In my residency at Autodesk, Pier 9 this fall I was pleased to cut a lot of spring steel sheets on the 400W Metabeam laser cutter.
Since metal is more difficult to cut then wood there were a few problems I ran into. So this Instructable is about these problems and how I could solved them. This is NOT a step by step guide for metal cutting. A few of these problems are metal cutting specific and a few for the Metabeam in general.
Step 1: Thermo Flexing
Since you applying a lot of heat to a material it could happen that your material starts to flex.
The metal cutting nozel has a capacitive sensor which normally prevent the nozel from hitting the martial and keep the cutting distance at a constant level of 0.02”. It could happen that your material flexes so much that the nozel crashes.
1) The most important step is to get the correct focus offset which is explained further in step nozel offset.
2) You can prevent the thermo flexing by distributing the heat over the whole material to give it more time to cool down. Instead of sending all your geometry on the same tool path layer it makes sense to separate close cuts from each other. The gif shows an example how you could do that. It gives the material more time to cool down.
3) As sone as you are cutting steel or a magnetic material you could use magnets to hold the material in place. Make sure your tool path is not cutting into the magnets! More about that in step position (metal).
Step 2: Position (metal)
If you have bigger sheets that doesn’t flex the best way is to cut on the big slot bed on the right.
In my case I had a 0.015” spring steel that was flexing a lot because of the tight geometry I was cutting and the compressed air pushing the material down. To solve that problem you can do two things:
1) Buy your own honeycomb(http://www.mcmaster.com/#9635k412/=zq1ftv) and replace the honeycomb on the left side. This gives the best support for your cuts. There are two down sides:
- The honeycomb will wear out very fast because the beam will always cut into your honeycomb.
- Whenever there is a cut where you cut your material and the honeycomb it will “weld” together. You can pull it apart but the cutting edge will have some slag.
2) Build you own standoff. I had to cut more then 25 sheets with the same geometry so I decided to build my own standoff out of 0.040” steel. It takes extra time to build it but you can make sure that you material is never weld to the standoff which gives the cleanest cutting edge. Also a benefit of the steel standoff is that you can place magnets on it to make sure that you part is not moving because of vibrations of the machine or the compressed air.
Step 3: Nozel Offset (metal)
This is the wired part... So far we were always setting the the nozel offset to 0.0 with the 1” block. That might work for some materials but at least for my 0.015” spring steel it wasn't working at all. I got a lot of thermo flexing, sometimes not cutting all the way through the material and a lot of slag on the backside.
After experimenting with a few thingsIi found out that a focus offset of 0.030”-0.040” worked very well. Clean cuts and no flexing and also the slag was almost gone. So get some extra material to do a lot of tests on that offset. It is worth it! In the left image you can see how my focus offset locks like. Set the offset to 0.0" and then go higher than the 1" block.
Quick note: imagine you were looking on the nozel from directly under it. clockwise -> increase the offset (0.01, 0.02, 0.03, …) counter clockwise -> decrease the offset (0.03, 0.02, 0.01, …)
Step 4: Software Slow/crash or Can’t Load Parameters (general)
This is an issue that me and a few others had. My personal assumption on that is the connection between the metabeam and computer fails.
There is an old but classic way to solve that problem… “did you tried turning it off and on again?” But just restarting the computer and metabeam is not enough. You need to cut the power for the entire circuit for a few seconds so that the computer and the metabeam can initialise again. To do that just turn off all fuses on the back of the Metabeam. Since the computer is connected to that circuit make sure you safe all your files!
One time i had an issue with one of my files. Whenever i tried loading it the software crashed. Even the off/on solution didn't helped. The only solution I could find for that issue was redoing the tool path in Laserlink.
Step 5: Slag and Power Ramping (metal)
If you get a lot of slag on the backside of your material the first thing you should check is your focus offset.(see step focus offset)
Another thing you should do is setting your acceleration to fast. Normally the power ramping option for metal should make sure that the nozel is moving at a constant speed. But it was not working for me. Setting the acceleration to fast helped a lot to get rid of the slag.
Step 6: Gas (metal)
compressed air: very good for cutting thin spring steel
nitrogen: could not find a big difference to compressed air
oxygen: very heavy unprecise cuts, probably good for thicker material
Step 7: Laser Won’t Fire (general)
Most of the times your probably forgotten to turn of the dry run future.
Some times it is because one of the interlocks (Gas, Door or exhaust). If one of the gas bottles are empty it could happen that all interlocks lock is fine before your hit start but as soon as soon the metabeam opens the valve for the gas it loses the pressure for the interlock and lights up. So double check the interlocks if the laser won’t fire.
Step 8: Auto Focus Fails (general)
If the auto focus keeps failing you need to clean the contact because there is dust causing a poor connection.
For cleaning get a cotton swab from the drawer and put some alcohol on one of the tips. Than gently clean the brass contacts as shown in the images.
Step 9: Capacitive Sensor Fail
Some time the capacitive which ensure that the nozel keeps the focus offset even when the material flexes fails. That could mean that your material is flexing to much that it hits the nozel. In this case check the thermo flexing step. Also make sure your material is completely flat.
Another possibility is that your focus offset is wrong means to close to the 1” block so you need to back up a little (turn red rung clockwise)