It depends on the CAD program used, the CAM software used, and how it was drawn/modeled so there is no one right answer to this. It is true that it has to be converted to a G-Code.

I have one type of CAM software that can open several different types of drawings. The problem with it is that even a simple AutoCAD .dwg or .dxf 2D file gets exploded when it's opened. This means that instead of sweeping lines or cuts, the machine will cut a short segment, return to zero, go back and cut another short segment, return to zero, and repeat over and over again. It's time consuming. Fixing the drawing can sometimes take longer than just redrawing it. For most simple things that can be done in 2D like flanges, this is no big deal. For 3D parts that are more complex it can be a nightmare.

I also have MasterCAM X-5. I'm still learning it. My preferred 3D software is Inventor but MasterCAM has an add on that allows you to take a Solidworks 3D model and load it straight through. MasterCAM will convert it to G-Code for you. I do have Solidworks too btw.

To do this makes some assumptions that only a good machinist is really going to be able to know. First off metals change size with temperature. Some more than others. For most things car related this won't be an issue but for pieces that are machined to high tolerances that rely on true position, this can be a nightmare. If you have a part that has a tolerance requirement of +- .003", what size was it modeled to? You may have modeled it right in the middle of the tolerance range but machining when cold as opposed to on a hot day may have a .003" size difference on the part. Depending on where it was when you machined it, it may or may not end up being within spec. That's the danger of going straight from CAD file to G-Code.

Fortunately for most things automotive related, tolerances don't have to be that high unless we are talking internal engine components so it is probably a non issue for most.

Keep in mind there is more than 1 way to draw a 3D model but only 1 proper way to do it. It is best to model something by starting with a solid piece and then cutting away at it to get the shape you want. This is how a mill or lathe would create a part so modeling it in 3D the same way is going to be best. Some people like to take certain features and model them up separately and then merge them together to make the finished piece. Yes it's easier up front but changing things later may be more difficult if it needs a revision to the design. Creating your machining. tool paths may be a bit more difficult as well.

 

here is an idea that isnt covered by others yet

how about something for the worldwide 12a guys
,, they have a unique problem where new stock housings,, and now even good s/h housings are rather tricky to source

the usual solution to this is to take edge worn 13b housings and mill them 5mm off each side to be a 12a housing with a large exhaust

the problem now is that the original 12a housing has grooves for water seal in the housing and the new style does not
- a good CNC guy can get around that
but the worldwide issue is that sometimes these services are exclusive , expensive, or elusive, often all three

now,, here is the clincher
86 onwards 13b ( exclude rx8 ) side plates have the water seal grooves instead of housing

so is possible to build a "12c" evolution of 12a using the later style of plate ( and oil pumps )
{ and large exhaust ports }

these "12C" engines will need a unique manifold adapter ,, as currently no OEM manifold will fit this new manifold pattern

it is a simple matter to make a dummy engine up out of some junked 12a housings and 13bt ( and 13b 6 port ) and FD plates

three styles of manifold patterns ( 13bt , 13b NA and 13b REW ) to fit the "12C" block, counter sunk
all with variations of outer to suit 12a carb manifold or 13bt , 13b 6p, REW manifolds
the EFI versions of which will require injector boss holes tapped


ie, ATM in oz i can get adapter to carb manifolds for 13b 6p or 13bt ,,,, but these are for 13b engines and not for the new "12C" path that many can now take

 

the original owner was a company up north that used it with a 4th axis to mill slots in aluminum pipe. The second owner used it very sparingly as was a home enthusiast with more than one machine. One clue to it's low use it the pendants membrane buttons. VF1 membrane buttons wear out and crack as they get used a lot. This machine has almost no detectable wear on said buttons. As compared to the condition others have bought their machines (as seen on the practicalmachinist forum) this one is pretty cherry (esp for the price). It does need a good bath ... and the door plexi is cracked on both doors. The tool changer door does not operate (stays open) so that must be remedied as well. The coolant tank is also in need of a blast and repaint.

Here are just a few pictures I took of delivery day. LONG story short it was a bit of a nightmare. Shipper was supposed to have it down on a Wednesday. They dropped the ball and it was delayed two days. Originally we had a 10,000lb shooting boom forklift scheduled to move it. We went back to schedule it for Friday and no such luck ... not available. We called everyone around the area looking for one. Ended up with a 10,000lb normal forklift and a set of machine skates. Other than the lift springing a leak it went better than expected. Our nerves were still pretty frayed from having to move this huge machine but all in all our story was a success ... well except the part where the lift bar shot me to the ceiling and hung me off the ground by my jacket ... that wasn't so hot.


THUMBNAILS (SO CLICK)

8 AM. Pretty cold morning (for Georgia)

















It was a TIGHT fit ... about 1/4 of an inch on top and bottom through the doorway ... once inside it wasn't so bad



Machine skate



The lift bar that A: gets the machine off the skates and B: launches and hangs people.



Putting the Z servo back on and reassembling the service loop.

 

thought of something. This is helpful for EVERYONE that has ever assembled an engine.



Make the same main pulley in the stock size!!!! No more worrying about the proper pulley/hub on that particular engine combo.

 

hahhaha you putting this beast in your garage ?? haha awesome want one

 

this idea has been in my head for a very very VERY long time.

 

That would be possible with a 4th axis but honestly those parts are something that you really need a turning center for (like a cnc lathe only more badass). I hope getting the 4th axis setup won't be so hard.

I'll also reiterate ... this is my brother's machine ... not mine. He's the one with the expertise and I'm just trying to feel out the business for him. So far a few ideas have been brought out that I feel might be worth giving a shot.

 

This isnt rx7 related but I know for a while alot of people were looking for sr20ve, yes ve not det, flanges for the intake and exhaust manifolds so they could build rwd intakes and exhausts for the front wheel drive engine swap into a 240sx. Just to give you some extra ideas. Congrats on to your bro on the nice machine. Look around all the diy forums have random needs.

 

Looks like a good buy then!

You're not the only guy I know with a machining center in his garage. How are you planning the power to it, if you don't mind me asking?

 

Rotary phase converter. My brother was thinking homebrew but I think he found a good deal on a commercial one. The power from a commercial model is much cleaner considering the motor is built for the purpose from day one. It has more windings on the third leg.

 

The fastest rotary 12a car has one of this (12c) engines.The motor was built using jc cosmo plates,milled 13b housings and 12a turbo rotors,semi PP combo capable off 900 plus hp with only 79 cubic inches.

 

This. I have yet to hear of someone making a durable replacement for the stereo trim. I have seen a carbon fiber one, but it was quite costly. If it did not leave the 1/4 inch gap around the sides like the stock one, that would be quite nice as well.

 

Just think about the size of the aluminum billet needed to do the radio surround ... that might be a bit impractical to be made in a CNC machine. Fiberglass/CF are much more practical ways of making that. It MIGHT be practical if it could be made in two pieces ... so that the upper portion could me milled from a much thinner piece and the lower curve could be machine out of a thicker block. The two could then be either tig welded together or held together by points machined into it and fasteners.