I think there's enough room for glue.

I now need to make some angle plates so I can machine these at the angles I need for the chairs.
I think you could make the tenons and mortices different shapes if required, which is an interesting option where multiple joints want to be in the same space, such as where two rails attach to the same upright.

Mortice and Tenon on CNC3020 Engraver

I need to do a lot of mortice and tenon joints if I'm going to do the chair project, and they aren't fun and never look very good in pine, as it's difficult to work with. So can you do them on the CNC3020?

Well, after 3d printing a clamping plate that attaches to the 4th axis mounting bolts on the front of the 3020, it turns out you can do some very consistent nice looking tenons and matching mortices:

These are test pieces, but they are very consistent, totally interchangeable and look nice.  The clamping bracket lets me put tenons on the end of long pieces of wood, I 3d printed it and it's strong enough to hold the work.

In order to get the spindle out in front of the bed of the CNC enough to do the entire tenon, I had to make a spindle extender attachment. I did this in wood as the 3d print was 6 hours or so, I may do a 3d printed one later if I use it much.

This gives me enough extra over the end of the machine to do the work I need for the chairs. I'm a bit concerned that there may be heat build up due to the insulating properties of wood as opposed to the aluminium heatsink arrangement the spindle normally has.

Of course, this is also going to be true if I 3D print a version. I may have a think about a 3d printed cylinder in the existing heatsink and an aluminium clamp attached to it that gives similar heatsinking as the current clamp. I don't think the machining will take too long so I won't be running for extended periods of time, but it may be better anyway.

Perhaps a 3D printed version with holes for ventilation?

Spindle Camera Mount

I made a quick little bracket for mounting the spdinle camera on the CNC milling machine while it is operating. I can then see what's happening without having to look at the spindle directly.

The shiny red bit is a mount off a cheap magnetic base from ebay. It works well, I may get some more. Unfortunately the base isn't very strong.

Here's a picture of some PCB milling going on:

here's a video of the same.

Spindle Camera

While trying to drill very small holes in punches I thought it would be easier to align the drill bit with the centre of the punch if I had a camera that could be used to do the alignment. There's quite a few spindle camera designs on the web, and I found one that used a particular webcam, so I bought one. I then dismantled it:

The PCB had its microphone removed and also the LEDs that could be used for illumination. The problem with them was that the didn't fit in the case I found on Thingiverse, and also that the LEDs were not pointing at the subject when looking at very small items.

I then printed the Thingiverse spindle cam case I found, after I'd modified it for the smaller collet nut I have on the engraver.

The PCB is held by the two halves of the case which are bolted together.

The collet nut slides into the back of the case and there's enough friction there to hold it while adjusting the alignment.

This is the camera on the spindle:

I used some dots on a white background and the trails feature of the camera script that was on Thingiverse. It seemed to work well once I had printed a holder that was a tighter fit on the collett nut.

It was then fairly easy to align the spindle on the end of a punch, then put a 0.1mm drill bit in and have a go at drilling a hole:

You can see some chips at the base of the drill there. The first attempt snapped the drill bit on removal just as it was nearly done. Not sure why, maybe too fast an extraction speed on the peck cycle.

I had another go and all worked well that time. This is a video of the camera output while drilling another punch hole.

These pictures were taken with the camera out of the spindle and held in a marking base I recently bought: