Small, quiet compressor to exclusively run a syringe dispenser - Page 1
Forum section: electronics / projects

author: jeremy
author_rank: Super Contributor
timestamp: February 14, 2018, 02:43:22 am
content: Hi all,I’m looking for a small compressor that will be used solely to drive a syringe with solder paste, glue, etc. It will be right next to the desk that it is being used from, and it needs to be quiet. Does anyone know of a compressor like this? Bonus points if it is oil-free.

author: whalphen
author_rank: Regular Contributor
timestamp: February 14, 2018, 02:51:03 am
content: Small compressors are used for air brush painting. Check craft and art supply shops. In the US we have a chain of discount hardware stores that sell mostly Chinese imports at low cost. They have small compressors at low prices. I haven't used any and don't know if they are reasonably quiet. The compressor I use is a loud 2 horsepower unit but I installed it out in my garage with a switch and airline indoors next to my work bench.

author: Ian.M
author_rank: Super Contributor
timestamp: February 14, 2018, 03:03:07 am
content: How many PSI do you need?If all you are doing is driving syringes, you don't need much volume, so an air pig you can charge off a larger compressor located elsewhere, or even a small CO2 cylinder may be a better option rather than trying to find an affordable quiet small oil-less compressor.If you are willing to do some tinkering, small refrigeration compressors are pretty quiet, however you have to do a lot of work to get oil-free air from them. They wont start into a high output pressure load so you'd need to add a check valve and unloader, and they need an oil trap and filter + for a long life, you need to change out the oil for one that isn't hygroscopic.

author: Teledog
author_rank: Regular Contributor
timestamp: February 14, 2018, 03:08:31 am
content: I'd suggest NOT using any sort of compressor, as a typical syringe always has a bit of back pressure (worked in the industry)If you want a finite amount of goop out of the said syringe, lock the syringe into a solid holder,and use a stepper motor (or hand crank?) with a fine pitch screw for dispensing.

author: jeremy
author_rank: Super Contributor
timestamp: February 14, 2018, 03:24:38 am
content: Quote from: Ian.M on February 14, 2018, 03:03:07 amNot sure of the PSI, maybe 80? Cylinders are an interesting idea, I didn't think of that.Quote from: Teledog on February 14, 2018, 03:08:31 amI've used many stepper-based syringe pump in my time, and while they are extremely accurate, they are a bit heavy and not really suitable for handheld use. Unless you know of one that is specifically designed for this purpose?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 14, 2018, 03:30:36 am
content: JUN-AIR is probably the standard for airbrush users. We have one at work and it's decently quiet, but not silent. It also puts a good transient on the line when it starts. For controlled dispensing, we use EFD. They're anything but cheap, but they can apply controlled reverse pressure and will dispense almost anything precisely and consistently. It might be possible to find a used JUN-AIR as they're so popular. An industrial EFD might be found surplus, but I've never looked.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 14, 2018, 03:34:03 am
content: My favorite small/quiet/oil free are the California Air compressors.I go my first one primarily for dispensing, now I have 6 of them.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: February 14, 2018, 03:39:29 am
content: You could use a smaller light weight stepper and combine it with a trapezoidal spindel for torque reduction. Needs a little engineering thoughAlso, there are a couple of miniature hydraulic systems with pumps, valves, cylinders, motors,... on the market for RC model construction. Those might very well suit your needs.

author: Teledog
author_rank: Regular Contributor
timestamp: February 14, 2018, 04:55:19 am
content: https://www.zaber.com/technologies here in Vancouver use a patented linear microscope slide/stages via tiny steppers (and mini screws.. I've seen them).Haven't researched their source...Also, medical PCA pumps are driven in the same manner.

author: jeremy
author_rank: Super Contributor
timestamp: February 14, 2018, 07:13:55 am
content: Quote from: Teledog on February 14, 2018, 04:55:19 amI've used many Zabers, and those things are too heavy for hand use and too expensive (smallish slide is easily $1k). I'm also not sure that the smaller ones would be able to generate enough force for highly viscous solder paste. Medical/microfluidic syringe pumps, also which I have used in nL/uL metering applications, are also too heavy and expensive. I totally get where you are coming from, but it seems you need a certain amount of rigidity to be able to meter such small amounts, and that rigidity comes with weight.The California air tools stuff looks great, but unfortunately not available in Australia as far as I can tell

