Part 2-Machining the Crankcase Top

Now that the crankshaft split surface and related features are machined the rest of the machining process for the part is easier. If all of the previous scanning, QC and OP1 processes went correctly then this stage should be a breeze. Hopefully I don't regret that statement!

We are starting here, a part located on the fixture plate with the majority of machine work yet to be done.

The next machining steps are as follows:

• machine the generator side features: gasket surface, mounting holes, and main galley oil passages, and logo cleanup

• machine clutch side features: gasket surface, mounting holes
  

The logo on this side was left as-cast to see which looks better. I prefer the milled one.


The part then gets rotated 90 degrees for the following operations:

Bank1:

• Face deck surface with 6" face mill. The 6" diameter tool machines the deck surface with one sweep, crating a very flat and consistent surface.
  

• Rough mill cylinder bores. I use a long 3/4" diameter 6" long 3 flute carbide end mill held in a milling chuck, both from Mari Tool, for maximum rigidity. The cut was deep but clean with no chatter. It was a good enough finish to send directly to the platers but I wanted the extremely straight bore that a finish pass with a boring head would provide.
  

• Cleanup coolant port passages. This was step one in showing how well the internal coolant ports were aligned to t he core and cope of the mold. One bank had excellent alignment, one bank needed a bit of tweaking, but this is the area where we expected a large tolerance stackup. Harmony will likely revise the gauges used to place the cores to all
  

• drill and tap cylinder head bolts and dowel holes

• Finish cylinder bore to .008" oversize in preparation for nickel silicon carbide plating by Millennium Technologies. This was done using one of the single point boring bars from Microbore with a TCGT ground and polished carbide insert.
  

Then repeat the same operations for Bank 2.



Valley:

• coolant ports gasket surface milling
• coolant port mounting holes drill and tap
• oil pressure sensor drill and tap

So far so good. No crashes, although I did nearly break a couple of tools from unforeseen interference between the trunnion tailstock and the long tools installed in the toolchange umbrella.

In general the entire machining process was fault-free. The stiffness of the trunnion from Martin Mfg. was excellent. The large tools cut as if the part was clamped directly to the machine table, no ringing, chatter, or other abnormal tool behavior. The bore finish from the Microbore boring bars is better than expected.

Once the casting patterns have some slight revisions done they'll run 5 more parts that will then get machined.

I am very satisfied with the results so far. The sample casting for the girdle part just arrived, so now I can start directly on that and hopefully have just as good a time.

That's all for now.

Chris

Machining the Crankcase Top

Well, I finally got some time to get into the crankcase top sample casting. This post documents the first operation on the part. The QC results were mostly positive, there were only a couple of minor issues with the initial test pour which will be revised for the next run of parts. For a casting with multiple internal cores of this complexity I am very happy that the issues that were found were minor and easily corrected.


The first machining step is to clamp the casting upside down onto the mill table and align it with the machine X and Y axes. it is important to design features into the casting that will allow easy and repeatable initial positioning. This step was pretty easy as I already had a good idea on how accurate the casting was because of the previous QC scanning procedure. The 3 main datum points that define the XY plane and create the crankcase split plane were very accurate and enabled easy and stable clamping. Then 2 additional points to locate the x-axis orientation then one more point to locate the origin. 6 location points perfectly constrain 6 degrees of freedom and now the part is ready to go. Sorry about the crappy image but I started machining before I realized that no pictures were taken of the setup and had to grab this from a video.


Once the part was aligned I setup all the tools in the carousel and triple checked the program, then started making chips.

Machining o-ring oil seal grooves....



Drilling/tapping main bearing and case attachment holes.....




Done with operation 1!



After op1, I needed to make a fixture plate that matches the pattern of tapped holes I just machined into the part.

AutoCAD sufficed for this.....



The part clamped to the fixture plate.....



which is then clamped very accurately to the Jergens fixture pins built into the trunnion table.....



From here I will need to run 2 more programs, one for the each cylinder bank- decking it, oil and head bolt holes, etc, and the second for the side cover mounting faces and attachment holes.

I'll get to this soon and put up a post as soon as I do.

That's all for now.



Chris

QC on the Crankcase Casting Top

I received the crankcase casting top sample piece on Friday and got right down to seeing if it was within specification to the CAD model we used as a master. Overall the part looked very clean with all features well formed and no visible pitting or porosity, so it was a great pouring job by the guys at Harmony.I proceeded to setup a scanning station that would give good access and a stable platform to scan the part.





My approcach was to use the scanning arm to locate major planes of interest: cylinder deck, bearing split surface, and large external surfaces, then some cylinder primatives of bearing and cylinder bores, then create 3d profiles of more complex surface intersections.






