MAXI FIX Professional Heavy Duty Hot Glue Gun Teardown and Help! - Page 1
Forum section: electronics / general

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 20, 2012, 08:30:56 pm
content: Hi, I needed a "nice" glue gun and as the dremel ones are not on sale anymore I bougth one from UK:http://www.ebay.com.au/itm/MAXIFIX-CORDLESS-QUALITY-HEAVY-DUTY-HOBBY-HOT-MELT-HEATED-GLUE-GUN-11MM-STICKS-/320874669984?pt=UK_Crafts_Cardmaking_Scrapbooking_Glue_Tape_EH&hash=item4ab59ee7a0Inside:Well, as is from UK (I am not electronic/electric) my first perception is about as the gun is rated 240V will work with less temperature here with 220V, so I want to know if anyone can help me to do something, in the 200ºC setting, the gun takes 21 minutes to achieve 150ºC in the core as my tests show (the manual says 7 minutes):I took the measurements with a UNI-T multimeter... I am sure about the quality of the UNI-T temp probe but they seeem to be correct or at least stable.Any hint? I tested adjusting the pot to the right, and started to vibrate a lot (with a bit of electronic burn odor), so my guess is: this small board is controlling the heater-on-off based on the slider to set the temperature + some sensor? so probably the best way to rise the temperature is changing the resistor that is in series with the temperature sensor right? Any hint?Thanks a lot!

author: IanB
author_rank: Super Contributor
timestamp: April 20, 2012, 08:51:56 pm
content: Firstly 240 V to 220 V wouldn't make that much difference (it would be an 85% reduction in power). If the heater can't make 200ºC at 220 V I doubt it can make it at 240 V either.I'm sad to say it, but it doesn't much like a quality glue gun. It looks more like a low cost economy item. Especially at £16.99, which is not expensive in UK terms. Given that postage doubled the cost, couldn't you have found a better item locally in Australia?Well I know that isn't the question you asked, but as for fixing it I doubt you have any options. It seems to me like a design limitation, not a fault. I would guess the tool is simply not up to standard.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 20, 2012, 09:05:28 pm
content: Quote from: IanB on April 20, 2012, 08:51:56 pmThanks for your answer, it seems very well made to me inside, think about I used always a dollar-store one, not even kapton tape in the heating elementand as I am from Chile, shipping and some glue bars added like 80 usdbut is the 'tax' I paid usually for electronics.I also think 85% is not a lot but in temperature 200ºC- 15% is 170ºC so there is still mising some %. Maybe is the way the regulator works, can be the voltage a reference for the thermal sensor? + thermal element working with less energy?Will make any difference if I try to get the PCB schema and components to test how they work in a simulator? I like this gun, has a dock, so you can remove it to work, but 25 mins heating is a lot more than I expectedAny recommendation about a good glue gun?

author: IanB
author_rank: Super Contributor
timestamp: April 20, 2012, 09:50:58 pm
content: I don't know about good glue guns. I bought a small inexpensive glue gun from an arts and crafts store once (I use hot glue very rarely so it was more of a "toy" purchase). The gun I bought seems to take ages to get up to temperature before the glue flows. Much longer than is convenient in my opinion.As for a recommendation, I think maybe some of the guns on this page are more like "professional" models. Note how they have interchangeable nozzles, high power heating elements up to 200 W or more, and good customer reviews. They are going to be 120 V models, but maybe you can find similar 220 V models?http://www.amazon.com/Grizzly-H8141-Watt-Professional-Glue/dp/B000M631R6

author: david77
author_rank: Frequent Contributor
timestamp: April 22, 2012, 08:24:13 am
content: Steinel makes quite nice glue guns, I recommend the 5000 type. They are available as 120 and 230V versions.http://www.steinel.net/products/glueguns/diy_glueguns.cfm

