Pneumatic vise for desktop injection molding

A pneumatic toggle vise for desktop injection molding machines. Desktop injection molders often come from the factory with small vises for holding the mold halves together. This vise aims to be an upgrade to those, enabling the use of larger molds, cutting down on cycle time by eliminating the time to close the manual vise (and supporting C-clamps). The aim of this project is to be DIY friendly, using off the shelf parts, using aluminium, 2D milling / drilling operations. The research topic for this vise, and my journey of building it can be found here: https://community.preciousplastic.com/research/make-a-diyable-pneumatic-vise-for-injection-molding This how-to assumes knowledge of CAD and a tiny bit of metalworking.

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17 steps

1 Project files

Attached as vise_files.zip are the project files necessary to follow this walkthrough. The CAD part of the project is included as vise_complete for two file extensions - STEP and FCStd (FreeCAD openable). The zip also contains a Bill of Materials and printable schematics of the plates

2 Plate manufacture - optional printing step

This step is entirely optional. You can print out a 3d model of the vise plates and assemble a prototype. This allows you to make the entire vise, test the action of it and help you visualize it a little bit better. It also helps with alignment and can be used as templates for cutting out the aluminium plates. This does take a lot more time though, since you need to make a lot of tapped holes for a prototype.

3 Plate manufacture

The hardest and most time consuming portion of the build is manufacturing of the plates out of aluminium. Remember about the possibilty of having them made at a metalworking shop for you, if money is not an issue. If possible, order the material from the supplier already cut to size, at least for the largest 3 - 4 plates. Be extremely careful when metalworking, especially if you have little experience with it. Make sure everything is clamped and doesn't move. Go slow, stop if something doesn't feel right to you. Wear a respirator when cutting aluminium. The simplest way is to cut aproximate shapes of the plates / parts using a circullar saw with a blade for cutting aluminium. These blades have a large number of teeth and allow you to make very precise cuts. You do not need to follow the CAD perfectly and will still end up with a functonal vise. You don't need to filet the corners for instance and a rectangular piece will work just as well as the rounded one.

4 Plate manufacture - optional router step

You can achieve a very high degree of accuracy by using a woodworking router with a copying bushing and following a template. Be careful - this technique requires absolute certainty in your skills and your workholding. This technique is potentially dangerous and entirely optional in the manufacture of the vise. You can use a guide bushing in a wood router to follow a 3d printed / wood template of the plates to get the perimeter of the plates very close to the CAD model. To achieve this, you need to build a stable template rig. Offset (or scale) the perimeter of the plate by the difference between the bushing radius and the radius of the cutting bit. Use double sided tape to secure the template on the top of your stock. Sandwich your stock between three wood layers. MDF on the bottom, plywood in the middle and top. The middle layer needs a hole the size of your stock. Secure all layers with woodscrews, clamp to your workbench and cut out the perimeter going off of the template.

5 Plate manufacture - drilling

If going the DIY route, you will need to drill a lot of holes relatively accurately. The easiest method of achieving that requires a calibrated 3d printer and a transfer punch set. Export the plates to a slicer of your choice, scale them in the Z axis so they are less thick and don't waste as much filament. Alternatively, if you've printed the prototype, you can use plates from it as a template. Clamp down the template to the stock and transfer the holes onto the metal using the transfer punches. If you don't have a 3d printer, print the plans and use those to mark hole locations. Drill out the four large holes on the main plates using holesaws for metalworking. Start by drilling out a small hole in the middle of them. A holesaw has a guiding drill that will help you drill them precisely.

6 Structural rods preparation

For all four stainless 500x20mm rods, you need to cut an M20x1.5 thread on them. Start by grinding a bevel on the end of the rod. Clamp the piece in a vise and cut the threads. It should be around 60mm. This allows you to clamp the immovable external plate with two M20x1.5 nuts on each side. On the opposite side of the rod, you'll need to repeat the process, this time cutting a thread 100mm long.

7 SK10 rods preparation

To make the toggling mechanism, you'll need two sets of four tapped rods: 4x 10x70mm 4x 10x130mm You can cut them out using an angle grinder. Each rod needs an M10 thread at the end of it, between 20 - 25mm long. Assemble the rods by screwing on eyenuts on both sides. Don't overtighten them.

