WR561-1 Controller on heavy machines
I have purchased a chinese brand HMC WR561-1 controller for my old Claess/Pfaff/Textima 8346 (which is still continued by CL-Maschinenbau), in Germany.
It is a Shoe-maker, Leather-patcher or universal strong and durable machine, which I bought last year and it came with a work destroying clutch motor! I wonder how anybody can use this @all. No chance to have a slow harmonic sewing with it. So I did all by truning the handle myself.
But now the time had come to exchange the ancient clutch motor with a servo motor! Searching the web I found sewtex.de and they had some models.
The HMC WR561-1 was advertised as: For extra heavy machines, 0- set max RMP by foot pedal, needle upper or lower stopping! For 180€.
That's exactly it! I thought, and bought it.
After some Installation work on my machine, it turned out that most relevant features do not work!
Frankly speaking for me the complete offer appeared to me to be a kind of a lie.
See Photo of the complete thrown together setup after my first try.
1. The speed was in no manner adjustable by foot pedal, only from the controller setting -by pressing buttons repetively. What I absolutely did not want, facing away and taking hands away from the workpiece. When pushing the lever/pressing the pedal, the Machine made a jumpstart to the set speed. This was exactly not what I wanted. No way!
2. The needle positioning did not work either. 30-50% of the cases the Controller threw Error E-06 Needle positioning error after releasing the pedal. Restarting the controller took tooo many seconds.
The support from Sewtex was somehow fobbing me off with citiations from the awfull manual.
But never the less: I was able to figure out a fantastic solution.
To make the story short, here is the result first, and later how I did it:
1. The Machine now has variable speed using the foot pedal. Somehow the controller seems to support only steppings in speeds up to the set speed. And it does not start from 0 rpm, but something around 200.... maybe more. Still not as promised but it is OK!
2. The needle now can stop in upper AND lower position, depending on the position, where the pedal is released. If there is enough way to stop at the next needle up postion, then the needle will stop in the up-postition, same for lower postion! This is awesome! Even more awesome is the new usecase: with hits to the pedal, you can move the needle stepwise to up, down, up, down .... positions and work through critical areas of a seam. You can draw letters with a seem now, using motor drive! Or work through other complicated (pre-drawn) paths on a piece and have boths hands free for your piece.
And when pressing the pedal, the machine runs with respect to the pedals positions speed (with steps in speeds) and the max settings within the controller! This is really great with such a big machine!
Now the explanation:
1 st, why the controller seemed to have no variable speed:
The sensor for this is a Hall-Sensor, which is able to detect a magnetic field. Inside the Pedals sensor box, a magnet is attachted to a small lever, which moves the magnet over the hall sensor. This sensor seems to be rather sensible, and runs through its entire ananlog sensing range in only some angular degrees! So if you turn the lever by hand, and very carefully, you can see the motors speed beeing adjusted. For me it was not possible to reproduce this with my foot, when the lever is connected to the pedal.
Now I pulled the internal lever with the magnet attached/integrated some Millimeters out on its shaft. So that the plane of motion is now 2-3 mm away from its former plane. This flatens the ramp of the magnetic gradient and the sensors output ramp now covers a much wider area of motion of the input lever.
This helped! See Photo, where my final position of the internal magnet holing lever is visible.
I found out, that the variable speed is only available, if the max speed is set so something above 900 rpm. Below this it still behaves digital. ON or OFF. For my Claess 8346 I have a setting of 2000, so it is nice.
Background information: My machine has installed an intermediate timing-Belt gear, which might have a reducing ratio of 3. So when the Servo turns three times, the Handle turns one time. This makes more than sense to keep. Becasue it reduces the minimum speed and increases the torque on the handle. I like both!
But:
This caused E-06 Position-Sensor Error. Because. After releasing the pedal, the controller reduces speed and then waits ~ maximum one turn plus some extra way for the needle sensor. If the needle sensor does not detect the needle position, then the controller fires the error and quits working. Depending on the phase, when the pedal was released, in my case the motor had to turn possibly almost 3 more spins, to reach the needle up position! Too much to think everything is ok, from the perspective of the programmers of the firmware. What a pitty.
So the controller firmware software is just too inpatient, to wait for the needle trigger, in cases of an additional gear between motor and Handle.
Now I have checked, how the position sensor works exactly, and I found, that there's also a hall sensor inside. Above it spins a disk with two magnets in, which have opposing mangetic fields. One magnet faces with the northpole to the hall sensor, and the other with the south pole. With this, the Sensor can detect, if the needle is in upper or lower position, and with respect to the customers setting can stop at either position.
Now my idea was, if the path to my desired needle position is too long for the controller, so that it fires the error, I can reduce the path, if I flip one magnet around. Then with every half revolution the hall Sensor fires. But it fires only one event very half revolion. Needle up or needle down every half revolution (depending on which magnet was flipped around). .. but that's not a bug! Its great!
See Photo Position Sensor.
I had to adjust the needle setting in the controller, to detect the position, which my magnets indicate now. Otherwise it fires E-06 Error at all time, because no magnet indicates it.
And the result is, what I have described above:
Depending on the position, when the pedal is released it goes to either needle up or down, depending on what is the next possible.
And the really fantastic thing is:
Small Hits to the pedal moves the needle to the next clear position. Two hits are one complete revolution and stitch. This allowes a) turning the leather, with needle inside the leather and foot up, and also moving the leather by hand, when the needle is up. GREAT!
So guys, please let me know, if this was helpful for anybody!
Sorry for my english, I am not a native speaker.
Andreas.