author: ciccio
author_rank: Frequent Contributor
timestamp: April 22, 2012, 08:48:00 am
content: Quote from: IanB on April 20, 2012, 08:51:56 pmI'm sorry, but there is an error: the power reduction will be 16%:220 * 220 = 48400240 * 240 = 5760048400 / 57600 = 0.84 that is 16% less power.This will not be a problem, because (except the small, very low cost ones) practically all the glue guns I've seen use a PTC type heater, that result is a temperature stabilization effect.The one shown by the original poster seems more complex than most (it has a fuse inside !!!)and I think the trimmer could have one of two functions:1) adjust operating temperature or2) set maximum temperatureSome small adjustment (with due caution) while controlling temperature, could show the effect.Best regards

author: IanB
author_rank: Super Contributor
timestamp: April 22, 2012, 04:35:48 pm
content: Quote from: ciccio on April 22, 2012, 08:48:00 amIndeed. 100% - 16% = 84% (I rounded it up to 85%). As you say, such a relatively small reduction will not be a problem.

author: Monkeh
author_rank: Super Contributor
timestamp: April 22, 2012, 04:42:00 pm
content: Quote from: IanB on April 22, 2012, 04:35:48 pmYou said it would be an 85% reduction in power, not a reduction to 85% power.

author: IanB
author_rank: Super Contributor
timestamp: April 22, 2012, 04:50:58 pm
content: Quote from: Monkeh on April 22, 2012, 04:42:00 pmYou and everyone else know what I meant. To interpret that statement as a reduction to 15% of the original power would be absurd.

author: Fraser
author_rank: Super Contributor
timestamp: April 22, 2012, 05:00:39 pm
content: I have used a Bosch PKP18E glue gun for several years. I liked its extended nozzle that provides access in tight spaces. It has worked very well for me.See it here:http://www.screwfix.com/p/bosch-pkp18e-glue-gun-240v/25512;jsessionid=hQ22PJ4RpQhStWJ4Z9p9DJCcvLjzkCgvVq1t6kQTLXQhxrG0LbLP!-853497735?_requestid=174741Amazon reviews are available here:http://www.amazon.co.uk/Bosch-PKP-240-Volt-Glue/dp/B0001D1Q72Bosch sell Worldwide so you should be able to find it locally.Aurora

author: Monkeh
author_rank: Super Contributor
timestamp: April 22, 2012, 06:35:27 pm
content: Quote from: IanB on April 22, 2012, 04:50:58 pmAfter parsing it a few times to figure out your mistake, yes.

author: G7PSK
author_rank: Super Contributor
timestamp: April 22, 2012, 08:12:06 pm
content: Quote from: david77 on April 22, 2012, 08:24:13 amSteinel are the industry standard in the plastic welding and tarpaulin world here in the UK. I have one of those steinel glue guns I baught from Lidl's of all places at a knock down price. I also have a steinel hot air gun plastic welding gun which I have been using for over 20 years and it works today as well as the day I purchased it.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 22, 2012, 08:58:39 pm
content: Thanks a lot for the answers everybody!!,now I think the temperature control is much more simpler than I imagined. I am not an electronic but I tried to trace the small pcb and identify components and it seems there are 2 ptc heaters (no sensor) and one is controled by an intermitent circuit controlled by a triac:As initially I was thinking the EXTERNAL temperature control was setting a reference level for a temperature sensor, and that temperature control was in series with a 240k ohm resistor, so my idea was to replace that resistor to rise the temperature (200ºC = 0 ohms, 150ºC = 500k ohms) so I tried first a 200k resistor in R3, without much changes, then just a wire to get 0 ohms, without much changes (I was expecting >170ºC if relation were linear). I tried a 470K resistor, and the gun worked at less temperature.Quote from: Aurora on April 22, 2012, 05:00:39 pmHow much your BOSCH glue gun takes to heat up? when assembling things I constantly need the gun, it will be nice to find one heating up in less than 1 minuteQuote from: david77 on April 22, 2012, 08:24:13 amIndeed, I was just looking for that one, the have very good reviews. Too bad I can't find one with the dock in ebay and amazon don't send anything to Chile excepts books.Quote from: ciccio on April 22, 2012, 08:48:00 amAt the end, I am pretty sure you are correct, they use a PTC type heater, I found some datasheet for ones that work at 200ºC 8W (this gun is rated 35W, I measured the power consumption and it starts at 70W like few seconds then oscilates between 30-40W) and PTC heaters seems to support a wide range of voltages, from 120 to 240 usually.

