Machining of pipes

In 1st Opn. perfectly through the job.

In 2nd Opn. face with respect to first face. i.e., in 2nd opn. align the job (first opn. face) perfectly and machine 2nd opn with respect to first opn face.

while machining solid pieces, the flatness is less than 0.02mm but in this case (Pipe) i'm getting 0.2/0.25mm. Also in the 2nd opn, i'm resting the face of 1 opn.

Also the in both operations OD has been clamped. Runout of 0.15/0.2mm in the pipe. The OD has not been turned in both operations.

So to better understand your process, you start with a piece of pipe, chuck it using 3 jaw chuck in a CNC and face one end. Then unchuck and rechuck in (same or different) CNC and reface other end. At that point what you call flatness is off by a factor of at least 10 times?

milo

Another cause could be the chuck closing pressure! if your machine can use collets, this would spread the clamping over the whole diameter not just the three points which may just be deforming the tube enough to give the error! As has been said, a bar loader, parting off to length is an excellent method, but going through a collet! It all depends if your pipe is in long lengths or rough cut first!

Possibilities to check include alignment of tools to spndle alignment and trueness of 3 jaw chuck, camber of tubing, and rigidity of three jaw chuck. Plus alignment / runout of spindle

milo

Sounds like a problem with run out of the chuck or bad work holding! check out the two with a DTI. If the chuck is good (I suspect it is on a CNC) Then why not opt for an expanding mandrill which would hold the piece concentric and help stop any bad loading of the piece! Is the operator a competent engineer or one of the vertical brain dead who just push the button! (no offence, we all started somewhere!)

Probably due to misalignment when repositioning for 2nd op. Also with the thin wall section you chuck clamping pressure may be too high. If possible I would bar feed longer length bars thru the spindle bore and part off to length. This takes out any possiblility for positioning error when flipping the tube over.

Dear All,

I am looking for USA manufacturers of HDPE piping machinery. I do apologize for not being directly in the line of questions and answers but perhaps one member will supply this . The ultimate use of the of the piping is for drainage in c onstruction and sub-division of new homes. Thank you in anticipation for your assistance.

Labor

Respond to me by private emailing (click on my name in this post and find the send email link on my page) with your professional contact information including email and location and I will try to assist. WHat is your expected source of feedstock?

milo

as others have commented the best method is to part the pieces off as less handling means less errors, also by its definition pipe is not round and i would say you will not stand much chance of getting any consistence without considerable effort with a dial gauge and i get the impresion you want quick and easy answer. the last thing you could do is put the pipes on a mandrel and machine both ends in one opperation.