The result of this was a relatively confusing collection of surfaces, points, and lines randomly oriented on 3D space.


The next step is to make sense of all this data by aligning it to the CAD model it is supposed to accurately represent. First we align it to the CAD model that has extra machining stock on the appropriate areas:


After a careful alignment process the scanned data seemed to closely match the CAD model on all external areas. To ensure that my addition of machining stock was correct I then replaced the as-cast CAD model with a finish machined CAD model:


What I look for in this step is a gap (at least .030") between the scanned surface and the final machined surface, which indicates there is enough material to cleanly machine the surface.

So far the casting is well within specification, an excellent job by the casters considering the multiple stackup of cores and tolerances. I need to do a couple of more scans to capture the bottom/inside of the part and do a similar analysis. Then the part goes on to the mill, gets finish machined, then the deck gets milled out to examine the interior water passage core placement which has a large influence on will the cylinder wall thickness consistency.

Hopefully I'll be machining this week and have some more images and video of the process.

Chris

No Drips Around Here

I received a package of custom gaskets from Cometic today. They are the largest gasket maker in the country, supplying both OEM and aftermarket manufacturers in a variety of industries. They were really easy to work with on getting several engine case and oil pan gaskets cut from their bonded rubber AFM material and on having MLS head gaskets made from a modified version of a ZX6R part.


The clutch cover, generator cover, and oil pan gaskets are made from a chemically blown compounded nitrile synthetic rubber that is bonded to an aluminum core so they have a bit of strength and won't just rip like paper gaskets. The process was simple, I grabbed an outline of the appropriate surfaces from my CAD model of the engine, saved them as DXF files, and emailed them. A couple of weeks later- custom gaskets for a very reasonable cost. Cool stuff.

They can do the same for just about any sealing surface so if you have an old car, tractor, vintage bike, etc. that is hard to find gaskets for just give Mike Sauer at Cometic a call.

Head gaskets are not as simple a part as an engine cover gasket. They need to withstand high temperature and pressure loads cycling at a rate of over 200 times per second. For this reason I did not want to start from scratch and preferred to modify an existing Cometic part. They were able to modify one of their .018" thick Multi Layer Steel head gaskets to add material where needed and then trimmed the overall length to size.


Overall all the parts were within tolerances, so one more item completed on the road to a running engine.

That's all for now.

Chris

The Eagle Has Landed, with video.....

Or the trunnion table has been mounted on the mill. Spent the better part of a day cleaning and mounting and aligning the table properly then a lot of productive time turning the jog wheel back and forth watching the table tilt. Much more fun than watching paint dry.


Here's a short video sequence showing 1, 2, 3, and 4 axes of simultaneous movement. Many machines are really 3.5 axis which means the X, Y, and Z axes can move or the 4th axis can move, but not all at the same time. This machine is a full 4 axis machine. The last move shows the X, Y, Z, and U axis in a synchronized movement.




This added capability enables making complicated and high tolerance parts with a minimal amount of re-clamping operations but is also possible to quickly damage the part, tooling, and machine with any incorrectly programmed move.

The next steps this week are to get the suspension spider fixture plate mounted and machined then make a sample part. I'll tackle this part first as it is pretty simple compared to the engine castings.

Chris

Tooling Board Pictures

Harmony/TPI just sent me some full shots of the pattern used for the front suspension spider and clip-on mount. They are interesting to see- besides the part geometry there are riders and sprues, both of which are much larger than I would expect.

The suspension spider pattern:


The clip-on mount:


The patterns are made from Renshape, a tooling board material that is easy to machine with a good surface finish. The pattern material is protected from the abrasive casting sand by the thin plastic film draped over it. I like the fact that the film has dual purposes: to improve the surface finish of the cast part and to increase the lifespan of the tooling used to make that part.

After a bit of necessary contract work to pay the bills I'm now in the final stages of mounting and aligning the trunnion table. A post will follow shortly.

Chris

CRANKCASE PHOTOS!!!!!!!!!

I just got a great email from Harmony Castings showing some images of the first pour of the crankcase top casting.




This is the first sample and is now being x-rayed to check for porosity. Once it passes muster for that it will be sent to me.





I'll scan the part using a Romer Arm to make sure the exterior surfaces are within the tolerance range of the CAD model.


If the exterior surfaces are all within spec the next step will be to cut off both deck surfaces to check coolant passages for any signs of core shifting. Unfortunately, this will make the part unusable for anything but a machining test part.

I should get the part next week and start the process. The crankcase lower will be poured sometime next week and then i get to repeat the process.

Until then.

Chris.