PEEK vs Espuma PMI: Comparação de Corte com Fio de Diamante

Abstrair: PEEK and PMI foam sit at opposite ends of the material spectrum that a
Loop de fio de diamante has to handle – one is a dense, tough thermoplastic, the other a
low-density cellular structural foam. This comparison sets Ensoll’s two published slicing tests side by side:
uma 200 mm x 60 mm x 60 mm PEEK block cut into 6.5 mm slices with cutting fluid, and four 400 mm x 400 mm PMI
foam slices cut to 0.8 mm dry. It compares the failure modes, the parameter sets
(uma máquina de serra de fio diamantado dedicada in both cases) and the measured quality results, and gives the
rule for deciding which starting point to use.

Two Materials, Two Different Failure Modes

The reason PEEK and PMI foam need different process settings is not hardness alone – it is what happens when
the process window is exceeded.

PEEK is a high-performance thermoplastic with high toughness, wear resistance and heat resistance. Under
diamond wire cutting its removal mechanism differs from hard and brittle materials: because the material has
plasticity and toughness, the continuous action of the abrasive grains generates cutting heat. If that heat
cannot dissipate, the machining zone softens locally and cutting resistance rises, producing dimensional
deviation, edge burrs and degraded surface quality. The controlling variable is therefore
temperatura.

PMI foam is a high-performance structural foam with low density, a uniform cellular structure and good
specific strength and stiffness. Its porous interior gives a removal behaviour quite unlike a dense material:
the abrasive grains act on the foam skeleton, and if the cutting load is too high or the parameters are poorly
matched, the cells are compressed and torn and the cut face becomes uneven, which feeds directly into slice
thickness and surface quality. The controlling variable is therefore load.

Material and Workpiece Comparison

Parameter Comparison

Result Comparison

Reading the Differences: Three Rules

Rule 1 – Temperature-dominated materials get cooling; load-dominated materials do not

PEEK was cut with cutting fluid as the cooling medium to improve heat dissipation and lubrication at the wire
interface, limiting local softening, deformation and burrs. PMI foam was cut dry so that no liquid entered the
cells and no cleaning or drying step was needed afterwards. Choosing the wrong one is a process error in both
directions: dry-cutting PEEK risks a softened kerf, and wet-cutting PMI foam risks dimensional drift from
absorbed liquid.

Rule 2 – The soft material can run two orders of magnitude faster in feed

The PEEK feed rate was 3 mm/min; the PMI foam feed rate was 100 mm/min. That gap is not a machine difference,
it is the consequence of what limits the process. PEEK removal is limited by how much heat can be carried away,
so feed must stay low. PMI foam removal is limited by how much load the cell skeleton can take, and because the
foam is low density that ceiling is reached much later. Both tests used similar wire speed – 24 m/s for PEEK and
25 m/s for PMI foam – which confirms that feed rate, not wire speed, is the discriminating parameter.

Rule 3 – Compare each material against its own tolerance, not against the other

PMI foam produced TTV of 0.013-0.050 mm against PEEK’s 0.072-0.098 milímetros, but the slices were 0.8 mm and 6.5 milímetros
thick respectively and the tolerance requirement differs with the application. What both tests do show is a
stable process: PEEK held +/-0.037 mm thickness tolerance and PMI foam +/-0.043 milímetros, with Ra below 1 um in both
cases and edge chipping under 7.1 um in both cases.

Which Starting Point to Use

Common Mistakes When Switching Between the Two

• Carrying the feed rate across. A feed that is conservative for PMI foam is far too
  aggressive for PEEK, and a feed that is right for PEEK leaves the PMI cut polishing rather than cutting.
• Assuming coolant helps everywhere. On PMI foam, coolant is a dimensional risk rather than a
  safety margin.
• Judging the foam result by the plastic result. UMA 0.8 mm foam slice and a 6.5 mm plastic
  slice cannot be compared on raw TTV numbers.
• Chasing wire speed. In both tests the wire speed sat in the same 24-25 m/s band, which is
  the clearest sign that it is not the lever for quality on either material.
• Ignoring the entry edge. Both materials need the wire bow to settle before feed engages; uma
  60 s wire-bow tensioning time was used in both tests.

Full Test Data

The complete measurement sets – nine-point thickness readings, tolerance tables, Ra profiles and chipping
measurements – are published in the two source reports:
PEEK precision slicing with diamond wire loop and PMI foam precision slicing with
Loop de fio de diamante. The measurement method itself is described in the
nine-point TTV measurement guide.

Perguntas Frequentes

É mais difícil cortar PEEK ou espuma PMI com um fio de diamante??

Eles são duros de maneiras diferentes. PEEK é denso, tough thermoplastic: o risco é o aquecimento durante o corte, o que amolece o material no sulco e provoca desvios dimensionais e rebarbas. A espuma PMI é um sólido celular de baixa densidade: o risco é a carga de corte, o que comprime e rasga o esqueleto celular. Portanto, o PEEK precisa de refrigeração e avanço conservador, enquanto a espuma PMI necessita de controlo da carga e corte a seco.

Porque é que o PEEK é cortado com líquido e a espuma PMI a seco??

O PEEK é um termoplástico que amolece quando a zona de corte aquece, por isso usa-se fluido de corte para remover calor e lubricar a interface fio-material. A espuma PMI é porosa e absorve líquidos, por isso o refrigerante entraria nas células e teria depois de ser removido através de limpeza e secagem – daí usar-se corte a seco.

How different are the feed rates between the two materials?

Substantially. PEEK was sliced at a 3 velocidade de avanço de mm/min, while PMI foam ran at 100 mm/min. The dense thermoplastic needs slow feed to keep heat generation low; the low-density foam tolerates a much higher feed because removal is limited by load, not by heat. Wire speed was similar in both tests, 24 m/s for PEEK and 25 m/s for PMI foam.

Which material achieved better dimensional results?

PMI foam showed the smaller variation in absolute terms – TTV 0.013-0.050 milímetros (média 0.036 milímetros) against PEEK’s 0.072-0.098 milímetros (média 0.085 milímetros) – but the two are not directly comparable. The PEEK slices were 6.5 mm thick and the PMI slices 0.8 milímetros, and a thinner slice is measured against a much smaller nominal thickness. Compare each material against its own application tolerance.

Can one parameter set be used for both materials?

Não. The validated sets differ in wire diameter, taxa de avanço, tension and cooling method. PEEK used a 0.35 x 1880 fio totalmente revestido a mm em 150 N tensão com fluido de corte; espuma PMI usada a 0.60 x 3460 fio totalmente revestido a mm em 145 N tensão com corte a seco. Comece cada material a partir da sua própria janela validada em referência de parâmetros de corte de espuma PMI.

Conteúdo técnico revisto pela equipa de engenharia da Ensoll – um fabricante de laços de fio de diamante com 10+ anos de experiência em produção.