CNC Question

[studysession]

I have a CNC Mill:
http://www.cnczone.com/forums/showthread.php?t=7588

It is a 3 axis Sieg Model X1. Not very big but good enough for the size work I am working with.

I am having some problems understanding or knowing how to do somethings. I CNC a part and the parts is 100% finished (on one side). Now I want to turn the part over and do some CNC work on the reverse side of the work. How do I line it up to make sure all the cuts come out correctly?

There are some adaptors that I want to make for one of my RC cars and it will need to be CNC'ed on both sides of the item being milled.

Thanks in advance!!

[nervis1]

Same q I had a while back. The answer is that there are lots of ways.

A common one is to mill the inside features, like holes, slots etc and use those to fixture the part in the second operation like profiling the outside. You can build a fixture bu just drilling and tapping some holes in some plate aluminum that correspond to the holes in your part. Just use the fixture edge to line up the x so that you are parellel to the table, your tapped fixture holes should line right up.

If you need to you can indicate the part in too.

There are a hundred variations on this theme depending on the part.

You can also design in some tabs that hold the part from the outside, then flip the part in the software, and on the table. I use that one quite a bit.

[studysession]

Sorry - but you really confused me right now.

I am learning how to use AutoCAD. For my first item I am going to CAD is a set of wheel adaptors for one of my RC's. I am going to make some adaptors to allow me to use 1/8 scale 17mm hubs onto one of my trucks. I can buy these as after market parts, but want to make my own.

On side one I I will do everything I can except few minor things that have to be on side 2 of the aluminum being cut. How do I know where to place it on the milling table to make sure it is lined up correctly?

Sorry but this really confusing me.

Thanks for the help.

[Ken_Shea]

As Nervis1 says Studysession you will need to turn the part over in the CAD prior to creating the G-Code for the back side. When you turn the part over in the vise you will now need to adjust the work offset (X,Y) (using your preferred method, I use a high quality rotating edge finder most of the time), to reflect the new X,Y part position in the cad and also a new top of part position.

EDIT:
Maybe this will help a bit, you need to do the same set for the back side as you did for the top side.

In hopes it may make you feel a little better, this is a common beginners confusion, we all had/have it but in time it will become just another step.

[studysession]

I hope it becomes easier to uderstand. Right now it is still fuzzy.

Right now for learning AutoCAD I am going through a beginners book to get an idea and feel. I am at a point where I can draw and cut things that only need to be cut on one side and no where else. That I have become very comfortable in doing. Now I want to do these wheel adaptors which are NOT hard to do until I want to flip the aluminum over to cut the other side.

Still hard to understand - This coming week I want to do something to easy for learning this and getting it right before trying to do anything to complicated.

Also is there a way to have it CNC thread cutting while the stock is in the mill or does all that have to be done by hand? The every wheel adaptor will need to be threaded for a nut to go onto. I know a lot of my friends will want these adaptors as well to have something different at the track. The threading part can become time consuming if it is all done by hand only, but if that is the best method then that is what I would end up doing.

Thanks again for the help!

[JFettig]

I should have read the entire thread, but here is what I do for the most part:
I have a vice stop that I set as 0,0 and slide the parts right up to it if possible, otherwize I do something similar to what nervis1 described.
One thing you can do to make sure its very acurate is use ground dowel pins, or mill a recess into the fixture to push the parts against. preferably on 2 edges so you have x and y set.

Jon

[studysession]

It is starting to make more sense - I appreciate all this help -

You have a picture showing the ground dowel pins and how they are setup?

Thanks!

[JFettig]

I do not have any pictures, They can be found at places like fastenall, mcmaster, and lots of other places, they are basic round cylinders that have been ground. You will want to drill and ream the holes to about .0005 to .001 undersize and press fit them in.

Jon

[studysession]

Thanks again - This has definately given me a much better understanding. If anyone else has anymore tips/tricks/comments - it would be greatly appreciated.

[JFettig]

I just got my mill all set up, Here is my vice stop I made. Simple peice of steel, drilled 2 5/16" holes, one tapped to 3/8 and a m8 bolt passes through the other and is bolted to the side of my vice. It works wonderfully, very sturdy and always perfect parts.

[studysession]

Thanks - even though I do not see how that helps making sure the work is in correct position when you flip it over?

[JFettig]

well you set the stop as zero for x and the back of the vice as zero for y and work in the negetive coordinates. If the part is squair or something like that, you can flip it like you want and push it against the stop and tighten the vice. You can make stops out of all kinds of weird stuff, rods with nuts on them whatever you want, I sometimes use another vice with a peice of metal clamped into it.

Jon