CNC Machining Bearing Blocks

[magnets]

We're making an offseason drive base, and we'd like to make our own bearing blocks on our CNC mill, but I can't think of a good way to hold down these parts for machining.

Does anybody have a clever way to make these parts?

[R.C.]

Softjaw? Also Picture of what your trying to machine?

[magnets]

Originally Posted by R.C.

Softjaw? Also Picture of what your trying to machine?

Sorry, I should have been more specific. We're trying to make 6 or so of these:


Ideally, we'd make all of them from one big block of aluminum.

[techhelpbb]

Toe clamp the block and a piece of sacrificial material to the machine deck.
Tab the flange so they do not float till after all the isolation is done.
Then cut them loose.

Use a standard drill to rough out the pockets behind the flange and around the tube.
Then finish it with an end mill.

If the inside is for bearings probably want to use a boring head.
If the outside is a critical dimension you might also be able to use a boring head.

There are other options.
Like using a lathe.

[sanddrag]

We do ours out of 2x2" square bar stock that we hold in softjaws in a 6" vise. We do two at a time out of a piece of 6" long stock. We machine the bearing side first, then pull it out, machine the softjaws to that profile, flip it upside down into the softjaws, and then machine the side with the tube. Simple process. I recommend http://monsterjaws.com/

[Mr. Mike]

Saw stock slightly larger than finish size.
Put flange side down in vise. Hold onto slightly less than flange thickness.
Rough machine hub OD and ID then finish both.
Mount soft jaws in vice and machine a pocket to fit the hub OD.
Clamp part in soft jaw. Caution not to crush hub.
Machine flange shape and holes.

Option if you have a lathe and round stock.
Do all round features then go to the mill to finish flange shape and holes.

[Cory]

Do you have a reason for not buying these?

That's the best bang for the buck you're gonna get. If you want to learn to use your mill to the fullest extent of its capabilities, that makes sense. But this might be a problem to throw money at.

[Michael Hill]

Originally Posted by Cory

Do you have a reason for not buying these?

That's the best bang for the buck you're gonna get. If you want to learn to use your mill to the fullest extent of its capabilities, that makes sense. But this might be a problem to throw money at.

I'd second this. 6 weeks is a short build season. If you can buy it instead of build it, then buy it. This is a lesson I learned last year.

[magnets]

Originally Posted by Cory

Do you have a reason for not buying these?

That's the best bang for the buck you're gonna get. If you want to learn to use your mill to the fullest extent of its capabilities, that makes sense. But this might be a problem to throw money at.

Normally, we would do that, but money for buying robot parts has become an issue for us, and we'd still like to have a practice robot. We could save some money making these and the little cams ourselves.

My plan was to make some of the parts we usually buy on our CNCs on the first few days of build, as the CNC is not usually in use on these first days, and we have students who would do this.

I was originally planning to just do a row of 6 or 10 on one piece of aluminum, but I'm thinking it may be easier to take one, machine the top (the tube end that fits into the other side) all the way down to the base, then put it in a fixture plate with a 1.375" wide square with radiused edges to locate it to machine the outline, the mounting holes, and the bearing flange c-bore.

[kaliken]

Here you go. I remember seeing this a while back..

Blatantly stolen from team 254's 2011 build blog.

http://blog.2011.team254.com/wp-cont...1/DSC_3891.jpg

[Isaac501]

Originally Posted by magnets

Normally, we would do that, but money for buying robot parts has become an issue for us, and we'd still like to have a practice robot. We could save some money making these and the little cams ourselves.

My plan was to make some of the parts we usually buy on our CNCs on the first few days of build, as the CNC is not usually in use on these first days, and we have students who would do this.

I was originally planning to just do a row of 6 or 10 on one piece of aluminum, but I'm thinking it may be easier to take one, machine the top (the tube end that fits into the other side) all the way down to the base, then put it in a fixture plate with a 1.375" wide square with radiused edges to locate it to machine the outline, the mounting holes, and the bearing flange c-bore.

If $20 for a properly machined and toleranced part is a concern, a pair of drilled and tapped holes the appropriate distance from the bearing is "free".

