Multiside milling

[ssozonoff]

Hi,

I need to mill a piece as seen in the attachment out of a cube of delrin.

Since this is the first time I do multi side milling my question is how does one typically deal with holding and aligning the target correctly.

As seen from the side, lets say I start by profiling the inside, then the hole at the top of the triangle which I can use to hold down the part while I cut the outside profile. At this point I am done with this side.

Next I want to drill and bore from the to of the part (top of the triangle)
I will need to remove the part from the hold down and turn it upright.

How do I re-align everything so that when I set my new zero point I will get the holes in the correct place. For example the X axis aligned with the routing table X axis?

I guess I can think of solutions by making a special hold-down piece etc ... but what I am looking for is the little tips and tricks which might make this task simpler than I think. Especially since this is like a one time part.

P.S. Any thoughts on Rpm/Feedrate for delrin?
Whats a good endmill to use for Delrin?


Merry Christmas,
Serge

[rowbare]

You mention an attachment... Did you forget to post it?

[Geof]

To answer your rpm, feedrate and tool question first:

With coolant Delrin can be machined at the same speeds and feeds as aluminum.

Without coolant maybe halve the speed but keep the feed almost the same. You want nice healthy chips coming off and carrying most of the heat from the cutting away in the chip; a slow feed leads to more rubbing effect and possibly melting of the Delrin.

Ideally Delrin likes tools with zero top rake much the same as would be used on brass, but they have to be very sharp; do not use any tool if it has touched metal.

It is possible to use micrograin carbide tools intended for aluminum alloys. These have the mirror finish and do have considerable top rake so the Delrin has to be held very firmly which is difficult if it is just held in a vise as it has low friction and tends to ull out under the cutting load.

Fixturing and finding reference points:

If you can devise a fixture which you leave the part attached to as much as possible, and just flip the fixture around in a vise, that may be the simplest; without your picture it is difficult to make any other suggestion.

For re-finding reference points designate a corner or some feature that will be accessible in all the orientations of your part and then work from this. The reason for suggesting a fixture that the part stays with is because the reference point can be on the fixture, or there can be two or more reference points.

[ssozonoff]

Thanks guys,

I did forget the attachement, realised it in the car yesterday :-)
I have attached it now.

Geof, thanks for your tips. I will try and find an online store where I can find an appropriate endmill.

I have never milled alu either so I don't know what speeds and feeds one uses :-)

I would just mention that I am actually using a router for this so my rpm range is currently 10k to 30k

Merry XMas,
Serge

[audioandy1762]

Hi

Have a look here, might be some endmills suitable for your application

http://www.damencnc.com/damencnc.php...60831062d9bc52

Andy

[ZedB]

Hi Serge,
I am replying to your post just to contribute my two cents to setting the part on the machine and to set the offsets (datums) from which you can do the machining.
Looking at the date you posted the topic, I think you have finished the job already, but in case that not, I would machine fisrt the side with the profile and hole (as you sugested). Then I would make a jig to hold the part (cube) in place - a pin which would locate the part through the hole. Then I suppose you have a horizontal machining centre - you use the CNC Offset Calculator to set offsets on the three sides (say centre of the holes will be your datums). Then you set the jig on the machine, measure the position of the pin and your machine will calculate the offsets from the code generated by the CNC Offset Calculator. You can use AutoCAD dxf drawing to set offset positions in the CNC Offset Calculator. You can download a demo program from http://www.cncplusplus.com .
It may help you next time you do multiface machining.
Best Regards,
Zdenek

[ssozonoff]

Hi,

Thanks for this post and some very useful information.
Since I was basically prototyping I was looking for some quick and dirty solutions short of making a jig.

I ended up basically choosing a distinct feature to set as the reference point for the two sides I had to machine and then eyeballing it.

Thanks,
Serge

[LeeWay]

You can also take a look here.
http://www.vectric.com/WebSite/Vectr..._tutorials.htm

The Porsche at the bottom is 4 sided machining. Take a look at that video.

If you start with a large enough block, no special features or fixtures would be needed.
A simple vise could hold it with a stop.