Bellmouthing on sunnen hone

Hi,

We are honing some aluminum cylinders on our MBB-1660 Sunnen honing machine. Following the instructions from the manual we are getting some bellmouthing in the order of 5-10 microns on either end of the part. Have spent a fair bit of time trouble shooting but the problem persists.

At this point we will use the truing sleeve/true the stones, then run about five parts at 5 micron bellmouth. As we get to 15 or 20 parts the bellmouth gets to be about 10 microns at either end which we cannot accept.

I've heard that using this machine properly will yield nearly perfect bores. Would love to hear advice from those experienced honers out there!

Not sure if this is important but we are achieving .3 micron surface finish which is our target.

thanks,
Joey

Bellmouth is ussually caused by incorrect stoke length or pattern. The stone needs to be worn evenly to achieve precise tolerances. Make sure you are going far enough off each end to wear the stone ends.

Another cause would be rocking the part but youar getting the correct hole geometry for a few parts so stroking is probably the problem.

Athack

Sunnen tech services have helped me in the past, good people. With the tolerance #s you are looking for I'm surprised you don't have to true the stones more often. Does your machine have power stroking? It's easier to hold tolerance if your machine has it.

Use their troubleshooting chart. I think it will tell you to refine the stroke distance, but if that doesn't work, to change the length of the stone and/or the shoe by grinding them down.

CH

IME you are overstroking on each end. Continue to shorten the stroke until the bellmouthing ends. .0004" bellmouth is unacceptable, you should be able to tune that up in short order. How large and long is your bore, and how much do the stokes stick out each side?

Properly set up I wouldn't expect to ever need to use a truing sleeve on the proper stone after the initial break-in.

Sometimes you need to dress down the ends of the stones a little bit. or reduce the stone width at the ends so they wear faster.

(I just use an old stone and rub it against the honing stone in use ,to do the dressing)

This is not the perfect solution because there is a lot of trial and error involved, and the stones wear rapidly.

I had a repeat job ,for a time, honing 1 1/8 bores 12 inches long in stainless steel. I had a 12 inch long honing mandrel.

I found ,through long experience, that the best way to eliminate bell mouth was to keep the end stones dressed down and hone a barrel shape first. Then I carefully increased the stroke length and reduced the cutting spring pressure, to hone the ends and make the hole uniform in diameter for the full length.

I don't know what your parts look like , but the foregoing description will give you an idea of what is involved.

js is right, you need to cut down the end of the stones some, start by just chamfering them and keep cutting back to find the optimum length you need.
A stone will rarely work right out of the box, but it will require some cutting down.

Since you are consulting the manual I assume you might be new to honeing so I'll give you some simple general rules to live by.

To fix bell mouth or blowen ends:
Higher spindle RMPs, cut the stone lenght down, shorter - faster strokes.

To fix barrel shaped holes or blown middles:
Slower spindle RPMs, longer stone possibly longer mandrel, longer-slower strokes.

Bear in mind that maual honeing is a very operator dependent process and a setup that works perfect for me doesn't work for the next person that sits down to take the job over, or it take a few parts to get the setup to work.
Of course finding what works requires running the parts undersize and seting them aside untill you get the job running good.

As far as your question about the machine capability, yes, in the hands of experianced operator a Sunnen hone can produce hole geometry that will rival anything found on the planet made by any process. The finest holes are typically lapped on the machine, but honeing can be just as good if part geometry is favorible to honeing.

I haven't see a lot of honeing questions on here so I hope this helps. Let us know if any advise worked for you.

There has been some decent ideas offered here. Maybe your best bet is to rough hone and then turn to lapping. You will be able to hold 2microns all day without even thinking about it.

Good Luck

Athack

need more information

We need some more information to help you solve your problem.

What is the bore diameter?
What is the bore length?
Wall thickness?
What mandrel are you using?
What stone?
Pressure setting on the machine?
RPM?
Do you have a double adjustable spindle?

The machine will do the job, but with the tolerances you are try to hold everything has to be correct.

honing

JS and Tank are right on. I have years of exp. and you always want the barrel shape until getting to the end because hourglass is hard to get out. You have to cut out the two ends and use the middle of the stone until you get to the barrel shape again, then take the barrel out last.

You are probably using a longer stroke than necessary which increases your mandrel pressure onto a smaller area. Also don't use the heavy setting. Set that to zero. Use the light settings and try to stay in the middle of the pressure scale. You cannot use both at the same time so always check the heavy dial.

BTY, if you are fitting pistons in a multiple cyl block, always hone cyl's first, then start fitting the pistons to the largest cyl first. Then if you miss your tolerence, you have another cyl to go to without scraping the piston.

Good Luck.

BCook said:

JS and Tank are right on. I have years of exp. and you always want the barrel shape until getting to the end because hourglass is hard to get out. You have to cut out the two ends and use the middle of the stone until you get to the barrel shape again, then take the barrel out last.

You are probably using a longer stroke than necessary which increases your mandrel pressure onto a smaller area. Also don't use the heavy setting. Set that to zero. Use the light settings and try to stay in the middle of the pressure scale. You cannot use both at the same time so always check the heavy dial.

BTY, if you are fitting pistons in a multiple cyl block, always hone cyl's first, then start fitting the pistons to the largest cyl first. Then if you miss your tolerence, you have another cyl to go to without scraping the piston.

Good Luck.

Click to expand...

The idea of making a parts geometry incorrect and then fixing in the end is just wrong. If you can not achieve the hole geometry because of undercuts voids or uneven lands you need to try a different machining process.

Yes you can turn a part to .0003" but it is much more reliable to grind a part to .0003". Also the part has less variance in other factors. Roundness, wave and bow.

I think if you try lapping you will be very pleased.

sunnen honing bellmouth

Have not gotten a chance to get back on the machine. I have talked to sunnen tech and after reading all the replies I feel that I have a path forward. I feel better knowing that we are inexperienced over here and should be able to get good parts once we get to know this machine and the process.

So, we will shorten our stones, shorten the stroke and see what we get.

thanks for you input!
Joey

I've spent a lotta years doing submicron work on a Sunnen hone and there's no question that when you get the parameters right it will do the job. The only problem is that the whole thing is highly operator dependent. It takes conscious thought about how the process works, the right attitude and some practice to get really good at it.

CH

athack said:

The idea of making a parts geometry incorrect and then fixing in the end is just wrong. If you can not achieve the hole geometry because of undercuts voids or uneven lands you need to try a different machining process.

Click to expand...

I agree, what I ment was as you are figuring out your setup on the first few holes stop short of taking them into size with poor geometry, leaving yourself some stock to correct your set up parts. Of course this only works when you have multiple parts. Once you're running good there is no reason to run them u.s. and come back later.

Also, another point touched on here but not emphesized enought is to make sure your mandrel is running as true as you can get it. Runout will cause blown ends. Countless times I sat down to help someone on a hone and there was way to much runout. (I always check the runnout first thing when taking over someone else's setup). Some people stop and call the run out good when they are less than a minute and a half from having it run out perfect. This is one place where just a little more time spent on your setup will save you all kinds of time and frustration.

nailed the setup near perfect parts!

Okay!

After talking to sunnen a couple of times and shortening/eliminating stones and shoes I have good results. About 2 microns variation in the length of the 4 inch long part. No real barreling or bell mouthing anymore. This machine does leave a little up to the operator once the setup is right. Seems like getting perfect parts has more to do with consistent stroking by hand at this point.


So I am using a single three inch long stone for a four inch part. Over stroking about 1.5 inches on either side. Shoe length must match stone length for good results.

thanks for the help!
Joey