[Tr2sa]

If got your attention:

I am looking for a supplier for the parts, material is 1.4301/AISI 304, parts are described in attached drawings. Production quantities start at 1000 parts, yearly need is around 60 000 each. Validation and qualification samples are mandatory. If you have anything to clarify, feel free to ask.

To avoid previous pitfalls at the start:

*Tolerances are metric
*The radii are correct, 0.02 is maximum allowed
*Parts have to be concentric

[zedzero]

Tricky little job....just interested,how do you check the .02 internal radius

[Rapid Tech]

My guess would be an optical comparitor. A tricky job indeed.

[Tr2sa]

My guess would be an optical comparitor. A tricky job indeed.

Correct - the first test is optical compare. The main problem is that the assembly loses critical function if radii tolerance is not met.

[lerman]

Instead of the small radius? I wouldn't think that would impact the function.

Ken

[CNCDesk]

Is an undercut acceptable?

Ron
__________________
Ron Smith
"The Cyber Shop"
1424 Kansas Lane
Gallatin, TN 37066
Phone: (615) 772-7990

[handlewanker]

Hi, I would think that the quantity and tolerances involved would lend itself to sintering.
Ian.

[Tr2sa]

Unfortunately even small undercut can be cause of unwanted effects in assembled device. Modifications to the parts are not acceptable at the moment.

Is an undercut acceptable?
Ron

[Tr2sa]

Hi, I would think that the quantity and tolerances involved would lend itself to sintering.
Ian.

Sintering is an interesting option for micro manufacturing; I am not familiar with the current sintering possibilities. What I have found, is that lots should be bigger to be cost effective - monthly volumes around 100 000.
Also offered raw surface finish seems to be close but not enough without secondary smoothing operation. In addition to that there are ejector marks, differences related to stress tolerance and wearing.

[handlewanker]

Hi tr2, know what you mean, but when the desire outstrips the ability to satisfy the customer's needs, then it's back to the drawing board to modify until you can.

I was taught this by the chief mechanical draughsman in our drawing office, and it was a rule that he applied to all would be design engineers who made drawings of things that could not be made.

This concept was also applied to some of the designs of parts supplied by Rolls Royce at a firm I worked for in the UK in the '70s, and there were many modifications that otherwise would have made manufacture an impossibility.

At my last employ, before I retired, we had stainless steel sintered parts made that were vibro finished to give the surface finish required, as the volumes exceeded many thousand parts per week.
Ian.

[g-codeguy]

Yeah, been times I would loved to have some of these engineers make parts per their own drawings. (chair)

[robinhuxd]

Sintering is an interesting option for micro manufacturing; I am not familiar with the current sintering possibilities. What I have found, is that lots should be bigger to be cost effective - monthly volumes around 100 000.
Also offered raw surface finish seems to be close but not enough without secondary smoothing operation. In addition to that there are ejector marks, differences related to stress tolerance and wearing.

You can try automatic lathe machine that is used to make electricity plug pins. If qty is real, this can be made less than 0.10usd/pc. I do not have this machine but I can help if you are interested. My email is sumomoto@gmail dot com

[PixMan]

Two of my former employers do this type of work on their Star and/or Tornos single-spindle sliding headstock machines.

http://www.compsources.com/
http://www.swissturn.com/

If you're in Europe, the 1st is the better choice as they partner with several firms in France and Switzerland.

[Tr2sa]

Few sample lots have arrived. Few photos with problems encountered.

[handlewanker]

Hi looks like a parting off burr.

It appears that the part is made with the small diam being the last part to be parted off on as it has less material to go through, hence the burr in the bore.

I would suggest that if it was done on a double spindle CNC then the part should be parted off at the big diam and the second spindle would hold it on one of the smaller diameters for a clean drilling operation from the back, impossible to do if a regular capstan type machining set up is used.

The burr is pretty bad and it would appear that the supplier has not bothered to inspect the product before delivery, or that the specifications did not call for a "burr free" part.

In any case if the suppliers are using regular single spindle machines, they will have to have a secondary operation to clean drill the bore.

The other way the situation could be overcome is if the parting off operation was done in two stages, first down to a diam just a few .01mm's under the bore size, then when the drill goes to depth it will cut through and leave a burrless bore, only problem is to ensure that the drilling force doesn't break the part off the pip, so the drill would want to be done in two stages too, so that the final drilling just breaks through the bore.

Time wise it will add about 20% to the cost price for the extra ops, and if done in this manner with a single spindle CNC, there should be no problem with work stations as on a capstan type machine.

This is a problem for the supplier to worry about and if they are in the turning business and competitive, it should be a "piece of cake", LOL.
Ian.