Resin 3D printing and Temperature

I’m writing this after having my own 3D printing adventures with regard to temperature since it can throw up a lot of issues for some people and yet because a lot of people print in fairly warm houses or live in warm countries, its not something as many people are aware of when problem solving 3D printing issues. In addition whilst the solution might appear simple, it isn’t always quite that easy.

First up please note that any values of temperature I state in this are only rough values. Specific resins might vary, but what I say below should be a good general standard for most of the common home 3D printing resins. If you want more specific info contact the manufacturer of the resin that you’re using.

Resin, in its liquid and part cured state, is affected by its temperature and is very reactive to any changes in its temperature. Once fully cured its far more stable, however until that stage the temperature is a very critical property to mange for 3D printing.

In general the ideal minimum printing temperature is 20 Degrees Centigrade/68 Fahrenheit. Any lower and you start to get increasing problems, warmer environments can greatly benefit 3D printing, up to around a value of 35 Degrees Centigrade/95 Fahrenheit. This upper value is one I’m less sure of and might vary more so than the lower limit of 20. In practical terms I tend to treat 30C/86F as a good upper value to print at.

At temperatures below 20C/68F the chance of a failed print is greater since the resin becomes increasingly viscous. When the resin flows less readily it means that it might not flow back under the build plate fully when its lifted between layers. It also becomes increasingly sticky when in its part cured state, making it stick to the FEP more readily than normal.

This can lead to failures where you might get the base/burn layers of your print forming (since they also tend to generate more warmth from the increased reaction time) but then have a whole layer appear to fail when your support columns start to print. Almost as if you had a corrupt file on your USB. Leaving you with a raft on your build plate and a flat expanse of resin on the build plate. Almost as if you’d had a serious underexposure issue. However something like the Ameralabs Town, or other calibration prints, might well print fine and not show any apparent underexposure issues.

If you are just a little shy of 20C/68F by a degree or so you can get around this by:

1) Pre-warming the resin in the bottle prior to shaking and pouring into the VAT. This ensures that the resin begins the process warmer, with a view that the internal heat generated by the curing reaction, will help sustain the resins temperature for the duration of the print.

2) Insulate the printer, so that any heat from pre-warming and the curing reaction, is preserved.

3) Raise the lift height of the build plate in the printer settings. This gives the resin just a little more room and time to flow back under properly.

If you are further off 20C/86F at the time of printing, or the ambient temperature of the printing environment is going to drop way below during the print (eg starting a long print which will be completed overnight), then you have to start looking at heating the printer environment up. Broadly speaking this will likely happen in one of two ways

1) Heating the room the printer is within. This in general works well no matter what kind of heat source you use. So long as it has a thermostat to ensure that the temperature remains at a good value for printing it should work fine. The natural rise and fall of a room level of heating is unlikely to cause any adverse reaction of the printer to the changing temperatures, so long as they remain at or above 20C/68F. For many people this might not be affordable or practical if you’ve just the one printer for a hobby.

2) Heating the printer/insulated enclosure, alone. This has the benefit of costing far less because now you’re heating a much smaller area rather than an entire room. However resin is very reactive to heat and changes in temperature of such a small enclosed space can cause their own issues and that’s what we are now going to look at.

Below you can see lines on a flat printing surface, those lines can be easily felt with a finger and represent expansion/contraction of resin being heated by a small fan heater within an insulated enclosure. Flat surfaces will show this more readily, however the second photo shows a model where, on the mane, you can see the same ridges running downward at regular intervals.

Wraithful Kirin by Mini Monster Mayhem (Patreon and My Mini Factory)

To understand why this is happening we first have to understand how most fan heaters on the market work. They operate by having a built in on/off thermostat. These kind of thermostats work by turning the heater on to raise the temperature up to a set value. When the thermostat detects that this temperature has been reached, it turns off the heating element within the heater (it might also turn off the fan). It will then remain off until such time as the thermostat detects the temperature has dropped below a threshold value; it then turns the heating element and fan back on to the full extent of the selected power until the temperature rises again.
This on-off cycle is very regular for a stable environment and will generate those lines of expansion/contraction as the resin reacts to those sharp rises in temperature and the steady fall after.

To resolve this problem you have to use a proportional thermostat and proportional fan heater. Proportional setups differ because they work by raising the temperature to a set value, but then don’t turn off once reaching that value. Instead the power being sent to the heating element is reduced so that the temperature is maintained at the desired value. Any variation is often very slight and as a result you have a steady constant printing environment temperature.

Proportional heating setups are fairly specialist and can be hard to source for 3D printing. There are many proportional fan heaters on the market (they are commonly used for car heaters); however proportional thermostats for a fan heater are much less common. There are many proportional thermostats made for pets (eg fish and reptiles), however they are not made for fan heaters. They only work with ceramic heat lamps and heat mats, which in general do not work well for a 3d printer environment.
Fan heaters with proportional thermostats are more commonly found in egg incubator machines, however in many regions these are already built into an incubator, which means to use them for printing you will have to modify things.

I have managed to find one good source for a proportional thermostat and fan heater setup which is not built into an existing incubator. Incubator Warehouse (USA) produce a range called the Incukit which are ideal for 3D printing. I did have to import these and use their international version as I’m based in the UK. Note if you do get them see if you can source your own US to UK power connector since the ones they provided me don’t tend to hold the US plug very tightly (it slips out very easily). Their ebay store is also cheaper on postage than their main website for international customers Incubator Warehouse Ebay

There are two models on sale;

IncuKit Mini –
A 48Watt fan heater with proportional thermostat already attached. This is a small setup that, with a bit of work, you can place inside a printer hood (you might have to drill a small hole for cables for the fan and sensor to fit inside). It’s ideal for heating just 1 printer directly so long as its insulated as well and also not having to work at raising the temperature by a large amount.
The value you have to watch is its running power use, since its not ideal for the setup to be running near full power for a prolonged period of time (eg constant when it comes to 3D printing).

IncuKit XL for Cabinets –
A 125Watt 1 fan or 250Watt 2 fan heater. This option comes with a regular thermostat (on/off) by default so if you do order it you need to make sure to add the advanced thermostat which is the proportional one. This option is far more powerful even with just 1 fan and is thus much more suited to raising the temperature of an insulated enclosure up by a greater amount and being able to maintain it with less power being sent to its heaters (far better for long term use).

Personally I’ve tried both and, for my situation, I settled on the XL version since it allowed me to raise the printing temperature to 30C/68F and maintain that temperature without having to maintain high output to the fan heaters. I also believe that it will be far more suitable for the colder part of the year when the room temperatures can easily drop below 10C/50F. You can see the setup I’ve used below, a simple bit of wood nailed together to form a stand and the fans screwed into it (the set provides screws for this purpose).

In addition to the above, there’s one more bonus of a warm printing environment, support removal. When I was testing my printer and heaters prior to learning much of the above, I did two print runs of the same model with the same supports. One was at 20C/68F and one was at 30C/86F. The print at 20C/68F was much harder to remove from the supports, requiring the hot water trick and clippers to finally get it off the supports. Meanwhlie the one that was printed at 30C/86F and kept at that temperature whilst sitting on the build plate, peeled off its supports effortlessly.

It’s for this reason, as well as the reduced viscosity of the resin, that I try to keep my print environment at 30C/86F now. Whilst you can immerse the print and its supports into hot water to warm it up to make it easier to separate it from the supports, this results in resin contaminated water (even if you washed in IPA first); which then has to be processed to be disposed of safely.