Rotary Slitter for Cutting Paper or Packaging Materials - How to make it?

M

Miloc

To all Machining Experts and Enthusiasts out there,

We have a project which involves cutting/machining a rotary slitter or circular knife. I am not sure whether CNC Turning will be able to do the job but allow me to briefly describe the part description so that everyone understands what is required. The rotary slitter has dimensions as follow:

OD: 2.4"
ID: 1.6"
Thickness: 0.8 mm

There is a 30 degree taper at the OD to make it a sharp edge so that it can be used for cutting materials, for example, paper or packaging materials.

Hardness: 60 Rc

Ok, the above statement summarizes what is required for the circular slitter, now my questions are listed as follow:

1. What material is most suitable to be used for rotary slitter?

2. I would imagine that the part has to be made from some grade of tool steel and then hardened to the 60Rc level as required. Now the problem is, the thickness of the rotary slitter is very very thin, which will cause the rotary slitter to warp during the heat treatment and cause it to be out of shape. Besides that, even if the rotary slitter does not warp, will the sharp edge still be sharp? Or will it require additional touch up work to make it sharp again? I am guessing that we would need to grind it to make it sharp again. Please correct me if I am wrong about this.

Is there anyone out there who has handled the machining of a rotary slitter before? It would be great if anyone of you can share your experience with all of us here.

I am thinking of trying to hard turn the rotary slitter to try and eliminate the grinding process as well as to solve the warping problem due to the thin feature of the part.

I plan on taking a stock tool steel round bar with an OD of 2.5" and then cut it into say, a length of 75 mm. This is assuming that each rotary slitter requires 5 mm of material (for facing, part off, etc). The 75 mm length is allocated as such:

30 mm for soft jaw clamping
20 mm for clearance for parting tool
25 mm (5 x 5 mm) material for 5 pcs of rotary slitter

Hence, with the material cut to a 75 mm length, I plan to drill a hole and bore it close to the required ID size, leaving the tolerance required for heat treatment and hard turning process.

After that, this part will be sent for heat treatment and when its back, CBN or ceramic inserts will be used to turn the ID and OD Profile to the correct size and finally a parting tool to part off the rotary slitter.

My concern is whether, if there is a parting insert that can withstand the 60Rc hardness. (I checked Sandvik's catalogue and they seem to have it, will check with their tech support!) I have used inserts for OD and ID machining on 60 Rc & above parts before but never tried using a parting insert on such a hard part.

The 2nd concern is that whether the sharp edge will be sharp enough.

3rd concern will be whether the rotary slitter will still experience warping even after hardening to 60Rc?

Please advise if you feel that this method is not feasible or if you have another idea then that would be even better!

Hope to receive feedbacks and advice on this matter! Thank you in advance! :thanx:
 
Top Bottom