author: Ian.M
author_rank: Super Contributor
timestamp: February 14, 2018, 08:26:34 am
content: I'd be inclined to experiment with a car tyre foot pump with the check valve removed so releasing it removes all pressure from the system, and a much longer airline fitted. Bolt it down to a sheet of ply with non-skid matting glued to the underside so it doesn't run away from your foot, and couple it directly to the pneumatic syringe driver. It may not give enough pressure, but you could check that before modifying it.If you are looking at motorised syringe driver solutions, it really doesn't need a stepper unless you need metered volume control. A small RC servo modified for continuous rotation driving the plunger actuator screw via a reduction gear should do the job and be significantly lighter. The Futaba servo signal pulse width would control the drive speed. Set the ex-feedback pot so the neutral pulsewidth is somewhere near 0.75ms rather than the center 1ms so you've got more speed range in the dispense direction than the suck-back direction. Use an Arduino to control it using the servo library, with pots for dispensing speed, dispensing duration, and suckback control, and a switch to actuate it.Even if you need volumetric control, a modded servo can still be used - add an optical or hall sensor far enough back in the geartrain to get several pulses for the desired minimum volume increment, fed back to the external clock input of one of the Arduino's counter/timers to let you close the loop. You'd have to keep track of the number of pulses during suckback so you could deduct that number of pulses from the total to dispense in the next application. That would also compensate for backlash in the mechanism.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 14, 2018, 09:05:48 am
content: Why do you want to use a compressor for a solder paste syringe?Seems to me like a very unreliable solution for pushing out an exact volume of solder paste. In theory it should work, in practice, it would be hell to control it, and very prone to errors due to any small variations in the solder paste viscosity. Same with the glue.Instead of compressed air, I would rather use a piston with a screw. The screw will be turned by a small stepper motor, and thus precisely controlling the advanced of the piston and the quantity of squeezed solder paste/glue.

author: mikerj
author_rank: Super Contributor
timestamp: February 14, 2018, 09:55:56 am
content: Quote from: RoGeorge on February 14, 2018, 09:05:48 am100% agree with this; it may be possible to make it work adequately under very specific conditions but it will be almost impossible to make it repeatable. A positive displacement system is needed, if there is no room for a stepper/screw system at the syringe itself then mount it remotely and use hydraulics to transfer the force to the syringe.

author: sleemanj
author_rank: Super Contributor
timestamp: February 14, 2018, 10:33:25 am
content: Quote from: RoGeorge on February 14, 2018, 09:05:48 amI was assuming that the OP was talking about a compressor for an actual solder paste dispenser unit.I don't know how much air flow is required, they do us a venturi for the retract vaccum.As for stepper dispensers, I have it on my list of some-day projects to build one like this:https://www.robotshop.com/letsmakerobots/solder-paste-dispenser

author: iwtommo
author_rank: Contributor
timestamp: February 14, 2018, 10:43:01 am
content: If you do diy, avoid using the cheap 12v diaphragm fluid pumps that are all over ebay. Due to their design none are self priming so do not work for airI am using an automotive cruise control vacuum pump (picked from the scrapyard off some volvo) - the vacuum pump lets me do vacuum pick and place but because both ports of the pump are easily connected to i have the pressure side running to the solder paste dispenser.Ill try and get some photos for you in the coming days.

author: DTJ
author_rank: Super Contributor
timestamp: February 14, 2018, 12:08:17 pm
content: If you do decide to go the compressed air route look at re-purposing a refrigerator compressor.They run pretty much silently and are good for low flow work. The inlet side works well as a vac source. I've been using mine on and off for a year or so. You can pick them up free from junk collections.Search the forum there's a few discussions on the best way to go about using them.

