JoMama

There is a big difference in threads and it is more than just sewability. I started off getting cheap thread because it was convenient and cheap from Superiorthreads.com. Their "Bonded Poly" was not bonded and frayed as soon as it was cut. Not to mention, the black thread bled all over the Yellow 40oz PVC I was sewing. I've since switched to Coats Dabond and don't have any more fraying or bleading issues, and it does not jam up the machine like the cheap stuff. Sourcing it can be difficult in single spools, especially in the larger sizes that you are using or special colors. Good luck.

Moving the motor towards the rear of the table does not let you use the belt tension adjustment feature on the motor. Moving it below the pulley preserves that functionality. I'm a mechanical engineer and have a full CNC machine shop for my real work and if I had to do it again, I'd gladly spend the extra 30% for the bolt on reducer that drops the motor below the pulley. Some things are just not worth wasting time on.

You guessed wrong. The problem is that the speed reducer I bought does not attach easily, when there is not enough table to move the motor back or forward. I had to make a couple spacers and move the motor down 5". If I had more table I could have moved it back 4". The speed reducer I now wish I had bought will fit any table, appears to bolt right up with no drilling needed and a lot less fidgeting with alignment, not to mention it uses sealed ball bearings instead of cheap bushings and keeps the motor over the pedal so your linkage is not at some goofy angle.

I bought a speed reducer that looks like THIS one and it was a pain to install because you cannot tilt your machine back since the drive belt is no longer in line with the machine tilt pivot and machine pulley. I suggest getting one of THESE since it will save you at least $100 worth of headache. I wish I had. You will not have to cut a bigger slot in your table either.

...and when you get it, here's a thread to make it run even better with more control. http://leatherworker.net/forum/index.php?showtopic=55723&hl=

Thanks for the replies. I contacted Coats and they recommended Ultra Dee and Dabond, since they use a better dye process that the chemicals in vinyl do not affect.

So I got some #92 and #138 black polyester (Solar Gaurd) from Superior Thread and the stuff is bleeding all over my yellow 40oz PVC material and leaving all kinds of fuzz balls that also bleed. Where do you guys get your thread that is not made in China like this "not so superior thread"?

Just a note on the magnetic field, the strength of the field is an inverse cube relation to distance. By biasing the voltage from the hall sensor with the pot/switch to limit speed, you miss out on the long gradual taper of the sensors voltage curve, which improves the slow speed control, while still leaving plenty of top speed. Now if you are setting a speed limit and then running the machine at that limit for a bunch of pieces, that's completely different from what I'm looking for, which is to easy slow speed control via the pedal along the curves and tight corners and then still be able to open it up on the straights without stopping to adjust a dial. My speed limit is my foot. Cheers, Jo

I never checked it, since I did not see the speed LIMIT as the problem. The issue I had was a lack of range of motion on the motor control arm between zero and full speed. When I was first looking at it, I noticed that adjusting the speed slower, just increased the dead-band before the motor started to spin and did nothing to increase the arm's range of motion from zero to full speed. This motor controller does not adjust the travel range when you when you adjust the pot as you would hope. My guess is that the pot just provides an offset voltage to suppress the voltage from the linear hall sensor, limiting the speed by decreasing the effective output of the hall. Hench the decreasing resistance on the pot to limit the speed. I have used the same linear hall sensors in numerous other applications, and typically, you want the magnet to approach the sensor axially to its face, so the magnetic field extending from the face of the magnet gradually presents to the sensor. On this motor setup, the magnet approaches laterally, where the magnetic field lines are closer together and the transition from zero to full field strength happens with a shorter motion and is less linear. I have my FS-550 motor RPM set at 2830 RPM (two clicks below the fastest speed, 3450rpm) and it is easy to control the speed between 15 and 60 stitch/min, but it will also spin up to 300+ when I want it to, also totally controllable. I'd suggest you go back to the stock pot, set it between 75% and 100%, do the magnet mod, drill a line of holes in the side of your pedal and attach your pedal rod or chain to those, to see which position you like the best. The closer to the pivot you attach the rod or chain, the better your control will be. That can also limit the speed by not having the pedal movement that allows the motor control arm to travel into the faster region. edit: As pcox mentioned, you could increase the controllability by just moving the rod or chain closer to the pedal pivot, but the magnet mod changes the speed curve to have more linear speed control.

