Safety and Health

Dear Golem,

before you consider using the Jointmaster software in your application, please read this post on safety, health and responsibilities.Jointmaster contains functionality that can be used in an application/ product to make a very precise wood joint.
You will have to add other components (in addition to Jointmaster) to saw/ mill the joint. You might even have to make modifications to your existing machinery.  For this reason we cannot take the responsibility that your solution will be safe and complies with all norms/ directives. When using the Jointmaster software with a step motor and trapezium spindle, you will have to take the hazards explained below into account.

Given that you will use Jointmaster to create precise movements in order to enable an operator to make a precision cut, there is a chance (explained below) that there will be unexpected movements while the operator makes the cut.
These unexpected movements could lead to damage to persons, your workpiece or machinery. For this reason, you might have to take additional safety measures.

Causes of unexpected movements:
– Windows/ Android is no Operating System for so-called safety applications.
– Jointmaster software is not developed to aim for a certain so-called SIL(Safety Integrity Level).
– You might drop something on your keyboard and then Jointmaster will order the stepmotor to move.
– You or somebody else might by coincidence click on the Jointmaster continue button while making a precision cut.
– There might be interference from other Windows/  Android programs/ windows drivers with Jointmaster.
– Your computer memory might be bad. Leading to bit rot, causing inadvertant movement.
– There might be Electro Magnetic Interference in your workplace (for instance if you start a heavy motor), leading to bit rot, causing inadvertant movement.
– Jointmaster audio uses the soundcard to steer the step motor. If you play a song/ Windows beeps/ Your Android phone rings, there might be inadvertant movement. Note that this will not happen very easily because both stereo signals must have exactly opposite phase, but it might happen by coincidence. And of course, you have to make sure nobody can call you while using your phone for cutting joints (or take the additional safety measures stated below.)
– Step motor driver (step motor driver is explained here) generates inadvertant movement etc.

To stress once more, the Jointmaster software and windows/ computer environment might generate unexpected movements.
Thus you might need extra safety precautions.

Please take the following failure modes into account (even though the chances will be small that this will happen in reality):
– Jointmaster/ Windows/ Android/ computer generates movement when not expected.
– Jointmaster/ Windows/ Android/ computer keeps moving/ moves too far. (could also be caused by wrong user input/ installation errors)

Mitigations against these failure modes:
A) Clamping your workpiece before making a cut.
B) Safety Switch
C) Combination

A)   Clamping is very simple and very safe. Of course safety has a negative effect on availability. The time to make the wood joint will be longer because the milling machine might have to be stopped, clamp has to be removed and installed for every cut.
B1) Operator operates a safety switch. Not really recommended because operator could make mistakes/ shorts the safety switch on purpose.
B2) Safety switch is operated by the shifting part of your machinery when the workpiece is in a safe position to move.
C) Especially when working on expensive and big workpieces, you might consider A + B2 and even stop your sawing/ milling machine before shifting the workpiece.

ad. B2) The introduction of a safety switch only gives a big increase in safety if you would break the power supply to the step motor driver. This would lead to a undetermined step motor position once the power is removed (step motor might rotate due to vibration). Also you are breaking a DC voltage where the stepmotor is enabled and thus there will be sparks on the switch. Might not be the way to go in a dusty environment.

ad. B2) The line amplifier control scheme found here on the Jointmaster site gives possibility to add a safety switch in series to the enable signal to the step motor driver. This gives a limited increase in safety because the step motor driver itself can also fail and generate inadvertent movement. Please note, chances that this happens are probably very small but the Chinese manufacturer gives no so-called failure rate per hour. Because of this step motor driver failure mode, clamping might still be necessary.

Please note that taking sufficient safety measures is your choice. For example considering the switch options:
– You could decide to use no switch at all.
– You could decide to use a momentary switch from a refrigerator door
– You could decide to use a non-ATEX compliant safety switch conforming to a whole set of safety norms thus having a quantified failure rate. This will cost 20 euro to give some indication.
– Or you might even consider a 100 euro ATEX compliant safety switch.

There is always the question when is safe sufficiently safe. This depends on the region in the world. Here in the European Union there are many norms that guarantee health and safety. For example, machine directive, EMC directive, ATEX directive. Lets say you live in Europe, you make wood joint connections and you generate saw-dust. Saw dust means ATEX directive because of possible dust explosion.
Now if you want to comply with the ATEX directive, it could be that you decide to put all your electrical components into a ATEX compliant box that will cost you 500 euro.
You decide to use ATEX compliant safety switches, cables etc. Thus the solution to make mortise tenon connections will become very safe but also more expensive.

If you live in a region where there is little law, hardly government officials, you are lucky to be alive at all and you will not need a ATEX compliant safety switch.

And a safety switch comes at a cost. The switch costs money and needs to be maintained. Is it still operating correctly (how do you know, are you going to test this ?), The switch might malfunction due to dust, catch fire and explode. Thus the switch decreases availability and increases complexity and maintenance costs.

Once more, be aware that we cannot take responsibility for complying with all norms because we only deliver non-ATEX compliant components and no complete solution. YOU have to think carefully if what you want to do is safe and in agreement with norms/ directives. You can find some examples on this site and on www.goodlife.nu of how you can make relatively safe wood joints. This might not be sufficient to comply with all norms in your situation/ country of course. If you need ATEX compliant step motors, drivers etc. you will have to look elsewhere on the Internet.

Also note that we do not judge you for complying/ non-complying with norms. You are the only one who knows what is right and what is the truth (Sorry, only a prophet knows the truth, see wikipedia 😉 )

So you might wonder, how do the guys at www.goodlife.nu use the Jointmaster:

  • They do not clamp between making the cuts.
  • They do not use a safety switch.
  • They make sure the phone cannot ring because of somebody calling.

Why do they consider this sufficiently safe:
– They use Jointmaster in a set-up where operator fingers are always far away from the sawing blade. This is the set-up that is advertised on jointmaster.eu
– They use Jointmaster in a set-up where the blade is always cutting at the same position. Thus saw-dust is very easily removed.

Now that you know your responsibilities and Jointmaster limitations,

hurry to the shop, download Jointmaster, buy or solder your amplifier and enjoy !