Optimise Part Packing on the Formlabs Fuse 1!

Selective laser sintering (SLS) has a significant advantage over many other 3D printing technologies — it doesn’t require supports. The powder in an SLS printer’s chamber props up parts as they build, eliminating the need to create supports and remove them in post-processing. This feature gives SLS printers superior productivity compared to most other technologies.

But the SLS 3D printing process also introduces an issue. To achieve maximum productivity and material efficiency, you must fill the build volume with as many parts as possible. Maximising the number of parts in an SLS print run can be a daunting task — unless you know the proper approach.

Read on as we explore what packing density is, how it affects your productivity, and how you can fit the ideal number of parts in your SLS printer.

What Does Packing Density Mean in SLS 3D Printing?

Packing density is a crucial concept with SLS printers, such as Formlabs Fuse 1. Printer operators and engineers use this term to describe the percentage the printed parts themselves take up in the SLS printer’s build chamber. The calculation for packing density is:

• Volume of 3D Printed Parts / Total Volume of Powder

Packing density directly determines how productive your printing operation is. It also has a significant impact on material expenditure.

Theoretically, an ideal packing density would be 100%. At 100% packing density, the printer would completely fill the build chamber with parts, producing no wasted space or powder. But in practice, such an extremely high packing density isn’t feasible — unless you want a huge solid brick of plastic, of course!

Although 100% packing density isn’t possible or even desirable, you still want to maximise the packing density with every print run. A higher packing density means you’re producing more parts with a single run. Consequently, you’ll utilise the 3D printer to its fullest potential and keep your productivity high.

What Does Powder Refresh Rate Mean?

Since you can’t achieve perfect packing density, there will always be some unsintered plastic powder left after your SLS printer finishes the printing job. However, this loose leftover powder doesn’t have to be wasted material.

When buying an SLS 3D printer for your business, you should choose a machine with a high powder refresh rate. The refresh rate describes the amount of previously used powder the printer can use in a new print run.

For example, Formlabs Fuse 1 has a powder refresh rate of 70%. The printer’s maximum print volume, meanwhile, is a bit more than 8 litres. Some simple math tells us that you can add some 5.7 litres of previously used powder into the machine when you start a fresh print job.

Naturally, the more powder you can reuse, the lower your material expenditure and costs will be. The high heat of the SLS printing process does eventually degrade plastic powder, so you can’t reuse them indefinitely. Nonetheless, by recycling powder you’ll save significant amounts of money while also making your business more sustainable.

Calculating the Ideal Packing Density

You now know what packing density and refresh rate mean. Armed with this knowledge, you can determine the optimal packing density for your SLS printer. But how exactly does that calculation work?

The ideal packing density depends entirely on your printer brand and model and its refresh rate. For this example, let’s continue working with Formlabs Fuse 1.

You already know that Fuse 1’s maximum refresh rate is 70%. It logically follows that if we want to reuse the maximum amount of powder, 30% of the build chamber must be filled with 3D-printed parts. Consequently, you should aim for a packing density of 30%.

At this level, you can reuse the most powder in the next print run while still producing as many parts as possible. Of course, you can use a higher packing density to get even more parts to boost your productivity. However, you won’t have as much recycled powder left over for the next print job and will have to use more fresh powder, increasing your material costs.

But if you lower the packing density to, for example, 20%, you will have more recycled powder than you can safely use in the next print job. You can keep the excess powder for later, but it has to be stored very carefully or environmental degradation could ruin it. The degraded powder doesn’t produce good results.

Following this same calculation, you can easily determine the packing density to aim for with your SLS 3D printer. For example, if your printer has a refresh rate of only 30%, you should aim for a 70% packing density to avoid having recycled sitting around and going to waste.

Benefits of Optimal Packing Density

Every SLS printer operator should always aim for their printer’s optimal packing density. At this sweet spot, your good printing practices will bring you many benefits, including:

• Higher Productivity: By fitting more parts into the print chamber, you’ll increase your productivity and can deliver final components to more customers. However, note that going past the optimum packing density may incur extra costs in higher fresh powder consumption.
• Lower Cost Per Part: At the ideal packing density, your printer will take the same amount of time to produce the parts, no matter how many parts it’s actually producing. When you fit the greatest number of parts into the chamber at the optimum density, you’ll maximise machine utilisation and minimise cost per part.
• Lower Material Costs: Operating your SLS printer at the ideal packing density allows you to recycle as much powder as possible. Using less fresh powder in every print job lowers your material consumption and can save you significant amounts of money.
• Less Waste: Not only will packing your parts properly help your business but you’ll also do a service for the environment. Recycling powder produces less non-biodegradable plastic waste and saves the resources needed to produce fresh powder. What a great marketing angle for your business!

Fuse 1 — Better Packing, Better Productivity

But once you’ve calculated your printer’s ideal packing density, your job is still not done. You’ll now have to fill the available space with as many parts as possible to achieve maximum productivity. How many components you can fit into the chamber depends on the parts you’re looking to produce.

However many parts you’re looking to print, it can be very challenging to fill the build chamber optimally. Most print preparation applications let you position parts by hand, but this is an extremely time-consuming process that is unlikely to produce ideal results.

Computers can calculate part orientation and fit most parts into the build chamber much faster than humans. As such, it’s best to use print preparation software with a powerful, automated packing feature.

Formlabs Fuse 1 integrates seamlessly with the Formlabs PreForm software. PreForm includes a sophisticated, advanced packing algorithm to achieve the highest possible packing density with your machine. This fast and easy-to-use solution can significantly lower the amount of time spent on print preparation.

In PreForm, all you have to do is input the number of parts you want to produce in the print run. After setting part spacing, PreForm’s packing feature will determine the optimal part orientation to achieve the highest possible packing density in only a few seconds.

The software will clearly show you the final packing density of the parts. And since you now know how to determine your printer’s optimal packing density, you can quickly increase or lower the part count to achieve perfect results.

—– Want to learn more about maximizing your SLS 3D printing efficiency? The AM experts at Solid Print3D are happy to help you! Call us at 01926 333 777 or email us at info@solidprint3d.co.uk.