Thursday, March 13, 2014

Quick Update

It's been a while since my last post but I went ahead and ordered the parts for my CNC router. I'm still waiting for some components to arrive which will probably happen early next week. I'll probably take some time to calibrate it and to get used to the machine. Once that's done, I'll go ahead and start fabricating some pieces starting with the head and then I'll alternative between fabricating and designing additional components depending on how heavy the pieces will be.

Sunday, February 16, 2014

Update ShapeOko BOM

Okay, so here's the finalized ShapeOko BOM (not including cutting bits):

ItemPart NumberRetailerQtyUnitUnit CostQty CostS&HTaxSubtotal
ShapeOko 2 Mechanical Kit30206-01Inventables11299.00299.0027.060.00326.06
MakerSlide 1000mm25142-03Inventables41m21.8487.360.000.0087.36
GT2 Pulley26054-02Inventables316.4719.410.000.0019.41
Spacer, #12 X 1/425312-13Inventables2102.615.
Cap Screw, M3 X 12, SKT HD25285-10Inventables1102.
Midspan SupportShapeOko1240.0040.005.003.2048.20
DW660 MountShapeOko1115.0015.002.501.2118.71
NEMA 23 Stepper Motor (156 oz-in, 1/4 shaft)KL23H251-24-8BATI3115.9547.8513.330.0061.18
NEMA 17 Stepper Motor (76 oz-in, 5mm shaft)KL17H248-15-4AATI1112.9912.990.000.0012.99
Stepper Breakout BoardC10ATI1128.0428.040.000.0028.04
Power Supply (24V, 14.6A) SE-350-242146564Jameco1144.9544.957.304.2956.54
100 uF Capacitor29962Jameco1101.
DIP Switch ADF03202472Jameco310.391.
5V Voltage Regulator LM2576T-5245569Jameco112.
100 uH Inductor371856Jameco111.351.350.000.001.35
Schottky Diode 1N5822177990Jameco1101.601.600.000.001.60
1000 uF Capacitor93833Jameco110.390.390.000.000.39
Heatsink TO-220158051Jameco110.
Terminal Block208857Jameco410.993.960.000.003.96
Pololu DRV8825 DriverDRV8825Pololu4113.9555.805.950.0061.75
Stepper Motor HeatsinkPRT-11510Sparkfun411.957.804.010.0011.81
Thermal AdhesivePRT-09771Sparkfun113.953.950.000.003.95
Long HeadersPRT-10158Sparkfun212.955.900.000.005.90
Aluminum Extrusion 20mm Inline 6ft5537T117McMaster Carr16ft17.1917.190.001.5518.74
Aluminum Extrusion 20mm Inline 8ft5537T117McMaster Carr18ft21.5821.580.001.9423.52
Right Angle Bracket Fastener5537T454McMaster Carr442.5510.200.000.9211.12
M3 Flat Washer93475A210McMaster Carr11001.621.620.000.151.77
M5 Flat Washer93475A240McMaster Carr11002.572.570.000.232.80
M5 Hex Nut90591A146McMaster Carr11002.
M3 Hex Nut90591A121McMaster Carr11001.391.390.000.131.52
Cap Screw, M3 X 8, SKT HD91292A112McMaster Carr11004.
Cap Screw, M5 X 20, BTN HD92095A185McMaster Carr1505.
18-4 Shielded Wire56913599Home Depot1010.464.600.000.374.97
Aluminum Extrusion 20mm Corner Brace1155Adafruit810.957.604.250.0011.85
GT2 Belt (2mm Pitch, 6mm Wide)TDGT2BeltTriDPrinting31m2.507.503.950.0011.45

So, the subtotal cost is $830.11, shipping $73.35, and tax is $19.55, for a grand total of $923.01. So I saved about $17 from yesterday's estimate while adding an additional 2 feet of GT2 belting (as a precaution) and 2 more aluminum extrusion corner braces.

As for the cutting bits, I'm still deciding whether or not to buy them from eBay (there is a seller who has been recommended several times on the ShapeOko forums) or get higher quality ones from MSC since I get a discount.

I will have to go back into my WALL-E CAD model and see what types of cutting bits I'll need. If I remember correctly, I should only need:

.125DIA, .500 CEL, Square
.250DIA 1.500 CEL, Square
.250DIA 1.500 CEL, Ball

The CEL numbers are all off the top of my head so I don't know if they are correct at all.. they're just a guess. I know that the CEL are a little long so I may have to check each piece to see if I can shorten the required CEL at all.

I'm think I'll start ordering today or tomorrow but I want to give myself some time to think it over before committing $1K...

