Assembling giant vacuum wall

Months ago i agreed on designing and manufacture a 2100x2500 vacuum wall for Norwegian artist pushwagner´s photo studio.

After producing the technical drawings, the contract was signed, and the product taken into production at Fellesverkstedet

Below are som photos from the production of the vacuum wall.

The vacuumwall must be adjustable. Therefore, mechanical valves where added in form of PE slides.

As a consequence of this, the vall became very thick, and several hundred screws had to be used to keep it from imploding from the underpressure.

This is one of the two halves making up the vacuum wall under assembly.

Here, the two halves of the vacuum table stands ready for delivery and mounting at the customers photo studio:

Autodesk Fusion 360

Yesterday, i and Christian Anker from bitraf spent all day produsing parts using Autodesk Fusion 360's CAM module. We produced the toolpaths on my macbook air, then seamlesly beamed them over to the CNC machine using Dropbox.

The more we learn about production technology, the more we can reduce the turnaround time from concept to reality. For the case of the two copper pieces below, that time ended up at 43 minutes.

Before the copper parts where made, prototypes where made in aluminium. The 3D milling where done at 25mm/sek, with a 1/8 inch ballnose mill.

This assembly is the hammer parts of Koka nicoladze´s new instrument; the solenoid drummer.

As we did further adventures into CNC milling with the shopbot, Christian anker decided he wanted to produce the build platform for his huge part for his 3D printer.

As it must be perfectly flat, it had to be facemilled. We decided to do this with this 32 mm milling bit.

This is the finished part rigth after milling:

Since teaching Christian to mill aluminium with the shopbot CNC machine, he has produced a number of parts for his 3D printer:

Wooden screwdriver set

Even tho i am a big fan of mass production, the tray that my screw drivers came in was poorly moulded from crappy plastic. I decided to remake the tray in oak plywood and aluminium.

This was a good exercise in Autodesk Fusion 360 toolpath generation.

The brass screws where made from 8mm rod, and the slits where cut with a jewelers hacksaw. Then they where turned in the lathe so that they sit flush with the aluminium frame.

This is the toolpaths for the aluminium frame. it has roughing offsets, to make space for evacuating the chips from the cut.

This is where things gets complicated. The wooden tray is 3D milled. That means that the CNC machine is moving with all axises at the same time, to produce smooth edges with a round cutter.

Holddown

I prefer to use lasercut wood washers to mount the material on the CNC, aswell as keeping the piece from moving under cutting.

This part were cut from 5mm polyethylene, a very soft material. Therefor, it had to be secured well before cutting.

The washer are cut to spec, so that they fit exactly in the slot.

This part needed to be chamfered around the outer perimeter. To allow this, it had to be secured with a number of washers and screws. Itwas not possible to avoid collision with the washers on the thin parts, so these where hold down with wood washers, while the rest of the part where secured with steel washers.

In this example, i was making a table, and the legs where to be chamfered from both sides. To acomplish this, i cut a jig for the part from some scrap wood. As this jig where cut by the machine itself, i can now position the part perfectly in the machine each time.

What is stepover?

Stepover is the distance from the tool center between two passes. Increasing the stepover will result in shorter machining time, but also a rougher surface finish.

When milling with a flat end mill, or a facemill, the main parameters you can controll is machinetime and chipload, as the surface produced will be flat anyway. However, with a ballnose bit, it`s a different story. As the milling bit has a radius at it's end, It will leave a raised bit of material in between the passes.

This leftover material is called scallop.

The scallop heigth and width increases when stepover is increased, and decreased when the stepover is reduced. The scallop is marked in red in the following picture:

Using a previously generated toolpath, we can further investigate the stepover, and the effect it impacts on the surface. 

Shown below, is three identical shapes, where the toolpaths generated has different stepovers, ranging from 0,5mm from left, to 2,5mm in the middle, and 5mm stepover to the rigth

The choosen tool in this case where a 10mm ballnose, and the machining times where as following: 

0:09:17

0:02:09

0:01:16

When you have simulated a toolpath in Fusion 360, you can download the resulting geometry as an STL file. 

I downloaded all the resulting files, then rendered them lined up, to display the resulting surfaces.

The results appears to conjoin with the theory, a finer stepover results in a finer surface quality, at the expence of machining time.

The stepover parameter can be reached by selecting the 'passes' tab when producing 3D toolpaths.

Testing out 3D milling in Fusion 360 once more

Today i did some more testing of Fusion 360`s CAM module.

I made a sample 100 X 100 X 50 body, then made a  T-spline plane ontop of it. I then gave it some random topography to work with.

After boundary filling , the part is ready for Toolpath generation!

I intended to run the first files in foam, so i ramped up the feedrate to 3000mm/min @ 15000 RPM.

I used 10mm two flute HSS tools from GARR for this job, a ballnose for the topography, then a flat end for cutting out the part.

The results where good! At 2,5 mm stepover, the toolpaths are clearly visible.

I continued to use the same file for testing in wood. This was made using only adaptive clearing with a HSS 1FL6 from norswiss.

Rigid FDM delta printer

Altough we have a few FDM printers at Bitraf, i now see the need for having my own at my office. i started to develop a small scale delta printer last week.

The printer is constructed from a plates milled from sheet of 10mm 6082 t651 aluminium.

Movement is performed by NEMA17 steppermotors, and HIWIN linear bearing rails.

This is what i have modeled so far:

As the ultimakers, this design also equips the captured nut concept, in this case M6 nuts, as seen in this cutaway:

In this cutaway, the belt tenison system can been seen in the lower left corner. Notice the stiffening bracket in the middle of the linear rail assembly, and the milled weigth reducing pockets.

These are the main components of the printer, here laid out, ready for toolpath generation.

I decided to use this project as a testcase for Fusion 360`CAM strategies, in this case adaptive clearing.

The milling bits normaly break When peak loads is achived when running into a corner. Therefore, the feedrate must be reduced for the entirety of the toolpath when using normal CAM strategies for avoiding milling bit failure:

What adaptive clearing does, is to slowly dig the milling bit into the material, before performing a series of deep cuts at maximum depth, with optimal chipload. In this way, the tool will not experience peeks in loads, as the tool will have constand load. This reduces the runtime with a suposed 40%

I will spend the next weeks experimenting further with Fusion CAM. This is my first result with adaptive clearing:

Pulsejet sled update

Finaly got the time to do some welding on the Pulsejet powered sled. i added the reinforcement bars at the back, and prepared the aluminium bracket for welding. The jet sled is currently being exhibited at NDC oslo 2016 together with my hexapod.

Machining a brass hammer

At work some months ago, there where some scraps left of some aluminium broze screws, so i decided to make a hammer out of it.

Since then, it has become one of my favourite tools, and i use it several times a week when doing machining and assembly. Following is some pictures from the machinging of this tool.

Dust extraction for the shopbot

Today me and and Jens Dyvik assembled the new dust extractor for one of the shopbots.

The parts were previously milled out by Jens, using his CAM plugin for rhino, called barkbeetle.

Barkbetle can stream to our projector, so that we can preview files before we run them.

Seen here is the finished parts, along with the prewiew.