author: IanB
author_rank: Super Contributor
timestamp: April 22, 2012, 09:12:00 pm
content: Quote from: Erwin Ried on April 22, 2012, 08:58:39 pmIn my glue gun research over the past few days, I read that 7 minutes is described as a "fast" warm up time. Huh?Looking at more expensive guns, they can have heaters of 100 W or sometimes 200 W. The reviewers of guns with 200 W heaters say they are ready to use in seconds. You plug it in and you can start gluing right away. The same reviewers say that 100 W guns are "slow".I think therefore that the "hobby" style guns with a 35 W heater normally take several minutes to reach operating temperature. I have a Surebonder H-270 gun with a 40 W heater and it does require a few minutes before I can use it.http://www.amazon.com/Surebonder-H-270-Full-Size-Temperature/dp/B000BQM5CO

author: IanB
author_rank: Super Contributor
timestamp: April 22, 2012, 09:30:52 pm
content: I just timed it with the Surebonder H-270 glue gun. From switch-on to glue flow took approximately 2 1/2 minutes. You could call it 3 minutes for good measure.I am using all purpose glue sticks like these:http://www.amazon.com/All-Temp-Hot-Glue-Sticks-Package/dp/B000FAFJEW/

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 22, 2012, 09:59:47 pm
content: Did you get it working then?Based on your schematic it looks like the internal POT is used to fine-tune when the TRIAC is triggered. Setting this to a lower setting should trigger the TRIAC more frequently and raise the temperature.If it still doesn't get hot enough you can tweak the value of the resistor that is in series with the TRIAC gate. Lower values will make the TRIAC trigger sooner in the cycle, therefore increasing the temperature. Don't short this resistor! Read the TRIAC datasheet and make sure you respect the maximum gate current.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 22, 2012, 11:26:38 pm
content: Quote from: TerminalJack505 on April 22, 2012, 09:59:47 pmNo, it always reach 153ºC. It may be 2 heaters, one rated 100 and another rated 150 and the external pot only controls that one, but less than 240K should not change anything on heating speed or hotness. I am clueless don't get a lot how the pcb works because there are some pieces missing, and I tried to simulate the circuit in multisim, but more clues appeared, like what TRIAC should I use (I didn't found a "Virtual triac" only rated ones, etc)Quote from: IanB on April 22, 2012, 09:30:52 pm3 mins sounds very nice! I saw one in Dealextreme at 20 usd, 120W that heats up in 45 secs hehe, a guy disasembled it and seems very nice contructed. Anyway I can sure use this maxifix one for a while, I found very interesting to see how the gun was working to tweak it.

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 23, 2012, 12:33:33 am
content: QuoteYes, based on your schematic one of the heaters is on permanently. The other is turned on based on the temperature setting potentiometer. The one that is on permanently must be setting a base temperature.

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 23, 2012, 04:16:06 am
content: You need to double-check your schematic. I drew up a schematic in my simulator based on yours and, as you can see, it is incorrect.Heater #1 needs to be connected to the TRIAC. I'm guessing the connection to R4 is incorrect and it should be connected to the TRIAC's A2 pin, instead.Also, I'm suspicious about POT2. I don't know if it should be paralleling POT1 and R5 like that.Also, is C3 really connected to the TRIAC's A2 pin?