Saturday, February 15, 2014

CNC Router

I took a little break from working on WALL-E this week and looked into ordering parts for the CNC router I would need. At this point, I've decided to go ahead and use the ShapeOko 2 to fabricate most of my pieces. The reason I've waited this long to decided on a CNC router was because I wasn't sure what the cutting area requirements would have been. Now that I've modeled most of my larger pieces, I would need a cutting area of at least 18"x18". This means that I will have to upgrade my ShapeOko 2 to have longer X and Y axes.

I went ahead and began creating a BOM for the ShapeOko. The mechanical kit, which consists of only the hardware and fasteners, costs $299 while the complete kit, which includes everything you need to get started, costs $649.

In order to upgrade my X and Y axes, other parts such as the stepper motor and drivers needed to be upgraded to handle the higher loads. So, I've decided to purchase the mechanical kit and purchase the rest.

As it stands, my ShapeOko 2 without the cost of cutting bits will costs around $915 including tax and shipping.

The BOM is as follows:

ItemPart NumberRetailerQtyUnitUnit CostQty CostShippingTaxSubtotal
ShapeOko 2 Mechanical KitInventables11$299.00$299.00$29.33$0.00$328.33
MakerSlide 1000mmInventables41000m$21.84$87.36$0.00$0.00$87.36
GT2 Pulley26054-02Inventables31$6.47$19.41$0.00$0.00$19.41
Spacer, #12 X 1/4Inventables210$2.61$5.22$0.00$0.00$5.22
GT2 BeltInventables81ft$1.99$15.92$0.00$0.00$15.92
Terminal BlockInventables41$2.50$10.00$0.00$0.00$10.00
M3 Hex Nut8$0.00$0.00
Cap Screw, M3 X 12, SKT HDInventables110$2.14$2.14$0.00$0.00$2.14
Cap Screw, M3 X 8, SKT HDInventables210$2.09$4.18$0.00$0.00$4.18
Cap Screw, M5 X 20, BTN HDInventables210$2.35$4.70$0.00$0.00$4.70
Midspan SupportShapeOko1$40.00$40.00$5.00$3.20$48.20
DDW660 MountShapeOko1$15.00$15.00$5.00$1.20$21.20
NEMA 23 Stepper Motor (156 oz-in, 1/4 shaft)KL23H251-24-8BATI3$15.95$47.85$13.33$0.00$61.18
NEMA 17 Stepper Motor (76 oz-in, 5mm shaft)KL17H248-15-4AATI1$12.99$12.99$0.00$0.00$12.99
Stepper Breakout BoardKL-DB25ATI1$28.04$28.04$0.00$0.00$28.04
Power Supply (24V, 14.6A)SE-350-24Jameco1$44.95$44.95$7.30$3.46$55.71
100 uF Capacitor29962Jameco110$1.20$1.20$0.00$0.00$1.20
Pololu DRV8825 DriverDRV8825Pololu4$13.95$55.80$5.95$0.00$61.75
Stepper Motor HeatsinkPRT-11510Sparkfun4$1.95$7.80$3.93$0.00$11.73
Thermal AdhesivePRT-09771Sparkfun1$3.95$3.95$0.00$0.00$3.95
Router Speed Control43060Harbor Freight1$19.99$19.99$0.00$1.60$21.59
Aluminum Extrusion 20mm Inline 6ft5537T117McMaster Carr1$17.19$17.19$0.00$1.38$18.57
Aluminum Extrusion 20mm Inline 8ft5537T117McMaster Carr1$21.58$21.58$0.00$1.73$23.31
M3 Flat Washer93475A210McMaster Carr1100$1.62$1.62$0.00$0.13$1.75
M5 Flat Washer93475A240McMaster Carr1100$2.57$2.57$0.00$0.21$2.78
M5 Hex Nut90591A146McMaster Carr1100$2.08$2.08$0.00$0.17$2.25

This final cost is assuming I group orders where possible to avoid additional shipping charges. I could in theory reduce the cost a bit if I don't purchase the DW660 mounts (I think I've seen them mounted for cheaper) and if I don't purchase the router speed control which may not be necessary. Some small fasteners I may be able to acquire from work or school and if I'm really lucky, I may be able to machine the midspan supports myself at school.

So, the price range I'm looking at is around $824 to $915, but to be honest, I'll probably end up purchasing everything in this list... :)

I went back and added some additional components to purchase to account for almost everything I'll need. I've added a 5V regulator (along with the necessary capacitors, inductors, diodes, and heatsink) for the stepper drivers and breakout board, 2cm long headers for the stepper, right angle brackets and hardware for the t-slotted extrusions, and some 18AWG 4 conductor wire for the stepper motors. I've also sourced some hardware I was originally going to buy from Inventables to Jameco and McMaster Carr to save a buck here and there.