Use button head screws as retention for a flanged bearing.

[Cory]

If you want to make these for the season, make a few now to understand the best sequencing and workholding.

They're relatively simple parts but they do require good tolerancing and concentricity to be held between the bearing bore and the OD/ID of the sleeve on the backside (depending on which side you're making). You can easily create scenarios where the shaft is hard to get through both bearings, or doesn't spin nicely if you don't do it right.

I would caution anyone from blindly copying the fixture that 254 made that was linked by two posters in this thread. That was the first fixture I designed and is suboptimal in a number of ways. It took 4 years to get a combination of good fixturing/setup practices and CAM tweaks to get programs we can confidently run for good parts the first time, every time, with minimal operator intervention and without ejecting parts from the fixture/breaking tools/not holding tolerances.

Far better to start out with soft jaws, as you will need to know how to cut them for far more parts than just bearing housings.

[Jared]

Our team is considering a similar process.

Cory pointed out that runout can be an issue with these parts, so you may want to consider creating the sleeve OD and bearing bore on a lathe, then cutting this part in half and using each as one side. This way, you have matched sets of bearing blocks. Also be sure to use one of these round fixtures to locate the part when setting up on the CNC.

These likely wouldn't be difficult parts to make by hand if you were willing to give up the neat shape on the outside and the rounded corners on the 1.375" square.

The procedure I've come up with involves one 0.25" thick 3" x 3" fixture plate with a 1.375" wide square with .250" radiused corners for the square feature on the bearing blocks. The plate would also have two threaded 10-32 holes for the two mounting bolts in the bearing block.

My most efficient setup is as follows:

3" x 12" x 1.25" aluminum stock for 6 blocks (stock is extra tall so that the vice can grip the bottom 0.250")

1. Machine bearing bores, sleeve OD, rounded square feature on base, .196" holes for six bearing blocks.
For this operation, hold the stock in a vice (or two) so that the lowest point of the stock is about 0.25" below the face of the vice jaws.
Because the stock is a little bit oversize, zeroing only needs to be accurate to .050" or so.
Also, the bearing bore and the sleeve should have little runout as they are machined in the same operation.

2. Cut out individual blocks on bandsaw
Again, this doesn't need to be super accurate. It's good as long as you don't cut into another bearing block.

3. Put in lathe and face off 0.250" (the stock was .25" too tall)

4. Flip upside, put in fixture. The 1.375" square should fit nicely into the fixture plate, and you can put two 10-32's through the bearing block into the fixture plate to hold it down.
Now, locate part with a dial test indicator using the bearing bore. You should be able to get within .001" with a decent dial indicator. You shouldn't have to re-zero between bearing blocks if your fixture plate has good tolerances. It may be worth making the 10-32 clearance holes in the bearing blocks the next size down (0.1935") so that the fit more accurate with this fixture.

Now, machine the bearing flange c-bore and the outside profile. Use a countersink bit on a drill press for the two 0.196" holes.

You could honestly skip this last step and put in the bearing flange counterbore on a lathe and just the cut the outside profile on a bandsaw, and you could skip the fixture plate.

If my poorly written description doesn't make sense, let me know, and I'll put up a picture.

[AdamHeard]

I'd argue that more time should be put towards fundraising, and COTS should be used more.

The in house CNC is more useful during that time for prototyping, or for machining things that can't be bought.

Imo teams should only be making bearing blocks now if they are continuing a legacy design of their own (and therefore can use previous year's for practice bots).

[Richard Wallace]

Originally Posted by Cory

Do you have a reason for not buying these?

That's the best bang for the buck you're gonna get. If you want to learn to use your mill to the fullest extent of its capabilities, that makes sense. But this might be a problem to throw money at.

Thanks for the link, Cory. I knew these existed but had forgotten where to look. Pretty sure I first saw them on one of your team's robots many seasons ago.

Two questions not immediately addressed at the WCP link (since my iPad doesn't run CAD): (1) what is the material? and (2) do these blocks accept FR8 bearings?