Viewing 18 posts - 1 through 18 (of 18 total)
  • Mechanical engineers – machine project help.
  • Premier Icon MrSparkle
    Free Member

    We are thinking about making a new product at work and want to rig up a temporary machine to manufacture some samples to evaluate before building a ‘proper’ version.
    The idea is to make it a simple (read: cheap) as poss.

    The product is sheets of t & g MDF approx. 1200x600mm with glue being applied in 6 equally spaced lines length ways. These are then taken and racked for the glue to go off for 24 hours. The real deal will probably have a conveyor belt and an overhead gantry, with glue being pumped through nozzles held in a gantry above the belt.

    The trial version will need a glue pump and nozzles. To apply the glue at the right spacing and amount etc it will need to be fed at a set speed so that rules out feeding the boards through manually. I was wondering about a table with a motor driven rubber wheel feeding it through.

    Anyone got a better idea?

    Premier Icon slowol
    Full Member

    Have you tried talking to your adhesive manufacturer?
    I worked with a firm on a project a while ago and the adhesive manufacturer can help as they want to sell you their equipment and adhesive once you set up a production line.
    Having said that for prototyping, which was as far as the project got, it was just hand held tubes and scrapers or you can get a device with a trough above a roller. I think you can also get powered sealant gun devices for even application.
    Some examples of available kit linked below:
    https://www.henkel-adhesives.com/uk/en/products/equipment.html

    Premier Icon scruffythefirst
    Free Member

    Frame out of 80/20 (mbs, rexroth, etc) with stops or guides to set spacing, rubber wheel and motor as you say and glue dispenser. Depending on the glue you might get away with a compressed air fed mastic gun and set air pressure and nozzle size. A bit of experimentation and you’re not far off being able to define requirements for a proper line.

    Premier Icon docgeoffyjones
    Full Member

    When i designed a device to cut plastic tubes into equal lengths we used an encoder wheel on the feeder so we new exactly what length of tube had passed under the blade and when to intiate the cut. you could use a similar system for glue application.

    Mechanicaly/PLC wise it is a fairly simple process. I used to design plastic extrusion systems. a lot of my work and devlopment focused on maintaining the temperature and feed of the plastic to ensure a consitent product. I think you might run into similar diffculties with the glue it self.

    As above I would speak to a glue manufacturer, as stopping nozzles from blocking and ensuring a good application each time would be my main areas of concern and i would imagine a lot of that is going to be to do with the glue used and any secondary systems to maintain the glue viscosity, temperature and feed rate.

    I don’t know much about glue, but is there anyway you could buy the glue/adhessive in a premade strip that you could just apply to the boards

    Premier Icon MrSparkle
    Free Member

    Thanks for the responses. The glue used is a special one (natch) but the product is an existing one so the properties of the glue it are known. We can’t avoid using it.

    Premier Icon moff
    Full Member

    I see two options: Move the Wood or Move the Glue.

    If your limited for space, moving the glue would be a good option.
    Either way an adaption of a CNC Router kit could work as a base point, swap the router head for a the glue dispenser?
    Or use the stepper motors and control to move the wood below a fixed glue dispenser.

    Premier Icon MrSparkle
    Free Member

    Yep.
    We’re not too limited for space tbf. Good shout with the router. In fact we have an existing table that we could maybe cannibalise.

    Premier Icon stumpy01
    Free Member

    It’s hard to come up with a solution without knowing your sort of budget & how many items constitute a trial.
    If you are making hundreds/thousands of samples over several months you probably want something different to if you are making a one-off of 10 samples.

    If you have the space, I would expect the easiest solution to be keeping the glue delivery system stationary & moving the wood underneath it. You can get conveyor belt systems relatively cheaply with some kind of simple speed controller that might have the range of speed you will need.
    If you need more precision, you might need to create your own speed controller with an encoder sending signals to the glue delivery system to modify the extrusion of adhesive based on the real-time speed of the belt.

    For a rough & ready system, I would look to find a conveyor that will fit your speed needs & then fabricate a lead-screw driven feed system for the adhesive. If the adhesive is supplied in ‘silicone gun’ style tubes you could probably have a common ‘pusher bar’ that shoves adhesive out of all 6 tubes at once, linked to a lead screw that could be set to feed at a given rate for a certain conveyor speed.

    Alternatively, as mentioned above there are numerous ‘cheap’ CNC router machines out there. Something like the Root3 CNC, MPCNC, RS32-CNC. You wouldn’t have any concerns over rigidity as it wouldn’t actually be cutting anything. You could just build it with enough bed size to fit a board onto & then use the control system to move the head containing the adhesive dispensers at a very precise speed over the board.
    You could then automate the dispensing of the adhesive as the head moves over the board.