8 Mounting the SK10 supports and 10mm rods

Cut four 10mm x 90mm rods. Screw the SK10 blocks into the external and moving plate. Do note, that the external plates are asymetric - they have extra material on the bottom. Make sure you're screwing in the SK10 blocks with the tightening screws pointing upwards - you'll be locking in the shafts later. Insert the 10mm shafts into the SK10 blocks, mounting the previously prepared (step 9) eye nut rods. Make sure the longer ones (10x130mm) are on the outside of the vise, with the shorter on the inside. Repeat the process on the moving plate.

9 Mount the bearings to the moving plate

Check for alignment of the structural rods - mount the 20mm rods to the external plate, clamp it with M20x1.5 nuts. Then slide the bearings with the flange on the side of the toggle mechanism. Put the moving plate on the structural rods, insert the bearings into the movable plate. Make sure nothing is binding up. If everything is sliding correctly, it's time to screw the bearings onto the moving plate. Drill out and tap holes to secure each of the four bearings.

10 Mounting the piston, piston plates

At this point, screw in the plate with ten corners to the opposite side of the internal moving plate. Prepare: 2x10x100mm rod 2x10x160mm rod Assemble the lower piston plate by screwing in SK10 blocks. Thread the shorter shaft through one side of the shorter eye nut rods. Repeat for the other side, you should end up with the vise looking like the last picture. This step may require you to adjust the eye nut rods by screwing in / unscrewing them to get prope alignment for the rods. You can expect to have to use a hammer in this step to get everything aligned. .

11 Mounting the piston, piston plates pt2

Bolt the SC80 piston to its piston plate. On the underside of it, screw in four SK10 blocks. Screw in the M20x1.5mm piston into the lower piston plate, going as far as possible. Be mindful of the input / output of the pneumatics - best having it on the side of the vise instead of front -> back.

12 Mounting the upper piston plate

Now use the longer eye nut rods to secure the upper piston plates. Put in the longer shafts from step 12 into the SK10 holders. Mount the eyenuts onto them. Screw and unscrew the eye nuts to adjust for distance. Expect a lot of trouble lining everything up. You will need to use a hammer and a lot of force here. The end result should have the plates parallel, the piston straight up. Check for the vise moving properly and not binding. You can do this by either assembling the pneumatics and giving it air, or by pushing on the bottom piston plate and the moving plate, extending the pneumatic cylinder manually.

13 Rear plate final assembly

One of the final things to do is to secure the SC50 cylinder to the external plate opposite the toggle mechanism. It'll be used for actuating ejection pins. Screw in the spacers - for the ejection pins and the ones offsetting the piston itself, lock the rear plate with M20x1.5mm nuts on the structural rods on both sides.

14 Pneumatics assembly

The setup for pneumatics is really simple. Start out with a reductor with a water filter. This will let you change the force the piston is exerting onto the lower piston plate by lowering the pressure. Then run a line into the middle hole of the 5/2 pneumatic lever valve, on the side with three holes. This is your input. Run two lines from the other side of the valve, to the upper and lower input of the piston. Depending on the position of the lever, this might extend the piston when you provide air to it, so be extremely careful when plugging it in. If you want to switch this behavior around, switch around the pneumatic outputs going into the piston. The speed control valves let you increase the speed of either closing or opening the vise. You achieve this by turning the knobs on the piston inputs.

15 Vise tuning

The vise needs to be setup for each mold thickness. The way it works is you adjust the external plate on the opposite of the toggle mechanism, to bring it closer or further away. There's a "leveling" process for the external plate - you need to keep it as parallel as possible to the moving internal plate. You achieve that by disconnecting the pneumatics from the air supply. You then move the vise into the closed position - by pushing on both the lower piston plate and the moving plate. Put the molds in between the spacers mounted on the external plate, and the moving plate. Push down on the lower piston plate and try to wiggle the molds You can then feel where the molds are loose and where they are clamped already, and which nuts to adjust in or out to spread the clamping force.

16 Vise tuning pt 2

After tuning the vise to a mold and securing the external plate nuts, screw in the mold into the vise. Test the vise and see if it's toggling properly. If the mechanism (and the shorter links) isn't locked straight, move the external plate out. If the links go "too far" and don't stay straight, instead bending in the other direction, bring the external plate closer.

17 The end!

This concludes the assembly of the injection molding vise. Feel free to replicate, suggest changes, modify it to your needs. It is easily modifiable for use in a horizontal injection molder for instance. You are free to replicate this design to sell it on the Bazaar as well. You can contact me directly by emailing adam@glia.org for help in assembly or any questions you might have about the device. Good luck, and happy injecting!

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