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 23, 2012, 05:33:33 am
content: Oh nice! Thanks!! I was trying too to simulate the pcb but it is very hard to extract the components and links because the pcb is very small and I don't know any special technique to do that job, I was looking for some "reverse engineering" pcb app, but I didn't found any simple one. I aligned the 2 frontal images in photoshop to identify the copper pads and links but my best attempt to get the circuit was the draft in my whiteboard.About the internal pot, it was a small one, when I turned it to the right half turn I hear some buzzing sound and felt a bit of transformer-burn odor, so I imagined it was controlling the ratio of switching for the Triac.Here are the photos of the PCB and components:As for the DIAC, I guessed is a diacbut I am not 100% sure, the simbol in the silkscreen looks like this:And it says C502:Blue and white cables wire the (I guess) heaters (they are covered in kapton tape, on both sides of the main metallic cilinder that ends with the nozzle, can't remove them without destroying the gun). The red cables are connected to a pot that says 500K and it is labelled 150 - 200º C in the gun case.

author: T4P
author_rank: Super Contributor
timestamp: April 23, 2012, 02:37:44 pm
content: Yes that's a diac , if there's a triac there usually is a diac , like those CFL's ( not the cloned 936's , they use the opamp to drive the triac ... go figure , the original 936 uses a triac driver)

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 23, 2012, 05:18:11 pm
content: Here's the schematic based on your latest pictures. I'm still not so sure about POT2. I couldn't tell where it is based on your pictures so I left it where it appeared in your draft schematic.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 23, 2012, 05:27:56 pm
content: Neat! what simulator do you use? can you upload the file to play with your schematic? the pot in the picture is placed here:

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 23, 2012, 05:48:37 pm
content: The schematic is correct then based on your latest picture. You might double-check it, though.The simulator I drew the schematic up in is called QUCS. You can download it for free. The schematic I drew up won't simulate without making further changes. I really just used the simulator to capture the schematic since I was interested in how the circuit worked.I might play around with it later and see if I can make it simulate. I'll upload it if I can.Note that the schematic shows a couple of things of interest...First, the fuse is improperly placed. They put it on the neutral side instead of the hot side.Second, you will need to be careful when adjusting POT2. The schematic shows why you might have smelled 'magic smoke.'

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 23, 2012, 09:40:22 pm
content: Something that you might want to do now that you know the circuit is 'hotwire' heater #1 and run your temperature test again just to see if the glue gun gets anywhere near the temperature you are trying to achieve. If it doesn't then you'll at least know it won't be possible since you won't be able to get any more heat out of it.So long as you're monitoring the temperature it should be safe to just short either the A1 and A2 leads of the TRIAC or R1 (in my schematic, I'm not sure what the board says.) This will basically just take everything in the schematic to the right of Heater #1 out of the circuit and keep heater #1 continuously while you run your test.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 23, 2012, 11:12:15 pm
content: Quote from: TerminalJack505 on April 23, 2012, 09:40:22 pmSounds logical, I can even remove the pcb and hotwire both heaters, I guess PTC heaters don't require any fancy, just like a light bulb. Anyway as the temperature I measure is in the nozzle and in the metal body, maybe it is designed to heat inside, so I measure 50ºC less because of that (supposedly the gun can stay 10 minutes without connection, like wireless).

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 24, 2012, 08:11:48 pm
content: I played around with the circuit and got it working in the simulator. I'm guessing that I misread the value of the internal POT. I read it as 502 (5k) but I'm guessing it's really 205 (2M.)Here's the final circuit. The internal POT is obviously used during manufacture to calibrate the temperature. Lower values will keep the heater on longer. The value of the pot can't go below about 10k, however. Otherwise, too much current will flow through R4 D2 and the gate of D1.Here's the output of the simulation showing the relevant waveforms. Note that I just guessed at the resistive values of the heaters.I've attached the simulator files if you want to play around with them.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 24, 2012, 08:50:30 pm
content: Quote from: TerminalJack505 on April 24, 2012, 08:11:48 pmHAHAHAH! coooool! you reversed the gun perfectly! nice!!! I still haven't tested hardwiring the heaters, mainly because the screws in the gun are a little "damaged" right now so I will check your simulation first to be sure what test to do over the gun and open it for the last time

