Question HF500 spindle pump on/off -> twitching motors

Dear all,

I've noticed that the pump for my HF500 spindle causes the stepper motor to twitch when I turn it on/off. This means that I randomly loose steps when I cycle it. The only way I've found to mitigate this is to draw power from another room in my apartment, which is drawing power from a different group in my central power distribution box. Proximity of the pump to the Stepcraft system or the UC400ETH that I use does not appear to make a difference.

However, I just finished building a relay box with opto-isolated relays with the intention to control both my exhaust system and the spindle pump. The control signal is taken from IO port 2 on my UC400ETH. Turning the exhaust system on/off works fine, but unfortunately switching the spindle pump on/off still causes the motors to twitch when the IO port is used on the UC400ETH even though I draw all current from another room and make use of the fact that the relay board has opto-isolated inputs.

I've emailed CNCDrive to pick their brains for some advice, but I also want to hear if anybody else are having issues with the HF500 spindle pump?

Best regards,

Per Takman

Hi Per Takman,

i have a similar problem.

All parts, like pc, steppi and hfspindle are on the same powersource.
After this i have 1 switch for hfspindle + pump.
Sometimes when i poweron hfspindle (and pump too) my usb connection to steppi ist lost.
Yes, the poweron spike do this.

So, when im using hfspindle i put it always on (until job is done).

Hi Nonaga,

If I were you I would consider supplying power to the pump from an outlet on a different fuse group in your home. This works for me, but I manually have to turn the pump on/off.

For the HF-spindle, I would not keep it powered during tool changes. I've noticed that UCCNC has randomly enabled the spindle on a few occasions. I would not consider the software enable safe enough to risk my fingers.

I'm curious to hear if anybody has managed to mitigate the disturbance somehow.

Cheers,

Per Takman

Hi,

It sounds very much as though there is an earthing problem on your systems - your mains supply earth should have continuity through from wall plug to 0V on the controller. Check with a test meter - it shouldn't exceed a few ohms at most

Additionally add an earthing connection between the 0v and the metalwork of the Stepcraft. I my case (no optical isolators) there is also a connection via the USB cable to the earth of the PC/laptop that's doing the clever stuff.

My controller ground connection.

Hi peterg1000,

I've used the supplied grounding cable from Stepcraft as well and fastened it to the bottom of the chassis of the system. This ensures that protective earth reach also the PCB of the system since it is mounted on stand offs.

In my case, the UC400ETH has opto-isolation between PC and the stepper drivers, so they should not share ground.

Are you using the HF500 spindle with the pump supplied by Stepcraft without seeing any twitches when you plug in/out the supply?

Cheers, Per

Hi Per,

I have an HF350 rather than an HF500, other than that I use the Stepcraft supplied main PSU and air pump.

All system accessory and computer power is from the same wall outlet via a multi way extension socket, but I've never had a glitch even when switching on my 500 watt vacuum system.

Have you actually confirmed a low resistance between all the nominally grounded points? I've checked my system and there is never more than 1 ohm between grounded points. My reference point is the earth connection on the multi way extension.

Regards,

Peter.

Hi Peter,

I've checked that I have < 1 Ohm resistance from the protective earth (PE) ground on the power strip that I power the entire machine from including my laptop to control it. The PE ground is also directly connected to one of the stand offs that is mounted on the PCB that also act at the support for the bottom cover using the supplied grounding cable from SC. I've also measured resistance (and voltage) between chassis of the machine and the supply ground for the stepper driver and there is continuity there as well.

I don't understand your extra ground wire on the PCB stand off to what appears to be terminal 4 from above. In my schematics this is the limit switch loop for X/Z. What is the purpose of grounding terminal 4? Can you explain in more detail why you put it there? Were you instructed by SC to put it there?

Thanks for helping out!

/Per

Hi Per,

Originally there was no connection between power supply 0V - on my picture labelled with an "earth" symbol, and the Stepcraft metalwork, hence my link. Not an SC idea, it comes from years of experience as an electronics engineer.

Fast transient voltages between control board 0V and SC metalwork could conceivably couple capacitively into sensitive parts of the control board - hence the link which ensures this cannot happen as the two are now bonded.

I now have a good earth connection to both Y-axis extrusions and the T-slot machine bed as well as all the internal metalwork. Unfortunately the gantry is still isolated since the hard anodising on the roller tracks is a good insulater - if ever I need to rewire this area I will add a separate grounding wires to suitable points on the gantry.

Cheers,

Peter

Peter, which pump is your system equipped with? Mine is from Hailea and the model is called ACO-208. From what I can tell it does not have any built in EMF suppression.

Nonaga, which pump is your system equipped with?

I meet with Stepcraft at the Messe in Friedrichshafen and they were not aware of the problem.

