Hi crew,
Can a simple crankshaft (see pic) be made in a Haas ST-15Y? If so, I’m using Inventor, what operation would be used to make the connecting rod journals?
(high school project - for display only)
Have a great day!
-Kevin
Here is a video of what I’m trying to do:
What autodesk CAM operation would this be with the endmill and groove tool?
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@KevinJanota
You might try posting this question on Facebook as they have a lot more members there with more experience.
@Rumpelstiltskin
Great idea, thank you!
I don’t believe you will able to get tool path out of FUSION with out major sketch/relationship work to drive the tool paths.
I don’t believe that eccentric turning is native to fusion.
did you figure out your tool path yet by chance?
While I can’t speak about programing with Fusion, I have machined many billet cranks for full-sized racing engines over the past 56 yrs … Making a demo crank like this, on a lathe (especially your ST15Y) is relatively easy. You don’t give any dimensons, but let’s assume it’s sized well within the working envelope of your ST15-Y, From your pic it appears to be a 4 rod / 5 main crank, although one of uncommon rod pin indexing. Most 4 cyl cranks are “clocked” with the two outer pins ( aka rod journals) at TDC, while the two inner pins are at BDC. This not only helps balancing the crank but also balances the firing order torsional loads; More importantly, for your demo, it also significantly simplifies making the crank. Another couple of design change you may want to consider: 1. Make the rod journal and main journal diameters as large as reasonably possible, so they overlap radially as much as possible, given the stroke. Bias the main’s diameter so it is larger than the rod journal diameters. For example, a crank of 86mm stroke, would typically have a 60mm main with a 50mm rod journal. This gives a radial overlap of [(60 + 50)2] - (86/2) = 12mm. This adds significant stiffness to the crank, both as a beam and torsionally. Most of all the added stiffness over your current design will make the crank much easier to machine. Another reason for main & rod overlap is so the crank can be drilled, if needed, for oil passages to get lube from the mains to the rod pins.
2. Depending on block cyl bore spacing, connnecting rod bearing width, as well as main bearing width, design the crank with minimal width between rod & main brgs; keep the counterweights’ OD as small as possible (this helps reduce tool overhange) and keep the counterwts narrow; make the “snout” and flywheel end of the crank as short as possible. This makes balancing much easier, and also adds stiffness - making it easier to machine.
For your demo crank, take a look here:
http://modelenginenews.org/techniques/crankshafts.html
There are many ways to do the job, but I would suggest machining between centers ( using off-set center drilled holes to index/stroke the crank’s rod pins). Easy to program as relatively simple turning. Best of luck with your project and, please, keep us updated.
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Hi Marcus, some reference sketches might be a good idea. I was able to get the general motion with a multiaxis contour, but it just makes a single loop around. I did copy that operation and just change the offset each time to create a step-down effect. But, when I try to post process I get an error.
We’ll keep trying!
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Hi Tom, thank you for all of the great information! The crank is for total display purposes only : )
Its a project a student found in an old book and wanted to give it a shot and learn some CNC along the way. The stock is set for 2" diameter and 9" long, so not very big. I’ll be sure to pass your info along to the student as I think he will want to make the adjustments you suggested to make it more realistic. The offset center drilled holes is a good idea, I did not think about that until you mentioned it, thank you. We were hoping to use our live tooling and Y axis to make it…just because, no other good reason. If we are able to program the motion we want I’ll be sure to post it here for all to see.
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Hi Kevin, you could use the the live tool / Y axis to rough out much of the metal between counterwts at the rod pin locations. I have a long-time friend, Tom Leib who owns Scat Crankshafts (www.scatcrankshafts.comhafts.com/) and this is how they often mill / turn some cranks they manufacture. This is often much easy than using a turning tool with long “hang over” on the interrupted cuts. Basically, Scat mills a “flat” or arc above the rod pin, starting with the pin at BDC from the live-tool’s axis, then index the crank 15° and repat, with cuts to a depth needed to rough out the pin, then turning round.
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Fusion is not the best cam for this part. I bet after hours of work you could develop tool path.
I would Rgh/fin OD, Groove to rod journals dept. then a C-axis approach to rough out journals, the tool should move like a piston rod. tool normal to the tangent of journal. while X,C make moves.
If possible on HAAS eccentric turn the rod journals, I don’t believe the HAAS Control can do that… maybe?
@Tom-AMS has so really good ideas for mill/turn approach.