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 26, 2012, 06:54:48 pm
content: Hey! I removed the internal pot to measure the factory default setting and it is 1.25 M ohms, what value do you thing is appropiate? I remember when I turned this pot to the RIGHT the circuit smoked and buzzed (and for the right the resistance increases), I have plenty of freedom to the left nothing seems to happen, can I set this pot to 100 kohm for example to get neat the max temp? I am not quite sure about how this circuit works, AC things are confusingI copied your circuit to multisim to try to understand it a bit more (I didn't find how to change things while the simulation is running in the simulator you said)

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 26, 2012, 07:37:57 pm
content: Yes, a setting like 100k should increase the time that the heater is on and, therefore increase the temperature.The circuit basically works as follows...Capacitor C2 is charged through the two pots and R3 (which is in series with the external pot.) The smaller the values of these two pots, the quicker the capacitor charges. Until the capacitor's voltage is greater than the DIAC's breakover voltage the TRIAC is off. When the TRIAC is off the heater is essentially off as very little current is flowing through it.When the voltage across the capacitor finally (if ever) reaches the DIAC's breakover voltage the TRIAC is triggered. Once this happens there is a low impedance path for current to flow--through the heater and the TRIAC back to neutral. The voltage across the TRIAC drops and the remaining voltage is dropped across the heating element.The TRIAC will turn off when the current through it drops below a certain value. This happens twice every cycle when the voltage crosses 0V.You can see all of this in the screenshots of the waveforms that I attached.So lower values for the two pots will cause the TRIAC to be triggered sooner, essentially.You don't really need to dynamically change component values to understand how the circuit works. Just choose some settings, run the simulator, make note of the behavior, repeat.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 26, 2012, 07:54:01 pm
content: Quote from: TerminalJack505 on April 26, 2012, 07:37:57 pmThanks a lot for the explanation and for your time! Lots of learning from a 25 usd glue gun! Will make more tests about temperature today with some fixed small resistor values!Quote from: TerminalJack505 on April 26, 2012, 07:37:57 pmYes I know, but it is like a small detail that helps me a lot to understand things.

author: Rufus
author_rank: Super Contributor
timestamp: April 26, 2012, 08:12:40 pm
content: Quote from: IanB on April 22, 2012, 09:12:00 pmI have a glue gun from this placehttp://www.hotmeltgluegunsticks.co.uk/which looks like a useful site for glue/gun information.Had it for ages and the model is long obsolete. Never paid much attention to it before, it just works.I checked and from cold it draws about 270W for 90 seconds then cycles about 90 seconds off and 15 seconds on. Obviously has on/off thermostatic control.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: April 27, 2012, 02:36:16 am
content: Hey TerminalJack505, can I ask you a final question?:http://screencast.com/t/wSkqtTfXaBI noticed about the current over heater #2 when internal pot is very low, as you said before: will this damage something? (I mean, I used 100K recently in the real gun, and It does not seems to affect the heat a lot, maybe because the gun is just cheap the temperature I read now is actually the max) but just to do a final test to close the case, it is safe to replace the pot with just a wire? or it is safer to remove the pc and just hardwire the ptc's?

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 27, 2012, 05:17:36 am
content: You can't replace the POT with a wire. That will allow too much current to flow through R2, D1 and D2.If you are wanting to keep the heater on permanently, you can replace R1 with a wire.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: May 10, 2012, 07:34:15 pm
content: Finally I ordered a "JOER" chinese 150W glue gun, much cheaper (mainly because shipping to Chile from China is way cheaper than from UK) and way better!heats in 2 mins to 200ºC and it has a pot from 140º to 220ºSo, for those who need a quick heating glue gun on the cheap:http://www.ebay.com/itm/250963772048Some extra info: Starts using 122W, then drops to 90W and then to 0W and 70-90WUltra Cheapo things FTW!