The only things left to add to the BOM are the hardware to mount the terminal blocks (which I can probably find somewhere instead of buying), the hardware to attach the heatsinks (which I might end up just using the thermal adhesive), and the cutting bits.

I looked into the speed controller a little bit and it seems to be a toss up on whether or not I should use one. I suppose that these routers and cut-out tools weren't designed to be used with a controller (but it doesn't mean it can't be used with one) but I'll hold off on buying that for now.

So, the total cost now stands at $940.36, of which $69.13 is shipping and $21.25 is tax. To be honest, the shipping costs were all very reasonable for the amount I was buying and luckily I wasn't charged tax on many items.

Now comes the hard part of deciding whether or not to start buying everything... 

Saturday, February 8, 2014

Fingers / Arms

I think I may have been working on WALL-E too much. The reason I say this is because last night, I actually dreamed about building WALL-E... haha.

Anyways, I was having some trouble determing what size actuator I should use for the shoulder pivot and rotate so I will start from the fingers and work backwards towards the shoulder. I'm also contemplating whether or not to include the arm extend and retract motion. It'll look nice but I'm not sure if it's worth the extra weight.

At the moment, I am planning on the following movements for the arms:
1. Upper finger open and close
2. Lower finger open and close
3. Wrist rotate
4. Arm extend and retract (Maybe)
5. Arm swing in and out
6. Shoulder rotate

Here's the Rev. 0 version of the arm...

... and here's what I have so far for the final revision

There will likely be major changes to what I currently have depending on how the fingers and the wrist turns out.

Alright, time for some breakfast and then I'll be back to do some work.

I had a pretty bad headache today so I didn't get a chance to work on WALL-E today.

Thursday, February 6, 2014

Motor changes?

While I was working on the shoulder joint actuators, I was looking at what the motor requirements would end up being for different types of actuation.

The current design makes it easier to implement the shoulder rotate motion but requires a lot of torque for the shoulder arm out and in because the leverage is at the joint with a pulley of diameter 1-1.125 inches, which isn't that much compared to the overall length of the arm.

I know I mentioned that I didn't like using the linear actuator mounted further up on the forearm, I'm starting to lean towards that more. The only problem with that is in order for the shoulder rotate to work, I would need the linear actuator to go through the joint. I'll take another look when I get home.

While I was working on that, I ran some numbers in the eye socket movement as well.

The mechanism is a stepper motor connected to a set of reduction pulleys which is connected to a acme lead screw.

The stepper motor has a holding torque of 76.4 oz-in. At 1200 pps, the torque is still relatively high, maybe 50-60 oz-in. I ran the numbers with 76.4 oz-in but with that number I'm getting roughly 70 lb axial force on the lead screw running at maybe 0.75 in/sec. With the reduction gear I'll probably get a slightly higher torque with a slower ipm.

So, 70 lb is way more than what I need so I'll switch the pulleys around.. Maybe I'll get an even larger pulley if it'll fit to get a faster ipm on the lead screw. I want to aim for something at least 1 in/sec which I think I can accomplish.. I'm just worried about space now. If it doesn't make too much of a difference, I want to use a smaller, lighter motor to reduce the weight.

Alright, time for work.


So, I tried looking for a set of timing pulleys that would increase the speed of my eye socket movement but I can't seem to find a pair that would work. It looks like the set I currently have is the best I can do. The fact that the stepper has a 5mm shaft and that the lead screw is 3/8 makes it a little difficult. What I'll try next is to see if there's a 1/4" acme rod that I could use. Currently, I'm using a 3/8-8 acme rod but I don't remember seeing a 1/4 acme rod with 8 or less TPI... maybe 1/4-10 or 12 but not 8. So that would mean that I would need at least a 2:1 timing pulley to match what I currently have. Hmm.. time to search the web!

Nope. There are some but they are extremely expensive... $90+. Oh well, I guess I'll keep the eye socket as it is.

I thought about the shoulder a little more today and I think that I'll just keep the current setup, or at least work on it a little bit to see the feasibility of it a little bit more before changing it over to the other design that I mentioned earlier.

Tuesday, February 4, 2014

Bumper Success! (And Shoulder Update)

After spending way too much time I was finally able to model the front lower corner bumpers! I had to change some geometry of the structure behind the bumper and using several lofts and intersection curves, I was able to make them, finally!

It does make him look a lot better than before, huh? It feels more complete now (even though I'm not!)

