[RustedOut]

For example, I think they made petals with those little clips to prevent any balancing issue.

I think you're right about those little tabs, keeping the pedals spaced around and not being able to shift. Some of the mills these are used on run pretty darn fast. One thing I've read is the gripper needing to have the ability to center itself above the pull stud. So I've wondered if that was what the o-rings were for, a slight cushion to allow a minute amount of movement in the bore.

Bob

[Azalin]

That is partly true. Sometimes my 16 months young daughter wakes up in the middle of the night and once she's awake she wont sleep again. So we play until morning.

[G59]

In a 1 piece design, you don't need the little tangs or spacers.
The one piece design is much simpler and only one part. No springs or spacers or special collets holding it all together.
If you take time to figure out the sleeve and the proper size it should be, you'll never run into balance issues, as the petal will become closed when pulled into the sleeve.
The advantage of the multi part gripper is of reduced wear on said sleeve as it is of low tension design. Just lubricate as needed. You could also say it's more serviceable as compared to single piece design.
As for balancing, it's no really a matter of keeping small or exact spacing, as I have told you, once the petals are compressed, they butt against each other and on the circumference of the pull stud of the tapered tool holder.
That is what keeps it in perfect alignment and maintains the proper spacing of the petals.
If your dead set on making the multi piece design, just say so and I'll refrain from making anymore comments on how to make a pull stud gripper one piece.

[Azalin]

Here are the tools. They don't look sweet but I believe they'll just work.

[engnerdan]

Here is how the 4 pedal gripper is made on my BT30 spindle.
Attachment 301162Attachment 301164



-Dan

[Azalin]

Thanks engnerdan.

Well, I just finished mine.

[Azalin]

How do you determine how many belleville washers is needed? Does the drawbar tension dependant to the amount of belleville washers? I mean I have 50 washers right now and I'll start the solidworks design but I don't know if the washers I have is enough and If needed more or less.

[G59]

Washers when compressed give so many mm. How many mm depends on how far you have to push the drawbar to ensure full release of the tool.
So if a washer can compress 1 mm(exaggerated for simplicity's sake), then for 10mm stroke you need 10 washers.

[Azalin]

OK Thanks.

[mactec54]

How do you determine how many belleville washers is needed? Does the drawbar tension dependant to the amount of belleville washers? I mean I have 50 washers right now and I'll start the solidworks design but I don't know if the washers I have is enough and If needed more or less.

It's not only the movement that you need as G59 has stated, each belleville washer has a load rating, so you have to know what this is for the belleville washer you have, from this number you will be able to calculate the number of belleville washers you need to get the lbs rating you need, stacking them different ways can also affect how they are rated, movement is never the issue

The normal load for a 30 Taper is 5340N or 1200lbs-F, if this was a threaded draw bar it would be 40 foot lbs

[G59]

It's not only the movement that you need as G59 has stated, each belleville washer has a load rating, so you have to know what this is for the belleville washer you have, from this number you will be able to calculate the number of belleville washers you need to get the lbs rating you need, stacking them different ways can also affect how they are rated, movement is never the issue

The normal load for a 30 Taper is 5340N or 1200lbs-F, if this was a threaded draw bar it would be 40 foot lbs

Yup, you beat me to it, I was just going to add the washer rating. But you have to consider travel also.

[Azalin]

Thank you both.

The drawbar travel will be 5 to 6mm. I think it's time to add the 8bar 24l compressor I have to the calculation. What I don't have yet is an air cylinder. According to the online converter 5340N is equal to 52KG F. I need a cylinder that can generate that force with 8 bars.

The washers I have are 10x20x(1mm thick if I remember correct). I bought them from a local hardware shop so I need to find the appropriate datasheet online.

Sorry if I'm making no sense. Trying to learn things for hobby.

[mactec54]

Thank you both.

The drawbar travel will be 5 to 6mm. I think it's time to add the 8bar 24l compressor I have to the calculation. What I don't have yet is an air cylinder. According to the online converter 5340N is equal to 52KG F. I need a cylinder that can generate that force with 8 bars.

The washers I have are 10x20x(1mm thick if I remember correct). I bought them from a local hardware shop so I need to find the appropriate datasheet online.

Sorry if I'm making no sense. Trying to learn things for hobby.

I'm sure there are many listings for belleville spring washer ratings, here is one just for an idea, as for your air cylinder you can make this yourself, you can make a multistack air cylinder ( more than one piston 3 or more ) to get a more compact cylinder, for the force you need

McMaster-Carr

[RotarySMP]

Mactec, thanks for the advice on the grease ring, and design.

Suat, nice work turning the gripper.
Would you mind posting a drawing of your gripper dimensions please?

You missed a Zero. 5000N is about 500kg force, not 50kg. That is why you will probably need a multi stage cylinder to get the required unlock force instead of a huge diameter cylinder using shop air.

Stack bellvilles back to back "...)))..." and the force is multiplied for the same travel. Stack then front to back, "...()()()..." and the travel is multiplied for the same force. The design I picked up somewhere has about 78 bellville washers in groups of three . like this...

((()))((()))((()))((()))...

Mark

[Azalin]

Mark I'd like to but I made fingers in my manual lathe so I don't have it BUT if you allow me a few days I can draw them in solidworks and will happily share with you.

I waited to start the SW design because I was unsure if I'd use finger style or ball style gripper. Now that I made the finger style gripper I'll start the designing.

There is one more thing I need to make to the fingers. I haven't grind the angle to allow the O-Ring to open. I am still thinking on that but still don't know how do I to that. I can grind by hand but I don't like this idea as I want each fingers grounded equally.

@Mactec54
Yest that's the one. Thank you for the link.

[Azalin]

Mark
I did a quick sketch of my gripper but the dimensions are quite funny (because I cut it without a sketch) so the drawing needs be revised. Let me know if you still want it.

[RotarySMP]

Yes please.
Mark

[Azalin]

OK.

I made a new one. It is a little shorter than previous, much similar to the ones that Chinese sell. I'll send the files of both. Just PM me your email.

[Azalin]

You missed a Zero. 5000N is about 500kg force, not 50kg.

Can you send me link for a suitable air cylinder that can provide such force using an 8 bar compressor?

[mactec54]

Can you send me link for a suitable air cylinder that can provide such force using an 8 bar compressor?

Here is one, you can make it yourself,they cost lots to buy them, you can also do air over oil this can be very effective for this type of operation

Multi-Power Cylinders ~ Fabco-Air, Inc. ~ Gainesville, FL