Cheers, Per

Hi Per,

My air pump is a Tetratec APS300 and according to its data sheet should only consume 4.5watts. It's incredibly basic - an iron cored solenoid with an vibrating armature attached to a diaphragm pump. Shouldn't need any EMI suppression itself during operation as there are no breaking connections inside.

However it's a different matter if the device is unplugged or switched off - since the device is highly inductive it can potentially produce very high voltage spikes causing arcing and RFI when switched. This RFI is probably being radiated from your house wiring, so needs suppressing - preferably on both sides of the mains connector or switch.

This link will give you some food for thought as regards a possible cure.

Cheers,

Peter.

per.takman wrote: Peter, which pump is your system equipped with? Mine is from Hailea and the model is called ACO-208.

Mine is also the Chinese made Hailea model which was supplied with the Stepcraft HF500 spindle package. Its air delivery rate seems very feeble, but perhaps that is deemed to be fit for purpose for creating a low pressure air blanket to keep dust out of the Stepcraft HF series spindles?

I did a quick search Amazon for your Tetratec APS300 and other small air compressors for use in aquariums and none seemed to get consistently good reviews.

Some people recommended the Interpet Airvolution 4 and some a Fluval Q2 but all of them were both noisy and quiet, great value for money and a total waste of money, powerful and useless, packed in after 3 months, etc. This is what you get when you let people with no general or specific technical/engineering knowledge review products.

Doug

Thank you Peter for your suggestion! My colleague actually recommended something similar. I've conducted the following experiment today.

1. Remove the parallel cable from the Stepcraft PCB and cycle the pump by plugging in/out of same power strip as the Stepcraft power supply was attached to. No signs of twitching.
2. Mount the parallel cable to the Stepcraft PCB and cycle pump. Very few twitches.
3. Mount the other end of the parallel cable to the UC400ETH and cycle pump. Many twitches
4. Add one ferrite to parallel cable and cycle pump. Almost no twitches
5. Add another ferrite to parallel cable and cycle pump. Can't hear/feel any twitches

Unfortunately, when I add my relay box the problem reoccurs both when switching pump and vacuum machine. My colleague also suggested trying a solid state relay which switches at zero transition. www.electrokit.com/productFile/download/6205

It seems like I have found how the disturbance is entering the Stepcraft stepper driver. I've understood that stepper drivers can be sensitive to this and I don't know how much that can be done to improve robustness against picking up this type of disturbance. However, the fact not everybody see this problem could the due to the fact that I'm using the UC400ETH instead of the UC100. But then again, without the UC400ETH, I would not have a second IO port to use for relays.

As for the pump I must say that the CE mark makes me suspicious. It would not be the first time in history that a Chinese supplier put it there without being able to back it up with actual measurements of the product complying with the relevant standards.

I'll keep you posted on my possible progress on this topic.

Cheers, Per

I've now found one configuration where I at least can power up the vacuum machine using the relays and the pump manually.

This configuration requires:

1. Two ferrites on the parallel cable close the PCB of the Stepcraft system.
2. That my relay box draw power from a separate wall socket in the same room.
3. That I power the pump from a wall socket in another room using an extension coord.

This way I can at least get a notification that a cycle has finished when the vacuum machine shuts down. However, turning the pump on is still manual which means that there is a risk I forget it.

The next step is to play around with solid state relays instead to see what I can accomplish with those.

Cheers, Per

Hi Per,

Your system is growing like Topsy !! Take care not to over complicate it - adopt the KISS principle if possible.

A word of warning - with an inductive load the current is at a maximum as the applied alternating voltage crosses zero, therefore switching the SS relay off at voltage zero crossing will be breaking maximum current. This will effectively maximise any RFI generated !

Cheers,

Peter

Hi Peter,

I realize that I've taken a larger piece of the electronics cookie than I could swallow initially, but I don't think that the functionality I'm looking for is unreasonable. In fact, I was disappointed that these features were not built into the system from the beginning.

I understand your point regarding breaking the circuit at maximum current. Do you have a better suggestion on how to automatically switch the pump on/off without introducing noise into the system?

What could I do to suppress the disturbance right at the pump?

Cheers, Per

Good news!

I've now found a solution to avoid the motors twitching when turning the spindle pump on/off.

1. A high quality line filter between the pump and the supply.
2. Two snap on ferrites on the parallel port cable close to the SC PCB.

I have to say that it is a disappointment that SC release a product that have not been properly tested for immunity to pickup disturbances. Especially when the disturbance is coming from their own choice of spindle pump.

I hope that SC will find a better pump and that users of the forum benefit from the effort I've made.

Cheers,

Per Takman

Hi Per,

Glad you have finally overcome your interference problem. Trouble is that system interference suppression is still somewhat of a black art, and what works for one configuration may well fail for another.

For every unfortunate user ( such as yourself ), there are probably dozens who have never had a hint of a glitch - and this includes me! At least your problem succumbed to a logical approach and will be a good guide for others with similar problems.

Cheers,

Peter