    Premier Icon MrSparkle
    Free Member

    Interesting. I think the glue will be in a tank and will be pumped through nozzles.

    Premier Icon richmars
    Free Member

    Some sort of a mask (like used for solder on SM PCBs)? Or something like a silk screen?

    I’ve used glue robots from Epson on a much smaller scale but I’m sure something like this would work, so, as above, speak to them about a loan. I remember that the speed of the part and the pressure in the glue dispenser is very important, so while not impossible to make something, I don’t think it will be quick or cheap, given the accuracy you need to learn anything

    Premier Icon docgeoffyjones
    Full Member

    <span style=”font-size: 0.8rem;”>Interesting. I think the glue will be in a tank and will be pumped through nozzles.
    </span>

    <span style=”font-size: 0.8rem;”>As stumpy said it is hard to predict what variables you need to control without knowing what your cycle time target is and how precise the delivery needs to be. The faster and more precise the requirements the more variables you are going to have to think about and the more control systems you need.</span>

    <span style=”font-size: 0.8rem;”>You may find a pump (glue) that matches your delivery requirements of flow rate and pressure, or you may need secondary valves to control that. As with any design there is quite a lot of balancing required, in this case between the glue delivery rate and the feed speed of the boards. You will need to ensure you have features that let you vary this, so you can tune the system.</span>

    <span style=”font-size: 0.8rem;”>It does sound like using a router type machine and a fixed board might be a good starting point so you have less variables to control in your prototype phase and most importantly can get making prototypes as quickly as possible. </span>Even if your prototype machine does not match your intended production solution there will still lots you can learn from it.

    Premier Icon stumpy01
    Free Member

    Thinking about this over lunch…how large are the strips of glue being applied? I was thinking like a bead from a silicone gun but could be miles off the mark.
    How viscous is the glue?

    As richmars says – you could potentially use a masking system – if you had a suitably ‘liquid’ glue and want to make quite wide strips could you have some kind of spray delivery system & mask that sits over the conveyor area where the wooden sheets pass below?
    You could have a trigger such as a roller switch (end-stop type switch) that starts the spray system as the wood approaches & just spray the area while masking out the bits you want to remain clean.
    Again, this depends on a million variables so hard to know whether it would be suitable – probably not OK if its a really viscous glue or some kind of niche stuff that costs an absolute bomb as you won’t be able to tolerate any wastage.

    Premier Icon MrSparkle
    Free Member

    Yes, like from a silicone gun. Glue is for damping so it has to bead rather than be sprayed. It gets racked for 24 hours and then another piece of mdf is put on top.

    Premier Icon richmars
    Free Member

    The systems I’ve used aren’t really pumps, just a syringe full of adhesive and air pressure to force it out. You have control of the air pressure and needle size so can control the bead size very well, but you need a consistent linear spread, even on the corners.

    Premier Icon fettlin
    Free Member

    Are you using the glue to hold the T&G together (ie: structural)? Depending on the open time of the glue you my need to also think about handling & storage for the 24hr cure.

    we use automotive grade glue and the open time can be anything from 60sec to 40mins. Moving a part within the 40mins compromises the structure of the glued joint.

    All our gluing op’s are manual at the moment: prep, purge, application from an air-fed gun etc. most of them are 2pac, so mixed at the point of application to save wastage. we also use a calibrated spacer within the molding to keep the gap between the surfaces consistent (most of the glues have an optimum bead thickness/cure time ratio).

    Premier Icon MrSparkle
    Free Member

    Noted. Good point that. Cheers.

    Premier Icon lerk
    Free Member

    You might also find that telling the glue supplier about the process you hope to achieve will select a different product to apply/cure faster.

    The very easiest method would be to sit the piece tongue down and run it through a bath of adhesive before manhandling it together, clamping and storing, but that would be subject to the availability of a suitable glue.
    For an interrupted glue area a roller to lift the workpiece intermittently would suffice.

    I have a history of packaging machines which use hot melt glue in pellet form which can be sprayed at the workpiece, but these require a very fast (1-2seconds) make up time once glued so you would need to apply and build simultaneously.

    Premier Icon MrSparkle
    Free Member

    Update: I have passed all relevant info to our MD. At the moment this is on the back burner but might happen at some point in the future. For short term we may go for double sided self adhesive strips and then move on to a glued system in the future.
    Thanks to everyone who has chipped in here. It is appreciated,

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