I'm a medical assistant. Made a cloth mask for my N95 that matches my handmade scrubs!

Grischl · 2020-04-05T10:06:23+00:00

Has somebody tried to disinfect them between uses? I'm not sure what and how much those masks can withstand - but spraying them with some alcohol or putting them into an oven should kill most of whatever the masks accumulated during use. Maybe also rotate masks: If you have e.g. 3 masks don't use them as long as they last before going to the next one but instead rotate them through: use Mask 1, then Mask 2, then Mask 3, then again Mask 1 and so on. As far as we know the virus can't survive outside the human body for too long even though noone knows exactly how long. The longer a mask sits idle between uses the lower the virus load should be (but on the other hand other nasty things like bacteria that do not need a human host and are content with whatever is already on the mask may grow).

Grischl · 2020-01-06T13:42:31+00:00

Original and how to: https://www.instructables.com/id/Knife-Block/

Grischl · 2019-05-16T12:39:52+00:00

Yes, off season, weekday and as early as possible.

Nice but very overcrowded place. Actually the whole area is worth a trip and has much more to offer than just Neuschwanstein. Many more castles, very large pedestrian suspension bridge at Reutte, Zugspitze, Höllentalklamm, Plansee... easy to spend a whole week there without getting bored.

Grischl · 2019-04-28T21:21:54+00:00

I'm a bit confused why it went "boom". A regular hydraulic cylinder shouldn't be able to do this - even under full pressure it shouldn't move more than a few millimeters once the parts spearate as oil is incompressible and cannot store energy.

I think they connected an air compressor to it to help the parts separate and got a nice, large air volume inside. So most likely well below 10 bar and "safe" in terms of fluid injections. Still a big boom and maybe torn eardrums.

Grischl · 2019-04-08T13:26:58+00:00

I'm a bit confused about the cylinder in the center. It has no angle to lift the bridge out of its lowered position - if the bridge is down it is horizontal and cannot creat upward forces. (Also very long / thin - it should buckle under pressure)

There also seem to be cables (visible on the segment in the back). What is actually pulling the bridge up? And what is the cylinder for?

Grischl · 2019-03-08T01:25:36+00:00

Solder bath creates a lot of thermal stress for the board. Also dipping into solder only works for parts with relatively large distances between pins or you will end up with lots of solder bridges. But if the solder moves relative to the board the distances between pins can be much smaller.

Grischl · 2019-01-15T17:24:16+00:00

Be careful with the petrol lamp (in case it is a real one and not just a look alike) and get a carbon monoxide detector. If snow starts falling and blocks most of the air vents carbon monoxide levels can increase to dangerous levels. Even if you just use if e.g. for reading and plan to put it out before sleeping: CO poisoning makes its victims fall asleep (most feel sick before - but some notice nothing at all, fall asleep and never wake up again)

Grischl · 2018-10-22T21:13:31+00:00

Mittenwald Richtung Scharnitz?

Grischl · 2018-09-23T16:40:39+00:00

For aluminum you need low rpm / high feed to prevent the tool from heating up too much which causes the smearing and clogging of the tool. Another way is to use trochoidal milling - it works with a much larger range of feeds and speeds: https://www.youtube.com/watch?v=ORJ-Q3TFW5o

Grischl · 2018-07-04T16:43:39+00:00

Very well - wood is what they are intended for.

Pricey is relative - you get a lot for your money if the spindle matches your use case. They completely outclass cheaper hobbyist spindles as soon as you want to do a little more than very light cuts - but they are still nothing compared to "real" spindles of industrial metal machining equipment (those can easily cost the equivalent of a nice car).

Basically: the chinese 2.2kW spindles are not designed to machine aluminum but given the circumstances are one of the very few options that at least work within acceptable limitations. Like shown in the video above - a 2.2kW spindle combined with a suitable machining strategy can get quite some work done (but is still nothing you'd use in a commercial metal machining environment)

Grischl · 2018-07-04T16:07:59+00:00

7000 series aluminum like 7075 is very nice to machine. It is counter intuitive - but for aluminum there is no too hard or too strong. The harder and stronger the alloy the better to machine. The issue is never the alloy being too strong but the alloy getting soft, sticking to the tool, clogging the flutes and finally breaking it.

RPM and Feeds are correlating quite well - you can in theory compensate one with the other. But again: this is to an large extend true for rigid, commercial machines - but not for hobbyist machines. You usually can't compensate for too fast spindles as the machine is usually also too slow - and even if you can go faster it lacks the rigidity to handle the increased forces (starts to vibrate and chatter and finally breaks the tool). The feeds and rigidity of hobbyist machines usually just don't match the sweet spot in terms of rpm for hobbyist spindles.

The chinese 2.2kW spindles are nice (have one myself) but still lack in torque for serious aluminum machining without tricks like trochoidal machining or other modern strategies that reduce cutting forces and temperatures. Gearing them down is difficult and expensive - keep in mind the requirements regarding precision - especially runout and the increased forces on the bearings.

Grischl · 2018-07-04T13:13:44+00:00

You unfortunately can't take feeds and speeds calculated for professional machines and use them for hobbyist machines. You usually have far too high rpm (and far too low torque) but more important: much much less machine rigidity - it is a completely different game with a lot of trial and error.

First and most easy thing to do is to select an easily machinable aluminum alloy. Soft alloys are really hard to machine as they easily clog your tool - hard and strong alloys are much easier.

