My CNC Setup & Newbie Questions

[Chuck]

Hi all,

as promised, I'm posting pictures of my new CNC setup. It's still a virgin as I have yet to figured out how to cut my first part. I was hoping someone in this forum could help me out.


The following are the front & back view of the parts that I'm trying to make. The third image show how the part is orientated to be clamped and machine. It's a container to hold 2 RC servo motors. I've got the CAD drawing, I've also generated the g-code. I just can't figure out how to clamp and cut the parts.


Here's are the problems:
1) How do I cut the outer profile, without cutting my milling table, since it needs to cut all the way to the bottom?

2) How do I cut such a deep inner pocket, since the cutting part of my end mill is short and the non cutting part of my end mill will collide with the sides of the inner pocket when it is cutting too deep?

3) My aluminum stock is too long and I do not have a jig or band saw, is there any way of cutting it will my mill? I know it will shorting the life of the cutting tool but I do not have the budget or space for a saw <br> <br>

[HZM]

Hi chuck,

Nice job manz. really nice to see another hobbyist into CNC machining

Had not done any 3D profiling but I would like to give it a try.

1) I would hold the whole part on a vise ( w a small pc of wood underneath. Industrial practice use parallel bar to set the height and remove after the job is securely held between the jaw of the vise ) and work on the "inside" first. Like you mentioned, it pretty deep and chances are you had to get a long cutting length end mill. I am not sure but wonder if there is such end mill w diameter 4mm and shank 3mm. In this way, you probably don need one that is really long. I saw 3 point which looks to me that taping is require.

2) Get a flat wood, drill 3 holes bearing the same position of 3 taped holes. You probably need to counter bore it. Then screw your job from the bottom of the wood with top facing up. Using a hold down clamp, secure the wood onto the table. Guess in this way, you can machine all the way to the wood.

What is the size of your raw material and what is the size of your job? At times I prefer to buy another pc of aluminium as it is not worth the trouble machining down to the size I need to work on.

Nice cad drawing there, what software you used?

Cheers

Mike

[numerical control]

Agreed with Mike, but I would prefer to use a flat pc of engineered plastic such as derlin, drill 3 small holes and use sell tapping screw to secure your part to the derlin, and use clamping kit to secure the derlin onto the mill table.

But your wall seems to be too thin, do not have your dimension. But the part seems unsuitable for machining, more suitable for injection moulding. The part may crack during machining. Thicken the wall will help.

[HZM]

NC got a point engineering plastic definitely a better choice

1 more thing, I notice the joining between the "taped" column and the surface of the wall. Looks to me like a 90 degree sharpe angle. This may give an error when processing. Usually there is a small corner inwhich relative to the radius of your end mill used.

Chuck, I suggest you try some simple 2D CNC on flat plate first. Get a feel then proceed w block machining.

Keep us posted

Mike

[cdckjn]

My two-cents worth (in red)

Hi all,
Here's are the problems:
1) How do I cut the outer profile, without cutting my milling table, since it needs to cut all the way to the bottom?
you can 1st cut all the internal profile, then when completed then physically clamped the workpiece on the side and then slowly feed in until the desired wall thickness.

2) How do I cut such a deep inner pocket, since the cutting part of my end mill is short and the non cutting part of my end mill will collide with the sides of the inner pocket when it is cutting too deep?
This one, difficult question. Silly answer - buy a small end mill with longer shank so that you can clamp.


3) My aluminum stock is too long and I do not have a jig or band saw, is there any way of cutting it will my mill? I know it will shorting the life of the cutting tool but I do not have the budget or space for a saw

Just rough cut 1st, then do like in the 1st question, slowly feed to cut to the desired wall thickness.

[Chuck]

Hi guys,

thank you all very much for your great advise.

1) Why didn't I think of it (cutting the inside first)? I did thought of using wood at the bottom too but was concern with the uneven height and rough surface. Delrin sounds good, but where can I get that stuff? Also if any one knows where to get machinable wax (e.g. http://www.freemansupply.com/MachinableWax.htm) let me know also. Freeman Supply won't entertain my order as it is too small


2) Looks like I need to get some end mill and parallel bar. Mike, do start brining in the accessories fast ya. I search the Sherline' site, they have the parallel bar but I can't seem to find an end mill that has a larger cutting diameter than shank. Heard that using a end mill that is too long is not advisable as it tends to vibrates and chatters.

Mike will you be also bringing in other Sherline compatible accessories (esp. the end mill mentioned above)?


3) Just found an article that converts a mill to a saw at http://www.nutsnbits.com/nutsnbits_000003.htm. Not sure if thats good enough to cut my stock (4cm x 6.5cm x 30cm). Looks like it could.


Can't wait to start my first cut