I know it's not perfectly the same as the real WALL-E but I'm fine with how it turned out and I don't want to spend any more time on this.

On of the bad things is that I'll probably have to 3D print this piece, like I'll probably do for the rear bumpers as well. Let's see how much it'll cost...

For the basic white plastic it'll cost:

Shapeways: $112
i.materialise: $208
Scultpeo: $128

Yikes... that's a little bit on the pricey side. Fortunately, Shapeways sells the ceramic version for $33 which I could probably make a rubber mold of.. but I would still need to purchase 2 of them (LH and RH). 

i.materialise does sell the multicolor material version for $69. Hmmm...

Time for a break and then I'll be back for more!

Update: Here's what I have so far for the shoulder joint:

It's a little difficult to see what it is so I'll try to explain. The lower piece is the component that will go into the body. The upper piece is the upper clevis where shoulder meets the body.

Here's a view looking downwards a little bit. That top piece attached to the shaft is a face mounted shaft collar. You can also see the cut out for the wiring that will eventually go through to the arms and fingers.

... and here's the side view. So, as you can see, a timing belt running from inside the body will connect to the timing pulley on the lower piece. The timing pulley and the shaft collar are locked onto the shaft so when the timing pulley turns, it'll turn the shaft collar as well. The shaft collar has a face mount so it'll attach to the rest of the arm and allow it to pivot. Underneath all this will the second clevis and I'm still deciding whether or not to add a second shaft collar on there to mirror the top portion. These pieces are not cheap... :(

The other way of achieving the shoulder pivot would probably be to use some sort of linear actuator and attach it a little ways from the pivot point. It would probably require less power due to the leverage but it might be deviating from the real WALL-E a bit...

Another way is to possibly use a worm drive. The worm would come in at an angle and the worm gear would be where the timing pulley is. The only problem with that is the cost. I think it'll end up being somewhere 2-3 times more expensive just for the hardware like the worm and worm gear versus the timing pulleys and belts.

Anyways, everything is subject to change and if I find something better, I'll change my design. But until then, I'll continue on with the rest of the arm tomorrow!

Monday, February 3, 2014

Outer Body Shell Complete (Sort of)

So here are the latest renders of the body:

As you can see, I'm almost done with some exceptions. The overall to do list is as follows:
  1. Front corner bumpers
  2. Cutout for arms and legs (will wait until later)
  3. Modify rear corner bumpers
  4. Design front charge panel removal
  5. Design front hatch removal
  6. Design rear hatch removal

In the movie, the fasteners were flat head type fasteners but because my material is very thin, I didn't have enough thickness for the countersunk heads. So, I decided to change them to button heads with the exception of the red button panel which will have socket head cap screws.

I'll make some adjustments to the WALL-E logo on the front as well. Right now, they are just raised above the surface. I'll go back and add a fillet to attachment point and on the top to make it look like it was metal stamped on there rather than keeping the current sharp look of it.

Here's the rear body of WALL-E. I still need to work on those bumpers on the bottom but besides that, I'm very pleased with how it came out.

.. and here, I went ahead and changed the height of the lower portion of the piston to make them different from the top.

Here's the rear hatch. It will come off as a single piece for rear access. Hopefully the handle will be strong enough to support the weight of the Igloo Playmate Elite cooler. If not, I'll have to increase the length of the inner bracket or have a cross support bracket from flange to flange and attach it to that.

It's currently just bolted to the inner side walls. I may have to use MDF for these walls as a precaution.

Well, that's it for now. Good night.

Update: Actually, I was going to sleep but something was weird when I was trying to mate some pieces. It's been happening for a while but some mates wouldn't work and it would say that it would overdefine my components when it would just fully define them. I was really confused for the longest time.

Here's the culprit:

For some reason, the bottom and the left side (which is suppose to be perpendicular) was 90.20 degrees. I have no idea how that happened. A lot of my components are made using external references so when I created another component based on this component, that 90.20 degrees would carry over to the new piece and then another piece would carry that on and so forth until most of my rear hatch assembly pieces were all off by 0.20 degrees.

I didn't know this and it actually carried over into my Rev. A model as well. Honestly speaking, it wouldn't have made much of a difference during assembly because of the tolerances in the machining but it's nice to know why SolidWorks was giving me problems.

Now that's out of the way, I can finally sleep.

Sunday, February 2, 2014

Rear Body Update

Luckily, the outer body shell is pretty straightforward. There weren't that many changes I needed to do for the final revision.

As you can see, the rear lower bumpers are incorrect but I'll decide later on whether or not to change it. I was going to 3D print the bumper but found out that instead of being $22 to print, it's actually around $82. When I uploaded the file, it assumed the dimensions were in CM instead of IN... oh well. At that price point, I'll probably split up the bumper into smaller pieces and use the CNC router instead.