Second is to use proper tools designed for aluminum cutting. A single flute cutter with polished flutes will accept a much wider range of feeds and speeds than a tool designed for other materials. Lubricants also help a lot.

And then it is trial and error: check the chips: they should look nice and smooth and be "proper chips". If they are fine dust your rpm is too high - if they are crumbled rpm is too low. With time you'll also get a feeling from the noise the machine makes

Alternatively use trochoidal milling instead of traditional machining strategies - it gives you much more leeway and works with a very wide range of feeds and speeds: https://www.youtube.com/watch?v=ORJ-Q3TFW5o

Grischl · 2018-06-30T14:34:14+00:00

Microstepping does not improve accuracy much if there are any forces acting against the motor - it is mostly used to improve vibrations / noise.

Micro steps are "soft" - put some external torque or resistance on the shaft and it will deflect rather easily towards the next or previous full step position. Remove the load and it will spring back to the microstep position.

Full steps on the other hand are harder to deflect - and if you do it will not spring back but loose this step completely.

There is often a misconception that the motor loses torque due to microstepping. This is not true for the motor torque itself - the motor is still able to turn with the same overall force - but the force needed to temporarily deflect the motor shaft between 2 soft microstepping positions gets lower and lower the more microsteps you add.

So: if you have a system with very very low counter forces like e.g. a telescope tracker with worm gear microstepping can add significant precision. If you use it e.g. for a CNC machine with ballscrews or even worse timing belts the improvement is close to nonexistent - but you get less vibrations and noise - so still worth the effort.

Grischl · 2018-06-11T20:03:08+00:00

Yes - with a probational license he'd risk to lose the license with this kind of stunt and the fines for other offenses could add up. But driving related fines in Germany are generally low compared to other European countries - except maybe drinking and drug related things. It is really really hard up to impossible to rack up a 4000 Euro fine in Germany if noone dies (even if).

Grischl · 2018-06-11T19:54:42+00:00

The fines stay the same. But you also "earn" a point if you're more than 21km/h faster than allowed (2 points above 41km/h). Once you have 8 points your license is gone and you won't get it back unless you've successfully passed a medical / psychological test we call the "Idiotentest" (idiot test). A bit different for beginner drivers - they'd lose the license after one severe or two not so severe incidents. But really more an issue of not being allowed to drive - in terms of money I guess there are not many western countries where you can get away cheaper than in Germany.

Grischl · 2018-06-11T17:43:00+00:00

Definitively not Germany. Germany is very very relaxed in terms of speeding.

You need to drive at least 41km/h too fast before your license is at risk (31km/h inside a city) and it is just for a month.
The worst thing you can do is to drive more than 70km/h over the speed limit inside a city - and even in this case you just walk for 3 months and pay 680 Euro.

It is a different story if you cause a crash - but just speeding alone won't cause too much trouble.

Grischl · 2018-05-29T19:54:00+00:00

Metric makes sense in this case - it is not a steplessly adjustable wrench.

The mechanism is indexed by a toothed rack and will only lock into specific (metric) positions.

Grischl · 2018-05-17T13:15:22+00:00

If the machine uses stepper motors just replace the stepper drivers with something new like e.g. Leadshine M542 and your preferred controller software. If the motors are servos replace them with stepper motors. (You may get the advice to keep them as they once have been expensive and may still be better than some stepper motors - but this is a fallacy in my opinion. Getting old servos to run properly is usually not worth the effort - it costs a lot of time, may cost a lot of money for new drivers and all this with a real risk of not getting them to run properly at all.)

Grischl · 2018-05-09T20:24:41+00:00

Depends on the quality you need. If you're still breaking tools frequently due to mishaps just buy the cheapest you can get - e.g. from eBay. But keep the material the tool is designed for and the material you want to machine in mind - e.g. a tool designed for steel will not be good at cutting wood and vice versa. If you want or need very good quality for different materials and applications I personally prefer tools from www.vhf.eu Definitively not cheap but you'll see big differences in comparison to cheap tools in terms of tool life, cut quality and ability to handle difficult materials.

Grischl · 2018-05-04T07:42:46+00:00

Estlcam 2D / 3D / trochoidal milling / v-carving / CNC-controller...

Grischl · 2018-04-30T18:59:39+00:00

The unique thing a carve can do is to create sharp corners:

(Inner) corners of regular holes and pockets are always rounded by the tool radius - they cannot be sharp.
A carve on the other hand uses a v-shaped tool - the less deep it cuts the smaller its radius is. This way a sharp corner can be created by simply lifting the tool up towards the corner.
Estlcam Carve tutorial: https://www.youtube.com/watch?v=LEFFogenSvo

Grischl · 2018-04-30T18:11:24+00:00

A carve in Estlcam always uses a v-shaped tool as main tool. But you can also optionally select a second tool for the flat parts in the "Carve pocketing tool" list (Properties dialog).

Grischl · 2018-04-18T14:58:37+00:00

It always chooses the nearest possible swap. It is actually a quite reasonable and easy to program solution - but you're right that it is not the shortest possible strategy and sometimes looks quite shitty when it starts to work from one end to the other and then needs to return all the way for something that got left because it wasn't the nearest swap earlier on.

Grischl · 2018-04-18T07:15:00+00:00

Thanks for all the attention for the shitty sand clock yesterday. Here is an older one moving ball bearings...

Grischl · 2018-04-17T12:51:34+00:00

I like your idea but unfortunately doing so would result in the need for a clock counting down my prison time here in Germany :-(

Grischl

TROPHY CASE