Thursday, March 24, 2016

Repair the slide cutter on your Heat Sealer.

Standard 16" Heat Sealer
If you have ever used a Heat Sealer with a built in slide cutter to cut the bags, you know two things. One that the slider part will wear out over time, causing the tip of the blade to start scraping on the aluminum plate, prematurely ending the life of your $10 blade and Two even if you can get a replacement part for it , you will pay a fortune for it. So many companies end up purchasing a new heat sealer for several hundred dollars just to avoid the hassle. So what if I told you that you would be able to repair your heat sealer for under $20, how about $10 or less? Would you be interested?

So first off, let me explain one thing. There appears to have been dozens of manufacturers over the years of heat sealers, both with and without cutters. But one thing that most have in common if they include the cutter is they use the same blade, and also almost exactly the same cutter slide. There maybe slight varying dimension but they are all within about .5 mm of each other. So the fixes I will propose here will help you get a longer life out of your heat sealers regardless of manufacturer.

What's the problem?
Blade bottoming out in tray
Over time with regular use your slide on your cutter will start to wear on the bottom edge where it is
in contact with the top painted surface of the heat sealer arm. This is just normal wear and tear. The results of which cause your blade to go too far down below the bag that you are trying to cut. When it gets worn enough you will start seeing scratch marks in the aluminum tray under the bag clamp area. This will roll the end of a brand new blade over in a few passes and then eventually wear it clear down and and make your expensive cutter blades junk in a hurry.

How to fix it?
Over the years we have tried numerous fixes/band-aids that never really seemed to be a long term solution. I will give you some of our fixes here and let you decide what your final solution should be.

Fix #1 - One I am sure you have all tried. Just adding Duct tape or masking tape in layers to the top of the heat sealer arm under the slider. While this is a way to raise the slider, the duct tape is not a very good sliding surface and masking tape is more abrasive than the paint on the arm and will increase the wear time of your slider even more. Causing irreparable damage if left long enough. The other issue I have with this solution is that the tape is eventually going to wear out and you will need to remove it. If you have ever dealt with removing the adhesive in these situation, you know it is a pain like no other.

Fix #2 - While similar to fix number one, this is the solution that we used for a long time to get a little more life from our cutters. What we used in place of tape is the same material you use to put over the heating element. The PTFE Teflon tape with the adhesive back. One strip down each side and you will raise it a little. You may have to apply it two or 3 layers thick on each side, depending on how worn your slide is. One advantage to this right away is that the Teflon tape is a very slick and low wear surface compared to the Duct/masking tapes and even the painted surface for that matter. So right away you are slowing the wear of your Slide and making your heat sealer work better.

Fix #3 - While any of the previous two ways will help you temporarily, you will eventually reach a point where they can no longer do the job. Mainly because from day one of running your slider back and forth the one property you cannot overcome is friction. Two surfaces rubbing against one another will always wear down the softer of the two. In this case the plastic cutter slide loses in a big way. So I started thinking of a way to put the wear onto something else and revive the 6 cutters we are currently using. We were looking at a $1500.00 bill to replace all 6 cutters if we didn't figure something out. My solution is to create a shim that sits under the slide to raise it up the amount of the worn away material. It should also serve to slide with less resistance than the hard plastic, wear longer and be easily replaceable if the shim itself eventually wears out.

If you read my blog , then you know I am currently in the process of finishing up the final tweaks and adjustments on a do it yourself CNC mill I built from scratch. So my thought right away was to use this machine to manufacture a shim that would fit well and be reproducible for replacements. Your shims do not have to be this elaborate, but what I will tell you is that though a simple flat shim will do the job. It doesn't stay in place as well and quite frankly mine just plain looks cooler. But feel free to use the dimensions I give you here to make a workable flat shim to get you back in business.

Part Design
Any time you are dealing with CNC you first have to design your part. For this I am using an absolutely amazing program provided for free by Autodesk, the manufacturers of AutoCAD, to hobbyists called Fusion 360. This amazing program takes you from Design in CAD, to CAM for your paths and then even exports the Gcode that you need to load into Mach3. I started by measuring the slides on all the cutters we have with a digital caliper. This is were I found that all the cutters slides were generally the same as we have 3 different manufacturers in our midst. I created a shim with a small 1mm lip that would wrap around the edge of the slide to hold it in place.

I made my shim out of some High Density Polyethylene sheeting that I had laying around. You could realistically make it out of any plastic type material that has a low friction coefficient. Nylon, Teflon and my personal favorite Delrin are other choices you may use.

The one dimension that
is going to be unique to each slider is the thickness of the shim. This will be based on how much wear you have. I started with 2mm thick for the base, but it turned out to be too much, and the cutter would not cut through all the way on the ends. I finally settled on 1.5 mm and it worked perfect on almost all of mine. I still had to straighten up some edges on the bottom of some of the sliders due to uneven wear patterns. When done the shim will look something like the image at the right here. Mine is a little rough around the edges, because I didn't have a mill that would work for chamfering the edges, So I did it by hand with a utility knife, and on something this small that is not easy to make look nice. But realistically no one else is going to notice once it is installed.

Installing the shim is pretty straight forward, remove the cutter slide. This is a process, you do not have to remove the knob to do it. you just have to have the right angle when you slide the screw through the slot there. Once the slide is out, remove the screw that holds the blade holder and blade in place. This would be a good time to place a new blade in the holder. Your old one is shot anyway from the bent tip. just start new. Slide the shim on the shaft, with the pocket facing up. if you have one. Slide it all the way up till the lip snaps around the top section. Put the screw back in and reinstall in the cutter slider.

Final Results and Link to Drawing
Your installed shim will look nice and work great for a long time to come. I hope this saves you some
time  and money. If you would like to make this shim for yourself, or have someone else with a CNC mill make. it I have created a public link on Fusion 360 to allow you to download and use it free of charge for non-commercial personal use only. The link is This is setup using a 1/8" 2 fluted flat tip mill. You can modify it however you like to use what bits you have on hand.


No comments: