Foil Hot Plate issues

We are trying to foil using a 220v 15amp Boss controller with a hot plate running 3 Watlow firerod 300w 240v cartridge heaters. All the parts are very used and I only have 3 out of 7 rods working the the bad ones cut out and removed. We are having trouble getting enough temp to get a good pull away and wonder if the 300w heaters are the issue or is the fact I only have 3 an issue. We dont know if we need a high watt rod or what to do. In theroy they should be able to go high enough based on specs but we seem to be stuck around 185-200 or less. What watt elements do you all reccomend. How are you setup up. What is your favorite craft beer ( cant work all the time). Any ideas we are are listening

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ya, that is not high enough for almost any foil out there. you want your die temp to be around 225F-265F. (that will start a controversy) so, foil……. three main things you need for foil to work. 1) Heat, 2) Pressure, 3) Time…… there are a million other variables, such as stock density, surface, area, coatings,Etc.
1) heat ; you need the heat at the die. and then a reserve of it depending on die area and production speed.
2) Pressure; Foil for the most part is either On the sheet or Off of it. even pressure will play a big role here as foil acts much more “Digital”. Whereas ink being more “Analogic”.. ink will go down in gradients with a variance in pressure. foil will either stick or not.
3) Time; this is in reference to the actual time that the die is in contact with the sheet. In many circles, this is called “Dwell”. on a production press, the faster you run the press, the shorter the Dwell time. results are more sheets per hour.
You need these 3 to be in a balance. if you slow a press down, you may need to turn down the heat. if you can only hit the sheet with a light pressure, then a higher heat, or slower press speed, more dwell, is required. if you need to run a foil “Cooler” to keep fine work clean, then a higher pressure or slower speed.
I fully admit to the press nazis out there that are a million other things to consider. but keeping in mind these 3, will keep you on the right track.
So, to answer your question, it depends on where your heat is going. if you are heating the press frame, then 900W is not enough. Again, you want the heat at the die. you will want to insulate your hot plate from the press as much as you can. A sheet of mica behind hot plate is effective,but this is delicate, fragile, stuff. it can be incorporated into your hotplate, if you are using a hotplate with a backplate. if your hotplate is simply drilled and rods insert up into it, your situation is more difficult.
a good pyrometer will help you to determine if your readout is accurate. expect the control indicator to read hotter than your actual die face temp.

Thank you for the feed back. We are working with a windmill and hope by slowing down our dwell time will be OK. We think the big problem is heat and we cant get enough heat out of the current rods. We are not sure if the 300 watt are strong enough or if they are just shot., they have a lot of years on them It looks like they have been connected and reconnected a number of times before we got them and wonder if a weak electrical issue is also part of the problem also. We will let you know what happens.

a few things could be checked by someone with a little advanced electrical knowledge.
1) Is this unit running on correct supply voltage? If system is set up for 200-240V, and you running on 110, it will not perform as designed. (If this setup came from europe, it could even be set for 460V.)
2) go into controller case and check the contacts. these are likely mechanical and can be visually inspected. if there is a “Big arc” when they contact, then it is likely they are shot, or they look “all melted” they are not allowing all current to pass. a small to medium arc is normal for these. (I know it depends on what you are used to seeing as far as arcing goes). these generally cannot be “fixed” just replaced. if yours look shot, and replaceable, Ebay is a first option to find new ones.
3) check amperage draw on each heater rod. (you would have to disconnect one end, of each one to check individually, or you can check it together. put 900W in the formula) Watts=VoltsxAmps, so 900W or 300W/Volts=Amps. if the formula does not work out, something is wrong.

Good morning. We have checked the box and all seems OK. We have run a volt test of the leads and they are at 208. We tested the continuity of the rods and they test OK. Today we hooked up one rod straight to the leads right at the rod tips and it heats high and fast. One thing we noticed that we have done was to change the wires from the main leads to the cartridge heaters. I had gone to Granger with the whole plate and showed them the existing wire which was not is good shape and wanted to redo it. They sold me Thermocouple wire type J 20 gage to use for connecting the main wire leads to the rods. I am wonder if this is the wrong product since Thermocouple wire is normally use for temp sensing and not power transmission. I explained what we were doing and they said it was the correct product and it looks like the correct wire. The rods are a type J format but I am not sure what sort of wire is used to power it. It might explain why we are having so much trouble generating heat.The plate had a back plate that looked like Phenolic board that was warped and cracked so for now it is off.

Your thermocouple is a Type J which won’t have any bearing on the heater cartridges.

If you’re trying to wire the heater cartridges to the PID head unit, then type J thermocouple wire is a recipe for disaster as it’s going to build up a good amount of heat with that much current passed through it. Heat at the plate is good, heat in the wires to the heater cartridges means fire.

There’s no particular wire necessary to use to connect the heater cores. I believe both of ours are wired using stranded 16 Gauge copper wire which has low enough resistance to operate for long periods of time without heat buildup.

One thing to note is that your PID temp controller/ head unit basically creates an algorithm that it uses to precisely maintain heat. Removing heaters, changing the size of the baseplate drastically, or changing the wattage of heaters will require retuning the temp controller to allow it to control temperature to a reasonable accuracy.

The newer watlow PIDs have an autotune feature that will remap to accommodate changes in the system but I’m not sure of the series 808 that your system is probably using.

I’d recommend skipping Grainger as a source. The PID systems for foiling are too specialized and outside of their knowledge base. West Coast Plastics is a US Watlow distributor and extremely knowledgeable. I’d recommend you contact them with questions.

Thank you for the input. We did a full rewire and got it going only to ground and short a rod during heat up - a coupling was to close to the rod top and arced. We are going to get new wires and do this the correct way and it should work.