The rear panel will be detachable so I can access the internal space of WALL-E.

I just need to work finish designing how all the parts will stay together as an assembly. Most of the pieces will be glued together but I'm thinking about fastening the two cylinders using socket cap screws.

The next thing I'll probably do right now is sketch on the BnL logo on the rear hatch. I'll re-render it after I'm done. The other thing to work on the rear hatch is WALL-E's lunchbox hanger/hook. I'm planning on hanging a real Igloo Playmate Elite Cooler on the back but I'm still thinking about what to put in there. At first, I wanted to put some electronics in there but being a cooler, I'm worried about heat getting trapped in there and overheating the components. If not electronics, what else is there to put in there besides more props? The two ideas I had were to either put the shoe with the plant or place weights in there to balance WALL-E. Hmm...

One more thing to note about the rear hatch is the upper cover. Currently, it's a single component.

I'm hoping the CNC router will be able to fabricate this piece. Using a combination of a regular end mill and a ball nose end mill, I should be able to but we'll see how the surface finish will turn out...

Update: So here's the BnL logo engraving on the rear hatch upper cover:

Next up is the lunchbox holder!

Update 2: And here's the final update for tonight probably:

The handle is slightly different from the actual WALL-E. It should be slightly thicker at the base and at the handle so I'll work on that a little bit tomorrow.

What I'll end up doing tonight is finish the rear hatch portion. I need to design the handle attachment pieces and some extra supporting pieces to keep the rear hatch together. Once that's done, I'll design how I'll be able to remove the hatch for inner access.

Update 3: I just noticed that the cylinders are incorrect. The bottom portion of the cylinder should be shorter than the upper portion. I'll get that fixed tomorrow.

Saturday, February 1, 2014

Body Update

Here's an updated look at the body so far:

I enabled contour lines so you could see the WALL-E decal on the front. So far, the body is coming along nicely. Like I mentioned earlier, I'll probably get the body shell completed first and then work on the inner structure using the t-slot extrusions.

As for access panels, I'm thinking about making the front hatch, the charging panel, and the rear body removable to access the inside. Some other modifications I need to make are the cutouts for the arm attachments. Since I haven't started on the arm quite yet, I'll leave that until later.

As for materials, I'm leaning towards mostly balsa and HDU where possible and opting for 3D printed plastics for the more delicate and thin pieces. There'll also be some MDF and aluminum for structural supports.

Alright, time to work on the rest of the body sides!

Update: So here's the rest of the body I did today:

The first problem that I have right now is modeling the front lower corner bumpers. For some reason, I just can't get my head to figure out how to model it. One of the problems is that the rounded corner between the front hatch and the side is incorrect, especially towards the bottom. Unfortunately, I'm going to keep it like that for now and I don't feel like it's a priority. The bumper, however, I need to get that modeled for sure. Hmmm...

The other problem is that the rear corner bumpers aren't correct as well. It's suppose to extend slightly towards the middle on the backside but on Rev. 0, I didn't model it for some reason. I'm not sure if I can model the rest of the bumper without interfering with what I have so far.

Let's see, I'm also working on the rear cylinders right now as well. 

I still need to finish the piston but I'll do that tomorrow. The clevis and brackets will be machined while the shafts and pistons will be PVC pipes. I had to make some adjustments to the dimensions to fit the available PVC pipe sizes. Luckily, they are pretty close so it'll be very small changes.

One final note I remembered is the status of the CNC router I need to build. I'll be using the ShapeOko 2 and modifying it to cut larger pieces. So far, my largest pieces will be the side panels of the body and the top panel of the body. The top panel is 18" X 18" so I'll probably upgrade my ShapeOko to have 24" X 24" rails.

Alright, it's time for some sleep!

Slight Problems and Body Update

So I was working on the neck and the head swivel mechanism and found out that the head swivel actuator might be underpowered for the task at hand. Due to the space constraints, I had to design it with a 9 kg-cm servo. I'm currently trying to modify the neck to see if I can fit a 30 kg-cm servo instead but it's giving me some trouble. I'll probably have to sleep on it for a bit.

...because of that, I decided to get started on the body.

It's mostly the same as before but I did make some modifications to make life easier when fabricating like splitting components into smaller machinable pieces. I'm also trying to keep serviceability in mind as I make the final revisions such as hatches and openings to access the internal guts if something were to go wrong. What I'll probably end up doing tomorrow is work on the rest of the body and then put in the basic internal support frames made out of t-slot extrusions.