Update number 3!
First cuts on the project! Sure feels nice! I have not gotten around to edit the video footage. Gifs to be ninja added in the original post and a separate post I think. Also working on a youtube video. Hopefully it will be up later this weekend If I don't run into trouble with little to no experience using adobe premiere...
Tried to describe the whole process as good as I could. Took a looooong time so I will probably not do this every time. But I thought it would be good for those wanting to get into CNC! Hope you enjoy!
A fresh start, with a fresh spill board!
I use these small 12 mm hardened shafts to align the work piece to make sure it is parallel.
As you can see here the aluminium sheets gets pushed toward 2 of these to achieve perfect alignment along the Y axis.
Very soft aluminium clamps. Too soft maybe, but they usually scratch instead of the material.
Bottom side of the clamps. Allows for a range of about 2-10 mm thickness to be clamped.
I used six of these to secure a 8 x 300 x 1000 mm 5754 aluminium sheet.
Very flexible, I constantly have to bend these back when I get too rough with them. That's not good since they flex past the yield point and will eventually break. But I just have to make some new and improved versions then!
This is the part I am machining today. The very bottom part of the case.
4 mm polished end mill for soft metals like aluminium, brass, copper etc. Also suitable for plastic.
These are ER25 collets that holds the milling tools in place.
Here is a pack of them. Goes from 1 mm to 16 mm. And to the right you can see the special tool that fits over the "clamp nut" (name?) that squeezes the collets and consequentially squeeze the tool.
Here it is, fastened in the spindle.
No rush, measure everything twice. And then again to be sure. Then doubt yourself and measure again
I am centering the program on the bottom left corner. I need to make sure I don't have a collision with the holding clamps and also don't go too far.
The chassis is 235 mm wide. This means I have about 20 mm of space left on each side for the tool path (takes about 12 mm on all passes on each side) and the clamps.
The contour cuts, and holes are made on the main/first side I mill. The lines you see here are tool path lines.
About to plunge down into the aluminium!
Here you can see the chip evacuation. I am having a hard time showing you since the dust shoe is in the way. I even lifted it up to get some better shots, resulting in a mess! But it was worth it
Very nice surface finish. Really sharp edges with no rubbing or vibration marks.
Cleaned up the cut a bit with some compressed air.
First tool cut done, now on to bigger (and better?) tools!
Up from 4 mm to a 10 mm end mill! I do not have any tight inner corners this time, and a larger diameter tool produces a better cut than a smaller diameter tool. So I will use this 10 mm for the contour cut!
Auto Zero after each tool change. Goes out to the reference position and adjusts the ZERO-plane after the new and changed tool height.
I use these droplet canons on each side to apply coolant/lubrication fluids. Works really well. You don't have that mist all over the shop and it also evacuates chips.
Now using a bigger ER25 collet! And, you guessed it, the 10 mm collet for the 10 mm tool
The inner profile cut under way. This is the first roughing pass. I am taking about 2 mm per pass with a feed rate around 600 mm/min.
Tabs are starting to show! That means we are close to cutting through the stock.
Inner contour done. Now I just have to get that thing out of there...
These are the tabs I am talking about. They hold the part in place so it does not come loose during the cutting passes. The part coming loose will result in either the tool breaking, or damaging the part, or pushing it loose from its clamps. A pain in the ass, but better than the alternative.
I use a rotating tool that uses air as propellant. And I use these small and neat cutting disks. Much more robust than a Dremel disk, for example.
Cut done. But you can see that I am now left with these partially cut tabs sticking out. So that's no good at all.
This is solved with another pass. In programming I saved about 0.5mm for a finishing cut. Where I remove the last bit of material and at the same time improves the surface finish quality even more.
This will go in the bin with scrap parts that I might have use fore later. It's big enough that I don't want to just toss it.
Surface finish is really good. Now I just need to keep it this good until final sanding and glass bead blasting.
This is the second side of the part. Chamfers and some M4 holes were made here. You can see that my stock is defined as XYZ with the Z-axis starting on the top of the stock here instead of the bottom.
With the outer contour coming next, I need to secure the piece to the table since the outer clamps will do nothing when the piece is nearly free from the stock. If you don't have clamps securing the piece from "inside" like this, you must either use tabs or you'll get a V-shaped artifact when the piece comes loose, as the tool will push the part away the last millimeter or so. This may cause the part to bounce back into the tool and cause all kinds of issues. And because you lose the position of the part when it comes off the stock, that makes it very hard to do a final pass on it to clean up tabs. This is a real issue if you can't clamp it down. I will have some parts like that later, I fear.
I got a bit worried about marks so I put some plastic pieces to protect the surface of the piece.
This is what the code looks like. Some basic G-code for those interested, the S defines the tool speed, so in this case 13610 RPM. The M3 turns the spindle on in clockwise direction. M8 turns mist cooling on. Then G0 followed by XYZ with numbers tells the computer to go to that position in rapid speed (the maximum speed you have set it to). G1 works the same way but with the difference that it does not go to XYZ in rapid but in a specified feed rate (F). So for example, G1 Z11.5 F317 tells the motors to move the Z-axis to 11.5 mm above the 0-plane in with a speed of 317 mm/min.
The purple crosshair shows the machine's current position. You can also see some G-code, for example those dotted red lines are rapid moves in the XY-plane.
Sharp corners. Always nice to know that the machine is capable of that. You can sometimes get round corners, especially when the machine is trying to keep a constant velocity.
After a few minutes the cut is done. Here is the result. Now I have to release the clamps and turn the piece around and do the other side. There are some chamfered holes and a few more holes to be drilled.
Was deciding on the width for the chamfers so I did a few tests on an aluminium sheet that I was in the bin. Decided on 9 mm for the M4 screws and 7 mm for M3. A bit smaller than the ISO standard of 10 and 7.5 mm respectively. But I think it looks nicer with the smaller diameter so that is what I am going with.
10 mm Chamfer end mill. 90 degrees with a sharp tip. Used for plastics, aluminium, iron etc. Some kind of titanium coating, if I remember correctly.
Surface finish is very nice, except from that oxidized surface due to storage... I'll have to sand that down.
Really pleased with the first part! No mistakes as of yet!
One completed bottom piece!