Semi finish or not?

[DavidB]

I have roughed out a 4330V componenet to have 1mm stock pre heat treatment.

 

After heat treatment part is now 220 – 240 KSI, (48Rc)

There is a lot of surface machining required.

I normally semi finish with a ballnose leaving say 0.2mm (.008") then finish with another ballnose to keep wear down on the finishing tool.

 

Do I need to semi?

Would you go straight in with a finish cut?

 

Cheers Dave

[ostie01]

For me, a finish cut will always have it's place.

 

Jeff

[gaijin_2007]

I'd semi.

Every time.

 

It's the only way to guarantee the consistency of the finishing process.

Most of the issues I've ever come across with finishing has been due to previous processes, inconsistent material depths being the most common culprit.

[DavidB]

I've always semi finished but thats because I came from a tool making back ground.

Now I do Aerocraft components I didn't know if a semi was overkill.

 

[ 09-11-2009, 01:36 AM: Message edited by: DavidB@Rosebank-Engineering ]

[Colin Gilchrist]

Lots of factors here Bruce, so it kind of depends.

 

How big is the part? How rigid is the Setup? What tool(s)? What machine?

 

If you have this on a 5 axis machine and can rotate the part/tool to keep the cutting away from the tip and out where there are some flutes it would help.

 

In general, semi-finishing the part down to a consistent layer of material to be removed will help increase your feed rates. Remember that you have to program your feeds for the worst cutting condition that tool will encounter.

 

What kind of scallops are left over from the roughing? If you have a very consistent material depth, you could probably save some time and just finish right to the net part shape.

[Gordy Programmer]

I do mostly medical and aero and for the most part I do not use a semi finish. We will just rotate tools as required (finisher becomes the rougher and put a new finisher in).

[cadist]

With 48Rc I always prefer semi-finish leaving 0.1mm stock, so the finishing is consistent.