Category: Ghost Elevator

Elevator status report

My sister picked up the remaining two elevator shafts in early November. Since then she has been busily finishing the whole set of three. I saw them over the Christmas holiday and they are looking great. There are just a few more artistic features she needs to finish. Once it is done, hopefully I’ll be able to get some pictures and a video posted here.

One down, two to go

A few weeks ago I delivered the first completed elevator to my sister and picked up two more to automate. With warmer weather arriving, progress on these has been a bit slow. Also, there was a diversion. I had purchased a multi-process welder to replace my MIG welder and I needed to fabricate a new cart for it, since the multi-process welder will accommodate two shielding gas cylinders at once (one for MIG, one for TIG) and most carts only handle only one cylinder. Anyhow, the cart is now done, so progress on the two remaining elevators should get a little quicker.

The MIG welder I gave to my sister, along with a quick welding lesson. She turned out to be a natural welder and was making good looking beads almost immediately. In case you are wondering, there is in fact a welded part in the elevator: the bracket that fastens the belts to the counter-weight was TIG welded together.

The completed two cylinder welding cart, with only one cylinder. Actually, it is not quite complete, since the handle is not done yet. The other benefit over the previous cart is that it will hold my plasma cutter.

Elevator in Action

The Ghost Elevator continues to come together. Everything but the stuff in the car is working. The video shows it in action. Only the center door has a pointer, but the pointer motor is actually working on all three doors. It is a bit hard to see the figure in the car since the light is not implemented yet.

More Elevator Progress

The circuit boards for the elevator electronics came in a few days ago. Actually it was the third set, the first two attempts having fatal errors (don’t ask). The third set had only a minor error easily fixed by adding a wire. The board is now installed in the frame and I am wiring things up, testing and bringing up code. The wiring is somewhat tedious since there are a lot of crimp terminals to install.

The elevator electronics installed in the frame of the shaft. The three 12 wire cables go to the three doors.

At this point, almost everything is working (most of the time) with the exception of the floor indicators, which I’m holding off on until I get everything else working well. There have been a few glitches. One was that it would periodically get a call to the first floor all on its own. This was due to the relatively long cable run to the first floor door resulting in the PWM to the door stepper motor coupling to the call signal. This was fixed with some digital filtering which could be implemented in the PSoC CPLD. I also had a stepper driver board fail and the first one I replaced it with seemed to be DOA. The next one has been working so far, but there may be a QC issue with this board. The other issue is the second floor door is sometimes getting stuck, so the mechanics need to be looked at. Overall, things are going reasonably well so far.

The Elevator is coming together

A couple of weeks ago my sister came to visit and brought one of the elevator shafts and cars along with more door assemblies. We spent the weekend retrofitting doors with the new mechanism, but there was not time to get the car operating in the shaft while she was here. My first idea for driving the car worked fine, but I realized it had a potential drawback. The car is being driven with a stepper motor and a “GT2” timing belt. While the belt is operating well below is rated operating tension, if it should break it would be a disaster since neither the car nor the counter weight has a brake. I decided it would be a really good idea to use a double belt system, so if a belt broke, the other would prevent a crash. Between coming up with a double belt system and wiring up doors, it was only today that I got the car operating again.

The video shows the car in action. The doors are not operating yet since I am waiting for the circuit boards for the controller to be fabricated.

CNC Holes

As mentioned in previous posts, the Miniature Elevator needs a lot of precisely located holes and I decided to commission my CNC mill to drill them. I show here a movie of the CNC mill in action drilling elevator door carriage plates. The plates have eight holes each, but there are three size holes and also a spot drill operation so there are three tool changes involved (four if you count the first set up). Ideally, the mill would have an auto tool changer and each plate would be placed on the mill and it would then drill all the the holes changing bits as required. I don’t have that, nor do I even have quick change tooling, so tool changes are a slow operation. So it is faster to set up the mill with one bit at a time and swap all the plates through it, since it is faster to swap a plate than change a bit. So in the movie you will see first the mill doing the spot drilling of eight holes and then you will see four of the holes being drilled. The plate then requires two more passes through the mill to drill two more pairs of holes. In all, with 18 doors and 8 holes per plate, there were 144 holes to drill.

CNC mill spot drilling then drilling four of eight holes in an aluminum carriage plate.

The finished product may not look like much, but remember there are 18 of them and the holes on each one are probably within a couple thousandths of an inch of where they should be.

A finished carriage plate.

The CNC Mill

Several years ago I purchased a Little Machine Shop HiTorque Mini Mill, a ball screw kit, steppers and controller, in short, all the stuff need to assemble a CNC milling machine. However, I never got it to the point of actually machining anything until recently. There are several reasons for that. One is that it took some time to figure out the kinks and get issues with the control software resolved. The other is that when I needed to mill something, it was easier just to do it by hand on my Sherline mini mill than do it with CNC. Also, I hadn’t found a CAM processor.

For those unfamiliar with CNC there are several stages to doing it. First, you design the part with a Computer Aided Design (CAD) program. Then the CAD design is processed with a Computer Aided Manufacturing program (CAM) that turns the design into instructions that tell the Computer Numerically Controlled (CNC) machine how to make the part. You can in principle program the machine in a language called G-code directly, but this tends to be error prone and works mostly for simpler parts. After looking at and trying various CAM programs, I finally discovered that Autodesk Fusion 360, which is a cloud based CAD program, also includes a CAM processor. Best of all, it is free for individuals and small companies to use.

While Fusion is in some ways easier to use than TurboCAD, which I have used for years, I found aspects of it frustrating, in part because it is so different from TurboCAD. So I imported my design into Fusion and then used the CAM processor to generate the G-code to run the machine. After a trial run cutting air, I was able to successfully drill 8 holes in my carriage plate with the CNC mill. I wanted to put a video of this here, but I discovered the free edition of WordPress doesn’t allow this. So until I decide I like this blog thing enough to pay for WordPress all you get is a picture of the CNC mill.

Holes

The carriage plates for the elevator doors (Miniature Elevators) are aluminum flat bar with a bunch of holes in them, eight in fact. The two pairs of these which mount the ball bearings must be precisely located, since there is almost no adjustment. It turns out there is some adjustment because the bearings have 3-mm IDs and are mounted with M3 screws, which are just slightly smaller in diameter than 3-mm. Because there are so many of these plates, 18 in fact, it is useful if all the holes are precisely located so everything just goes together and fits. One of the best ways to do this is to drill the holes on a mill. I have a Sherline miniature mill with digital readout (DRO) on which I made the first few plates, but is surprising how easy it is to screw up a hole location even with the DRO. But I was pleasantly surprised when I made the first plates, that the bearing holes were in the correct location, even though I’d located them based on measuring the v-groove bearing since I did not have manufacturer’s dimensions of the v-groove.

However, it became apparent, based on the screw up rate and the large number of these plates that needed to be made that now would be good time to finally commission the CNC mill I’d put together some time ago, but not actually used yet.