author: jeremy
author_rank: Super Contributor
timestamp: February 14, 2018, 02:21:51 pm
content: Thanks for all your responses everyone.Firstly, just to point something out: screw based systems have their problems too; if the syringe/plunger materials have any elasticity (and they usually have tons, unless you are using glass syringes), it can be difficult to stop the flow at the exact amount you want (I’ve watched one of these screw pumps fail at this under a microscope). In air pressure systems, you don’t need a plunger, and you can pull a vacuum on the syringe cavity to suck the drop on the end back in. You can even stop fluids from dripping out with the right vacuum setup.In mechanical dispensers you have to deal with the mechanical hysteresis in the syringe/plunger clamp (think gear backlash), so you can’t just reverse them quickly like with air, and the amount of hysteresis changes every time you remount the syringe, so you need to recalibrate it each time. If you make the clamp much tighter to reduce this issue, then it becomes slow to change between syringes. Air based systems have none of these problems.Mechanical dispensers are much more prevalent in situations where a small, constant flow is required and the pump doesn’t repeatedly perform short reversals, like anaesthetic delivery or pumping microfluidic circuits. As far as I know, the industry standard is air pressure based systems for automated dispensing machines (glue dots, solder paste, etc) and handheld syringes. See the company “nordson efd” as mentioned above.Now to clear up some confusion, I already have a completely working setup (controller and all) and I’m happy with the dispensing performance. Problem is that the compressor is loud as heck, so I’m looking for another way to get air.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: February 14, 2018, 02:40:21 pm
content: Quote from: jeremy on February 14, 2018, 02:21:51 pmThen repurposing a refrigerator compressor (as suggested above) and adding an air reservoir or installing an air supply ring line in your workshop with the compressor and air reservoir in another room would be the approach I would take.Having access to pressurized air all over the workshop is awesomeEdit: Of course there are also options on the market like the Bambi BB8 etc. that use quiet compressor pumps. Since you do not seem to need a lot of throughput you might want to take a look at compressors for airbrushing. Don’t know what brands are typically widely available to you down under though.

author: John Heath
author_rank: Frequent Contributor
timestamp: February 14, 2018, 02:47:02 pm
content: A small 2 inch sub bass speaker air tight with a check valve in and a check valve out. It would not be high pressure but it would be quiet at 10 or 20 Hz.

author: packetbob
author_rank: Contributor
timestamp: February 14, 2018, 04:45:52 pm
content: I have the same dispenser that sleemanj shows in his post...I run it off of a compressor that is remotely located so noise isn't an issue for me...However I did make up an Instructional on setting the system up and I looked at using a portable air tank for people that didn't have access to a compressor...You'll find details here (look in Step #7):https://www.instructables.com/id/How-to-set-up-repair-adjust-and-use-a-solder-paste/Using a 9 gallon portable air tank I was able to get about 1100 shots before the tank was empty (testing with something similar in viscosity to solder paste).This may work for you assuming getting the tank refilled isn't too much of an issue.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 14, 2018, 06:08:33 pm
content: Quote from: rx8pilot on February 14, 2018, 03:34:03 amI have one of these and it is really nice. I use it for tire inflation and light use of pneumatic tools (finish nailer/stapler). It should be more than enough for a paste dispenser.

author: Benta
author_rank: Super Contributor
timestamp: February 14, 2018, 07:26:25 pm
content: Buy a blood pressure meter and scavenge the pump. They cost around $30 and are quiet. For the pressure you need for a syringe, it should suffice.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 14, 2018, 07:35:20 pm
content: Quote from: Benta on February 14, 2018, 07:26:25 pmWhat kind of pressure do those things make? I run my syringes at 40-45 psi (3bar). Seems high for anything dealing with blood.

author: Benta
author_rank: Super Contributor
timestamp: February 14, 2018, 09:22:54 pm
content: Quote from: rx8pilot on February 14, 2018, 07:35:20 pmOK, forget my suggestion, I had no idea you run pressures this high. The blood pressure tester will probably go up to 400 mm Hg.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 14, 2018, 09:27:18 pm
content: The paste is very thick and needs to be pushed though a very small aperture.Short and misplld from my mobile......

author: Corporate666
author_rank: Unknown
timestamp: February 14, 2018, 09:41:36 pm
content: Quote from: Ian.M on February 14, 2018, 03:03:07 amI second this idea.I have an $8,000 Jun Air compressor at work that's so quiet you can have a conversation right next to it while it's running. One of the best purchases I ever made, but I am glad I made it years ago and no longer remember the hit to my wallet.For your purposes, I would get one of these:https://www.amazon.com/Craftsman-9-15200-Gallon-Horizontal-Square-Inch/dp/B007KHBM8UAnd then charge it with any compressor you want. Those foot-pedal dispensers as shown in the photo use very little air, and a 5-gallon air tank like I linked to on Amazon charged to 130psi would last a long, long, long time if you are dispensing at 30-50psi and would be totally silent (other than the dispenser itself). Then just charge it with whatever compressor you have available to you. You can get those air tanks even cheaper than the one I linked, too.