With a 3:1 reducer, I still use the stock multi-position switch and just leave it set a couple clicks below the fastest speed. Before the magnet mod and rod repositioning on the pedal, the motor would go from zero to full speed using only 10-15% in the middle of the pedal range. After the mods, the first 10% of the pedal movement is dead-band (intentional) and the last 90% is variable. When I say pedal range, I mean hard-stop to hard-stop on the pedal, as if the control rod was disconnected, not the stops on the motor arm limiting the pedal movement. I'm typically only doing 30-90 spm, but when I want to go faster (300+), I don't have to turn the knob to a faster setting, I just floor it, because the control is soooo much better. I see no reason to change my switch for a lower resistance pot.

I did the magnet mod above on a Family 550 servo, but the motor is the same as this Cowboy motor with a slightly different electronics box. Running a 2" pulley on the motor, a 3:1 speed reducer and setting the rotary speed limit switch to around 3000 rpm. I get easy control from 15 spm to around 400 spm. I also put an extension on the control arm coming off the motor (not shown in the pictures posted earlier) and moved the bottom control rod attachment point from the piece that bolts to the top edge of the pedal, down to the side of the pedal, after drilling a hole in the side of the pedal. You don't need the arm extension if you drill the hole in the side of the pedal closer to the pedal pivot. Now, there is no reason to set the speed limit lower, because the foot pedal has much more range, for better control. It uses the full range of the foot pedal now.

Cheap 3 phase motors do not do well with VFDs at low speed. They heat up and the voltage spikes can breakdown the insulation. Inverter duty motors can be run down below 10% of the normal speed, but cheap 3 phase clutch motors probably would not last long running below 25% of rated speed. The "servo" motor being discussed in this thread is a two pole DC motor with PWM driver, not really a servo.

Thanks for the feedback. I'm seeing a trend, which is "I'd rather have bought a Juki" My thread kept coming out of the roller tension as well until I noticed a tiny tab at the 11:00 position that it needs to go over, but is impossible to do without using something sharp to help it around the tab. Anyway, the decision was made for me when I sat down at the machine yesterday and noticed another problem, the tension will not release because the linkage does not even begin to touch the release pin with the foot up. I'm not sure if that can be adjusted, but I'm done with it. Too many things wrong in the first few days is a good sign that the people that built this machine were asleep at the wheel and the "inspected by" tag is just a hood ornament. It's going back and getting replaced by a Juki 1541S. I probably should have considered the time of year when buying something Chinese. All the workers go home for a month during Chinese New Year and many of them do not return to their jobs after, so there is always a lot of worker training going on in March and a couple months later that product hits the US market.

The magnet modification made the biggest difference on my machine. With the knob set to the maximum speed, I can still control the foot pedal to get anything between about 50spm to 1500spm. The only problen with that long, skinny, 2 pole motor design is that is does not as have much torque when run in the bottom 5-10% of its range. It is a motor designed to run at 3400 rpm and anything less than 340 RPM, they don't like and it can oherheat the windings, which is why I have a speed reducer on the way. That should take it down to 17-500spm of controlable speed.

Maybe it is has different electronics. The knob on the front (circled in blue) is the speed LIMIT and only sets the maximum speed. On mine it is a multi-position rotary switch with detented positions, but it could just as well be a potentiometer which would be smooth, while turning. The speed CONTROL comes form the linear hall sensor circeld in red and it varies the speed between zero and the maximum set by the knob, in relation to how far the foot pedal is pushed down. Modifying the magnet angle increases the range of motion that the arm travels between zero and maximum (set by the knob) and makes it more controlable.